MMSE Journal Vol. 15 2018

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Sankt Lorenzen 36, 8715, Sankt Lorenzen, Austria

Mechanics, Materials Science & Engineering Journal

April 2018

MMSE Journal. Open Access www.mmse.xyz

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Mechanics, Materials Sciences & Engineering Journal, Austria, Sankt Lorenzen, 2018

Mechanics, Materials Science & Engineering Journal (MMSE Journal) is journal that deals in peer-

reviewed, open access publishing, focusing on wide range of subject areas including, engineering, materials science, physics, FEA etc.

MMSE Journal is dedicated to knowledge-based products and services for the academic, scientific, professional, research and student communities worldwide.

Open Access model of the publications promotes research by allowing unrestricted availability of high quality articles.

All authors bear the personal responsibility for the material they published in the Journal.

The Journal Policy declares the acceptance of the scientific papers worldwide, if they passed the peer-review procedure. Published by industrial company Magnolithe GmbH MMSE Journal Editorial Board Dr. Girish Mukundrao Joshi, VIT University, India Prof., Dr. Murch, Graeme E.,University of Newcastle, Australia, Centre for Geotechnical Science and Engineering, Callaghan, Australia

Prof. Amelia Carolina Sparavigna, Politecnico di Torino, Italy Dr. Zheng Li, University of Bridgeport, USA

Prof. Kravets Victor, National Mining University, Ukraine Dimitrios Vlachos, Associate professor, University of Peloponnese, Department of Informatics and Telecommunications, Greece Hovik A. Matevossian, Russian Academy of Sciences, Russian Federation Dr. S. Ramesh, KCG College of Technology, Karapakkam, India Dr. Yang Yu, University of Technology Sydney, Australia Ph.D. José Correia, University of Porto, Portugal

ISSN 2412-5954

Design and layout: Mechanics, Materials Science &

e-ISSN 2414-6935

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Engineering

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GmbH)

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CONTENT I. Materials Science MMSE Journal Vol. 15 ................................................................................ 5 Screening of Potent Antimicrobial Activity of Encapsulated Nanometric Neem Oil Emulsion Against Vibrio Alginolyticus. Swathy J.S., Amitava Mukherjee, Natarajan Chandrasekaran ........ 6 Orange Oil Nanoemulsion- a Biocompatibility Profile of Lymphocytes. Saranya Vinayagam, Usha Tamilarasan, Amitava Mukherjee, Chandrasekaran Natarajan ............................................ 18 Development of Lead Free Piezoelectric Material for Sonar Applications. Madhuri W., M. Penchal Reddy, N. Ramamanohar Reddy, K.V. Siva Kumar .......................................................... 24 Growth and Characterizations of ZSM-5 Zeolite Added TGS Crystals. A. Priyadharshini, S. Kalainathan .............................................................................................................................. 28 Laser Shock Peening on Microwave Sintered Aluminum Alloy Nanocomposites. S. Prabhakaran, Prashantha Kumar H. G., S. Kalainathan1,b, Anthony Xavior M., Kaustav Chakraborty .................................................................................................................................. 36 Tuning the Surface Properties of Modified Polymer Blends as a Function of Plasma Treatment – A Mini Review. E. Dhanumalayan, Girish M. Joshi................................................ 42 Sonochemical Method for Casting the Polymer Nanocomposites: A Mini Review. D. Arthisree, Girish M. Joshi ............................................................................................................. 47 Thickness Dependent Optical Properties of Sol-gel Based MgF2 – TiO2 Thin Films. Siddarth Krishnaraja Achar, Akhil Punneri Madathil, Naveen C.S., Baijayanthi Gosh, A. R. Phani ............ 52 Biomedical Applications of Hydroxyapatite Based Composites: A Brief Review.

M.J. Joshi ..................................................................................................................................... 62 Nonlinear Optical, Mechanical, Electrical, Photoconductivity and Surface Morphology Studies of Thiourea Potassium Hydrogen Phthalate (TKHP) Nonlinear Optical Crystal for Frequency Conversion. A.L. Kavitha........................................................................................... 68 Comparative Study of API 5L X60 and ASTM 572 Gr50 Steel Exposed to Crude Oil and Seawater. Marcy Viviana Chiquillo Márquez, Janaína André Cirino, Magda Rosangela Santos Vieira, Severino Leopoldino Urtiga Filho ..................................................................................... 78 Synthesis of Nanosilver Doped Water Soluble Macromolecules: an Investigation from Antimicrobial Coating Perspective. C. Kavitha, V.Gowsalya ..................................................... 91 II. Mechanical Engineering & Physics MMSE Journal Vol. 15 ............................................. 100 Part 1. Numerical Integration over a Family of Quadrilateral Elements for Elliptic Partial Differential Equations by Galerkin Finite Element Method. K. T. Shivaram, G. Manjula, K. Lakshminarayanchari ............................................................................................................. 101 Innovative Approach for Preparation of Skilled Engineers. K.A. Ziborov, T.O. Pismenkova, S.O. Fedoriachenko, A.V. Merkulova, I.K. Ziborov...................................................................... 107 III. Electrical Complexes and Systems Vol. 15 ....................................................................... 115 Improved Design of Low-speed Inductor Generator for Wind Turbines with Vertical Axis of Rotation. Shkrabets F.P., Tsyplenkov D.V., Kolb A.A., Grebenuk A.N., Panchenko V.I........... 116 VI. Environmental Safety Vol. 15 ............................................................................................ 127 Impact Study of Different Natural Factors to Agricultural Vegetation Development by Using MODIS Images and GEOBIA Method (Case of Syr-Darya Province, Uzbekistan). Shamshodbek Bakhtiyarovich Akmalov, Aybek Mukhamedjanovich Arifjanov, Luqmon Nayimovich Samiev, Tursunoy Ubaydullaevna Apakxo’jaeva ...................................................................................... 128 MMSE Journal. Open Access www.mmse.xyz

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I . M a t e r i a l s S c i e n c e M M S E J o u r n a l V o l . 1 5

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Mechanics, Materials Science & Engineering, Vol. 15 2018 – ISSN 2412-5954

Screening of Potent Antimicrobial Activity of Encapsulated Nanometric Neem Oil Emulsion Against Vibrio Alginolyticus 1

Swathy J.S.1, Amitava Mukherjee1, Natarajan Chandrasekaran1,a 1 – Centre for Nanobiotechnology, VIT University, Vellore, Tamil Nadu, India a – nchandrasekaran@vit.ac.in DOI 10.2412/mmse.41.4.285 provided by Seo4U.link

Keywords: azadiractin, high-pressure homogenization, neem oil nanoemulsion, sodium alginate, sodium alginate- gelatin composite, vibrio alginolyticus.

ABSTRACT. Nanoemulsion prepared using essential oils can act as an alternative strategy to control the pathogenic infections. Neem oil, widely used essential oil with high medicinal value and properties. Azadiractin, one of the major bioactive compound present in the neem oil, exhibits a good antimicrobial property. Neem oil nanoemulsion prepared using high pressure homogenization method, in which coarse emulsion comprises of neem seed oil as oil phase and aqueous phase contains Tween 20 and Milli-Q water. The ratio 1:3 prepared at 20000psi (25th pass) result in hydrodynamic size of 26.5±2 nm, which exhibit a good physicochemical stability and antibacterial activity against vibrio alginolyticus.

Encapsulation of formulated neem oil nanoemulsion using suitable bio-polymers prevent the degradation, rapid oxidation and uncontrolled release of bioactive compounds on exposure to environment. Encapsulation of stable neem oil nanoemulsion (1:3 ratio) was achieved using sodium alginate (3%) and sodium alginate (3%) – gelatin (2%) composite via cross linking with calcium chloride solution which resulted in the formation of hydrogel beads. The scanning electron microscopy images of encapsulated beads exhibit spherical in shape with a diameter of 1.8mm respectively. The concentration of azadiractin in encapsulated beads (3% Na-alg -1:1 ratio) was analysed using reverse phase HPLC technique was found to be 5.46mg/L. Finally, the results suggest that after encapsulation the antibacterial activity of neem oil nanoemulsion remain same with a sustained release of active ingredient, making it potent therapeutic agent.

Introduction. Nanoemulsion is considered to be kinetically stable (20nm - 200nm) consist of an oil phase and aqueous phase, which is immiscible in nature due to its high surface tension [1]. Surfactant helps to reduce the interfacial surface tension present between the two phases, thus forming a homogenous colloidal system [3]. Most commonly used method for the preparation of nanoemulsions are low-energy and high-energy methods. and Low energy method includes PIT (Phase inversion temperature) method, emulsion inversion point (EIP) and the spontaneous emulsification (and High energy methods mainly consists of microfludization and ultrasonication. In high-energy method, mechanical energy is used to create a forces which can break up the both phase (such as oil and water phase) and result in the formation of nanodroplets [4].

Essential oils are lipid soluble, low molecular weight and which can be considered as a secondary metablites that plays an important role in plant defence mechanism [5-6]. Microbial activity exhibited by essential oil against wide range of microorganism is due to the presence of active compounds such as terpenes and terpenoids [7]. Hydrophobic nature of essential oil helps them to interact with lipid membrane and mitochondria results in loss of cell membrane permeability, which finally leads to the leaking of the intracellular components,cell lysis and cell death [8-11].Nanoemulsion prepared using these essential oils helps to replaces the widely used antimicrobial agents, which is toxic in nature.

Neem seed oil is one of the traditionally used essential oil due to its therapeutic properties such as anti-bacterial [12], antifungal [13] and antiviral. Azadiractin, one of the major bioactive component present in neem seed oil nanoemulsion, which contributes major therapeutic properties [14]. Even 1

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though, essential oils have many therapeutic properties, but there is some restriction due to their insolubility, rapid oxidation, high volatility and degradation, when it exposes to environment [15,16.

These problems can be solved by encapsulating the neem seed oil nanoemulsion using suitable biopolymers. Bio encapsulation of nanoemulsion was considered as one of the important emerging and promising techniques.

Encapsulation of nanoemulsion using suitable biopolymers helps to improve the stability, sustain the therapeutic potential of active ingredients and control release of component present in it. Selection of Encapsulation material was based on the important criteria’s such as cost, application and safety.

Encapsulation techniques help to protect the active ingredient from environment and also easy in handling. Most commonly used natural biodegradable polymers includes pectin, guar gum, chitosan, carrageenans, sodium alginate and gellan gum, which have been used in all multidisciplinary fields [17, 18] Alginate is one of the naturally available biopolymer, which has several properties such as gelling, film-forming, stabilizing, thickening, and act as a matrix for entrapment [19]. These astonishing properties makes alginate suitable for the different application in the all fields, which helps in the controlled release of the active ingredient at a controlled rate [20]. Gelatin is another important biocompatible and biodegradable polymer, which is soluble at the body temperature and widely used in food and pharmaceutical applications[21, 22].

In our study, Neem oil nanoemulsion was formulated using microfluidizer, which was further encapsulated using sodium alginate (Na-Alg) and gelatin beads to enhance the stability and controlled release of active ingredient azadirachtin. Sodium alginate bead formulations were characterized using swelling studies, drying rate, surface morphology, and in vitro release. Antibacterial activity of formulated neem oil nanoemulsion was evaluated against vibrio alginolyticus.

Experimental. Materials Neem oil, Tween 20 were procured from Sigma Aldrich Inc., USA. Sodium alginate, Gelatin and calcium chloride were purchased from Himedia Laboratories, India. Milli-Q water was used for all experiments. All other reagents used were of analytical grade.

Methods.

Formulation and characterization of nanoemulsion using high-energy method Neem oil nanoemulsion of ratio 1:3 was prepared using high energy method such as microfludization (110-P, Microfluidics, Newton, USA) (Anjali et al 2011). Coarse emulsion was formed by proper mixing of neem oil (6%), surfactant (18%) and Milli-Q water (76%) using ultra tauraxx homogenizer (IKA T25 Ultra Tauraxx, Germany) at 10,000 rpm. Further the prepared nanoemulsion was subjected to microfluidizer at 20,000 psi for 25th cycles, which result in a transclucent emulsion.After the preparation nanoemulsion was store at 4°C for the further analysis [24-29].

Dynamic Light Scattering.

Droplet size of formulated neem seed oil nanoemulsion was measured using Dynamic Light Scattering technique (Nano Particle Analyzer, SZ100, Horiba, Japan). The mean hydrodynamic droplet size measurements were carried out in triplicates.

Zeta Potential.

The zeta potential of the neem seed oil nanoemulsion was measured using Nano Particle Analyser (SZ100, Horiba, Japan). The zeta potential measurements were also carried out in triplicates.

Thermodynamic stability.

Formulated neem oil nanoemulsion were subjected to preliminary stability studies such as Centrifugation, Freeze- thaw stress cycle and Heating –cooling cycle, which results in a stable,

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formulation [30,31]. The thermodynamic stability study was performed using the following methodology: 1. Centrifugation: formulated neem oil nanoemulsion was subjected to centrifugation at 6000rpm for 30 min and observed for phase separation.

2. Heating – Cooling cycle: formulated nanoemulsions were subjected to two different temperatures (4 °C & 45 °C) for a duration of 48h. Formulations were exposed to six cycles and were examined for their stability.

3. Freeze – thaw cycle: the formulations were subjected to freeze- thaw cycle between -20°C and +25°C. Formulations were exposed to each temperature not less than 48 hrs.

In vitro Analysis.

Bacterial culture.

The bacterial culture, Vibrio alginolyticus (4182), was procured from Microbial Type Culture Collection and Gene Bank (MTCC). The biochemical scheme provided by Bergey’s Manual of Systematic Bacteriology (Vol 2, Second Edition) was used for the confirmation of the procured bacterial culture [32].

Well diffusion method.

The antibacterial activity of the formulated neem seed oil nanoemulsion was checked using the well diffusion assay. Bacterial culture (Vibrio alginolyticus) were inoculated into the nutrient broth and then optical density was adjusted to 10 7 -10 8 CFU/ml using phosphate buffered saline (PBS). The Bacterial culture (50 μL) was swabbed on the nutrient agar plates using a sterile cotton swab. Wells were made using sterile cork borer. 50μl of neem oil nanoemulsion formulated (ratio 1:3), Tween 80, Neem oil and Ciprofloxacin (positive control) were added to each well respectively. The plates were incubated for 24 – 48 hrs at 37 °C [34, 35].

Micro-broth dilution assay.

Micro-broth dilution assay was used to evaluate the antibacterial activity of formulated neem oil nanoemulsion against vibrio alginolyticus. Neem oil nanoemulsion, Tween 80 and Neem oil were serially diluted with sterile NB in a 96-well plate. Further, the serially diluted components were inoculated with 50 μl of bacterial culture with 1x108 CFU/ml. The Plates were incubated for 24- 48hrs at 37°C. MIC was determined by checking the highest dilution showing no bacterial growth. Sodium hypochlorite (0.1%) was used as the positive control and sterile deionized water instead of nanoemulsion was considered as a negative control [36, 37].

Encapsulation of formulated neem oil nanoemulsion using biopolymers.

Preparation of sodium alginate beads.

Sodium alginate beads were prepared by mixing different concentration of sodium alginate (3,4 and 5%) to neem oil nanoemulsion in different ratios (1:1 and 1:2) using magnetic stirrer. After mixing thoroughly, polymeric solution containing neem oil nanoemulsion was added dropwise into 3 % CaCl2 solution using peristaltic pump. Encapsulated bead formed was kept at constant stirring for 30 mins. Further, in order to remove excess calcium, the beads were washed using distilled water and then dried in an oven for maintaining temperature (60°C). Similarly, bead without nanoemulsion were also prepared as control[37,38].

Preparation of sodium alginate-gelatin beads.

Beads were prepared by adding the different concentration of sodium alginate (3,4 and 5%), and gelatin (2%) to neem oil nanoemulsion in different ratios (1:1 and 1:2) using magnetic stirrer.

Polymeric solution containing nanoemulsion was added dropwise into 3 % CaCl2 solution using peristaltic pump. Encapsulated bead formed was kept at constant stirring for 30 mins. Further, in order to remove excess calcium, the beads were washed using distilled water and then dried in an MMSE Journal. Open Access www.mmse.xyz

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oven for maintaining temperature (60°C). Similarly, bead without nanoemulsion were also prepared as control.

Drying Rate Study.

This study was carried out by selecting few beads after preparation and initial mass was noticed. Mass of beads were checked at fixed intervals of time and it was repeated until the constant mass was achieved. Bead mass was measured using mettler single pan balance. Experiments were done in triplicate [37, 39].

Swelling study.

This study helps to understand the percentage of water uptake by formulated beads. Selected beads were incubated in beaker which contains distilled water. Mass of the selected beads were recorded at fixed time intervals. All the mass was measured using mettler single pan balance and experiments were done in triplicate [37].

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Scanning electron microscopy (SEM).

Morphology of prepared beads was analysed using Scanning electron microscopy. Selected bead samples were kept on brass holder and further sputtered using gold. Observation has been made using a high-resolution scanning electron microscope (FEI Quanta FEG 200, USA) operated at 5 kV [37, 40].

HPLC. The available concentration of the active ingredient (azadirachtin) present in the neem nanoemulsion was analysed by Reverse Phase-High Pressure Liquid Chromatography (HPLC), LA-Chrom Elite, Hitachi, Japan. An aliquot of nanoemulsion was dissolved in acetonitrile, and 10 ¾L of the analyte was injected into HPLC through auto sampler (L-2200, Hitachi, Japan). The isocratic separation of azadirachtin takes place in the column (Waters Sun Fire C18 -5 lm 9 150 mm 9 4.6 mm), maintained at a constant temperature of 37 ºC. The mobile phase consisting of 65% (v/v) of water, and 35 % (v/v) of acetonitrile was programmed at a flow rate of 1 mL/min. The detection of azadirachtin was carried out at 215 nm (L-2420, UV–Vis Detector, Hitachi, Japan). The analytical grade azadirachtin obtained from Sigma-Aldrich Pvt. Ltd., India was used for the analytical standard preparation. Calibration curve of the analytical standard was used for determining the available azadirachtin concentration in the nanoemulsion. Concentration of azadiractin in sodium alginate and gelatin encapsulated bead were analysed [41, 42].

Result and Discussion Formulation was carried out using the method described by Anjali et al., 2011. Neem oil nanoemulsion consist of neem oil (oil phase), tween 20 and Milli-Q water (aqueous phase), which were mixed thoroughly using T25 Digital Ultra Tauraxx, IKA Korea for 5 min. This will result in coarse emulsion which was further subjected to microfludizer (Microfluidics, 110-P, Newton, USA) to obtain a transcluecent nanoemulsion system. was maintained inside the chamber using a chiller.

The optimisation of the pressure and cycle was conducted before the nanoemulsion formulation.

There was a significant reduction in the average droplet size as the homogenization pressure and no. of cycles increases [43]. The optimized pressure and cycle on neem oil nanoemulsion fromulation was found to 20,000 psi at 25th cycle, which results in droplet size of 28Âą 1.53nm (fig1). Prepared nanoemulsion was stored at 4 ÂşC for further stability studies and to check the antimicrobial efficacy [44-46].

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a)

b)

Fig. 1. Hydrodynamic size distribution of neem oil nanoemulsion (ratio 1:3) using high pressure homogenizer at an operating pressure of 20000 psi (25th pass) was found to be 28±1.53 nm (A) and zeta potential was found to be-19.7±1.22 mV. The different ratios of neem oil nanoemulsion formulated at 20,000 psi (25th cycle) were subjected to thermodynamic stability studies such as centrifugation, heating - cooling cycle and freeze – thaw cycle. After centrifugation, phase separation and increase in turbidity was observed in 1:1 & 1:2 ratio of neem oil nanoemulsions formulated using Tw 20 [47]. After all these preliminary stability studies, the other ratios such as 1:3, 1:4 & 1:5 showed a good stability. When the surfactant concentration is taking into concern, ratios 1:4 & 1:5 were ignored. This high surfactant concentration present in neem oil nanoemulsion may also screen the therapeutic activity of neem oil. Among all the three ratios of both formulation, 1:3 ratio was chosen and was further studies. The droplet size of neem oil nanoemulsion was found to be 28± 1.53 and also the Zeta potential was found to be -19.7±1.22 mV. Antibacterial activities of Neem oil, NONE and Tween 80 were analysed using well diffusion method and Micro broth dilution method against aquaculture pathogen Vibrio alginolyticus. From the data it is inferred that the zone of inhibition was 14.6 ± 1.3 mm for neem oil nanoemulsion as compared to Tween 80 (9± .5 mm), and Neem oil (10.9± .99 mm). As the droplet size decreased which lead to the easy penetration and membrane disintegrate leading to cell mortality. Compared to Tween 80, neem oil itself shows a good zone of inhibition, which indicates that antibacterial activity of formulated emulsion is due to the presence of bioactive components in the neem oil. The MIC value of formulated neem oil nanoemulsion was found to 0.93 µg/ml. Lower concentration of neem oil nanoemulsion itself inhibiting the antibacterial activity of Vibrio alginolyticus.

Azadiractin is one the important bioactive compound present in neem oil nanoemulsion and it determined using HPLC analysis. The stable neem oil nanoemulsion was encapsulted using suitable biopolymers such as sodium alginate (Na alg) and the blending of sodium alginate and gelatin (Naga). Generally, alginate beads were formulated when a solution of sodium alginate was added to a solution of the calcium salt. Gel formation was occured due to the chemical reaction and the calcium replaces the sodium from the alginate. Different concentration of sodium alginate (3, 4 and 5%) was mixed thoroughly with neem oil nanoemulsion at different ratios such as 1:1 and 1:2. Proper bead was formed at 3% alginate and the both ratios such as 1:1 and 1:2. Increase in the concentration of sodium alginate leads to the formation of harden beads (Table 1) [37]. Similarly, if we are increasing the nanoemulsion ratio, improper beads were formed. Concentration of azadiractin in sodium alginate encapsulated bead was determined using HPLC analysis. Concentration of azadiractin present in 3% alginate encapsulate bead at 1:2 ratio was found to be 5.46 ± 1.23 mg/L whereas for 1:1 ratio it was found to be 2.84 ± 1.9 mg/L. Similarly, the sodium alginate bead formed at 4%alginate contains an concentration of 1.84± 1.1 mg/L. Drying and swelling studies revealed that the bead formed using MMSE Journal. Open Access www.mmse.xyz

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3% alginate at 1:2 ratio exhibit good swelling and drying property compared to other two sodium alginate beads (fig. 2, 3). Maximum water uptake was shown after 24 hours of interaction whereas for the other two ratios such as showed maximum water uptake after 2hours of exposure. Release profile of azadiractin was analysed using the three water matrices such as Aquaculture farm water, Lake water and Seawater. Alginate bead formed using 3% at 1:1 ratio was used for checking the release profile in different water matrices. Controlled release was observed in the case of sodium alginate bead prepared using 3% alginate at 1:2 ratio. Bead formed are spherical in nature with a diameter of 1.8 mm, which was confirmed using SEM analysis (fig. 4). Encapsulation of nanoemulsion was achieved by mixing Sodium alginate – gelatin with neem oil nanoemulsion.

Different concentration of sodium alginate (3, 4 and 5%) and 2% of gelatin were choosen for the encpasulation study. Proper sodium alginate- gelatin encapsulated beads were formed on the ratio 1:1:1 (3% alginate- 2% gelatin). Azadiractin concentration in the encapsulated bead was measured using HPLC and was found to be 3.46mg/L. Swelling and Drying rate showed good water uptake and drying rate(fig 5, 6). Controlled release of azadiractin was observed in all the three water matrices such as aquaculture farm, Lake and Sea water. Bead diameter was analysed using SEM and found to be 1.7 mm (fig. 7) [37].

Table 1. Encapsulation of neem oil nanoemulsion using sodium alginate.

SL. no 1.

Different ratios (Na-alg:neem off) Ratio 1:1

2.

Ratio 1:2

Na alginate

Calcium chloride 3% 3% 3% 3% 3% 3%

3% 4% 5% 3% 4% 5%

Water uptake (%)

0,2

Observations Beads formed Beads formed, hard in nature Beads formed, hard in nature Beads formed, soft in nature Not in proper shape Not in proper shape 3A1

3A2

4A1

0,15 0,1 0,05 0 0

2

4 8 24 Time period (hrs)

Fig. 2. Swelling rate.

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48

72

Dry weight (mg)

Mechanics, Materials Science & Engineering, Vol. 15 2018 – ISSN 2412-5954

0,2

3A1

3A2

4A1

0,15 0,1 0,05 0 0

24 48 Time period (hrs)

72

Aza concentration (mg/L)

Fig. 2. Drying rate.

6

Farm water

seawater

Lake water

5 4 3 2 1 0 24

48

72 96 Time period ( hrs)

Fig. 3. Release profile of Azadiractin in different water matrices.

Fig. 4. Size of the sodium alginate bead 1.8mm.

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Table 2. Emulsion ratios.

Ratios (Na-alg:gelatin:neem off)

Na alginate

Gelatin

Calcium chloride

Observations

25%

29%

39%

Beads formed, soft in nature

39%

29%

39%

Beads formed, hard in nature

49%

29%

39%

Beads formed, hard in nature

29% 39%

29% 29%

39% 39%

Not in proper shape Not in proper shape

49%

39%

39%

Not in proper shape

29% 39%

39% 39%

39% 39%

39%

39%

Beads formed, hard in nature

29%

39%

39%

Not in proper shape

39%

39%

39%

Not in proper shape

49%

39%

39%

Not in proper shape

Ratio 1:1:1

Ratio 1:1:2

Ratio 1:2:1

49%

Ratio 1:2:2

Beads formed, soft in nature Beads formed, hard in nature

Drying weight (mg)

0,2 0,15 0,1 0,05 0 0

24 48 Time period (hours) 2A1 3A1

Fig. 5. Drying rate.

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72

Water uptake (%)

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0,2 0,18 0,16 0,14 0,12 0,1 0,08 0,06 0,04 0,02 0

2A1

0

2

4 8 24 Time period (hours )

3A1

48

72

Fig. 6. Swelling study.

Farm water

seawater

Lake water

Aza concentration (mg/L)

3,5 3 2,5 2 1,5 1 0,5 0 24

48 72 Time period (hours)

96

Fig. 7. Release profile of AZA from neem oil nanoemulsion beads in different water matrices.

Fig. 8. Bead size was found to be 1.7 mm.

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Summary. Neem oil nanoemulsion was formulated using high pressure homogenizer at 20000psi (25th cycle). The formulated neem oil nanoemulsion exhibit a good physicochemical stability and antibacterial activity against vibrio alginolyticus. Encapsulation of stable neem oil nanoemulsion (1:3 ratio) was achieved using sodium alginate (3%) and sodium alginate (3%) – gelatine (3%) composite via cross linking with calcium carbonate solution which resulted in the formation of hydrogel beads.

The SEM results showed encapsulated beads were nearly spherical in nature. Among all the beads, Na-agl: Gelatine: neem oil nanoemulsion (1:1:1) control release found, showed better swelling rate, drying rate at a duration of 72 hr. Encapsulation of nanoemulsion using these polymers helps to avoid the reduction of active component present in it. Thus this strategy helps in control release of the active ingredient which can be applied in various fields.

Acknowledgement.

We extend our sincere thanks to DST-SERB (SB/SO/AS-040/2013) for funding aid and VIT University for providing lab amenities to carry out the research work.

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Orange Oil Nanoemulsion- a Biocompatibility Profile of Lymphocytes 1

Saranya Vinayagam1, Usha Tamilarasan1, Amitava Mukherjee1, Chandrasekaran Natarajan1,a 1 – Centre for Nanobiotechnology, VIT University, Vellore, India a – nchandrasekaran@vit.ac.in, nchandra40@hotmail.com DOI 10.2412/mmse.62.34.395 provided by Seo4U.link

Keywords: orange oil nanoemulsion, microfluidezer, lymphocytes, toxicity.

ABSTRACT. Nanotechnology is the booming field for the recent advancements in the medical and biological fields.

Nanoemulsion based delivery system is one of the growing interest in field of nanotechnology. It has also been widely used for the several the field for the medical and industrial applications. In every field, there is constant interaction of nanoemulsion with human system and it is necessary to evaluate the toxicity profile of such nanoemulsion in the human system. Orange oil nanoemulsion was interacted with lymphocytes with different concentration. The nanoemulsion was formulated with tween 80 and milli q water. The size and shape of the nanoemulsion droplet were optimized with DLS and SEM. The cytotoxicity studies were carried out using MTT assay and the total protein was also estimated. Our findings showed that the orange oil nanoemulsion has no toxic or less toxic at the higher concentration to the normal lymphocytes.

Introduction. Nanoemulsions has wide range of biological properties for various biological and medical treatments. The emerging use of such nanoemulsions in the field of cancerous treatment is gaining more attention for the highly target specific cancer treatments. The formulation of nanoemulsion using essential with medicinal property for the targeted drug delivery in cancerous treatment. Nanoemulsions are oil in water soluble colloidal suspensions which are highly stable in nature, generally the nanoemulsions projects a very small size in the suspension which exhibited in the size range of 10-100nm with a nonionic surfactant [1]. The Orange oil is well known essential oil for its medicinal and therapeutic value and our present study reported with formulation with microfludizatin technique and its toxicity towards human lymphocytes. The oil also reported to have a traditional values against various disorders like gastric problems, flatulence, antidepressant, mild sedative and chronic bronchitis also reported to have antifungal activities against a foodborne pathogen [2, 3].

Orange (Citrus sinensis) oil contains essential bioactive components responsible for various activities and the D-limonene considred to be a major compound [4]. The use of orange oil and preparation of nanoemulsion through microfludization technique is a booming field in science, especially in the field of biomedical research for the anticancer drug development. But, the nano formulation and applied research are the emerging techniques. With the very few available literature, the nanoemulsion was formulated in microfludizer with different pass. The reported monoterpenes (D-limonene) are useful in various chemotherapeutic treatments like prostatic, breast, mammary and pancreatic tumours. The nano formulated orange oil with the active monoterpene derivatives exhibited potent anticancer activity. Therefore, formulation of nanoemulsion with the medicinally important orange oil could be the effective step ahead in the field of cancer treatment and drug delivery system. Hence, it is essential to assess the toxicity of O-NE to healthy human lymphocytes. The in vitro toxicity of nanoemulsion is key to evaluate the biocombatility of the drug delivery. The present study was also focusing on the genotoxicity assessment and cytotoxic behaviors of the orange oil nanoemulsion (O-NE) in the human lymphocytes © 2017 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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Materials and Methods. All the chemicals were purchased from Sigma and Hi-media.

Nanoemulsion Formulation. Nanoemulsion was formulated in microfluidizer and it was operated at homogenization pressure of 15,000 psi (1034 bar). Orange oil and tween 80(nonionic surfactant) in different ratio like 1:1, 1:2 and 1:3 v/v were used for the formulation. The bluish apperence of the milky white. [5].

Characterization of O-NE. The particles size and disturbution of the nanoemulsion droplet were analyzed by dynamic light scattering (particle size analyzer, Brookhaven Instrument Corp, USA).

Stability of O-NE. The nanoemulsion stability were analyzed by assessing the size and turbidity for 4 weeks. The turbidity can be quantified by measuring the emulsion at 600nm in UV-Vis spectroscopy.

Blood sample collection. Heparinized tube were collected with the healthy individual blood at age range 25 – 30 and the blood was processed immediately. Ethical clearance has been obtained from institutional ethical committee (Ref.No.VIT / IECH / 014 / Jan24.2015).

Lymphocytes isolation. The collected samples were processed for the lymphocytes isolation according to the method [6]. Briefly, plasma of the sample were isolated by centrifuged at 1500 rpm.

Further, histopaque were used to isolate the lymphocytes. Equal ratio of histopaque and separated plasma was added and centrifuge at 2000 rpm for 30 mins. The middle layer were collected and washed for 2 to 3 times with 1x PBS and pellet was resuspend in RPMI medium. The lymphocytes were counted in Haemocytometer and approximately 1X105 cells seeded in 96 well plate.

Cytotoxicity assay. Cytotoxicity of the nanoemusion was evaluated by MTT assay according to the protocol [7]. Different concentration of orange oil nanoemulsion was added to the 96 well plate seeded with the 1x105 lymphocytes cells per well used to assess the lethal concentration. (LD50).

After 24 hours of exposure, MTT dye were added and incubate for 4 hour at 37ºC. Here the live cells converts the MTT dye in to purplish formazon and the reaction was stopped by addition of DMSO. The viability was assessed by measuring the intensity at 590nm in ELISA plate reader (Powerwave XS2, Biotek, USA).

Protein estimation. The protein content in the lymphocytes were evaluated through Bradford method. Concisely, lymphocytes sample treated with orange oil nanoemulsion were interacted with Bradford reagent and then measured at 595 nm after 5 mins of incubation. The protein concentration was calculated using standard graph plotted with known concentration of BSA [8].

Results and Discussion.

Orange oil nanoemulsion formulation. The O-NE was formulated by microfluidization technique with different pass from 1st pass to 25th pass. The O-NE was formulated with 1:1, 1:2, 1:3 ratio of orange oil and tween 20 respectively and the coarse emulsion was prepared using magnetic stirrer for 30 to 60 mins. Further, the coarse emulsion was injected in to high pressure homogenizer and the sample was continuously subjected to different passes. Fig. 1 represent with visual image of orange nanoemulsion before and after homogenisation. The visual appearance of the formulated nanoemulsion showed the emulsion before sonication was found to be like milky and turbid in nature.

Subsequently, the emulsion after homogenization found to be transparent bluish in colour. Since, the clear and transparent emulsion was formulated with 1:2 ratio, the formulation was optimised with the same.

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Fig. 1. Visual observation of formulated orange oil nanoemulsion using microfludizer (A) Before homogenization (B) After homogenization.

Characterization. The optimized formulation was further characterized with DLS for the determination of size and UV-VIS spectroscopy at 600nm to estimate the turbidity. The orange oil and tween 20 at 1:2 ratio respectively formulated with the stable droplet size of 18 nm & polydispersity index of 0.364 which is shown in the (Fig. 2A). The size of the nanoemulsion was also plotted against different ratio 1:1, 1:2 and 1:3 after homogenization (Fig. 2B). The formulation procedure and droplet size distribution have been optimized and stabilized according to the report which exhibited 16nm of droplet size with different combination of surfactant [3]. The results obtained in our study corroborated with the same formulation of orange oil nanoemulsion and nonionic surfactant ratio in the suspension found to be highly stable. The turbidity of the nanoemulsion was analysed through UV spectroscopy reading at 600 nm which indicated the transparency of the emulsion. Fig. 2 C represent with OD value of orange oil nanoemulsion before and after microfluidization. Concluding with the characterization result, the nanoemulsion after homogenisation found to be more clear and stable with the smaller size. However, the size of the emulsion was reduced to each passes. The size was further declined from10th pass to 25th pass, hence the 10th was optimized for the further toxicity process.

A

B

C

Fig. 2. Characterization of formulated orange oil nanoemulsion (A) DLS graph of optimized emulsion. (B) graph ploted against size of the nanoemulsion repective with diiferent ratio. (C)UV VIS spectroscopy to determined the turbidity at 600nm.

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Haemolysis. It is essential to assess the biocompatibility of the orange oil nanoemulsion before evaluating the toxicity of human lymphocytes specifically in case of human related products. Any form of nanoemulsion administration needs to travel through blood stream in order to reach the target site. Henceforth, the determining toxic behavior of RBC and the lymphocytes of healthy humans is requirement for the evaluation the toxic behavior of orange oil nanoemulsion. The percentage of RBC get lysed can be determined through hemolysis assay. (Fig. 3) explained with the toxic behavior of emulsion to the RBC, where the percentage of RBC lysis seems to be equal to the control. There is no signification changes were observed hence, the O-NE could be safer to handling and for further utilization. Since the RBC has no nucleus, all other assays were carried out with lymphocytes.

Fig. 3. Heamolysis assay of orange oil nanoemulsion (1:2 ratio) with different concentration.

Cytotoxicity of Orange oil Nanoemulsion. Cytotoxic activity of orange oil nanoemulsion was evaluated in healthy human lymphocytes with a varying concentrations from 6, 12, 24, 600, & 6000 ppm. MTT assay was performed to assess the cell viability of orange oil nanoemulsion treated cells with 24 hours of exposure.

A

B

Fig. 4. Cytotoxic behaviour of orange oil nanoemulsion after homogenization with different concentration (a) protein estimation, (b) MTT assay.

The results revealed that the percentage of viable lymphocytes upon the interaction, which exhibit 50% viable lymphocytes at the higher concentration of orange oil nanoemulsion at 6000 mg/l (Fig. 4, a). Lymphocytes has the major cell in human body responsible role in immune system [9], hence MMSE Journal. Open Access www.mmse.xyz

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orange oil nanoemulsion interaction would be the essential step for the toxicity assessment. Moreover, there are no major significant differences found in reducing the cell viability of lymphocytes. Our results correlate with the previous report, which reported that the Citrus sinensi has no cytotoxicity effect to the healthy human epithelial cells [10]. The dose depended toxicity are due to the easy penetration of smaller size nanoemulsion than the human cell [11]. Toxicity can be promoted through the interaction of nanoemulsion to the cells which colud damage the function of internal organelles and the molecules. Thus, further induce the apoptosis via mitochondrial pathaway (57). The toxicity was further analysed by identifing the protein production. To understand the protein degradation upon nanoemulsion interatcion, the protein concetration from whole lymphocytes were estimated. Fig. 4B explained with the protein concentration with different concentration of orange oil nanoemulsion.

Summary. As a concluding remarks the O-NE has formulated with microfludizer with diverse concentration at different passes. The biocompatibility of the nanoemulsion was analyzed against human blood cells and the results are neither cytotoxicity nor genotoxicity in lymphocytes. The toxicity towards blood cells also shows no significant damages. Our study proves that the Orange oil emulsion could be used for the drug delivery and the treatment of cancer treatment without any inference to healthy blood cells.

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[11] Mahmoudi M, Simchi A, Imani M, Milani AS, Stroeve P (2009), An in vitro study of bare and poly(ethylene glycol)-co-fumarate-coated superparamagnetic iron oxide nanoparticles: a new toxicity identification procedure, Nanotechnology, 20(22), 225-104, DOI: 10.1088/0957-4484/20/22/225104.

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Development of Lead Free Piezoelectric Material for Sonar Applications 1

Dhananjay Kumar1, Dibyasmita Priyadarsini1, S.K.S. Parashar1,a, Kajal Parashar1, Rahna K. Shamsudeen2, T. Mukundan2 1 – School of Applied Science, Nanosensor Lab, KIIT University, Bhubaneswar, Odisha, India 2 – Naval Physical and Oceanographic Laboratory (NPOL), Thrikkakara, Kochi, India a – sksparashar@yahoo.com DOI 10.2412/mmse.2.99.702 provided by Seo4U.link

Keywords: BZT-BCT, ferroelectric, ball milling.

ABSTRACT. In this study lead free 50BZT-50BCT having stoichiometry formula 0.5 Ba(Zr 0.2Ti0.8)O30.5(Ba0.7Ca0.3)TiO3 nano piezoelectric ceramic has been synthesized by high energy ball milling. The synthesized powders were calcined at 1100 oC. The 50BZT-50BCT ceramics were sintered from 1300oC to 1400oC for 2h. It resulted in homogeneous and highly dense microstructure with 96-98% of the theoretical density. Sintering temperature had a strong influence on the structural, dielectric, piezoelectric and ferroelectric properties of BZT-BCT. BZT-BCT simultaneously exhibiting excellent ferroelectric properties that may have significant technological promise in novel multifunctional devices.

Introduction. Ferrroelectric material are gaining interest in the field of research in material science.

It is the property of some specific material which have spontaneous polarization which can be reversed when electric field is applied [1]. The main attraction towards this material is due to its unusually high and unusually temperature dependent values of the dielectric constant, the piezoelectric effect, the pyroelectric effect, and electro-optical effects, including optical frequency doubling [2]. It’s applications in various fields like high dielectric constant capacitors, piezoelectric SONAR and ultrasonic transducers, radio and communication filters, medical diagnostic transducers, stereo tweeters, buzzers, gas igniters, ultrasonic motors, thin film capacitors, thin film ferroelectric memories etc. [3]. Lead based ferroelectric ceramics have been at the forefront of ceramic industry since decades due to their excellent dielectric, piezoelectric properties and electrochemical coupling coefficients. Biological observations have revealed that it lead remains in the environment for a long time then there is a chance for it to get accumulated in the human body and cause damage to brain and nervous system [4, 5, 6, 7]. So it is very essential to make a lead free material so that environment damage can be reduced. Lead free ceramics is only a fraction of the Pb-based ferroelectric ceramics.

BZT-BCT is the lead free material. In recent time many researchers have higher attention on lead free ceramic materials to replace highly toxic lead containing material and its wide applications in the fields of energy harvesting devices, sensors, communication and healthcare industries. Barium titanate is one of the most widely studied lead free ceramic, but it has a long standing issue of much lower piezoelectric coefficient and low Curie temperature. However, recent studies have reported improved piezoelectric coefficient (600 pCN-1) with Curie temperature (93 °C) for (BaZr0.2Ti0.8O3) – x (Ba0.7Ca0.3TiO3) abbreviated as BZT- x BCT with x =0.5 which is half way to high end of PZT [8].

Various reviews and literature state a composition of (xBa(Zr0.2Ti0.8O3)-1-x(Ba0.7Ca0.3TiO3)) has lived up to the expectations and has shown appreciable properties as a piezoelectric material with reported d33= 620 pC/N with kp=0.56. Barium titanate being a material of high permittivity and easy © 2018 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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manufacturing process has been chosen. This type of substitutions reduces Tc and broadens the εr~t curve [9]. As the Zr4+ content increases, the phase transition temperature of orthorhombic to tetragonal transition increases, while the tetragonal to cubic phase transition temperature decreases.

As a result, for certain Zr content (Zr/Ti>0.1) the three relative permittivity peaks merge into a single maximum broad peak [10]. Liu et al. reported that the composition 0.5Ba(Zr0.2Ti0.8O3)0.5(Ba0.7Ca0.3TiO3) lies close to the tricritical point of rhombohedral, tetragonal and cubic phases.

They had investigated the composition-piezoelectric constant relationship. It was found that the above mentioned composition showed piezoelectric constant value (d33~620 pC/N) very much comparable to the commercially available PZTs. They showed that as this composition was very close to morphotropic phase boundary (MPB), it showed a large d33 value.

Experimental procedure. Lead free 50BZT-50BCT was prepared by high energy ball milling (HEBM) technique. The precursor materials BaCO3, CaCO3, ZrO2 and TiO2 of (99% purity) were taken in calculated amounts in a ball to powder ratio 20:1 and grinded using high energy ball milling machine (Retsch PM400) for 10h in toluene. As-synthesised powers were calcined at 1100 ⁰ C for 2 hrs to realize complete phase formation. The calcined aglomerrate powder were ground manually in a mortar pestle to form fine powder. The milled calcined powders were mixed with 1 wt% polyvinyl alcohol (PVA), which is known to increased the strength of the green pellets. The powder and binder mixture was ground for 1 hour and compacted into pellets of 9.10 mm diameter and 1.45 mm thickness at an optimized pressure 400 MPa using uniaxial hydraulic press. Initially the green pellets were heated at 500⁰ C for 2hrs at a slow heating rate of 3⁰ C/ min for binder removal. After excluding PVA binder, the pellets were subjected to sintering in a fast firing furnace. In the present study sintering of green pellets was carried out at 1300⁰ c to 1400⁰ C for sintering time of 2hrs at heating rate 5⁰ C/min.

The sample were cooled down to room temperature at an average cooling rate of 5⁰ C/min. The relative densities of the sintered pellets were determined using Archimedes method. The X-ray diffraction (XRD) measurements were carried out by using Cu-Kα radiation. For the electrical measurements, the sintered pellets were coated with silver paste and fired at 500 °C for 15 mins at the heating rate 5⁰ c/min. The variations in dielectric constants were observed by LCR meter (HIOKI-50 LCR HI-Tester).

Results and discussion. XRD Analysis. The X-ray diffraction patterns of BZT-xBCT with x = 0.5 powders is shown in figure 1, which are prepared via high energy balling technique with different milling hours and a single phase crystalline structure was achieved at temperature of 1100 °C / 2 h.

The XRD patterns of as-synthesized powders are indexed as tetragonal structure with a space group of P 4 mm, which are matched with pure BaTiO3 JCPDS No: 89-1428, a = 4.006 Å, c = 4.017 Å respectively.

Fig. 1. XRD pattern of the calcined 50/50 BZT-BCT sample.

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Density Measurements. The bulk density of the pellets were measured using Archimedes principle.

The pellet was sintered at different temperature and the density of the pellet was found to be approximately 5.6 gm/cc at 1300 °C whereas the reported standard density of BZT-BCT is 5.78 gm/cc. Above 1300 °C the density was gradually decreases as shown in the figure below.

Fig. 2. Sintering temperature versus Density of 50BZT-50BCT. The plot of 50BZT-50BCT in the figure indicates the property of temperature dependence material.

Dielectric Analysis

Fig. 3. Dielectric constant verses temperature.

The graph of temperature vs dielectric constant is given in fig. 3 the graph is potted between the frequency from 1KHz to 100 kHz. The graph is showing no variation with respect to frequency and MMSE Journal. Open Access www.mmse.xyz

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it is temperature dependent in nature. Initially the graph gave an increasing trend from temperature 30 °C to 130 °C, after 130 °C the graph gave a decreasing trend to 300 °C. Sintering temperature has also effected the graph trend leading to more densification of material. The dielectric constant graph shows its peak at 4000 at temperature 130 °C. The material gave the higher value of dielectric permittivity in the initial rise in temperature, which symbolizes the storing capacity of electricity in the lower temperature. The boarding of peak was similar throughout frequency and was also non relaxer material.

Summary. The lead free BZT-BCT was synthesizes successfully using high energy ball milling. It was observed from X-ray tetragonal structure was obtained. Maximum density 5.6 g/cc was obtained

by Archimedes principal analysis. From dielectric analysis we observed that non relaxer material and suitable for sensor application. The phase transition was found to be at 130 0C. Acknowledgment. The authors would like to acknowledge, DRDO, NRB Project No. DNRD/05/4003/NRB/277 for providing financial support.

References [1] Werner Kanzig (1957), Ferroelectrics and Antiferroelectrics (Solid state reprints), Academic Press.

[2] Kittel Charles (2007), Introduction to Solid State Physics Seventh Edition, John Wiley& Sons, 13, 393-394.

[3] A. Safari, R.K.Panda and V.F. Janas (1996), Ferroelectricity: Materials, Characteristics & Applications, Key Engineering Materials, 122-124 ,35-70, DOI: 10.4028/www.scientific.net/KEM.122124.35.

[4] (2010), Active materials: Piezoelectrics clean up, NPG Asia Materials, 2, DOI: 10.1038/asiamat.2010.47.

[5] Wenfeng Liu, Xiaobing Ren (2009), Large Piezoelectric Effect in Pb-Free Ceramics, Phys Rev Lett., 103(25), 257602, DOI: 10.1103/PhysRevLett.103.257602.

[6] Dezhen Xue, Yumei Zhou, Huixin Bao, Chao Zhou, Jinghui Gao, Xiaobing Ren (2011), Elastic, piezoelectric, and dielectric properties of Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 Pb-free ceramic at the morphotropic phase boundary; Journal of Applied Physics, 109(5), 054110, DOI: 10.1063/1.3549173.

[7] Wei Li, Zhijun Xu, Ruiqing Chu, Peng Fu (2011), High piezoelectric d33 coefficient of leadfree (Ba0.93Ca0.07)(Ti0.95Zr0.05)O3 ceramics sintered at optimal temperature, Materials Science and Engineering B, 176(1), 65-67, DOI: 10.1016/j.mseb.2010.09.003.

[8] Wenfeng Liu, Xiaobing Ren (2009), Large Piezoelectric effect in Pb-free ceramics, Phy. Rev. Lett., 103(25), 257602, DOI: 10.1103/PhysRevLett.103.257602.

[9] DA Berlincourt, F. Kulesar (1952), Electromechanical Properties of BaTiO3 Compositions Showing Substantial Shifts in Phase Transition Points, J. Acoust. Soc. Am., 24(6), 709, DOI: 10.1121/1.1906961.

[10] Indrani Coondoo, Neeraj Panwar, Harvey Amorín, Miguel Alguero, A. L. Kholkin (2013), Synthesis and characterization of lead-free 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 ceramic, J Appl.

Phys., 113(21), 214107, DOI: 10.1063/1.4808338.

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Growth and Characterizations of ZSM-5 Zeolite Added TGS Crystals 1

A. Priyadharshini1, S. Kalainathan1,a 1 – Centre for Crystal Growth, VIT University, Vellore, India a – kalainathan@yahoo.com DOI 10.2412/mmse.2.99.702 provided by Seo4U.link

Keywords: triglycine sulphate, ZSM-5 zeolite, morphology analysis, FTIR, optical transmittance.

ABSTRACT. Optically transparent single crystal of pure and in the addition of ZSM-5 zeolite added TGS crystals have been grown by the slow evaporation solution growth technique at the room temperature. The effective morphological and optical changes of the ZSM-5 zeolite additive added TGS crystals have been made in order to investigate the changes occurring due to increasing the concentration of additive on the TGS solution. The ZSM-5 zeolite has the influence to change the morphology of the TGS crystal without affecting its crystal structure. Moreover, the addition of the ZSM-5 zeolite additive improves the quality of the crystal and yields highly transparent crystals with well defined features. Single crystal XRD elucidate that there is no appreciable change in the lattice parameters on the addition of ZSM-5 zeolite on the TGS crystals. The well defined sharp peak in the powder XRD pattern reveals the good crystalline nature of the titled crystals. The presence of the functional groups of the grown crystals elucidated from the FTIR spectral analysis. The UVVis spectra showed pure and ZSM-5 added TGS crystals having the lower cut-off wavelength (λ = 238 nm) in the visible region, which shows an increased percentage of transmittance window as the result of increased additive concentrations.

Introduction. In the journey of past two decades, the nonlinear optical material made the greatest revolution in the optoelectronic and photonic field based on the frequency conversion, light modulation, optical switching, optical memory storage and optical second harmonic generation (SHG) [1,2]. In a recent year a new type of NLO materials are discovered, which combines the incredible advantage of organic and inorganic materials, are so-called semi-organic materials. The new search of the NLO materials physical, optical, electrical and mechanical properties should be modified either by adding some functional groups or dopants or additives. The Triglycine sulphate (TGS) is a familiar semi-organic NLO material having unique ferroelectric, piezoelectric and electrooptic properties, and also, it is well known a potential candidate for the fabrication of infrared pyroelectric detector [3]. The monoclinic structure for the pure TGS crystal was reported by Hoshino et al [4]. Consequently, TGS crystal signifies a typical second-order ferroelectric phase transition at the Curie point Tc = 49o C. Below the Tc, TGS possesses the polar point symmetry of group 2 of the monoclinic system, spontaneous polarization (SP) arises along the b-axis and above curie point it possesses the non-polar point group 2/m of the monoclinic system [5]. However, many researchers concludes that pure TGS crystals have the (a) tendency of depolarization by electrical, mechanical and thermal means, (b) ferroelectric domain exhibit high mobility at the room temperature, therefore it is necessary to stabilize domain and (c) low Curie temperature [6]. In order to rectify these disadvantage either variety of dopants or additives (organic, inorganic compound and amino acid) have been introduced in the TGS crystal.

Zeolites are crystalline, hydrated aluminosilicates having microporous, regular structures. The zeolite holding adsorption, catalytic and ion exchange properties of paramount importance in both the chemical industrial field and the study of new applications related to process intensification, green chemistry, hybrid materials, medicine, animal food uses, optical and electrical based applications, reaction and sensing microsystems, and nanotechnology [7]. Zeolite has an influence to make the © 2017 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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materials optically transparent [8]. Due to this reason herein the author introduced the most prominent compound of the ZSM-5 zeolite into the TGS crystal. The objective of this present work evaluates the effect of ZSM-5 zeolite changing the morphology of the grown crystal without affecting the crystalline structure of the TGS, to taken this into the account, the fact is the crystalline quality and other optical properties of the grown crystal further increasing due to the concentrations of additive.

The pure and additive added TGS crystals have been characterized by different instrumentation technique namely XRD, FT-IR, Morphology analysis, UV-Vis spectral analysis. The obtained results are discussed.

Experimental Procedure.

Synthesis and Crystal Growth. The triglycine sulphate was synthesized by taking AR (analytical reagent) grade glycine and concentration sulfuric acid in the 3:1 molar ratio according to the following reaction

3 (NH2CH2COOH) + H2SO4 ď‚Ž (NH2CH 2COOH)3.H 2SO4

(1)

The reactant was thoroughly dissolved in Millipore water and continuously stirred by magnetic stirrer until it yields the homogeneous solution. Then the resultant solution was filtered by using high-quality Whatmann filter paper and kept for the petri dish to allow the slow evaporation at the room temperature. After 3 times repeated recrystallizations, well transparent colourless TGS crystals were obtained in the period of 18 days. To obtain the ZSM-5 additive added TGS crystals, 10 ppm, 50 ppm and 100 ppm of ZSM-5 zeolite added separately to the saturated solution of TGS. The size and shape of the grown crystals changed significantly with the addition of ZSM-5 on the TGS and is shown in Fig. 1 (a-d). The grown crystals (with and without addition of ZSM-5 on the TGS) are stable in an environment without scarifying crystals transparency.

The adsorbent nature of the ZSM-5 zeolite plays a predominant role on the TGS crystal. The ZSM-5 zeolite has the influence to change the morphology of the grown crystals. It may be able to create the apparent changes when the different concentrations of zeolite added to the TGS crystals. Through the examination of these aggregate indicates that the shape and size of the grown crystals significantly changed when ZSM-5 added to the TGS solution. It should be noticed the morphology of 10 ppm ZSM-5 zeolite added TGS crystal (Fig. 1, b) expose different shape compare to pure TGS crystal (Fig.1a). Further increase in the concentrations of ZSM-5 zeolite (50 and 100 ppm), leads to give the different size of the crystals with an elongated shape which can be visualized (Fig.1c and Fig.1d).

The greater advantage of adding zeolite into TGS is to increase the quality of the crystal with an identical shape. From the observation of Fig.1(a-d), the variation in the morphology presumed that the surface diffusion has been enhanced in the ZSM-5 zeolite added TGS crystals. The high concentration of ZSM-5 (100 ppm) promotes the elongated shape of good quality crystal compare to other concentrations (The morphological analysis of all the grown crystal done at the Saif, IIT Madras). On the other hand, the morphological change attains due to increasing the concentration rate of adsorption onto the crystal surface that affects solution properties by modifying interfacial surface tension leading to changes in its anisotropic growth rate [9].

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Fig 1. The observed Morphological changes for (a) pure TGS, and addition of (b) 10 ppm (c) 50 ppm and (d) 100 ppm ZSM-5 zeolite added TGS single crystals.

Results and Discussion.

Single Crystal and Powder X-ray diffraction analysis. Single crystal X-ray diffraction studies implement the lattice parameters and the crystal system of the grown crystals. A well-qualified pure TGS and ZSM-5 zeolite added TGS crystals were subjected to this study by using Bruker Kappa APEX II single crystal X-ray diffractometer. Table 1 shows the comparison of the lattice parameters of the grown pure TGS and various concentrations of additive added TGS single crystals (10, 50 & 100 ppm ZSM-5), and these are found to be good agreement with the literature report [10, 11]. It was seen that there is only a slight variation in the lattice parameters of pure TGS and ZSM-5 additive added TGS crystals with same space group and same crystal system. It declares that the crystal structure is not changed due to the presence of additive (with different concentration) but, the influence of the ZSM-5 additive with respect to change the other properties for further investigation.

A fine powder of pure TGS and ZSM-5 zeolite added TGS crystal were subjected to the powder Xray diffraction analysis using the BRUKER X-Ray diffractometer with the CuKα radiation (λ=1.540598 Å). The recorded XRD pattern of the pure TGS and various concentrations of (10, 50 and 100 ppm) ZSM-5 added TGS crystals depict in Fig. 2 (a-d). A well sharp, prominent peak at the specific angle (2θ) confirmed the crystalline nature and phase purity of the grown crystals. For lower concentration (10 ppm), there is no significant changes in the XRD pattern, compare to pure TGS crystal. However, there is a slight shift in the peak position of the intensities of some of the prominent faces at higher concentrations (50 and 100 ppm ZSM-5).

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Fig. 2. Powder X-ray diffraction patterns observed for (a) pure TGS, and the addition of (b) 10 ppm (c) 50 ppm and (d) 100 ppm ZSM-5 zeolite added TGS single crystals.

Table 1. Comparisons of Lattice parameter value of pure TGS and ZSM-5 added TGS crystals.

Lattice parameters

Pure TGS

Crystal System

Monoclinic Monoclinic

Monoclinic

Monoclinic

Space Group

P21

P21

P21

P21

a (Å)

5.709

5.713

5.718

5.736

b (Å)

12.541

12.590

12.662

12.607

c (Å)

9.118

9.162

9.162

9.190

α (degree)

90

90

90

90

β (degree)

110.21

105.53

105.43

105.63

γ (degree)

90

90

90

90

635.47

639.58

640.57

Unit (Å3)

cell

Volume 645.01

10 ppm ZSM-5 added TGS

50 ppm ZSM-5 100 ppm ZSM-5 added TGS added TGS

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FT-IR spectrum analysis. The dynamic analysis of FTIR spectrum is used to identify the functional group present in the grown crystals. It is also accomplished to understand the chemical bonding and provides information about the molecular structure of the grown crystals. The resulting FTIR spectra for pure and different concentrations (10, 50, 10 ppm) ZSM-5 zeolite added TGS crystals shown in Fig. 3(a-d) respectively. FTIR spectra have taken for the fine powder sample of the grown crystals using KBr pellet technique with the spectra were recorded in the wavelength range 400–4000 cm-1.

The resultant FT-IR spectra show no major different in the functional group analysis.

The high-frequency band at 3143 cm-1 and 3007-3180 cm-1 for pure TGS and ZSM-5 added TGS was assign to the presence of amine group by the NH2 stretching vibration [12, 13]. The peak CH3 stretching mode of vibration was observed at 2877 cm-1 in the pure one that is shifted to 2328 cm-1 for ZSM-5 added TGS, due to increasing the concentration of the dopant. The C=C stretching and C=O Stretching vibration of carboxyl group appear as a sharp band at 1741 cm-1 and 1707 cm-1. The C–C stretch vibration assigned at 1610 cm-1. The absorption peak at 1423 and 1492 cm-1 indicates NH3+ symmetric and asymmetric stretching vibration that indicates the presence of glycine molecule in the zwitterion form. The asymmetric S=O is stretching scrutiny at 1373cm-1. The N–O stretch vibration present at 1296 cm-1. The peak observed at 1120 cm-1, and 1109 cm-1 are evident for the CN stretching vibration. The strong narrow peak at 1078 cm-1 assigned to the SO3 symmetry stretching.

The presence of C-H in plane bending is confirmed at the 1051 cm-1. The peak occurring at 1014 cm1 is associated with the SO4 vibrations due to the sulfate part of the molecule. The peak position of 975 cm-1 and 862- 896 cm-1 reveal the CH2 out of the plane deformation. The presence of C-S stretch was identified in the range at 755 cm-1. The C-S stretching peaks are attributed at 611cm-1.The transitional oscillation of NH+3 groups appears at 495- 567 cm-1. The FTIR spectra of ZSM-5 additive added TGS crystals show similar features as pure TGS spectrum. All the observations clearly confirm the presence of the functional groups in the grown crystals. Compare to the pure TGS crystal, there is a very slight shift was observed in band position of ZSM-5 added TGS crystals, this may be due to the effect of increasing the additive concentrations (10, 50 & 100 ppm) on the TGS crystals.

Fig. 3. FT-IR spectrum of (a) pure TGS, (b) 10 ppm, (c) 50 ppm and (d) 100 ppm ZSM-5 zeolite added TGS crystals.

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Optical transmittance. This auspicious optical spectral study gives the information of nature, quality, electronic band structure, optical transition and cut of the wavelength of the crystals. The optical transmittance spectrum of grown pure TGS and different concentrations (10, 50, 100 ppm) of ZSM-5 added TGS crystals in the wavelength region of 190-1100 nm as shown in (Fig 4). The pure and all ZSM-5 added TGS crystals have a same lower cut-off wavelength 238 nm along with a large transmission window in the entire visible region. The observed cut-off of wavelength (λ =238 nm) grown crystals are due to the n→ π* electron transitions. The UV range from 200 to 400 nm is essential for the realization of SHG output in this range using diode lasers [14]. Optical transmittance range and lower cut-off of the single crystal are important factors for optical applications [15] The wide optical transmission window is an encouraging optical property as seen in TGS and ZSM-5 additive added TGS crystals and is of vital importance for NLO device applications. Hence, it is concluded that the ZSM-5 additive added TGS crystals shown enhanced transmittance than that of the pure TGS crystal. The transmittances are increased due to the additive (ZSM-5) concentrations level in the TGS crystals. The pure TGS has 87% transmittance, and 88%, 90% and 92% of transmittance obtained for the 10, 50 and 100 ppm ZSM-5 added TGS crystals respectively. The good transparency with lower cut-off wavelength makes these materials might be useful for the optoelectronic and NLO device applications [16].

Fig. 4. Transmittance spectrum of pure and various concentration ((10, 50, and 100 ppm) of ZSM-5 added TGS single crystals.

Summary. Identical good quality transparent single crystal of pure TGS and various concentrations (10,50,100 ppm) of additive ZSM-5 zeolite added TGS were successfully grown by the slow evaporation solution growth technique. It has been noticed that there is significant morphological changes (size and shape of additive added TGS) occurring when increasing the concentrations level of additive on the TGS crystal. The lattice parameters and crystal system of the grown crystals were confirmed by the single crystal XRD analysis. Well sharp high-intensity peaks established the good crystalline nature of grown crystals through the powder X-ray diffraction analysis. The FT-IR spectral analysis confirmed the vibration mode of dynamic functional groups present in the grown crystals.

UV-Vis spectral studies address that pure TGS and ZSM-5 added TGS crystals possess almost same lower cutoff wavelength (λ = 238 nm) in the visible region. Even with the percentage of optical transmittance is increased as the concentration level of ZSM-5 increases in the TGS crystal, which ensure these crystals are active in the nonlinear optical device applications. All these studies reveal that ZSM-5 additive play a key role to improve the optical properties of the TGS crystal.

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References [1] Kitazawa, M., Higuchi, R., Takahashi, M., Wada, T., & Sasabe, H. (1994). Ultraviolet generation at 266 nm in a novel organic nonlinear optical crystal: l‐ pyrrolidone‐ 2‐ carboxylic acid. Applied physics letters, 64(19), 2477-2479, DOI 10.1063/1.111602.

[2] Wang, W. S., Aggarwal, M. D., Choi, J., Gebre, T., Shields, A. D., Penn, B. G., & Frazier, D. O. (1999). Solvent effects and polymorphic transformation of organic nonlinear optical crystal Lpyroglutamic acid in solution growth processes: I. Solvent effects and growth morphology. Journal of crystal growth, 198, 578-582, DOI 10.1016/S0022-0248(98)01041-0.

[3] Novotný, J., Březina, B., & Zelinka, J. (2004). Growth and characterization of TGS and DTGS single crystals doped with Pt (II), Pt (IV) and L‐ alanine. Crystal Research and Technology, 39(12), 1089-1098. DOI: 10.1002/crat.200410294.

[4] Hoshino, S., Okaya, Y., & Pepinsky, R. (1959). Crystal Structure of the Ferroelectric Phase of (Glycine) 3· H 2 S O 4. Physical Review, 115(2), 323, DOI 10.1103/PhysRev.115.323.

[5] Muralidharan, R., Mohankumar, R., Dhanasekaran, R., Tirupathi, A. K., Jayavel, R., & Ramasamy, P. (2003). Investigations on the electrical and mechanical properties of triglycine sulphate single crystals modified with some rare earth metal ions. Materials Letters, 57(21), 3291-3295, DOI 10.1016/S0167-577X(03)00050-8.

[6] Chang, J. M., Batra, A. K., & Lal, R. B. (1996). Growth and properties of urea-doped triglycine sulfate (UrTGS) crytals. Journal of crystal growth, 158(3), 284-288, DOI 10.1016/00220248(95)00448-3.

[7] Urbiztondo, M. A., Pellejero, I., Villarroya, M., Sesé, J., Pina, M. P., Dufour, I., & Santamaria, J. (2009). Zeolite-modified cantilevers for the sensing of nitrotoluene vapors. Sensors and Actuators B: Chemical, 137(2), 608-616, DOI 10.1016/j.snb.2009.01.047.

[8] Simon, U., & Franke, M. E. (2000). Electrical properties of nanoscaled host/guest compounds.

Microporous and Mesoporous Materials, 41(1), 1-36, DOI 10.1016/S1387-1811(00)00291-2.

[9] Parimaladevi, R., Sekar, C., & Krishnakumar, V. (2010). The effect of nitric acid (HNO 3) on growth, spectral, thermal and dielectric properties of triglycine sulphate (TGS) crystal.

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 75(2), 617-623, DOI 10.1016/j.saa.2009.11.027.

[10] Deepthi, P. R., & Shanthi, J. (2014). Optical, ftir and xrd analysis of pure and l-histidine doped triglycine sulphate crystals-a comparative study. International Journal, 2(12), 815-820.

[11] Parameswaria, A., Dhasa, M. K., & Beniala, A. M. F. (2014). Vibrational spectroscopic studies on amino acid doped tgs single crystals: an experimental and theoretical approach. Int. J. Sci. Eng. Res., 5, 249-252.

[12] Bharthasarathi, T., Shankar, V. S., Jayavel, R., & Murugakoothan, P. (2009). Growth and characterization of biadmixtured TGS single crystals. Journal of Crystal Growth, 311(4), 1147-1151, DOI 10.1016/j.jcrysgro.2008.10.114.

[13] Sinha, N., Goel, N., Singh, B. K., Gupta, M. K., & Kumar, B. (2012). Enhancement in ferroelectric, pyroelectric and photoluminescence properties in dye doped TGS crystals. Journal of Solid State Chemistry, 190, 180-185, DOI 10.1016/j.jssc.2012.02.030.

[14] Rao, K. V., & Smakula, A. (1965). Temperature dependence of dielectric constant of alkali and thallium halide crystals. Journal of Applied Physics, 36(12), 3953-3954, DOI 10.1063/1.1713986.

[15] Jananakumar, D., & Mani, P. (2013). Structural, thermal, mechanical, dielectric and optical properties of magnesium sulphate doped in potassium borooxalate: a new nonlinear optical material.

Int. J. ChemTech Res., 5(1), 113-120.

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[16] Sivakumar, N., Kanagathara, N., Varghese, B., Bhagavannarayana, G., Gunasekaran, S., & Anbalagan, G. (2014). Structure, crystal growth, optical and mechanical studies of poly bis (thiourea) silver (I) nitrate single crystal: A new semi organic NLO material. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 118, 603-613, DOI 10.1016/j.saa.2013.09.010.

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Laser Shock Peening on Microwave Sintered Aluminum Alloy Nanocomposites 1

S. Prabhakaran1,a, Prashantha Kumar H. G.2,c, S. Kalainathan1,b, Anthony Xavior M.2,d, Kaustav Chakraborty2 1 – Centre for Crystal Growth, VIT University, Vellore, Tamilnadu, India 2 – Metal Matrix Composite Laboratory, School of Mechanical Engineering, VIT University, Vellore, Tamilnadu, India a – spkaran.kmd@gmail.com b – kalainathan@yahoo.com c – prashanthakumar.hg@gmail.com d – manthonyxavior@vit.ac.in DOI 10.2412/mmse.21.51.721 provided by Seo4U.link

Keywords: graphene, Laser Shock Peening (LSP), nanocomposites, ultimate tensile strength.

ABSTRACT. The current work focusses on low energy laser shock peening (LSP) on graphene (0.4 wt %) – AA 2900 nano-composite fabricated through powder metallurgy (PM) technique. The added graphene serves the pinning effect and blocks the grain growth in the composite. Further, LSP has been carried out on the developed composites. As a consequence, LSP contributed the additional grain refinement effectively to the nanocomposites leading to large texture strengthening. Improvement in the hardness and tensile strength achieved with the addition of graphene and further improvement due to LSP process is achieved for the prepared nanocomposites.

Introduction. Material processing is the one of most active field of research in the improvement of material properties by combination of unusual distinct strengths leads to enhancing the properties over individual one. In achieving these demands, a certain development in process and smart combinations of materials has been followed. The conventional materials using presently are heavy, expensive and problem in manufacturing complex shaped structures, also been tried for improvement through known techniques of alloy additions, heat treatment grain refinement etc. Most of the studies on Aluminum and its alloys based on metal matrix composite pose highest strengthening efficiency with the carbon, ceramic based reinforcements and other improvers. However, Aluminum alloys also have number of positive features together with low density, resistance to corrosion, thermal conductivity etc. In addition of small content of reinforcement to the Aluminum alloys can improve the stiffness, hardness, fatigue resistance and effectively on tribological properties with appropriate quantities and it leads to achieve needed properties to enrich the efficiency and cost saving in industries manufacturing. Aluminum MMCs generally had not yet achieved extensive industrial applications. This situation attributable to extensive reaction between the matrix and the additives also high production cost. Thus development of MMCs with uniform dispersion of reinforcements, very low porosity formation, strong interfacial bonding with controlled reactions are really demand in the market. Powder metallurgy practice has gained popularity and significance because of its near net shape, effective strength, alloy flexibility and its ability to reduce the complication of multileveled engineering components. However, processing parameters in powder metallurgy poses challenges that are yet to be fully understood to develop the engineering parts.

Graphene is an allotrope of carbon atom and it is a single atomic layer of graphite organized into a hexagonal lattice. The stand-out properties is its inherent strength (For all temperatures) and found © 2018 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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to be strongest material ever discovered compare to other materials possessing distinctive wear and frictional properties also well-defined mechanical, electrical and optical properties leads to innovative applications by addition in nanoscale range becomes a promising reinforcing material in many engineering applications specifically in ceramics, polymers including metal or its alloys. Compare to all other reinforcements, Graphene possess a high strengthening efficiency and the extent of the improvement is related directly to the degree of homogeneous dispersion of the graphene in the polymer matrix and improvements are obtained at very low filler loadings in the Graphene Polymer Matrix Composites (GPCMs) and addition of graphene in ceramic composites lead to a variety of light and strong composite which suit to many real time engineering applications and found to be potential to improve the fracture toughness of Graphene Ceramic Matrix Composites (GCMCs), but research on Graphene Metal Matrix Composites (GMMCs) are in infancy stage due to its challenges in homogeneous dispersion and development of composites additionally the extensive reaction between metals interfaces during high temperature processing conditions. An unique mechanical properties of Graphene such as Elastic modulus (0.5 – 1 TPa), [1] Specific Surface area (2630m2 g−1), Tensile strength 130 GPa [3] Thermal conductivity (5.3×103 Wm-1K-1) [2] is predicted that, it can replace the existing reinforcing ceramic based like SiC, Al2O3 or other carbon allotropes like carbon nanotubes (CNTs) and graphite. CNTs also got immense applications as reinforcement for polymers, Ceramics, and Metal Matrix but dispersion of CNTs without causing agglomeration is quite challenging. The drawback of CNTs over graphene includes, at high pressure processing of carbon nanotubes leads to collapse of tubular structure of CNTs [4] as well there is a strong interfacial bonding between graphene planar sheet like 2D structure but CNTs - only point to point contact [5] and possess least tribological properties. [6] but consideration of graphite as additive to the composites leads to positive result in creating solid lubricant between metal to metal surface by reducing wear and frictional losses but its depends on nature of surface, sliding conditions and content of graphite in composite[7]. Graphene in particular research serves as both solid or colloidal lubricant between the two sliding surfaces exhibiting its superior tribological advantage with very minimal usage (0.1 to 0.3%) and found to be appreciable reduction in the wear loss and friction.[8] Graphene being used as additives to lubricant such as oils and grease in nanoscale range provides the higher load carrying capacity compare to that of oil or grease without the addition[9] and it is found to be very less, limited studies on aspect of effect of graphene content in AA alloy MMCs prepared by powder metallurgy approach and on its mechanical and tribological applications [9,10]. So this paper gives the outlay of influence Graphene content in AA2900 on tribological aspects under dry sliding conditions. For many years, work has been done to enhance the surface properties of materials in enduring the heat, wear and friction through coating or surface modification. Although various advanced materials with significant properties were developed, nevertheless when it concerns a particular surface engineering application, materials property is the factor to be considered, apart from the feasibility, cost and time consumption. Due to the rapid advancement in the surface engineering field, conventional techniques for surface treatment like carburizing and flame hardening have been replaced by techniques using advanced heat sources such as plasma, laser, ion, and electron.

Currently, high power lasers have become increasingly accepted as tool for many applications from cutting, to surface modification methods [11,12,13].

Experimental. Dispersion of graphene in AA 2900 alloy powder. Aluminum alloy powder synthesized by gas atomized commercial grade AA 2900 with particle size ranging from 30 to 35 µm shown in Fig.1a (from Ampal Inc.) was taken as a matrix material and the chemical composition of AA 2900 is given in the Table.1. Graphene (from Angstron Materials) shown in Fig.1b as reinforcement was ultra-sonicated initially to disperse in metal matrix in acetone as solvent for 1hr in an ice bath to avoid evaporation and to maintain the constant dispersion efficiency. To achieve the smart dispersion, AA 2900 powder is directly added to acetone containing graphene slurry and sonication continued further 30 min. After sonication, acetone in slurry was evaporated on hot plate with magnetic stirring (To avoid the sedimentation of nano particles) at 60ˑc for 3hrs followed by drying the powder mixtures in oven at 90ˑc for 24hrs.

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Nanocomposite preparation. Powder metallurgy technique is used to develop the composite. The AA 2900 and graphene mixture were compacted according to ASTM standard B925–08 (Standard Practices for Production and Preparation of Powder Metallurgy Test Specimens) using carbide die with chromium hot-work tool steel (40 to 48 HRC) die case by preheating the powder and compacted at 300 MPa to obtain a green billets with zinc stearate as a dry lubricant. The complete process is and obtained green compacts are shown in the Fig.2. The green compacts further polished with fine emery (1500 to 2000 grade) paper to remove all the lubricants and dirt’s and subjected to microwave sintering furnace (Delta power controls make, INDIA) at 510˚C for 30 min under argon gas atmosphere followed by furnace cooling.

Fig.1 SEM of (a) AA 2900 (b) graphene precursor.

Laser shock peening of nanocomposites. Thus fabricated nanocomposites are laser shot peened (LSP) with a Q-switched Nd: YAG laser operating at the fundamental wavelength of 1064 nm. The LSP was performed at room temperature (25 ̊ C) by using Poly vinyl chloride (PVC) tape as a thermal ablation protective coating for the current LSP process. Laser shots are delivered to the material surface with the help of a dichromatic mirror (kept at an angle of 45 ̊) followed by bi-convex lens of focal length 300 mm as shown in the Fig. 3.The specimen was mounted on computer controlled X-Y translation stage (SVP lasers, India). A short program was written to control the movement of this XY translation stage. A thin jet of tap water was used as a confinement layer (1-2 mm) and also to continuously remove the ablated material from the specimen surface so as to keep the surface clean while subjecting to LSP throughout the process. The lens was protected from the water spilling during the time of peening by an electric drier which is placed near the lens. The LSP parameters Pulse energy(Ep) – 300 mJ, Pulse density(Np) – 2500 pulse/cm2 are used for the surface modification process. The laser pulse density (Np) of the laser can be controlled by controlling the velocity of the transitional stage. The pulse density was kept constant in this experiment.

Table 1. Element composition of AA 2900.

Element

Cu

Mg

Si

Fe

Sn

Al

2900 Weight %

3.25

1.47

0.30

0.09

0.67

Remaining

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Fig. 2. Schematics of AA 2900 – graphene composite synthesis.

Fig. 3. Schematics of laser shock peening of AA 2900-graphene nanocomposite.

Results and discussions. Micro hardness data were recorded by micro-indenting on the surface and transverse cross sections respectively for the AA 2900 - graphene nanocomposite and LSPed specimens. AA 2900-graphene nanocomposites were observed to have higher hardness (HV-128) compared to monolithic alloys (HV - 82). This increase in hardness is owing to addition of Graphene, which signifies the strong interfacial bond between graphene at 0.4 wt. % concentrations and the matrix followed by dispersion strengthening mechanism irrespective of the precipitations formations.

Further, LSPed process on the AA 2900-graphene composite found to result in significant (HV=135) improvement in hardness. The hardness of the specimen as a function of depth for composite and LSPed samples shows the inhomogeneity at the surface due to thermal effect caused by laser material interaction and decreases gradually towards the subsurface of the material. This phenomenon occurs because the intensity of the shock waves is maximum at the surface layer and it decreases as it propagates further deep in to the material.

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Tensile results for the AA 2900 - graphene nanocomposites and LSPed sample are listed in Table.2 AA 2900 - graphene composite exhibited a tensile strength of 290MPa with 10.50% elongation compared to the AA 2900 alloy (228MPa) due to the addition of only 0.4 Wt.% of graphene flakes.

Thus, addition of graphene found to be huge potential and ideal reinforcement for the aluminium alloys in particularly for AA 2900. Further, such a significant improvement is due to inherent fracture strength (125 GPa) of graphene [10] which is singly dispersed and aligned in the extruded direction ie in the tensile direction. Orientation of the graphene flakes in the composite has strong influence on designed composite material. It is also well noticeable that the strength of the composite has linear relation with measured hardness values. The composite hardness found to be much higher than the base alloy which suggests the strength of the composite enhanced greatly. In the fabrication of composites, the graphene nanoplatelets were assumed to be aligned uniformly in one direction (length of the graphene is more than the thickness) related to orientation factor was accounted. Such a strengthened AA 2900-graphene nanocomposites are subjected to surface modification through LSP and found to be further improvement in the UTS (438 MPa) and reduction in the percentage elongation by 11.83%. This signifies the positive effect of LSP for the novel composites through the uniformly refined soft grain structure on the peened surface and increased in hardness. The reason behind this is, LSP produces a hardening effect on both sides of the specimen which reduces the ductility of the specimen and the percentage elongation observed comparatively low due to the induced compressive stresses after the LSP [11].

Table 2. Summary of tensile test results.

Ultimate Tensile Strength (UTS), MPa

% age elongation

AA 2900

228

16.76

AA 2900 – Graphene

290

10.50

AA 2900 – Graphene - LSPed

338

11.83

Samples

Summary. The current research work is focused on the synthesis of metal matrix composites with Graphene as reinforcement (0.4 wt. %) and AA 2900 as matrix material. The consolidation is carried out through powder metallurgy (PM) followed by compaction and microwave sintering at optimized parameters. Thus developed nano composite are surface modified through low energy laser shock peening (LSP). As a consequence, a strong AA 2900- graphene nano composite is evolved with substantial improvement in the microstructure after LSP. The improvement in hardness due to addition of graphene and after the LSP is observed. Addition of graphene is found to have positive effect and significant improvement in the Ultimate Tensile Strength (UTS). LSP contribute further improvement in UTS and reduction in percentage elongation.

References [1] Soldano, C., Mahmood, A., Dujardin, E. (2010), Production, properties and potential of graphene, Carbon, 48(8), 2127-2150, DOI: 10.1016/j.carbon.2010.01.058.

[2] Jang, B. Z., Zhamu, A. (2008), Processing of nanographene platelets (NGPs) and NGP nanocomposites: a review, Journal of Materials Science, 43(15), 5092-5101, DOI: 10.1007/s10853008-2755-2.

[3] Kumar, H. P., Xavior, M. A. (2014), Graphene reinforced metal matrix composite (GRMMC): a review, Procedia Engineering, 97, 1033-1040, DOI: 10.1016/j.proeng.2014.12.381.

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[4] Kim, D. Y., Han, Y. H., Lee, J. H., Kang, I. K., Jang, B. K., Kim, S. (2014), Characterization of multiwalled carbon nanotube-reinforced hydroxyapatite composites consolidated by spark plasma sintering, BioMed research international, 2014, DOI: 10.1155/2014/768254.

[5] Yu, M. F., Lourie, O., Dyer, M. J., Moloni, K., Kelly, T. F., Ruoff, R. S. (2000), Strength and breaking mechanism of multiwalled carbon nanotubes under tensile load, Science, 287(5453), 637640.

[6] Lahiri, D., Singh, V., Keshri, A. K., Seal, S., Agarwal, A. (2010), Carbon nanotube toughened hydroxyapatite by spark plasma sintering: microstructural evolution and multiscale tribological properties, Carbon, 48(11), 3103-3120, DOI: 10.1016/j.carbon.2010.04.047.

[7] Baradeswaran, A., Perumal, A. E. (2014), Wear and mechanical characteristics of Al 7075/graphite composites, Composites Part B: Engineering, 56, 472-476, DOI: 10.1016/j.compositesb.2013.08.073.

[8] Lin, J., Wang, L., Chen, G. (2011), Modification of graphene platelets and their tribological properties as a lubricant additive, Tribology letters, 41(1), 209-215, DOI: 10.1007/s11249-010-97025.

[9] Zhamu, A., Jang, B. Z. (2014), U.S. Patent No. 8,652,362, Washington, DC: U.S. Patent and Trademark Office.

[10] Lee, C., Wei, X., Kysar, J.W. and Hone, J., 2008, Measurement of the elastic properties and intrinsic strength of monolayer graphene, Science, 321(5887), 385-388, DOI: 10.1126/science.1157996.

[11] Prabhakaran, S., S. Kalainathan (2016), Compound technology of manufacturing and multiple laser peening on microstructure and fatigue life of dual-phase spring steel, Materials Science and Engineering: A, 674, 634-645, DOI: 10.1016/j.msea.2016.08.031.

[12] Prabhakaran, S., Aniket Kulkarni, G. Vasanth, S. Kalainathan, Pratik Shukla, Vijay K. Vasudevan (2018), Laser shock peening without coating induced residual stress distribution, wettability characteristics and enhanced pitting corrosion resistance of austenitic stainless steel, Applied Surface Science, 428, 17-30, DOI: 10.1016/j.apsusc.2017.09.138.

[13] Prabhakaran, S., S. Kalainathan (2016), Warm laser shock peening without coating induced phase transformations and pinning effect on fatigue life of low-alloy steel, Materials & Design, 107, 98-107, DOI: 10.1016/j.matdes.2016.06.026.

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Tuning the Surface Properties of Modified Polymer Blends as a Function of Plasma Treatment – A Mini Review 1

E. Dhanumalayan1, Girish M. Joshi1, a 1 – Polymer Nanocomposite Laboratory, Center for Crystal Growth (CCG), VIT University, Vellore, Tamilnadu, India a – girish.joshi@vit.ac.in DOI 10.2412/mmse.2.67.472 provided by Seo4U.link

Keywords: polymers, blends, composites, plasma treatment, surface properties.

ABSTRACT. In view of engineering, the materials for industrial and domestic applications, optimization of barrier properties are considered as highly important. The barrier properties of polymers include low or high surface energy, relative contact angle (θ), surface roughness and work of adhesion. These parameters of a polymer surface can be tailored by applying plasma treatment without the loss in its bulk form. The effect of plasma treatment on the surface of polymers has been characterized by determining the variation in contact angle and the relative surface free energy. In this review, we consolidated the tunable surface properties of polymer composites and filler modified polymer blends with the help of different types of plasma treatment employed with varying magnitudes. Plasma treatment is highly effective to tailor the surface of polymer blends hence providing an open opportunity to the community of material science.

Introduction. The global scenario of material science research is advancing day to day for the exploration of the new materials. In particular, polymers are inevitable materials due to the availability and ease of production. Presently existing polymers are processed as blends, composites and modified polymer blends to achieve the desired properties which may not be possible for a virgin polymer system. The blending of two or more polymers could potentially improve the properties.

Specially made additives and reinforcing fillers in micro and nano forms are also introduced into the blend matrix to enrich the chemical and physical properties. This type of systems is called modified polymer blends having significant interest for a wide range of engineering applications [1].

Barrier properties of modified polymer blend systems are important for a material because, the surface plays the role as a protective layer for the whole bulk system. The interface of two materials also deals with the surface. Hence the surface properties are significant to study and it helps to tune the nature of the surfaces by either physical or chemical method. The hydrophobic (when θ > 90°) and hydrophilic (when θ < 90°) nature has been categorized depending on the wetting and spreading of liquids (water, oil and acids). These nature of the surfaces was finely tuned after the exposure to plasma treatment. The virgin polymer systems such as Polytetrafluoroethylene (PTFE), Polyethylene terapthalate (PET), Polymethyl methacrylate (PMMA), Polyvinylidene fluoride (PVDF) as well as blends such as (PP)/Epoxized lignin, PVDF/PMMA and the modified blends were recently studied and the properties are defined [2, 3]. The major advantage of plasma treatment is that it enhances the surface and interface by adhesion where the bulk properties of the system remain unaffected. The monomers and radicals are implanted on the surface to achieve the target applications. Plasma treatment is an industrial tool where it serves in large scales. In textile industries, printing and packaging applications, plasma treatment enhances the weaving, printability of inks and adhesion of labels on the containers [4, 5].

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The surface modification techniques are gradually evolving to customize the surface of the materials and plasma treatment is one among them. The present work reviews the significance of modified polymer blends and the tuning of its surface properties with the help of plasma treatment.

Reinforcement and Modification of Polymer Blends.

Polymer blends are versatile in properties by possessing both the characters of the virgin systems.

The major issue hinders the blend processing is the miscibility of the two systems. It is well known that the commonly available polymers are having less molecular segment interactions which create immiscible portions of the blend system. The compatibility between the two polymers can be improved by adding fillers (compatibilizing the polymers, oxides, ceramics, fibers, nano and micro entities). The reinforcement of the filler particulates in the blend matrix gives mechanical and morphological stability [6, 7]. Hence modification of the blend with fillers are important to overcome the issue of miscibility, stability and to improvise the compatibility.

Plasma Treatment. Plasma is known as the fourth state of matter. When a solid material is heated, the increase in temperature makes it undergo a phase transformation from solid to liquid and further to the gas phase. If the temperature is raised furthermore, the atoms of the gas molecules becomes an ionized gas. This ionized gas constitutes radicals, ions and charged particles which are feasibly used for wide range of applications [8].

Fig. 1. Various kind of plasma treatment available for broad range of applications.

Plasma treatment is used to improve the interface, wetting and cleaning of the surface. It could be done by choosing specific gas and monomers. Increasing the temperature of the gas molecules produces radicals and reactive species. The treatment conditions are depending upon the end uses.

Power and treatment time plays a crucial role in treating the surfaces [9]. The various types of plasma treatment present in today's technology are given in figure 1.

Plasma treatment for polymer, blends and modified blends.

Plasma treatment helps to develop a surface interface between modified polymer blends. Due to the low surface energy, the interface is poor and the surface itself resists the interfacial function. Plasma modification increases surface energy and hydrophilic properties depending upon the radicals of the plasma gas. The interfacial tension between the solid to liquid and liquid to gas phases can be determined by Youngâ&#x20AC;&#x2122;s contact angle equation [10, 11]. From the contact angle measurement, the variation in surface energy of untreated and plasma treated surfaces could be determined. The hydrophobic and hydrophilic nature of the surfaces can be controlled by choosing the specific gas. It is commonly known that the fluorinated polymers exhibits hydrophobic nature due to the C-F group which possess inert characteristics. The present research suggesting that the plasma surface modification of PMMA with the help of CF4 gas improves the hydrophobic character. This term is known as plasma fluorination which enhances the hydrophobicity of the surface. This shows that MMSE Journal. Open Access www.mmse.xyz

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some of the inert functional groups are implanted to the surface to enhance the hydrophobic surface characteristics [12, 13]. The interfacial function of filler paticles was modified and improved the interaction of carbon black filler in the Polycarbonate and Acrylonitrile butadiene styrene (PC/ABS) blend matrix [14]. The microstructure of the filler was modified due to the O2 and N2 plasma modification which was resulted in fine dispersion. To improve the biocompatible property of polymers, plasma treatment applied to enhance the cell to matrix interaction. The blood compatibility and the antifouling property of the polymer substrate such as poly-lacticacid was improved by various gas monomers and their properties were improved for bio active surfaces [15].

Fig. 2. Demonstration of surface properties as a function of plasma treatment.

Applications of Plasma Surface Treatment. The effect of plasma treatment on the surface chemistry and physics is well known in the present era. Plasma treatment not only enhances the surface property of the polymers but also enhances the miscibility of polymers and dispersion of fillers by improvising the interactions between them. A recent work demonstrated that blend preparation of polypropylene and polyamide-6 using an in-line plasma treatment fixed twin screw extruder. Due to the impact of plasma the interaction between the polymer components were increased then yielded good miscibility and impact strength [16]. Polymer blend electrodes made up of Poly (3,4 â&#x20AC;&#x201C; ethylene dioxythiophene) and polystyrene sulfonate (PEDOT/PSS). These electrodes were plasma treated instead of regular acid treatment methods. This approach showed the inherent application of plasma treatment by the improved inficiency of the perovskite solar cell [17]. The various applications of plasma treatment on polymer substrates is shown in figure 3.

Fig. 3. The application of plasma treatment on polymers by surface modification process.

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Summary. Plasma treatment and its inherent applications were discussed in this review. The major advantage of plasma surface modification technique is that it is used to manipulate the surfaces without affecting the environment. Since the invention, plasma was used in electronic, packaging and printing industries and the technique is advancing drastically in the present scenario. By combining plasma treatment with the polymers, blends and its modified forms the present and futuristic scope is broad for innovative technological applications. Hence plasma treatment is an inevitable tool for the better optimization of barrier properties.

Acknowledgement Authors are thanking Center for Crystal Growth (CCG), VIT university, Vellore-632014. for the encouragement to present the poster in ICAMST-2017.

References [1] D. R. Paul, Polymer blends. Vol. 1. Elsevier, 2012. ISBN: 9780323138895 [2] J. Drelich, E. Chibowski, D.D Meng, K. Terpilowski, Hydrophilic and superhydrophilic surfaces and materials, Soft Matter, 7(21), 9804-28, 2011. DOI 10.1039/C1SM05849E [3] L.R. Hutchings, A.P. Narrianen, R.L. Thompson, N. Clarke, I. Ansari, Modifying and managing the surface properties of polymers, Polymer International, 57(2), 163-170, 2008. DOI 10.1002/pi.2334 [4] M. Pascu, C. Vasile, G. Popa, I. Mihaila, V. Pohoata, Modification of polymer blends properties by plasma/electron beam treatment. I. Plasma diagnosis and bulk properties of plasma treated blends, International Journal of Polymeric Materials, 1, 51(1-2), 181-192, 2002. DOI 10.1080/00914030213031 [5] N. Venkatramani, Industrial plasma torches and applications, Current Science, 10, 254-262, 2002.

URL: http://www.jstor.org/stable/24106883 [6] W. Li, H. Li, Y.M. Zhang, Preparation and investigation of PVDF/PMMA/TiO2 composite film.

Journal of materials science, 1, 44(11), 2977-2984, 2009. DOI 10.1007/s10853-009-3395-x [7] E. Dhanumalayan, A.M. Trimukhe, R.R. Deshmukh, G.M. Joshi, Disparity in hydrophobic to hydrophilic nature of polymer blend modified by K2Ti6O13 as a function of air plasma treatment. Progress in Organic Coatings, 111, 371-380, 2017. DOI 10.1016/j.porgcoat.2017.06.001 [8] J.A. Bittencourt, Fundamentals of plasma physics. Springer Science & Business Media, 2013. ISBN: 9781-4757-4030-1.

[9] M.A. Lieberman, A.J. Lichtenberg, Principles of plasma discharges and materials processing. MRS Bulletin, 30, 899-901, 1994. DOI 10.1557/mrs2005.242 [10] Yuan Y, Lee TR. Contact angle and wetting properties. In Surface science techniques, Springer Berlin Heidelberg, 3-34, 2013. DOI 10.1007/978-3-642-34243-1_1 [11] R. Wolf, A.C. Sparavigna, Role of plasma surface treatments on wetting and adhesion. Engineering, 1, 2(06), 397, 2010. DOI 10.4236/eng.2010.26052 [12] R. Wang, C. Zhang, X. Liu, Q. Xie, P. Yan, T. Shao, Microsecond pulse driven Ar/CF 4 plasma jet for polymethylmethacrylate surface modification at atmospheric pressure. Applied surface science, 15, 328, 509515, 2015. DOI 10.1016/j.apsusc.2014.12.076 [13] J. Cheng, S. Wang, S. Chen, J. Zhang, X. Wang, Crystallization behavior and hydrophilicity of poly (vinylidene fluoride)/poly (methyl methacrylate)/poly (vinyl pyrrolidone) ternary blends. Polymer International, 1, 61(3), 477-484, 2012. DOI 10.1002/pi.3185 [14] B.B. Zhang, Y. Chen, F. Wang, RY. Hong, Surface modification of carbon black for the reinforcement of polycarbonate/acrylonitrile–butadiene–styrene blends, Applied Surface Science, 1, 351, 280-288, 2015. DOI 10.1016/j.apsusc.2015.05.106

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[15] T. Jacobs, R. Morent, N. De Geyter, P. Dubruel, C. Leys, Plasma surface modification of biomedical polymers: influence on cell-material interaction, Plasma Chemistry and Plasma Processing, 1, 32(5), 10391073, 2012. DOI 10.1007/s11090-012-9394-8 [16] C. Hopmann, F. Puch, H. Behm, M. Adamy, A novel approach for an in-line atmospheric plasma-treatment of polymers and reinforcements during extrusion Journal of Plastics Technology, 12(4), 295-310, 2016.

DOI 10.3139/O999.03042016

[17] B. Vaagensmith, K.M. Reza, M.N. Hasan, H. Elbohy, N. Adhikari, A. Dubey, N. Kantack, E. Gaml, Q. Qiao, Environmentally Friendly Plasma-Treated PEDOT: PSS as Electrodes for ITO-Free Perovskite Solar Cells. ACS Applied Materials & Interfaces. 9, 9(41), 35861-35870, 2017. DOI 10.1021/acsami.7b10987

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Sonochemical Method for Casting the Polymer Nanocomposites: A Mini Review 1

D. Arthisree1, Girish M. Joshi1,a 1 – Polymer Nanocomposites Laboratory, Center for Crystal Growth (CCG), VIT University, Vellore, TN, India a – girish.joshi@vit.ac.in DOI 10.2412/mmse.48.74.746 provided by Seo4U.link

Keywords: ultrasonic dispersion, polymers, nanocomposites, high and low power, cavitation.

ABSTRACT. The present nano science domain focussed on sample preparation and inhibition of chemical reaction achieved by several techniques based on the principle of cavitation process using ultrasonic frequency-sonochemical routes. The effect of sonochemical routes is highly advantageous in reaction methods such as triggering reaction pathways, inducing the speedy reaction of inter-particle collision. In polymers, high intensity ultrasound waves are used for the polymerization of monomers by step growth process. This review is an outlook of sonochemical approach for polymer nanocomposites, which follows the physics of ultrasonic frequency bands, chemical reactions and the properties of acoustic cavitation highly applicable for the development of modern target materials.

Introduction. The modern trend of material science follows various techniques to process the materials. Casting routes deals with various chemical and physical preparation processes which are suitable for building components with various applications. Sonochemical method is one of the most convenient and productive methods among various polymerization and polymer composite preparation techniques. It is achieved by applying high frequency ultrasound waves (20 kHz to 2 MHz) at the initial step [1]. The agitation of the solution due to the ultrasound irradiation produces cavitation. In this cavitation process, bubbles are formed and collapse routinely to evoke different types of chemical reactions. During the processing of polymer nanocomposites, in order to enhance the even dispersion of nanoparticles in the polymer matrix ultrasonic wave sonochemical method has been employed as a significant route [2]. This method is highly advantageous in the preparation of various fillers and polymer composites where fine dispersion of particles can be achieved [3, 4]. The interfacial region between the polymers and the fillers are tuned well with the help of ultrasound irradiation by varying the ultrasound frequency range from high to low. In the present investigation we have discussed various synthesized materials and their properties by sonochemical technique, physics and chemistry of sonochemistry, role of sonochemical route, advantages of sonochemical routes over bath sonication and its application in detail.

Properties and synthesized materials by sonochemical routes. Sonochemical method provides uniform dispersion, stimulated nucleation, fast reaction rate and less particle size than the conventional bath sonicator technique. Due to reduced particle size there may be expected change in the physical and chemical property of the material [5, 6]. Figure. 1 illustrates various physical and chemical properties and material synthesised associated with sonochemical technique. Many organic, inorganic, metal oxides and polymer blends have been prepared by this method. It has been reported that during the synthesis process high aspect mesopores Mg-MOF-74 crystals with particle size around 0.6 m were formed by crosslinking triethylamine with Mg (II) ions [7]. Fe3O4@NH2mesoporous silica @ PPy / Pd was synthesised by sonochemical route as a convenient way for producing core/double shell hybrid system. The prepared nanocomposite showed efficient catalytic activity, however it is reported that the synthesis method was time saving [8]. Gamma-zirconium 11

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phosphate with polyaniline nanocomposite was prepared by high-power ultrasound irradiation; the interaction of Îł-ZrP into polymer unit with high reaction rate was observed [9]. Metal nanoparticles (Au, Pt) dispersed in Polypyrrole polymer were obtained by sonochemical method, the metal nanoparticles were well dispersed in the polymer unit with an average diameter of 15nm for Au/PPy and 2-3 nm for Pt/PPy [10].

Fig. 1. Various synthesized material and their properties.

Physics and chemistry of sonochemistry. The physical parameter like density, pressure, temperature, cavitation phenomena and time of exposure directly plays an important role in fragmenting the particle [11]. Where else the chemical changes like catalytic activity, emulsification, and chemical bonding are responsible for intermolecular collision. In nanomaterials such as carbon when the particle size is scaled down (quantum dots) there is expected change in the discrete energy state that leads to chemiluminenscence applications [12]. Stability emulsion of oil in water was prepared by both mechanical turbulence and ultrasonication technique, where ultrasonication provided long lasting emulsion than mechanical turbulence [13]. It is an worthwhile tool for mass level production in the chemical and pharma domain.

Role of sonochemical routes. Sonochemical method used by the vigorously irradiated ultrasound exposure for about 20 kHz to 2 MHz also induces the chemical reaction. Figure.2 illustrates the experimental setup of sonochemical method. During such an occurrence of ultrasound irradiation, an intense heat and pressure causes acoustic cavitation that leads to the formation, growth and implosive collapse of micro bubbles during sample processing [14].

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Fig. 2. Experimental setup of sonochemical method.

Advantages of probe sonication over bath sonicator.

Table 1. Difference between probe sonication and bath sonication Probe sonicator

Bath sonicator

Physically the probe is immersed to the The medium of dispersion is kept inside solute. the bath sonicator.

Energy of propagation of ultrasonic Temperature controlled very easily, power is high (W-kW). energy or power generation is low in watts.

Probe tip inserted must be in contact with In bath sonication the sonic vibration is liquid medium in order to achieve given externally in order to achieve chemical reaction. dispersion.

Time of exposure is short depending upon Time of exposure is large depending upon the density/volume of the solute density/volume of the solute

Bath sonication is an indirect method in which the ultrasound irradiation is passed through the bath liquid and then reaches the sample suspension. But in direct sonication the probe is directly immersed into the sample dispersion to irradiate the ultrasound into the suspension. Table 1 describes difference between probe and bath sonication [15]. Direct sonication method is advantageous over indirect sonication as the energy of propagation of power is large and the yield product is highly efficient by giving collateral physicochemical interaction upon chemical bonding [16]. The method of dispersion MMSE Journal. Open Access www.mmse.xyz

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is non-hazardous and it brings about uniform dispersion, high quality particles production, deagglomerated surface, rapid reaction rate, high power and less time consuming.

Application of sonochemical method.

We do refer the sonochemical route in different domains for the biological treatment for water purification, crystallization, soil cleaning in agriculture domain [17], industrial processing like pigmentation, emulsification in chemical domains [18], and pharmaceutical drug blending [19], polymerization [20], nanoparticle preparation, dispersion of carbon allotropes for casting the commercial polymer, epoxy, thermoplastic blends, [21] make use of sonochemical method for their production purpose.

Summary. At present, sonochemical route is progressive because of the development and production of the new the materials for target applications. The processing method is highly controllable and calcination-free method for mass production of polymer blends and nanomaterial with less impurity and fine quality. However, energy consumption is the major drawback of this system but promising applications are expected in near future.

Acknowledgement Authors are thanking Center for Crystal Growth (CCG), VIT University, Vellore for supporting us to present our paper in ICAMST 2017.

References [1] Ficai, D., & Grumezescu, A. M. (Eds.). (2017). Nanostructures for Novel Therapy: Synthesis, Characterization and Applications. Elsevier.

[2] Suslick, K. S., & Price, G. J. (1999). Applications of ultrasound to materials chemistry. Annual Review of Materials Science, 29(1), 295-326.

[3] Yazdani, S., Hatami, M., & Vahdat, S. M. (2014). The chemistry concerned with the sonochemical-assisted synthesis of CeO2/poly (amic acid) nanocomposites, DOI 10.3906/kim-130633 [4] Li, Z., & Wang, Y. (2010). Characterization of polyaniline/Ag nanocomposites using H2O2 and ultrasound radiation for enhancing rate. Polymer Composites, 31(9), 1662-1668. DOI 10.1002/pc.20956 [5] Arthisree, D., & Joshi, G. M. (2017). Influence of graphene quantum dots on electrical properties of polymer composites. Materials Research Express, 4(7), 075045.

[6] Pandey, I., Arthisree, D., Sivakumar, A., & Joshi, G. M. (2017). Polymer Composites for Thermal Sensing Application14. DOI: 10.2412/mmse.2.26.724 [7] Yang, D. A., Cho, H. Y., Kim, J., Yang, S. T., & Ahn, W. S. (2012). CO 2 capture and conversion using Mg-MOF-74 prepared by a sonochemical method. Energy & Environmental Science, 5(4), 6465-6473. DOI: 10.1039/c1ee02234b [8] Snoussi, Y., Bastide, S., Abderrabba, M., & Chehimi, M. M. (2017). Sonochemical synthesis of Fe3O4@ NH2-mesoporous silica@ Polypyrrole/Pd: a core/double shell nanocomposite for catalytic applications. Ultrasonics Sonochemistry. DOI 10.1016/j.ultsonch.2017.10.021 [9] Wang, J., Hu, Y., Song, L., & Chen, Z. (2004). Sonochemical preparation of nanocomposite of gamma-zirconium phosphate (γ-ZrP) and Cu 2 O/CuO embedded polyaniline. Solid state ionics, 167(3), 425-430. DOI 10.1016/j.ssi.2004.01.028 [10] Park, J. E., Atobe, M., & Fuchigami, T. (2005). Sonochemical synthesis of conducting polymer– metal nanoparticles nanocomposite. Electrochimica Acta, 51(5), 849-854.

DOI 10.1016/j.electacta.2005.04.052

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[11] Capelo-Martínez, J. L. (Ed.). (2009). Ultrasound in chemistry: analytical applications. John Wiley & Sons. ISBN-978-3-527-31934-3 [12] Arthisree, D., & Joshi, G. M. (2017). Study of polymer Graphene Quantum Dot nanocomposites. Journal of Materials Science: Materials in Electronics, 1-9. DOI 10.1007/s10854017-6825-6 [13] Ramisetty, K. A., & Shyamsunder, R. (2011). Effect of ultrasonication on stability of oil in water emulsions. International Journal of Drug Delivery, 3(1).

[14] Lauterborn, W., & Ohl, C. D. (1997). Cavitation bubble dynamics. Ultrasonics sonochemistry, 4(2), 65-75. DOI 10.1007/978-3-319-38842-7 [15] Mason, T. J., & Peters, D. (2002). Practical sonochemistry: Power ultrasound uses and applications. Woodhead Publishing.

[16] Kowsari, E., & Faraghi, G. (2010). Ultrasound and ionic-liquid-assisted synthesis and characterization of polyaniline/Y 2 O 3 nanocomposite with controlled conductivity. Ultrasonics sonochemistry, 17(4), 718-725. DOI 10.1016/j.ultsonch.2009.11.018 [17] Mason, T. J. (2007). Sonochemistry and the environment–Providing a “green” link between chemistry, physics and engineering. Ultrasonics sonochemistry, 14(4), 476-483.

[18] Mason, T. J. (2000). Large scale sonochemical processing: aspiration and actuality. Ultrasonics sonochemistry, 7(4), 145-149.

[19] Sander, J. R., Bučar, D. K., Henry, R. F., Zhang, G. G., & MacGillivray, L. R. (2010).

Pharmaceutical Nano‐ Cocrystals: Sonochemical Synthesis by Solvent Selection and Use of a Surfactant. Angewandte Chemie International Edition, 49(40), 7284-7288.

DOI 10.1002/anie.201002588 [20] Pantoja-Castro, M. A., Pérez-Robles, J. F., González-Rodríguez, H., Vorobiev-Vasilievitch, Y., Martínez-Tejada, H. V., & Velasco-Santos, C. (2013). Synthesis and investigation of PMMA films with homogeneously dispersed multiwalled carbon nanotubes. Materials Chemistry and Physics, 140(2), 458-464.

[21] Okitsu, K., Ashokkumar, M., & Grieser, F. (2005). Sonochemical synthesis of gold nanoparticles: effects of ultrasound frequency. The Journal of Physical Chemistry B, 109(44), 2067320675. DOI 10.1021/jp0549374

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Thickness Dependent Optical Properties of Sol-gel Based MgF2 – TiO2 Thin Films 1

Siddarth Krishnaraja Achar1, a, Akhil Punneri Madathil1, Naveen C.S.2, Baijayanthi Gosh2, A. R. Phani2 1 – Department of Chemical Engineering, R.V. College of Engineering, Bengaluru, Karnataka, India 2 – Innovative Nano & Micro Technologies Private Limited, #4, T.M Industrial Estate, Mysore Road, Bengaluru, Karnataka, India a – siddharthk.ch14@rvce.edu.in DOI 10.2412/mmse.19.89.934 provided by Seo4U.link

Keywords: envelope technique, thin films, optical parameters, sol-gel, band gap, dip-coating.

ABSTRACT. MgF2 - TiO2 thin films were prepared by cost effective solgel technique onto glass substrates and optical parameters were determined by envelope technique. Thin films were characterized by optical transmission spectroscopy in the spectral range 290 - 1000 nm. The refractive index, extinction coefficient, Optical thickness and band gap dependency on thickness were evaluated. Thickness dependency of thin films showed direct allowed transition with band gap of 3.66 to 3.73 eV.

Introduction. Metal nanocomposites possess various properties which can be tweaked as per the application that is necessary. When different metal nanomaterials are mixed and deposited on a substrate, they show optical properties that can be studied and finally made use of. TiO2 is a metal oxide which when combined with a metal fluoride like MgF2 acts as a nanocomposite. MgF2, when coated on the surface of a solar cell can impart appreciable anti reflective properties with just a single layer [1]. TiO2 also has desirable properties like good transmission in the visible and near infrared region of the electromagnetic spectrum [2]. Hence, these two nanomaterials are used together in single or multi-layer optical coatings. Multi-layer coatings will not be that economically feasible when compared to just a single layer.

There are many methods of fabrication of this thin film. Sol-gel is one of the cheapest and easier ways when compared to chemical vapor deposition (CVD), Physical vapor deposition, Ion-assisted Deposition (IAD) etc. The disadvantage with the sol-gel technique is the formation of dense material of the thin film. Therefore, by applying multiple coatings may lead to the formation of dense columnar microstructures [3]. Other methods of preparing the coat like CVD, PVD or IAD give a comparably better packing density and columnar microstructure to that of the sol-gel technique. These techniques are quite expensive and complex, for instance, in the IAD method the property of the thin film can be altered just by adjusting the kinetic energy of the incident particles. In that case the sol-gel technique tends to be simple and cost cutting.

The paper is aimed at studying the optical properties, like the transmittance of visible light through the TiO2-MgF2 composite prepared by sol-gel method. The comparison of the transmittance of light, absorption coefficient, thickness and the extinction coefficient for different coating parameters is drawn. The calculations are done using envelope technique [4] that uses just the transmittance data to find these optical parameters. This technique can be a cheaper alternative to the conventional

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© 2018 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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spectroscopic ellipsometry [5, 6] for optical parameters and techniques like surface profiling stylus, Interferometric methods for thickness determination. [7-9].

Experimentation. Precursor synthesis.

Preparation of TiO2 sol. The solution for TiO2 was made by adding methanol and Titanium isopropoxide into a beaker, which was kept for stirring with the help of a magnetic stirrer. To this breaker acetyl acetate was added drop by drop by the help of a micro-burette.

Preparation of MgF2 sol. The solution of MgF2 was made by adding methanol to Magnesium acetate powder in a beaker, which was kept for stirring with the help of a magnetic stirrer. Small amount of Hydrofluoric acid was added drop by drop. Then acetyl acetate was added to make the mixture.

Both these sols (MgF2 and TiO2) were prepared simultaneously and allowed to stir separately in two separate beakers. After around 30 minutes, these sols were mixed into a single beaker. With the opening of the beaker sealed using paraffin wax, it was allowed to stir for around 24 hours.

Dip Coating. With the help of a dip coating equipment, this sol was coated on a three different glass slabs (substrate) with a refractive index of 1.54 with different dipping parameters. The first slab was set to a dipping speed of 750 micrometers per second and a returning speed of 750 micrometers per second. The slab was allowed to dip for 1 minute and was made to dry for 4 minutes (at 75oC). Each dipping and drying is regarded as one dip. The three slabs had the same dipping parameters as mentioned above, but the number of dips were set to 1, 2 and 3 respectively for those three separate slabs.

Annealing. Once the coating was done, all these three glass slabs were kept in a pre-heated muffle furnace for annealing. The temperature maintained inside was 300oC and the samples were kept for 1 hour Thickness Characterization. The transmittance data of the nine samples were taken by using a spectrophotometer. The data were made into three sets based on the composition of TiO2 in the coating. Naming of the samples are given in Table 1. The thickness of these samples were calculated by using the envelope technique.

Calculation of refractive index. For any sample that is taken, the maximum transmittance (Tmax) and minimum transmittance (Tmin) values are found out using its transmittance spectra. The corresponding wavelengths of Tmax and Tmin are named as Îťmax and Îťmin respectively. After the dip coating is done the refractive index of the thin film is found by using equation (1). nf = {N1 + (N12 - ns2 )0.5}0.5

(1)

Where N1 is given by, đ?&#x2018;&#x2021;

â&#x2C6;&#x2019; đ?&#x2018;&#x2021;đ?&#x2018;&#x161;đ?&#x2018;&#x2013;đ?&#x2018;&#x203A;

N1 = 2 Ă&#x2014; đ?&#x2018;&#x203A;đ?&#x2018; (đ?&#x2018;&#x2021; đ?&#x2018;&#x161;đ?&#x2018;&#x17D;đ?&#x2018;Ľ Ă&#x2014; đ?&#x2018;&#x161;đ?&#x2018;&#x17D;đ?&#x2018;Ľ

đ?&#x2018;&#x2021;đ?&#x2018;&#x161;đ?&#x2018;&#x2013;đ?&#x2018;&#x203A;

1.522 +1

)+(

2

)

(2)

Here ns â&#x20AC;&#x201C; is the refractive index of the substrate.

Calculation of thickness, absorption coefficient and molar extinction coefficient of thin film.

From the Îťmax values obtained from 2.4.1 the thickness of the thin film is calculated by using đ?&#x153;&#x2020;

đ?&#x2018;&#x161;đ?&#x2018;&#x17D;đ?&#x2018;Ľ d= 2â&#x2C6;&#x2014;đ?&#x2018;&#x203A; đ?&#x2018;

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(3)

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Where d â&#x20AC;&#x201C; is the thickness of the thin film. The absorption coefficient is calculated as Îą=

2.303 đ?&#x2018;&#x2018;

1

Ă&#x2014; đ?&#x2018;&#x2122;đ?&#x2018;&#x203A;(đ?&#x2018;&#x2021;)

(4)

Where Îą â&#x20AC;&#x201C; is the absorption coefficient of the sample; T â&#x20AC;&#x201C; is the transmittance values for all the corresponding wavelengths in the visible spectrum. đ?&#x203A;źĂ&#x2014;đ?&#x153;&#x2020;

k = 2Ă&#x2014;đ?&#x153;&#x2039;

(5)

Where k â&#x20AC;&#x201C; is the molar extinction coefficient of the thin film.

Table 1. Sample index based on number of dips and TiO2 concentration.

Sample Name

Number of Dips

TiO2 concentration

S-I(1)

1

2%

S-I(2)

2

2%

S-I(3)

3

2%

S-II(1)

1

1%

S-II(2)

2

1%

S-II(3)

3

1%

S-III(1)

1

0.5%

S-III(2)

2

0.5%

S-III(3)

3

0.5%

100 90

Transmittance (%)

80

S-I(1) S-I(2) S-I(3) plain glass

70 60 50 40 30 20 10

0 300 350 400 450 500 550 600 650 700 750 800 850 900

Wavelength (nm)

Fig. 1. Transmittance spectra for samples with 2% TiO2.

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100 90 80

S-II(1) S-II(2) S-II(3) plain Glass

Transmittance (%)

70 60 50 40 30 20 10

0 300 350 400 450 500 550 600 650 700 750 800 850 900

Wavelength (nm)

Fig. 2. Transmittance spectra for samples with 1% TiO2.

100 90 80

S-III(1) S-III(2) S-III(3) plain glass

Transmittance (%)

70 60 50 40 30 20 10

0 300 350 400 450 500 550 600 650 700 750 800 850 900

Wavelength (nm)

Fig. 3. Transmittance spectra for samples with 0.5% TiO2.

Results and Discussion. Transmittance spectra. The transmittance data is attained by using a spectrophotometer and the three curves are plotted and shown in Figure 1, 2 and 3 based on the TiO2 composition in them. These are compared to the transmittance curve of plain glass (refractive index of 1.52). It can be seen from Figure 1, which compares only samples with 2% TiO2, that when the sol was dip coated thrice on the substrate (S-I(3)) it showed an increase in transmittance from the transmittance of plain glass. Suggesting that the sample with three dips can be used more effectively as coatings for opto-electronic devices with high transmittance requirements. The transmittance curve for samples with 1% clearly tells that S-II(3) has better transmittance values when compared to the other two in that set. The fact that even with the increase in the composition of MgF2 in the whole thin film hasnâ&#x20AC;&#x2122;t caused the transmittance values to consistently cross the plain glass values in Figures 2 and 3. The percentage transmittance values for all the samples at 550 nm (median in the visible spectra) are given in Table 2.

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Table 2. Percentage Transmittance for all samples at 550 nanometers.

N bb

Percentage Transmittance S-I(1)

88.067 %

S-I(2)

91.169 %

S-I(3)

92.813 %

S-II(1)

89.813 %

S-II(2)

88.581 %

S-II(3)

90.648 %

S-III(1)

90.504 %

S-III(2)

91.154 %

S-III(3)

89.894 %

Band Gap evaluation. The optical band gap of these thin films were calculated by performing Tauc plots. The Tauc plot is primarily used to find the optical band gap by plotting energy (hυ) on the xaxis and the quantity (αhυ)1/r in the y-axis [10] . Here the value of r denotes the nature of transition.

For all cases here, the r value is taken to be 0.5 (for allowed transitions). Hence a plot of (αhυ)2 versus energy (in electron volts) is made for the three sets as given in figure 4, 5 and 6.

Fig. 4. (a) (αhυ)2 v/s energy (eV) (b) (αhυ)2 v/s energy (eV) (zoomed scale to find slope) for samples with 2% TiO2.

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Fig. 5. (a) (αhυ)2 v/s energy (eV) (b) (αhυ)2 v/s energy (eV) (zoomed scale to find slope) for samples with 1% TiO2.

Fig. 6 (a) (αhυ)2 v/s energy (eV) (b) (αhυ)2 v/s energy (eV) (zoomed scale to find slope) for samples with 0.5% TiO2.

Table 3. Band gap (in eV) and wavelength corresponding to the band gap (in nanometers).

Sample name

Band Gap (eV)

Wavelength (nm)

S-I(1)

3.70

335.97

S-I(2)

3.72

334.17

S-I(3)

3.73

333.27

S-II(1)

3.71

335.06

S-II(2)

3.71

335.06

S-II(3)

3.66

339.64

S-III(1)

3.66

339.64

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S-III(2)

3.72

334.17

S-III(3)

3.70

335.97

The band gap values for all the nine samples are listed in Table 3. The wavelengths are calculated by using:

λ=

1.2431×10−6 band gap energy in eV

(6)

These wavelengths are the threshold wavelengths beyond which there is an increase in the transmittance of light. This can be seen in Fig 1, 2 and 3, where the transmittance increases as they reach the wavelengths mentioned in Table 3 for respective samples.

Fig. 7. (a) Absorption spectrum v/s wavelength and (b) Extinction coefficient v/s wavelength for samples with 2% TiO2 concentration.

For samples with 2% TiO2 (S-I(1), S-I(2) and S-I(3)) the band gap increases with the number of dips, this can be called blue-shift. A red-shift is observed in samples S-II(1), S-II(2) and S-II(3) since the energy decreases with the number of dips. No such shifts are observed in S-III. Absorption coefficient plot and molar extinction coefficient plot. The plot of absorption coefficient (α) versus wavelength is used to verify that the absorbance of incident light in the visible region of the electromagnetic spectrum becomes almost negligible. This assurance helps in validating the fact that light that hasn’t been transmitted is majorly reflected. [11]

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Fig. 8. (a) Absorption spectrum v/s wavelength and (b) Extinction coefficient v/s wavelength for samples with 1% TiO2 concentration.

The molar extinction coefficient is used to find out how easy it is for incident light to penetrate through the thin film coating. The smaller the extinction coefficient, the smaller is the attenuation of light due to the medium, hence thee medium is comparably transparent [12].

Fig. 9. (a) Absorption spectrum v/s wavelength and (b) Extinction coefficient v/s wavelength for samples with 0.5% TiO2 concentration.

The values of absorption coefficient (α) is calculated using equation (4) for all values of transmittance.

This is plotted against the corresponding wavelengths of these transmittance values for all the three sets of samples as shown in Fig 7(a), 8(a), 9(a). These graphs indicate that all the thin films consistently show negligible absorbance of light in the visible region of the electromagnetic spectrum (around 350 to 750 nm).

The values of molar extinction coefficient (k) is calculated by using the equation (5) for all values of absorption coefficient (α) calculated previously for all samples. This is then plotted against wavelengths as shown in Fig. 7(b), 8(b), 9(b). These graphs indicate that all the coatings consistently

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show lesser extinction coefficient in the visible region. This indicates that the thin films do not cause much attenuation in the visible region and are transparent to visible light.

Thickness of the thin films. After assuring that the thin films are transparent enough and do not lead to attenuation of incident light, it is necessary to see the manner in which the thickness of the thin films affect the transmittance of visible light. The thickness is calculated by using the equation (3).

The λmax values that were calculated for each sample are used in this equation and n s is taken to be 1.52. The thickness of these samples are given in Table 4.

Table 4. Thickness (in nanometers) and percentage transmittance at 550 nm for all nine samples.

Sample name

Thickness in nanometers

Percentage Transmittance

S-I(1)

201.13

88.067 %

S-I(2)

204.27

91.169 %

S-I(3)

218.68

92.813 %

S-II(1)

183.54

89.813 %

S-II(2)

186.61

88.581 %

S-II(3)

187.12

90.648 %

S-III(1)

172.79

90.504 %

S-III(2)

203.84

91.154 %

S-III(3)

228.14

89.894 %

Table 4 indicates that with the increase in the number of dips, the sample thickness increases as well as predicted. The aim of the work is to make a sample with just a single layer of coating (not single dip). There seems to be no particular trend for the percentage transmittance values when compared to the increasing trend seen for the thin film thickness. From all the thin films that were coated, SI(3) is the most transparent to visible light. It has a thickness of 218.68 nm. Factors like absorption coefficient and molar extinction coefficient also don’t seem to depend a lot on the thickness.

Summary. Several optical parameters like absorption coefficient (α), extinction coefficient (k) and band gap were found from the transmittance spectrum data by using the envelope technique for thin films that differed in the number of dips and the TiO2 concentration. From the results obtained, the sample S-I(3) shows consistent percentage transmittance throughout the visible region of light. All the samples have low absorption and extinction coefficient. It was observed that the band gap of all samples are between 3.66 to 3.73 eV. The thickness of all the samples were calculated and its dependency on the thin film performance was evaluated.

References [1] Yang, H. H., Park, G. C. (2010), A Study on the properties of MgF2 Antireflection film for Solar Cells, Transactions on electrical and electronic materials, 11(1), 33-36. DOI 10.4313/TEEM.2010.11.1.033.

[2] Tsai, R. Y., Hua, M. Y., Wei, C. T., Ho, F. C. (1994), Characterizations of composite TiO2–MgF2 films prepared by reactive ion-assisted coevaporation, Opt. Eng., 33, 3411-3418, DOI 10.1117/12.179392.

[3] Hegmann, J., Löbmann, P. (2013), Sol–gel preparation of TiO2 and MgF2 multilayers, Journal of sol-gel science and technology, 67(3), 436-441, DOI 10.1007/s10971-013-3096-4.

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[4] R. Swanepoel (1983), Determination of the thickness and optical constants of amorphous silicon, J. Phys. E: Sci. Instrum., 16, 1214, DOI 10.1088/0022-3735/16/12/023.

[5] Yim, C., O'Brien, M., McEvoy, N., Winters, S., Mirza, I., Lunney, J. G., Duesberg, G. S. (2014), Investigation of the optical properties of MoS2 thin films using spectroscopic ellipsometry, Applied Physics Letters, 104(10), 103114, DOI 10.1063/1.4868108.

[6] Kar, M. (2010), Error minimization in the envelope method for the determination of optical constants of a thin film, Surface and Interface Analysis, 42(3), 145-150, DO: 10.1002/sia.3188.

[7] D. Poelman, P. F. Smet (2003), Methods for the determination of the optical constants of thin films from single transmission measurements: a critical review, J. Phys. D: Appl. Phys., 36(15), 1850, DOI 10.1088/0022-3727/36/15/316.

[8] A. M. Nasr, A. M. Sadik (2001), Interferometric studies on thin photoactive polymer films, J. Opt. A: Pure Appl. Opt., 3(3), 200, DOI 10.1088/1464-4258/3/3/309.

[9] C. Caliendo, E. Verona, G. Saggio (1977), An integrated optical method for measuring the thickness and refractive index of birefringent thin films, Thin Solid Films, 292(1-2), 255-259, DOI 10.1016/S0040-6090(96)08997-3.

[10] Tauc, J., Grigorovici, R., Vancu, A. (1966), Optical properties and electronic structure of amorphous germanium, physica status solidi (b), 15(2), 627-637, DOI 10.1002/pssb.19660150224 [11] Poruba, A., Fejfar, A., Remeš, Z., Špringer, J., Vaněček, M., Kočka, J., Shah, A. (2000), Optical absorption and light scattering in microcrystalline silicon thin films and solar cells, Journal of Applied Physics, 88(1), 148-160, DOI 10.1063/1.373635.

[12] McNaught, A. D., McNaught, A. D. (1997), Compendium of chemical terminology (Vol. 1669), Oxford: Blackwell Science.

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Biomedical Applications of Hydroxyapatite Based Composites: A Brief Review 1

M.J. Joshi1 1 – Crystal Growth Laboratory, Department of Physics, Saurashtra University, Rajkot, Gujarat, India a – mshilp24@rediffmail.com DOI 10.2412/mmse.66.60.864 provided by Seo4U.link

Keywords: hydroxyapatite (HAP), composites, bio-medical application, bio-activity, curcumin/HAP composite, collagen/HAP composite.

ABSTRACT. Hydroxyapatite, Ca10 (PO4) 6 (OH) 2 or HAP, is a mineral present in bone and tooth enamel, which finds numerous applications in the medical field, bone tissue engineering, implant materials, etc. HAP, being excellent biocompatible mineral with many applications, has attracted many researchers to develop different composites based on it.

There are some popular composites based on HAP gaining applications; for instance, HAP –metal and alloys, HAPpolymer, HAP-protein and collagen, etc. In the present author’s laboratory, HAP-curcumin and HAP-collagen nanocomposites have been synthesized and characterized. The HAP based certain important composites are reviewed from their synthesis, characterization and application point of view.

Introduction. Apatite is a group of several mineral having multidisciplinary interest and application, particularly, in the fields of mineralogy, geology, bio-mineralization, medicine, biomaterials, chemistry, etc. Apatites are represented as A5(BO4)3X, where A represents divalent cations (Ca2+, Pb2+, Ba2+, etc), BO4 represents trivalent anions ( PO43-, VO43-, SiO43-) and X represents mono-valent anions (F¯, Cl¯, Br¯, OH¯, etc). The name apatite originates from a Greek word “apatao” – (αпαταω) means- deceive.

Hydroxyapatite or HAP, Ca5(PO4)3(OH), is usually written as Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two molecules. HAP is a major component in bone and tooth enamel. It composes 70% of bone material in the human body and the rest is organic content which is called collagen [1]. HAP is a popular bio-material for the repair and reconstruction of bone tissue defects.

It is bio-compatible, bio-active, osteo-conductive, non-toxic, non-inflammatory and nonimmunogenic [2]. What is actually occurring inside the apatite structure is quite interesting due to its unique characteristics of ion exchange-ability. On the basis of 2000 carefully peer reviewed journals, Oshida [3] has given wide survey on HAP. Currently, HAP finds popular biomedical applications, such as HAP on titanium medical implants, ultra thin HAP sheets for dental applications, porous HAP for drug delivery, collagen-HAP composite for scaffolds tissue engineering and HAP for bone healing [4]. The structural aspects of fluorapatite, chlorapatite, carbonate apatite as well as hydroxyapatite in stoichiometric and non- stoichiometric forms are discussed by Elliot [5]. Moreover, the bio-ceramic, coatings and dental applications of HAP and other calcium orthophosphates are reviewed by Dorozhkin [6] very recently. HAP and Calcium pyrophosphate (CPP) are important biomaterials; it is worth noting that the review is available on applications of nano CPP [7].

A composite material is made up of two or more constituent materials with different physical or chemical properties and on combining them it produces a material usually with properties different from the individual components. Attempts have been made to develop composites of HAP with polysaccharides, starch, polymer, other organic compounds of natural origin, carbon

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nano-tubes, etc. An attempt is made to give concise review of HAP based bio-composites with recent advances.

Chitosan, a linear polysaccharide (a chain of basic unit carbohydrates) of randomly distributed glucosamine, is used as a bio-pesticide in agriculture and commercially derived from the shells of shrimp, coral, jellyfish and other sea crustaceans. Chitosan indicates strong adsorption interaction with HAP and increases osteo-conductivity, bio-compatibility, tailor-able biodegradability, low immunogenicity and better mechanical properties [8]. However, the recent studies includes, Mg, Zn, Sr and Si doping in nano-composites of HAP/chitosan [9]; composites of HAP/Chitosan/PVA as injectable bone substitute material [10] and porous HAP/Chitosan composites for bone regeneration in calvarial defects [11]. The acetylated chitosan/carbonated HAP composites were prepared by Park and Kim [12] for use as a guided tissue regeneration barrier.

Starch is a carbohydrate consisting of a large number of glucose units joined by glycoside bonds. It is natural bio-degradable, biocompatible, water soluble and inexpensive polymer in comparison to other biodegradable polymers. The polymer functionalization enhances the physico-chemical properties and strengthens the HAP structure, which may be useful for the bone filler material [13, 14].

Collagen is a natural protein available in bone and its composites are widely studied. The biocompabillity of HAP/Collagen/hyaluronic acid composite is reported by Bakos et al. [15]. The effect of mechanical strain and HAP/Collagen composite on the osteogenic differentiation of rat bone marrow derived mesenchymal stem cells (MSC) is reported [16] . The collagen/HAP composite is found to be a reliable molar augmentation [17]. The collagen/HAP composite for hard tissue repair is also studied by several authors as it is having more similarities to the natural bone [18, 19].

Moreover, Ficai et al. [20] reviewed HAP/Collagen composites in detail.

There are several other HAP based composites with novel applications. The HAP was surfacemodified by the addition of β-alanine (β-Ala), followed by the ring-opening polymerization of BLGNCA; a novel inorganic-organic nano-composite is reported by Yukai et al [21]. The cell adhesion of mouse fibroblasts is reported to the surface of novel HAP/fullerenol nano-composites [22]. The nitrogen doped carbon dots-Ag3PO4/HAP composite was prepared to improve visible light photocatalyst activity [23]. Very recently several composites are reported such as, the graphene oxide/HAP composites with improved mechanical properties [24], geopolymer/HAP composite [25], the multi-walled carbon nano tube /HAP composite [26], the HAP-barium titanate piezocomposites with enhanced electrical property [27] and the carbon nanotube-reinforced meso-porous HAP composites for bone replacement material application [28] . There is a high demand to design magnesium alloys with adjustable corrosion rates and suitable mechanical properties. The application of metal matrix composite (MMC) based on magnesium alloys is quite promising. A MMC made of magnesium alloy AZ91D as a matrix and hydroxyapatite (HA) particles as reinforcements have been investigated in vitro for mechanical, corrosive and cytocompatible properties [29].

Thus, the composites of HAP are made with different material with the aim of improving its medicinal properties. A very good review is available on bio-degradable and bio-compatible systems based on HAP with natural and synthetic polymer [30-32] and a well written book is available [20]. There are large varieties of HAP based composites and difficult to review in a precise manner, however, the author hereby attempts to review some important HAP composites synthesized in his laboratory.

Materials and Methods. The HAP can be synthesized with many techniques often using high temperature, high pH and high sonication routes. There are several synthesis methods adopted for HAP nano-composites, however, majority of the composites of HAP are with organic compounds with bio-medical applications and hence the low temperature or room temperature synthesis routs are preferred. The coating or grafting of HAP nano-particles with polymer compatible with the polymer/copolymer matrix is preferred. The polylactide (PLA) is easily grafted on the surface of HAP nano-particles through their surface hydroxyl groups and then incorporated in to poly(l-lactide-coglycolide)(PLGA) matrix to improve its tensile strength and dispersion ability [33]. The HAP nanoMMSE Journal. Open Access www.mmse.xyz

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particles can be embedded in carboxymethylated chitosan matrix using one step co-precipitation method in water [34].The low temperature (̴​̴​̴​̴ 100 0 C) wet1 chemical process is used for fullerenol/HAP nano-composites [35]. The co-precipitation method is used for HAP/Collagen composites [36] and the wet chemical technique is used for gelatine/HAP and chitosan/ HAP composites [37].

Fig. 1. Schematic diagram of the synthesis.

The present author employed surfactant mediated approach to synthesize the HAP/curcumin and HAP/ Collagen composites. Figure 1 describes schematically the process, which is given in detail elsewhere [38, 39]. This technique is quite reliable, inexpensive and easy to synthesize the desired composite. The synthesized nano composites of HAP have been characterized by various techniques.

Result and Discussion. Curcumin is the phytochemical compound of popular Indian spice turmeric (Curcuma Longa Linn), which is a member of the ginger family (zingiberaceae). Turmeric, a common Indian curry spice, also called “Haldi Powder” and “Indian Solid Gold”. Turmeric has shown wide range of therapeutic applications in the traditional Indian medicine [40] (B.B. Aggarwal, C. Sundaram, N. Malani, H. Ichikawa, Curcumin: The Indian Solid Gold, Ch. 1, Charak International (2006)), such as treating wounds, infections and other health problems. Curcumin (1, 7-bis(4hydroxy-3- methoxyphenyl) 1,6-heptadiene-3,5-dione) is bright yellow in color and finds common application for food coloring. The Curcumin/ HAP nano-composites have been extensively characterized by Jogiya et al [39] and the main biomedical findings are summarized hereby. Figure 2 shows the schematic diagram representing the importance of Curcumin/HAP nano-composite. The haemolysis results indicated non-hemolytic nature of the Curumin/HAP nano-composites and safer to use medically. From the antimicrobial study, it was confirmed that all the synthesized samples exhibited inhibiting activity against micro-organisms O. anthropi, P. fluorescens and B. cereus. The inhibition rate was found to be increased with the increasing concentration of the curcumin. The bioactivity study using simulated body fluid (SBF), it was found significantly higher activity in the Curumin/HAP nano-composites than pristine HAP so far as the formation of HAP particles was concerned on the surfaces of the Curcumin/HAP pellets, however, the Curcumin/HAP nanocomposites invited formation of NaCl along with the HAP.

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Fig. 2. The schematic diagram representing the importance of Curcumin/HAP nano-composite.

The HAP/Collagen nano-composites were treated with He+ ion implantation of different fluence rates.

The SBF studies showed improvement in the bio-activity of the implanted samples compared to the pristine one. The enhancement in the bio-activity of implanted Collagen/HAP composite is explained on the basis of electronic loss and electronic interaction through various processes making the surface of the composites charged leading to more surface deposition activity from SBF compared to the pristine one. Moreover, the surface roughness of the implanted samples enhances this [39].

The surface functionalization of nano- particles is an important aspect to study. By surface functionalization using water soluble bio-molecules, it is possible to extend and fine tune the bioactivity of nano- particles. In this regard, the amino acids are ideal candidates for the synthesis of bioinorganic HAP nano particles and bio â&#x20AC;&#x201C; nano composites due to their low cost, intrinsic biocompatibility and ability to interact with HAP surfaces [41,42]. The functionalization of HAP nanoparticles by amino acids has synergetic effects on their structural, morphological and surface properties, for example, the functionalizing HAP with amino acids resulted in to high protein adsorptive capacity [43]. Further, Zhang et al. [43] reported that the hydrophilic arginine with a guanidyl group onto the surface of HAP optimises its gene transfer efficiency. The effects of various amino acids on the particle size and morphology of HAP nano-particles along with their physical characterizations are reported [44-46].

The functionalization of HAP with L-arginine is found to very useful for bio-medical application [47]. The haemolysis ratio decreased with increasing concentration of L-arginine and remained in a category of non-haemolytic grade. The L-arginine functionalized HAP samples were found to be safe for bio-medical use. The DNA binding results showed that all the samples could successfully bind the DNA and the efficacy of DNA binding varied with L-arginine content, which finds further applications in gene therapeutic treatment. The DNA-binding study further suggested that HAP nanoparticles could successfully bind the DNA, suggesting its suitability to be used as vector in gene therapy. The SBF study confirmed good bioactivity of L-arginine functionalized HAP samples compared to the pure-HAP. Summary. Various successful attempts have been made my several researchers to synthesize and characterize various HAP based nano-composites for varieties of biomedical applications. Mainly these are centred to the bio-compatible materials compounds, i.e., collagen, chitosan, polymers, gelatine etc. The Curcumin/HAP exhibits excellent antimicrobial activity, non-haemolytic in nature and bio-activity in SBF study. The Collagen/HAP nano composites with He+ ion implantations exhibits higher bio-activity in SBF study. There is an ample scope for further development of novel HAP based composites for bio-medical application.

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Acknowledgements The author is thankful to Prof. H.H. Joshi, Head, Physics Department, for his keen interest and UGC for SAP DRS and DST for FIST funding and Prof. Vrinda Thakar (Department of Biosciences), Dr. Pawankumar Kulriya(IUAC, New Delhi) and Ms. Bhoomika V. Jogiya for inputs.

References [1] S. Joschek, B. Nies, R. Krotz, A. Gopferich, Biomaterials, 21 (2001), 1645 [2] M. Mucalo, Hydroxyapatite for Biomedical applications, Woodhead Publishing, Cambridge, U.S.A. [3] Y. Oshida, Hydroxyapatite: Synthesis and Applications, Momentum Press, New York, U.S.A., (2014) [4] V. S. Gshalaev and A. C. Demirchan, Hydroxyapatite: Synthesis, Properties and Applications, Nova Science Publisher, New York, U.S.A. (2012) [5] J. C. Elliot, Structure and Chemistry of the Apatites and Other Calcium Orthophosphates, Elsevier, Amsterdam, Netherlands (1994) [6] S. V. Dorozhkin, Hydroxyapatite and other Calcium Orthophosphate: Bioceramic, Coatings and Dental applications, Nova Publishers, New York, U.S.A. (2017) [7] S. R. Vasant, M. J. Joshi, Rev Adv Mater Sci., 48 (2017), 44 [8] J. Venugopal, M. P. Prabhakaran, Y. Zhang , S. Low, A. T. Choon, S. Ramakrishna,Phil Trans R Soc A., 368 (2010), 2065 [9] J. Ran, P. Jiang, G. Sun, M. Za, J. Hu, X. Shen, H. Tong, Mater Chem Frontiers., 1 (2017) 900 [10] F. S. Sugiarti, Charlena, Rasayan J Chem., 10 (2017), 570 [11] D. Zhou, C. Qi, Y. X. Chen, Y. X. Chen, Y. J. Zhou, T. W. Sun, F. Chen, C. Q. Zhang, Int J Nanomed., 12 (2017), 2673 [12] S. M. Park, H. Sung Kim, Macromol Res., 25 (2017), 158 [13] M. S. Sadjadi, M. Meskinfam, H. Jazdarreh, Int J Nano Dim., 1 (2010), 57 [14] M. Meskinfam , M. S. Sadjadi , H. Jazdarreh, World Acad of Sci, Eng and Technol., 6 (2012), 724 [15] D. Bakos, M. Soldan, I. Hermandez-Fuentes, Biomaterials., 20 (1999), 191 [16] Y. Huang, X. Niu, W. Song, C. Guan, Q. Feng, Y. Fan, J Nanomaterials., 16 (2014), 1971 [17] A. D. Augostino, L. Trevisiol, V. Favero, M. J. Gunson, F. Pedica, P. F. Nocini, G. W. Arnett, J Oral and Maxillofacial Surgery., 74 (2016), 1238 [18] D.A. Wahl, J. T. Czernuszka, Eur Cell Mater., 11 (2006), 43 [19] J. Venkatesan, S. K. Kim, J Biomed Nanotechnol., 10 (2014), 3124 [20] A. Ficai, E. Andronesca, G. Voicu, D. Ficai, Advances in Collagen/Hydroxyapatite Composite Materials for Medicine and Nano-technology, Ed. B. Attaf, INTECH, Rijeka, Croatia (2011) [21] Yukai Shan, Y. Qin, Y. Chuan, H. Li, M. Yuan, Molecules., 18 (2013), 13979 [22] A. Djordjevic, N. L. Ignijatovic, G. Bogdanovic, Rakocevic, First Int Conf of Young Chemist Serbia, 19-20 (Belgrade), 2011 [23] Q. Chang, X. Meng, S. L. Hu, F. Zhang, J. L. Yang, RSC Adv., 7 (2017), 30191 [24] Ö. Elif, Ö. Belma and Ş. İlkay, Mater Res Express., 4 (2017), 1

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[25] Saleha, A. Riska, A. Nisa Makmur, F. Ansar, Subaer MATEC Web of Conferences., 97 (2017), 01016 [26] E. Skwarek, Y. Bolbukh, W. Janusz, V. Tertykh, Adsorpt Sci and Tecnol., 35 (2017), 534 [27] M. Prakasham, M. Albino, E. Lebraud, M. Maglione, C. Elisaalde, A. Largeteau, J Am Ceram Soc., 100, (2017), 2621 [28] H. Li, X. Song, B. Li, J. Kang, C. Liang, H. Wang, Z. Yu, Z. Qiao, Mater Sci Eng C Mate Biol Appl., 77, (2017), 1078 [29] F .White, F. Feyerbend, P. Maler, J. Fischer, M. Stormar, C. Blawert, W. Dietzel, N. Hort, Biomaterials, 28 (2007), 2163 [30] N. V. Becerill, L. Tellez-Jurado, L. M. Rodriguez-Lorenzo, J Aust Ceramic Soc 49 (2013), 112 [31] M. Cziko, E.S. Bogya, M. V. Diudea, R. Barabas, Rev. Roum. Chim., 5992014, 353 [32] E.M. Rivera_Munoz, Hydroxyapatite based materials: synthesis and Characterization, in Biomedical Engineering Frontiers and Challenges Ed R. Fazal, Intech,2011 [33] X.F. Song, F.G. Ling, X.S. Chen, Acta. Polym. Sin, 1 (2013) 95 [34] A.S. Barna, G.Giobanu, C. Luca, A.C. Luca, Rev. Chim. 66 (2015) 1618 [35] D. Aleksandar, I. Nenad, S. Mariana, J. Danica, U. Dragan, R. Zlatko, J. Nanosci and Nanotechnol, 13(2013)1 [36] A.B.H. Yoruc, A.K. Aydinoglu, Acta. Physica Polonica A, 127(2015)1264 [37] M. Cziko, E.S. Bogya, R. Barabas, L.Bizo, R. Stefan, cent. Euro J Chem., 11 (2013)1583 [38] B.V. Jogiya, Ph.D. Thesis, Saurashtra University, Rajkot, 2017 [39] B.V. Jogiya, K.Chudasama, V. S. Thakar, M.J. Joshi, Inter J of Appl Ceram Technol., (2017)1 [40] B. B. Aggarwal, C. Sundaram, N. Malani, H. Ichikawa, Curcumin: The Indian Solid Gold, Ch.1, Charak International (2006) [41] A. Vasquez, J. V. Garcia-Ramo, J Bellanato An Quim., 85 (1985) 376 [42] B. Palazzo, D. Walsh, M. Iafisc, E. Foresti, L. Bertinetti, G. Martra, C. L. Bianchi ,G. Cappelletti, N. Roveri, Acta Biomater., 5 (2009) 1241 [43] Zhang Yan-zhon, H. Yan-yan, Z. Jun, Z. Shai-hong, L. Zhi-you, Z. Ke-chao, Nanoscale Res Lett., 6 (2011) 600 [44] W. H. Lee, C. Y. Loo, A. V. Zavgorodny, R. Rohanizadeh, J Biomed Mater Res A., 101 (2011) 873 [45] M. R. Gonzalez, C. J. Y. Chane, E. Vignaud, A. Lebugle, S. Mann, J Mater Chem., 14 (2004) 2277 [46] E. Boanini, M. Fini, M. Gazzano, A. Bigi, Eur J Inorg Chem., 10 (2006) 4821.

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Nonlinear Optical, Mechanical, Electrical, Photoconductivity and Surface Morphology Studies of Thiourea Potassium Hydrogen Phthalate (TKHP) Nonlinear Optical Crystal for Frequency Conversion 1

A. Anbarasi1, S.M. Ravi Kumar2,a, R.Srineevasan2, M. Packiya Raj2 1 – Department of Physics, Periyar Government Arts College, Cuddalore, Tamil Nadu, India 2 – Department of Physics, Government Arts College, Tiruvannamalai, Tamil Nadu, India a – smravi78@rediffmail.com DOI 10.2412/mmse.79.90.69 provided by Seo4U.link

Keywords: NLO crystal, Vickers hardness test, dielectric study, SEM, etching, photoconductivity.

ABSTRACT. A semiorganic nonlinear optical single crystal of thiourea potassium hydrogen phthalate (TKHP), was grown by slow evaporation solution growth technique at room temperature with dimension 13x6x3 mm3 in the period of 25-35 days. The single crystal X-ray diffraction study reveals that the grown crystal is an orthorhombic crystal system.

SHG efficiency of grown crystal was found to be around 1.23 times that of potassium dihydrogen phosphate (KDP) crystal. The microhardness test was conducted on the grown crystal suggests that the crystal has a relatively high mechanical strength. The scanning morphology was analyzed by surface electron microscope (SEM) carried out. The etching study indicates the occurrence of different types of etch pit pattern like terraced rectangle was investigated by microscope. Photoconductivity study confirms that the title compound possesses positive photoconductivity. The dielectric constant and dielectric loss of the compound was measured at different temperature with varying frequencies.

Introduction. The modern trends in material science focusing on non-linear optical (NLO) materials because NLO materials are having more applications in the field of optical communication, laser remote sensing, optical data storage [1-3]. Particularly, semiorganic NLO materials are having the combined properties of organic and inorganic compounds and also high optical nonlinearities, chemical flexibility, high mechanical strength, extended transparency region-down to UV and promising crystal growth characteristics [4]. Particularly, when the organic and inorganic substance mixed together a new material formed called semiorganic material. Those materials are showing very good nonlinear optical property with high mechanical strength and transparency [5-8]. Also, semiorganic NLO materials are attracting by the material scientist due to their applications in the field of optoelectronics and photonics [9-12].

With the great interest of semiorganic materials, we have tried to find a new semiorganic materials.

The literature pointed out that the semiorganic nonlinear optical materials based on thiourea shows excellent nonlinear optical property [13-16]. From the stand-point of the search for newer NLO materials, thiourea offer rich choice. Generally, thiourea is one kind of the simple organic substance with high crystallographic symmetry. The structure of thiourea contains C, N and S atoms and also large dipole moment and an extensive network of hydrogen bonded. As the thiourea ion is a highly versatile ligand that can coordinate to metal through either nitrogen or sulfur usually S bonded to soft and N bonded to hard metal. Beacause of these properties, thiourea can be act as a matrix modifier [17-18]. Therefore, thiourea can coordinate with metal ions and become a non-centrosymmetric material [19]. Non-centrosymmetric is one of the vital properties of the crystal to execute the nonlinear optical property [20].

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The reported articles based on thiourea supporting that the product of thiourea is having great deal of interest [19, 21-26]. The present work is the continuous of the previous work of our group [27] and in this the grown crystal of thiourea potassium hydrogen phthalate (TKHP) was subjected to nonlinear optical, mechanical, dielectric, photoconductivity and surface morphology studies and results are reported. In the grown sample of TKHP has pairing of dipole moment is initiated the bonding energy between acid-base linkage due this condition TKHP execute SHG activity [28-30].

2. Experimental Procedure 2.1 Synthesis The product of TKHP salt was obtained by dissolving thiourea (Merck, AR grade) and potassium hydrogen phthalate (Merck, AR grade) in equimolar ratio at room temperature with Millipore water (18.2 mΩ cm resistivity) as a solvent. The synthesized TKHP salt has been achieved by the following chemical reaction. [(NH2)2SC]

→

+ C8H5KO4

[(C8 H4O3K)∙(NH)(NH2) SC + H2O]

(Thiourea + Potassium hydrogen phthalate →

TKHP crystal)

2.2 Solubility A material to grow as a crystal, determination of its solubility in a particular solvent is an essential criterion because the solubility is the driving force for the rate of crystal growth. The recrystallized synthesized salt was used to measure the solubility of TKHP in Millipore water. A 250 ml capacity glass beaker containing 100 ml of Millipore water was placed in the constant temperature bath. The initial temperature of the bath was set at 30 oC. The synthesized powder sample of TKHP prepared as a solution by a motorized stirrer and it was continuing till the excess salt at the bottom of the beaker completely dissolved. The stirring was further continued, to ensure homogeneous temperature and concentration throughout the entire volume of the solution. After confirming the saturation, the content of the solution was analyzed gravimetrically. A 20 ml of the saturated solution of the sample was withdrawn by means of a warmed pipette and the same was poured into a cleaned, dried and weighed petri dish. The solution was then kept for slow evaporation in a heating mantle till the solvent was completely evaporated. The mass of TKHP in 20 ml of solution was determined by weighing the petri dish with salt and hence the quantity of TKHP salt (in gram) dissolved in 100 ml of water was determined. The solubility of TKHP salt in double distilled water was determined further for five different temperatures (35, 40, 45, 50 and 55 C) by adopting the same procedure. Figure 1 shows the solubility curve of TKHP. The positive slope of the solubility curve of TKHP enables growth by slow evaporation method.

80

Concentration (g / 100 ml )

70

TKHP

60 50 40 30 20 10 30

35

40

45

50

55

o

Temperature ( C)

Fig. 1. Solubility curve of TKHP crystal.

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2.3 Crystal Growth Solution method with slow evaporation technique was implemented to grow crystal of the synthesized TKHP salt. According to solubility data, the saturated solution of TKHP sample was prepared and constantly stirred for about 6 hours using magnetic stirrer. The solution was filtered using whattman filter paper. Then the filtered solution (pH = 5) was poured into a beaker and covered by perforated cover for controlled evaporation. The seed crystals of TKHP were grown within a few days by spontaneous nucleation. After a span of 25-35 days the quality TKHP crystal with dimension 13x6x3 mm3 was harvested. As grown crystal of TKHP crystal is shown in the Figure 2. The optimized growth conditions are presented in the Table 1.

Fig. 2. Photographs of grown crystal TKHP .

Table 1. Optimized Growth conditions.

Techniques

Slow evaporation

Solvent

Millipore water (18.2 mΩ cm resistivity)

Thiourea : potassium hydrogen phthalate

1:1 molar ratio

Chemical Formula

C8 H4O3K)∙(NH)(NH2) SC

pH

5

Period of growth

25 -35 days

Crystal size

13 x6 x 3 mm3

Temperature

Room temperature

3. Results and discussion 3.1 Single Crystal XRD Studies Single crystal X-ray diffraction is a non-destructive technique providing detailed information of the structure of the crystal. Single crystal XRD was carried out by Nonius CAD-4 diffractometer with MoKα (0.71073 Å) radiation, from which we obtain the accurate cell parameters of the grown crystal.

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The unit cell parameters of the TKHP crystal are a=6.439Å; b=9.565Å; c=13.241Å; α = β = γ = 90˚; and the volume is equal to 815.500Å3. From the result TKHP crystal belongs to orthorhombic crystal system.

3.2 NLO study Fine powdered sample of TKHP was subjected to Kurtz and Perry technique for analyzing the nonlinear optical property [31]. As per the principle proposed by the Kurtz and Perry, the magnitude of SHG efficiency was measured for TKHP crystal by illuminating Nd:YAG Quantum laser. The measured amplitude of second harmonic green light of TKHP crystal was 10.8 mJ and 8.8 mJ for KDP crystal. The powder SHG efficiency of TKHP crystal is about 1.23 times of KDP. This enhanced SHG efficiency of grown crystal reveals that the grown TKHP crystals can effectively replace conventional nonlinear optical devices.

3.3 Microhardness study The microhardness study is the well known technique for analyzing the mechanical behavior of the crystal. Therefore, TKHP crystal was subjected to Leitz microhardness tester fitted with diamond pyramidal indenter. The indentations were made at room temperature with a constant indentation time of 10 seconds for all indentations. The diagonal length of the indentation impression was measured using a Leitz metallax II microscope with a calibration ocular at 500 X magnification. Vickers microhardness values were calculated from the relation Hv = 1.8544 P/d2 kg/mm2 where P is the applied load in gram and d is the diagonal length of indented impression in mm. The correlation of hardness number with applied load is shown in the Figure 3. The load was applied from 25 to 100 g and the corresponding hardness number was measured. It is observed from the graph, the hardness number is increases with increasing load. At the value of load 100g, there is a release of internal stress generated locally by an indentation in the crystal due to this cracks was observed on the surface. The interconnection between the load, diagonal length and work hardening coefficient (n) was stated by Meyer’s law (p = adn). The value of n can be measured by drawing the graph between log(p) versus log(d) (Figure 4). From the graph, n was found to be 2.6. According the Onistch, 1.0 ≤ n ≥ 1.6 for hard materials and n > 1.6 for soft materials [32]. Hence, the grown crystal TKHP belongs to soft material.

90

2

Hv (Kg/mm ))

80

70

60

50

40 20

30

40

50

60

70

80

90

100

110

Load P in g

Fig. 3. Variation of Vickers hardness numbers (Hv) with load (P) for TKHP crystal.

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2.0 1.9

Log P

1.8 1.7 1.6 1.5 1.4 1.3 1.60

1.65

1.70

1.75

1.80

1.85

Log d

Fig. 4 Plot of log P vs log d of TKHP crystal.

3.4 Photoconductivity Study The photoconductivity study on TKHP crystal was carried out by connecting sample TKHP in series with a DC power supply and a pico ammeter (Keithley 6485). The details of the experimental set-up used in the present study were reported by Francis P. Xavier et. al. (1999) [33]. The measurements of both dark and photo currents were made at room temperature. The applied voltage was increased in steps and the corresponding dark current (Id) was recorded sample covered by black cloth. The sample was then exposed to the radiation from a 100W halogen lamp. The photo current (Ip) was recorded for the same range of applied voltage. The field dependent dark and photo currents of TKHP crystal is shown in Figure 5. It is observed that both dark and photocurrent increase linearly with the applied voltage and the strength of photo current is found to be greater than that of dark current, which is termed as positive photoconductivity. The positive photoconductivity exhibited by the sample may be due to the increase of charge carriers in the presence of radiation. The increase in mobile charge carriers during positive photoconductivity can be explained by the Stockmann model also, which was reported by Joshi (1990) [34].

0.7 0.6 0.5

Current (nA)

0.4 0.3 0.2 0.1 0.0 -0.1 0

100

200

300

400

500

Field (V/cm)

Fig. 5. Field dependent conductivity of TKHP crystal.

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3.5 Dielectric Study The measurement of dielectric constant and dielectric loss of TKHP crystal was carried out using the instrument, HIOKI 3532-50 LCR HITESTER. The sample TKHP was coated with silver paint on the opposite faces and placed between the two copper electrodes and thus a parallel plate capacitor was formed. Dielectric property is an important study, which gives the nature of atoms, ions, phase change and their polarization. The NLO materials having higher electro-optic and polarization coefficient are suitable for the device fabrications [35]. The dielectric constants of crystal at 308 K, 328 K, 348 K and 368 K were measured at different frequencies and the plots of log frequency vs dielectric constant are illustrated in the Figure 6. The variations of dielectric loss as a function of log frequency are illustrated in Figure 7. The dielectric constant decreases with increase in frequency, which is clearly observed in Figure 6. In high frequency region, both dielectric constant and dielectric loss are fairly remains constant. The high dielectric constant at low frequency is due to better orientation of dipoles in the molecules. With increase in frequency, the dipoles suggested to be oscillated in resonance to oscillating field. Broadly speaking, the graphs exemplify the fact that the dielectric constant and the dielectric loss are both sensitive to frequency as well as temperature. This is a normal dielectric behaviour that both εr and tan(δ) decrease with increasing frequency in the low frequency region [36-37]. This can be understood on the basis that the mechanism of polarization is similar to that of conduction process. The electronic exchange of the number of ions in the crystal gives local displacement of electrons in the direction of the applied field, which in turn gives rise to polarization.

With increase in temperature the dielectric constant decreases as the dipole can acquire thermal energy and deviated from better orientation. The low value of dielectric loss indicates that the TKHP crystals have lesser defects, which is a desirable property for NLO applications.

200

368 K 348 K 328 K 308 K

180

Dielectric Constant

160 140 120 100 80 60 40 20 1

2

3

4

5

6

7

log frequency

Fig. 6. Variation of dielectric constant with log frequency at different temperature of TKHP crystal.

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308 K 328 K 348 K 368 K

4

Dielectric loss

3

2

1

0

1

2

3

4

5

6

7

log frequency

Fig. 7. Variation of dielectric loss with log frequency at different temperature of TKHP crystal.

3.6 Scanning Electron Microscopy Study The surface morphology of TKHP was investigated by using a JEOL JSM-6360 scanning electron microscope (SEM). The Figure 8 shows the SEM image of grown TKHP crystal. It is seen form the SEM picture that the surface of the grown crystal has some clusters with different size. This may due to the inclusion of impurity while the crystal growing.

Fig. 8 SEM Micrograph of TKHP crystal.

3.7 EDAX studies Presence of elements in the grown sample was analyzed by Energy Dispersive Atomic X-ray Fluorescence Spectrometer (EDAX) (Oxford INCA). From EDAX spectrum, it is perceived that the presence of potassium in the grown sample of thiourea potassium hydrogen phthalate. The recorded EDAX spectrum of TKHP crystal is shown in the Figure 9.

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Fig. 9. EDAX spectrum of TKHP crystal.

3.8 Chemical Etching Crystals with lesser defects are most wanted for device fabrications [38]. Growth defects can be easily identified by the chemical etching analysis [39]. The performance and properties of materials are mainly depends on the defects present in the sample. Therefore, analyzing and identifying the defects is most important. Here, the chemical etching was made using water at room temperature. The etched surface was cleaned using good quality filter paper and the inspected immediately using microscope.

The etching study was demonstrated for 10 s and 15 s, and the observed etch patterns are shown in Figure 10, a and 10, b. From the figure, it is observed that there is a smooth surface and rectangle shape etch pits observed on the surface of the sample when etch pattern was taken with in 10s. In the etch pattern for 15 s, there are some rectangle shape etch pits (small size) and also the dark spot is observed. These etch pits due to the chemical impurities and crystal undergoes selective dissolution during growth.

a

b

Fig. 10. (a), (b) Etch pattern of TKHP crystal for 10s and 15s Summary. The titled compound TKHP was grown by solution growth technique and the cell parameters have been confirmed by single crystal XRD. Second harmonic generation efficiency of the grown crystal was found to be 1.23 times than that of KDP. The Vickerâ&#x20AC;&#x2122;s harness test was carried out and which implies that the grown crystal belongs to soft category material. The TKHP sample possesses positive photo-conducting nature. The dielectric constant and dielectric loss were measured with applied field for different temperatures. The presence of potassium was confirmed by EDAX spectrum. The surface morphology and nature of surface were analyzed by SEM and Etching studies.

Acknowledgement. The Corresponding author sincerely thank to Science & Engineering Research Board (SERB) (a statutory body of the Department of Science & Technology, Government of India) for funding research project (NO.EEQ/2016/000451) and also acknowledge Department of Physics, National College, Trichy for providing EDAX and SEM analysis.

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[27] R. Srineevasan, A. Anbarasi, T. Revathi, S.M. Ravi Kumar, Material Chemistry and Physics, 177(2016) 25-30.

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Comparative Study of API 5L X60 and ASTM 572 Gr50 Steel Exposed to Crude Oil and Seawater 1

Marcy Viviana Chiquillo Márquez1,a, Janaína André Cirino1,b,Magda Rosangela Santos Vieira1,c, Severino Leopoldino Urtiga Filho 1, d 1 – Department of Mechanical Engineering - Geosciences Technology Center - University Federal of Pernambuco. Av. Prof. Morais Rego, University City, Recife, Brazil a – marcy.chiquillo@ufpe.br b – janajac5@hotmail.com c – magrsv@hotmail.com d – urtiga@ufpe.br DOI 10.2412/mmse.5.45.904 provided by Seo4U.link

Keywords: HSLA, corrosion, crude oil, seawater, microhardness.

ABSTRACT. In the petroleum industry, the biphasic conditions in storage and separation tanks allow that the material to remain exposed to two different environments, causing its deterioration. In this article, an evaluation is made of the corrosive behavior and Vickers microhardness (HV) of two high strength low alloy (HSLA) steels and how their surfaces are characterized. The ASTM 572 Gr50 steel showed a lower corrosion rate in all systems after being immersed for 720 and 1440 hours. Characterizing the surface by means of Scanning Electron Microscopy (SEM) showed uniform and localized corrosion for the both steels, and revealed that the ASTM 572 Gr50 steel shows pitting corrosion in crude oil systems. The electrochemical results revealed that the corrosion potential of API X60 steel was more negative; however the ASTM 572 Gr50 steel had a higher current density and a lower polarization resistance when immersed in an oil/seawater mixture. It also observed that, after being immersed in the corrosive fluids, the microstructures of the steels were not modified and variations in their microhardness (HV) were minute.

Introduction. The need for excellent mechanical properties such as high resistance, good tenacity and weldability enhances the importance of alloy steel materials, which is why they are extensively used in the automotive industry, and for mining equipment, marine structures, sheet piling, and in daily life [1], [2]. It is a well-known fact that many uses are found for steel which contains small amounts of alloy elements such as Cr, Cu, Ni, Si and P. Such steel alloys develop good resistance to atmospheric corrosion, due to the growth of an adherent layer on the surface of materials [3-5]. In earlier studies, Y. S. Choi et al., [5] observed that elements such as Cr and Cu can produce high or low protective rust layers in aqueous environments also, just as happens when there is atmospheric corrosion. Later, Yanlei Zhou et al., observed that small amounts of elements like Cr, Mo Ni and V can enhance resistance to corrosion [3, 6]. API 5L X60 and ASTM 572 Gr50 steels are considered HSLA steels, and are widely used to manufacture stirrers, offshore platforms, pipelines and storage tanks [1], [7], [8]. The main advantage is their low cost, as compared with other steels; nevertheless, they need to withstand aggressive environments. Hence, they must manifest high resistance to them.

In the petroleum industry, seawater is used to recover fluid from wells. Two phases and one interfacial phase occur when seawater comes into contact with petroleum. The multiphasic corrosion created in the mixture can be considered as one of the major problems for the metallic materials involved in this process. The zone of interface can promote a synergic effect between the oil-seawater phases, which

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can in turn increase bio-corrosion and corrosion when extracting and recovering petroleum and seawater from wells, and when separating and storing petroleum [9-11].

Due to the intensive use of HSLA steels to transport and store fluids, serious problems are faced such as corrosion and the high costs of maintaining and replacing these steels [12]. This study sets out to make a comparative study between two HSLA steels with different chemical compositions, namely, API 5L X60, used in pipelines that transport petroleum, and ASTM 572 Gr50 structural steel, which is used in offshore platforms. Both are evaluated by examining the evolution of corrosion behavior, microhardness and their microstructure after these steels were exposed to seawater, crude oil and an oil/seawater mixture for a period of 1440 hours.

Experimental.

Test specimens. Test specimens made of 40x15x5 mm coupons of API 5L X60 pipeline steel and ASTM 572 Gr 50 steel were fabricated. Their chemical composition is shown in Table 1. The surfaces of the samples were abrasively sandblasted with glass microsphere, followed by cleaning them using ultrasound equipment first with isopropyl alcohol and then with acetone for 5 seconds. Finally the specimens were left to dry [10], [13].

Table 1. Chemical compositions of the API 5L X60 and ASTM 572 Gr50 steels.

Steel

C

Mn

Si

Ni

Cu

Mo

Cr

W

V

Sn

P

S

Al

Nb

Ti

A572 Gr50

0.09

1.13

0.23

0.12

0.21

0.04

0.07

0.005

0.025

0.007

0.006

0.010

0.007

0.003

0.002

API 5L X60

0.21

0.46

0.32

0.005

0.02

0.01

-

-

-

-

0.46

0.022

0.02

0.001

0.024

Simulated Static Corrosion Tests.

Simulated corrosion tests were carried out using fluid statics for 720 and 1440 hours. The specimens were exposed to three different fluids: seawater, crude oil and a mixture of crude oil/seawater. Table 2 shows the fluids used in the study. The weight loss was analysed using an analytic balance. The weight of the steels was measured before and after exposing them to the corrosive environments.

After immersion, the samples underwent a procedure for cleaning after testing based on ASTM G103 (Standard Practice for Preparing, Cleaning, and Evaluating Corrosion Test Specimens).

Hydrochloric acid was used as an etching acid (26 v/v %) and neutralization was accomplished by using sodium hydroxide (10% w/v %).

Table 2. Conditions of the fluids investigated.

Immersion systems API 5L X60 steel

Immersion systems ASTM 572 Gr50 steel

Fluids

SA

SD

Seawater

SB

SE

Crude Oil

SC

SF

Seawater + Crude oil (50% v/v)

Microstructure. After being immersed for 720 and 1440 hours, the samples were cut in cross section and the unexposed faces were sealed with thermoset resin. The working surface was subsequently sanded with 320, 400, 600 and 1200 grit emery papers and polished with 0.3 đ?&#x153;&#x2021;đ?&#x2018;&#x161; diamond paste in the polisher at 250 rpm as set out in ASTM E3-01 (Standard Guide for Preparation of Metallographic MMSE Journal. Open Access www.mmse.xyz

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Specimens). The microstructural analysis was conducted with an Olympus Bx51M Optical Microscope, from which images with magnification to 200X were obtained.

Characterizing microhardness and surfaces.

Microhardness tests were conducted using a microdurometer - INSIZE Auto-Turret Digital Micro Hardness Tester Model ISH-TDV1000-B. The samples were measured after they had been cleaned and their microstructure had been analyzed (see Sections above). A 1 Kgf load was used for the tests for 20 seconds of indentation. The surfaces were characterized by a TM3000 HITACHI TM3000 scanning electron microscope (SEM), to 500X magnification.

Electrochemical experiments.

Material test. Electrochemical tests were performed on the square samples of API 5L X60 and ASTM 572 Gr50 steels. The coupons were soldered to copper wires using tin welding before embedding them individually in epoxy resins and leaving an exposed surface area of 100mm2 as shown in Fig 1.

Before initiating the electrochemical measurements, the surfaces of the specimens were polished using 180, 320, 400, 600 and 1200 sandpaper and polishing with a 0.3đ?&#x153;&#x2021;đ?&#x2018;&#x161; diamond paste. Then they were cleaned with water and ethanol, and finally blow-dried in air.

Fig. 1. Coupons for electrochemical test.

Electrochemical Test. Electrochemical measurements were made on a three-electrode cell, with coupons (Fig. 1) as working electrodes (WE), Ag/AgCl (in saturated KCL) as the reference electrode (RE) and Platinum as a counter electrode in stagnant conditions. An Autolab Potensiostat PGSTAT 302N, operated by Nova 1.11 electrochemistry software, was used to perform the experiments. The open circuit potential (OCP) of the API 5L X60 steel versus that for ASTM 572 Gr50 steel was measured for 24 h. The linear polarization resistance (LPR) was measured by polarizing the specimens from -0.400 V to 0.400 V versus Ag/AgCl with a scanning rate of 0.5 mV/s.

Results and discussions.

Corrosion Rate. Figures 2a and 2b show the evolution of the weight loss and corrosion rate of both steels after 720 and 1440 hours of exposure to fluids. Figs 2a and 2b show that the corrosivity of the seawater is higher than that for the crude oil systems. Note that the SA and SD systems have a greater weight loss and higher corrosion rate when compared to those of the other systems. Wemming et al., and Miao et al., show that the presence of Cl- increases corrosion, thereby generating a greater weight loss in seawater systems. It is a well-known fact that the process of electrochemical corrosion results from the orderly flow of electrons. Hence, in the SB and SE systems, the phenomenon of corrosion is less because the crude oil is highly resistive, thus avoiding any flux and reducing the process of corrosion [7], [14], [15]. The SC and SF systems show high weight loss and a high corrosion rate in comparison with those of the SB and SE systems but less so than those of the SA and SD systems.

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This is expected because the high chloride content in seawater and different compounds in the crude oil can create a synergism that is increasingly aggressive towards the environment [2], [10], [11], [16]. Figure 2a shows a great weight loss in the API X60 steel when it is exposed to all the environments, as was mentioned above. Some elements present in the ASTM 572 Gr 50 steel can generate a layer of corrosion in aqueous environments, which can avoid attacks of corrosion on the environment, thus providing some protection for this steel and causing less weight loss as compared to that for the API X60 steel.

On analyzing the corrosion rate (Fig 2b), we observed a decrease of the values for the systems when the exposure time increases; when the samples are exposed continually to the corrosive environment, they began to corrode and biofilm grew on the surface of the material. This biofilm acts as a physical barrier, thereby hindering contact with the fluid and surface of the material and thus reduces the reaction rate. The samples of API X60 steel in the SA system do not display the same behaviour. In this case, the corrosion rate increases in the interval of immersion between 720 hours to 1440 hours.

This was attributed to the rust layer formed during the immersion process not being sufficiently stable and so it became detached, which led to electrochemical corrosion and hence, the corrosion rate increased. According to the NACE-RP-07-75 (Standard Practice Recommended Preparation, Installation, Analysis and Interpretation Corrosion Coupons in Oilfield Operations), the values of the corrosion rate of both steels are classified as being moderate, except the samples immersed in SB and SE systems which are classified as having low corrosion.

0.12

0.10

WEIGHT LOSS (g)

0.10

CORROSION RATES (mm/year)

API 5L X60 Steel (720 hours) ASTM 572 Gr50 Steel (720 hours) API 5L X60 Steel (1440 hours) ASTM 572 Gr50 Steel (1440 hours)

0.08 0.06 0.04 0.02 0.00

0.08

0.06

0.04

0.02

0.00 SEAWATER 100% CRUDE OIL 100%

CRUDE OIL/ SEAWATER 50% ENVIRONMENT OF EXPOSITION

API 5L X60 Steel (720 hours) ASTM 572 Gr50 Steel (720 hours) API 5L X60 Steel (1440 hours) ASTM 572 Gr50 Steel (1440 hours)

SEAWATER 100% CRUDE OIL 100%

CRUDE OIL/ SEAWATER 50% ENVIRONMENT OF EXPOSITION

b)

a)

Fig. 2. Results of API 5L X60 and ASTM 572 Gr50 steels, (a) Weight loss, (b) Corrosion rate.

Analysis of the microstructure and surface.

The main importance of the systems investigated in this study lies in the fact that they are of great use in the petroleum industry. The conditions of simulated storage tanks were studied as two phases of the fluids and an interface region formed. Fig. 3 shows the surface of the samples after sandblasting, without immersing them in any corrosive fluid. These were considered as a benchmark for comparison with the results after immersion. Fig 4 shows the morphologies of the surface samples after the corrosion product layer had been removed. The surfaces of both the steels, after being immersed for 1440 hours, seem to be more severely attacked when compared with the samples that were immersed for 720 hours. By comparing Fig. 3 and Fig 4 we can observe changes in the surfaces of all systems with the presence of uniform and localized corrosion. However, it is worth noting that although the corrosion rate is moderate or low as discussed previously, more care needs to be taken when localized corrosion is present in order to avoid future accidents. It is evident in all the systems that the presence of localized corrosion highlights the aggressiveness in the fluids of the petroleum industry (seawater and crude oil). The presence of high amounts of chlorides in seawater justifies the MMSE Journal. Open Access www.mmse.xyz

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localized corrosion, but it is also interesting that this mechanism was identified in the samples exposed to crude oil [1], [17], [18]. The existence and performance of microorganisms in metabolite acids can account for why this kind of corrosion arises and why localized attacks (pitting, shallow cavities, alveolar corrosion) occur [16], [19-21].

a)

b)

Fig. 3. SEM of surface samples after sandblasting. [a] API 5L X60 steel, [b] ASTM 572 Gr50 steel.

As Figs. 4a and 4e show, the API X60 steel immersed in the SA system presents alveolar corrosion with small cavities which have a maximum length of 108.0 đ?&#x153;&#x2021;đ?&#x2018;&#x161;. On the other hand, the ASTM 572 Gr50 steel immersed in the SD system has cavities with a maximum length of 86.17 đ?&#x153;&#x2021;đ?&#x2018;&#x161; , thus emphasizing most attacks on API 5L X60 steel exposed to this system have seawater only.

a)

b)

c)

d)

e)

f)

g)

h)

Fig. 4. SEM of surfaces samples after 1440 hours of exposure. [a] SA System, [b] SB System, [c] SC System (Seawater), [d] SC System (crude oil), [e] SD System, [f] SE System, [g] SF System (Seawater), [h] SF System (crude oil).

The systems containing crude oil only (SB and SE) showed localized attacks taking place through small holes with a diameter of 57.45đ?&#x153;&#x2021;đ?&#x2018;&#x161; in the API X60 5L steel. In the same way, holes with a diameter of 40.43 đ?&#x153;&#x2021;đ?&#x2018;&#x161;, can be observed in the ASTM 572 Gr 50 steel, some of which are considered as pitting corrosion as their surface diameters are greater than their depth. From Figs. 4, c, d, g and h, note that the presence of two different fluids in SC and SF systems generates uniform corrosion and MMSE Journal. Open Access www.mmse.xyz

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localized corrosion for both steels, thus highlighting that the zone exposed to the seawater has cavities of greater length and more holes than the zone exposed to the crude oil for the same sample. In accordance with Section of corrosion rate, the API X60 steel shows a higher corrosion rate than that of the ASTM 572 steel in all the fluids to which it was exposed and these micrographics (Fig. 4) enabled it to be corroborated that most attacks were on the surface of this steel.

Fig. 5 shows the microstructural results for the surface section of the API 5L X60 steel and the ASTM 572 Gr50 steel before they were exposed to corrosive environments. Our findings show the typical ferrite-pearlite microstructure of HSLA steels; here the microstructure has darker pearlite regions and lighter ferrite regions [22-24]. As described in Table 3, following the ASTM E112-13 Standard (Test Methods for Determining Average Grain Size), note that there is a greater amount of pearlite in the API 5L X60 steel than in the ASTM 572 Gr50 steel. This is expected because of the amount of carbon in its composition. The alloyed elements such as V, Ti, Nb present in the ASTM 572 Gr 50 steel make the grain more refined than that of the API 5L X60 steel. Note also that the size of the grain and the different types of constituents are some of the principal factors which can influence mechanical properties such as the strength, the ductility and the toughness of steels [6], [24- 26]. Fig. 6 shows the microstructure of the steels after 1440 hours of exposure in seawater. From Fig. 6a we identified that the microstructure of API 5L X60 steel is formed by alternate bands of pro-eutectoid ferrite and pearlite in a matrix predominantly of ferrite; magnification of the micrograph shows that the pearlite is completely resolved with alternate lamellae of ferrite and cementite (Fig. 6, b).

Table 3. Quantification of the phase and grain size of the surface section.

Steel

Compound

API 5L X60

ASTM 572 Gr50

Amount phase

Average size

(%)

(đ?? đ?&#x2019;&#x17D;)

Pearlite

11.308

Ferrite

88.692

Pearlite

9.488

Ferrite

90.512

29.468

18.847

The microstructure of ASTM 572 Gr50 is composed of a ferritic matrix and degenerated pearlite colonies with a lesser amount of cementite (dark) which is generated from the amount of carbon in it and the hot treatment received (Fig 6 c and Fig 6 d). After 1440 hours of exposure, none of the corrosive environments caused significant changes to the microstructures of the steel (intergranular corrosion, grain size, change of phases).

a)

b)

Fig. 5. Microstructure of steels after sandblasting. [a] API 5L X60, [b] ASTM 572 Gr50.

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a)

b)

c)

d)

Fig. 6. Results of the microstructure after 1440 hours of immersion. (a-b) API 5L X60, [c-d] ASTM 572 Gr50.

Microhardness. Fig. 7, a and Fig. 7, b show the results of the Vickers microhardness (HV) test for the API 5L X60 and ASTM 572 Gr50 steels after removal of the rust layer and metallographic preparation. It should be noted that the measurements of HV for the samples of SC and SF systems were made in the zones exposed to crude oil as well as in those exposed to seawater.

To evaluate the behaviour of the microhardness values throughout the process, we took a benchmark which gave values of 148 and 168 (HV1) for X60 and ASTM 572 respectively. Fig. 7a shows values where the ASTM 572 steel has greater microhardness; a high amount of elements such as Cu, Cr, Mo Si and Mn present in the steel, which slightly increased the strength of the ferrite, and also increased resistance to the penetration of steel. In addition, the elements Ti, Nb and V help to refine the grain, which is an effective strengthening mechanism to improve mechanical properties [3], [6], [24], [2729]. After immersion and following metallographic preparation, note that the samples show slight changes in their values as compared to the reference patterns which are normal due to the nonhomogenous microstructure (Fig. 5). The sample pattern after sandblasting has values of 205 and 224 (HV1) for API X60 and ASTM 572 steels, respectively. In Fig 7b, note that these values change slightly after the exposure time; the SA, SB and SC systems have values in the range of 196 to 211 (HV1) while the SD, SE and SF have values in the range of 199 to 227; the change perceived can be attributed to the corrosion suffered by the surface of the samples; ASTM 572 shows values above those for API X60 in proportion to the alloy elements present.

According to Gonzales and Machado, the sandblasting process can produce a change in the microstructure of steel near its surface, thereby generating a change in its microhardness values [30].

On analysing Fig 7a and Fig 7b, note that after sandblasting the microhardness values of the surface in the samples are higher than those obtained after metallographic preparation. This been attributed to the pressure exerted during sandblasting, and after polishing the affected zone is removed showing lower values are found as compared to those from immersion (after sandblasting).

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300

API 5L X60 Steel (720 hours) ASTM 572 Gr50 Steel (720 hours) API 5L X60 Steel (1440 hours) ASTM 572 Gr50 Steel (1440 hours)

250

MICROHARDNESS (HV)

MICROHARDNESS (HV)

250

300

200

150

100

50

API 5L X60 Steel (720 hours) ASTM 572 Gr50 Steel (720 hours) API 5L X60 Steel (1440 hours) ASTM 572 Gr50 Steel (1440 hours)

200

150

100

50

0 SEAWATER 100%

SEAWATER 50%

CRUDE OIL 100%

0

CRUDE OIL 50%

SEAWATER 100%

ZONE EXPOSURED

SEAWATER 50%

CRUDE OIL 100%

CRUDE OIL 50%

ZONE EXPOSURED

a) b)

Fig. 7. Vickers microhardness results, after 720 hours and 1440 hours of immersion (a) metallographic preparation, (b) the removal of the layer rust.

Electrochemical test.

Measurements of Open Circuit Potential (OCP). Electrochemical measurements of Open Circuit Potential (OCP) were made and Potentiodynamic polarization curves were plotted so as to determine đ??¸đ?&#x2018;?đ?&#x2018;&#x153;đ?&#x2018;&#x;đ?&#x2018;&#x; and đ??źđ?&#x2018;?đ?&#x2018;&#x153;đ?&#x2018;&#x;đ?&#x2018;&#x; . Fig. 8 illustrates the evolution of OCP over time for the API X60 and ASTM 572 steel after 24 hours of immersion both in seawater (SA, SD systems) and in a mixture of seawater and crude oil (SC, SF systems). The OCP curves show that at the initial test time a more negative potential value was obtained for the electrolyte from the SC system (-0.621 V/Ag/AgCl); after one hour of exposure, the analyses showed that the potential of the steels increased towards the more negative values from the first moment that the electrode was immersed. This was a result of an oxide film, which had formed on the work electrode surface, dissolving [1], [18], [31], [32].

The open circuit in the first 5h of exposure to the SA and SC systems of the API X60 steel has similar corrosion potential. These results show that the fluid stagnation in the mixture promotes little change in the aggressiveness of these fluids. In addition, from these time values, the behaviour of the potential is relatively stable which is due to the formation of the oxide layer that provided a partial protection for the steel, thus avoiding complete dissolution [1], [18], [31], [33]. For the two systems of ASTM 572 steel, after 8 hours of exposure to the fluids, the following values of constant potential were observed, -0.674 V (Ag/AgCl) and -0.682 V (Ag/AgCl) SD and SF respectively, which makes a small difference between their corrosion potentials. The OCP results indicate that the surface of the API X60 steel is less corrosion resistant than that of ASTM 572 steel over the same conditions; for longer times of exposure (24h), the behaviour of the materials is practically the same in both fluid conditions (seawater and oil/seawater), this being attributed to corrosion deposits forming on their surfaces.

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-0.4 API 5L X60 (100% Seawater) ASTM 572 Gr50 (100% Seawater) API 5L X60 (50% Seawater) ASTM 572 Gr50 (50% Seawater)

E (V, Ag/AgCl)

-0.5

-0.6

-0.7

0

20000

40000

60000

80000

Time (s)

Fig. 8. The OCP measurements for API X60 and ASTM 572 steels.

Potentiodynamic polarization measurements. Fig. 9 depicts the results of Potentiodynamic polarization for both the steels when placed in aerated, stagnant conditions, in seawater and in seawater/crude oil fluids. The values of đ?&#x203A;˝đ?&#x2018;? (cathodic) and đ?&#x203A;˝đ?&#x2018;&#x17D; (anodic) Tafel Slope, the corrosion current density ( đ??˝đ?&#x2018;?đ?&#x2018;&#x153;đ?&#x2018;&#x;đ?&#x2018;&#x; ), polarization resistance ( đ?&#x2018;&#x2026;đ?&#x2018;? ) and corrosion rate (đ??śđ?&#x2018;&#x2026;) obtained from polarization curves are listed in Table 4. The corrosion rate was calculated, as set out in ASTM G102 (Standard Practice for Calculation of Corrosion Rates and Related Information from Electrochemical Measurements), by using Equations 1, 2 and 3: đ??ľ

đ??˝đ?&#x2018;?đ?&#x2018;&#x153;đ?&#x2018;&#x;đ?&#x2018;&#x; = đ?&#x2018;&#x2026;đ?&#x2018;?

(1)

Where, (đ?&#x203A;˝ đ?&#x203A;˝ )

đ?&#x2018;? đ??ľ = 2.3(đ?&#x203A;˝đ?&#x2018;&#x17D; +đ?&#x203A;˝ đ?&#x2018;&#x17D;

đ?&#x2018;?)

(2)

Therefore, the corrosion rate (đ??śđ?&#x2018;&#x2026;) is calculated as: đ??śđ?&#x2018;&#x2026; =

đ??˝đ?&#x2018;?đ?&#x2018;&#x153;đ?&#x2018;&#x;đ?&#x2018;&#x; đ??žđ?&#x2018;&#x160; đ?&#x153;&#x152;đ??´

where đ??ž â&#x20AC;&#x201C; is a constant that defines the units for đ??śđ?&#x2018;&#x2026; (3272 mm/(amp.cm.year)); đ?&#x2018;&#x160; â&#x20AC;&#x201C; is the equivalent grams of steel (27.93gram/equivalent); đ?&#x153;&#x152; â&#x20AC;&#x201C; is the density of Fe (7.86 g/cm2); đ??´ â&#x20AC;&#x201C; is the area of the exposed surface of the electrode work in cm2 ;

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(3)

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It has been reported by several authors that the anodic reactions that occur in steels due to their being exposed to solutions containing chlorides can be described by Equations (5) and (6). The cathodic reactions in steels with or without the presence of oil can be explained by Equation (7) [1], [7], [17], [34-36]. đ??šđ?&#x2018;&#x2019; 2+ â&#x2020;&#x2019; đ??šđ?&#x2018;&#x2019; + 2đ?&#x2018;&#x2019; â&#x2C6;&#x2019;

(5)

đ??šđ?&#x2018;&#x2019; 3+ â&#x2020;&#x2019; đ??šđ?&#x2018;&#x2019; + 3đ?&#x2018;&#x2019; â&#x2C6;&#x2019;

(6)

đ?&#x2018;&#x201A;2 + 2đ??ť2 đ?&#x2018;&#x201A; + 4đ?&#x2018;&#x2019; â&#x2C6;&#x2019; = 4đ?&#x2018;&#x201A;đ??ť â&#x2C6;&#x2019;

(7)

When the surface develops a partially protective oxide layer, which can happen with different possible oxides, this can be described by Equations (8) and (9) 1

đ??šđ?&#x2018;&#x2019; + 2 đ?&#x2018;&#x201A;2 + đ??ť2 đ?&#x2018;&#x201A; â&#x2020;&#x2019; đ??šđ?&#x2018;&#x2019;(đ?&#x2018;&#x201A;đ??ť)2 1

3đ??šđ?&#x2018;&#x2019;(đ?&#x2018;&#x201A;đ??ť)2 + 2 đ?&#x2018;&#x201A;2 â&#x2020;&#x2019; đ??šđ?&#x2018;&#x2019;3 đ?&#x2018;&#x201A;4 + 3đ??ť2 đ?&#x2018;&#x201A;

(8)

(9)

According to Eq. (9), in the presence of aerated conditions the đ??šđ?&#x2018;&#x2019;(đ?&#x2018;&#x201A;đ??ť)2 can generate a rust layer (đ??šđ?&#x2018;&#x2019;3 đ?&#x2018;&#x201A;4 ) which provides partial protection to the surface of the steel, thereby limiting spontaneous degradation. It is worth noting that the rust layer can be dissolved when the potential applied is (positively) increased. Fig. 9 shows the Tafel curves. In general, all the samples exhibit an active behaviour in both electrolyte conditions. Fig. 9 shows that the API X60 steel, in the presence of oil (SF systems), has more positive values of corrosion potential and a higher cathodic current than those of the samples in seawater conditions. This is due the fact that an oily film is formed on the surface that acts as a partial protection for the steel. In addition, the dissolution of oxygen is more favourable in the oil/seawater emulsion. Oil does not contain any polar molecules of hydrocarbons which have better interaction with the oxygen apolar molecules, thus making it difficult to reduce oxygen (Eq. 7).

Zhang and Cheng conducted studies on potentiodynamic polarization for API X65 steel in oil/water emulsion conditions, and found a low cathodic current for the samples exposed to seawater. In our case the API X60 steel presented the same behaviour as in their investigation and ASTM 572 steel showed a higher cathodic current for the sample in the seawater system. The sample submitted to electrolyte constituted by crude oil/ seawater emulsion shows the highest current density (17.6 đ?&#x2018;&#x161;đ?&#x2018;&#x2030;) and the highest corrosion rate values (Table 4). Such behavior may be associated with the material being more susceptible to corrosion pitting which is generated because this fluid is so aggressive, as shown in Fig. 4 (SC and SF systems). The samples exposed to these systems showed corrosion pitting, in addition, to the dissolution of corrosive compounds from the oil phase, mainly to the sulphides typically derived from crude oil. This could cause this electrolyte to be more aggressive for these steels [10], [21], [36].

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0.0

E(V, Ag/AgCl)

-0.2

API 5L X60 STEEL (SEAWATER 100%) API 5L X60 (SEAWATER 50%) ASTM 572 Gr50 (SEAWATER 50%) ASTM 572 Gr50 (SEAWATER 100%)

-0.4 -0.6 -0.8 -1.0 -1.2 1E-7

1E-5

1E-3

0.1

2

Current Density (A/cm )

Fig. 9. Potentiodinamyc polarization results for API X60 and ASTM 572 steels.

Table 4. Parameters obtained from potentiodynamic polarization curves for SA, SC, SD and SF systems đ??¸đ??śđ?&#x2018;&#x201A;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;

đ?&#x2018;&#x2014;đ??śđ?&#x2018;&#x201A;đ?&#x2018;&#x2026;đ?&#x2018;&#x2026;

đ?&#x203A;˝đ?&#x2018;&#x17D;

đ?&#x203A;˝đ?&#x2018;?

đ??śđ?&#x2018;&#x2026;

(đ?&#x2018;&#x161;đ?&#x2018;&#x2030;)

(đ?&#x2018;&#x161;đ?&#x2018;&#x2030;)

(đ?&#x2018;&#x161;đ?&#x2018;&#x2030;â &#x201E;đ?&#x2018;&#x2018;đ?&#x2018;&#x2019;đ?&#x2018;?)

(đ?&#x2018;&#x161;đ?&#x2018;&#x2030;â &#x201E;đ?&#x2018;&#x2018;đ?&#x2018;&#x2019;đ?&#x2018;? )

(đ?&#x2018;&#x161;đ?&#x2018;&#x161;đ?&#x2018;Ś â&#x2C6;&#x2019;1 )

API X60 (Seawater 100%)

-705.7

4.66

82

380

0.050

API X60 (Seawater 50%)

-682.9

4.20

100

300

0.049

ASTM 572 (Seawater 100%)

-548.0

1.12

59

96

0.013

ASTM 572 (Seawater 50%)

-625.4

17.6

80

250

0.204

Sample

The potentiodynamic polarization curves evidence the increase of the anodic current density corresponding to the increase in the potential values for both steels, where the SD system (crude oil/seawater mixture) has a higher đ??¸đ?&#x2018;?đ?&#x2018;&#x153;đ?&#x2018;&#x;đ?&#x2018;&#x; compared with that of the SF system. It can corroborated that API X60 steel is more susceptible to the corrosion process than ASTM 572 steel which is less affected; despite the presence of the pearlite, the micro-constituent is more stable. It is worth mentioning that Fig. 5 shows that it is the microstructure of API X60 steel which has the greatest amount of pearlite along with ferrite present. This allows many more micro-chemical cells to be created resulting in more active sites that enhance corrosion.

By comparing the electrochemical results of SA and SD systems with the results obtained by gravimetric tests for the samples exposed to seawater, the corrosion rate for the 60 days of exposure shows that the values so obtained are different for the two methods. In the gravimetric test, the sample will be subjected to continuous changes in the surface of the material during the exposure time, thus generating more weight loss, and therefore the corrosion rate is modified (Fig. 2). While in linear polarization, an accelerated result is obtained from the test, this would not be exactly the actual exposure condition, since a potential difference is being established in the material. Another important factor worth mentioning is that this may have influenced the difference in the corrosion rate obtained for the different types of test. While in the weight loss tests, the parts were exposed to the corrosive medium after the abrasive blasting, the samples submitted to the Polarization test were submitted to the metallographic preparation procedure at the polishing stage.

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Summary. This article examined the corrosive behavior of API 5L X60 and ASTM 572 Gr 50 steels when exposed to seawater and crude oil by means of gravimetric, electrochemical, microhardness and surface characterisation. After 1440 hours of immersion, the corrosion rate of the ASTM 572 Gr50 steel was less than that of the API 5L X60 steel in the fluids. We conclude that the samples have a higher corrosion rate when immersed in seawater systems (SA and SD). The SB and SE systems show less weight loss due to the high resistivity of crude oil, and thus avoid accelerated corrosion.

But it should be noted that the samples have, nevertheless, suffered corrosion. According to NACERP-07-75, the corrosion rate for the steels obtained in this study is classified as moderate except the samples immersed in the SB and SE systems, which are classified as having a low corrosion rate. The corrosion process has no effect on the microhardness results after and before the immersion process, thereby highlighting that the ASTM 572 Gr50 steel has a higher value of Vickers microhardness than API 5L X60. This happened due to the alloys present. Characterization of the surface shows uniform and localized corrosion for both steels where it is observed that the ASTM 572 Gr50 steel is more susceptible to a pitting attack among all the systems studied. The electrochemical behaviour of different fluids for the steels was different, which showed that the ASTM 572 Gr50 steel has more current density when exposed to oil/seawater than API X60. Thus, less polarization resistance was seen in the SF system. The ASTM 572 steel showed less current density in the seawater systems.

Thus, these samples have the highest polarization resistance among all the systems, thus making this steel less susceptible to corrosion.

Acknowledgements This work was supported by CAPES, UFPE, FINEP, CNTM and the Laboratory of Composite Materials and Structural Integrity of the Department of Mechanical Engineering, Federal University of Pernambuco.

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[10] M. R. Vieira, Ph.D. Thesis, University Federal of Pernambuco, Brasil, 2013.

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[17] R. O. Rihan, Material Research. 2013, 16, 227 .

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[18] A. Rauf, E. Mahdi, International Journal of Electrochemical Science. 2012, 7, 5692.

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Synthesis of Nanosilver Doped Water Soluble Macromolecules: an Investigation from Antimicrobial Coating Perspective 1

C. Kavitha1, a, V.Gowsalya1

1 – Department of Chemistry. Adhiyaman Arts & Science College for Women, Uthangarai, Krishnagiri, Tamil Nadu, India a – kavithac1506@gmail.com DOI 10.2412/mmse.69.31.853 provided by Seo4U.link

Keywords: nanosilver, coating application, HBPE, antimicrobial application.

ABSTRACT. A novel macromolcule polymer with aromatic/aliphatic structure was synthesized by polycondensation method and was found to be a suitable scaffold for the preparation of nanosilver. The polymer was prepared via A2+B3 approach using triethanol amine as a core molecule and benzene 1, 4 dicarboxylic acid as a chain extender. A fine distribution of spherical and stable nanosilver was obtained in the HBPE by reductive technique and analyzed using XRD and UV. The antimicrobial activity of silver nanoparticle/polymer was tested against E. coli and S. aureus.

Introduction. Metal nanoparticles have received tremendous interest due to their unique optical, catalytic activity, electronic properties, antimicrobial activities, magnetic properties etc [1]. They are widely used for different application such as in medicine, electronics, biomaterials, energy production etc. The unique properties of metal nanoparticles are dependent on their particle size, shape and size distribution [2, 3]. An excellent control on these factors can be achieved by proper synthesis methodology. It is possible to taylor the final morphology of the product by choosing the right processing technique. Physical template methodologies in nanometal preparation is well known.

Solution phase methods are widely adopted and involves the application of a soft template for the production of nanomaterials for which the HBP’s are used widely [4, 5]. HBP’s are highly branched macromolecule with three dimensional dendritic architecture. They are characterized by low viscosity, high solubility, reactivity and good compatibility with other materials. The fact that HBP’s can be prepared by one pot reaction more rapidly and economically even on larger scales is increasing its popularity. These high network structures when used as template, metal cations will be localized before reduction leading to stabilized metal nanoparticle [6].

Macromolecules are characterized by good thermal, mechanical and chemical properties. Polyester can be synthesized from easily available and inexpensive raw materials have prompted many research groups to investigate Polyester in details. All aliphatic Polyester and all aromatic Polyester are reported by many researches [7]. The aromatic HBPE are brittle and have high Tg meanwhile the aliphatic HBPE have low Tg and there by less brittleness. However not much work exists on aliphatic/aromatic Polyester via A2+B3 method. However a few patents related to such works can be seen in patents. These aliphatic aromatic Polyester are expected to have moderate molecular weight and Tg and hence suitable for applications in coatings and resin formulations [8-10].

Silver nanoparticles have unique biological, electrical and thermal properties and are incorporated into products that range from photovoltaic’s to biological and chemical sensors. Examples include conductive inks, pastes and fillers which utilize silver nanoparticles for their high electrical conductivity, stability and low sintering temperatures. Additional applications include molecular diagnostics and photonic devices, which takes advantage of the novel optical properties of these 11

© 2018 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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nanomaterials [11]. Another increasingly common application of silver nanoparticles is for antimicrobial application in textiles, keyboard, wound dressings, biomedical devices etc. The new trend in coating technology is silver nanoparticles that continuously release a low level of silver ions to provide protection against bacteria. In particular, silver ions have long been known to exert strong inhibitory and bactericidal effects as well as to possess a broad spectrum of antimicrobial activities.

It is reported that the bacterial plasma or cytoplasmic membrane, which is associated with many important enzymes and DNA, is an important target site of silver ions [12,13]. Once bacterial growth gets inhibited, silver ions deposit into the vacuole and cell walls as granules. They inhibited cell division and damaged the cell envelope and cellular contents of the bacteria [14].

In the present work, hydroxy-terminated Polyester with aromatic/aliphatic structure were synthesized by polycondensation of triethanol amine as a core molecule and benzene 1,4 dicarboxylic acid as a chain extender. Triethanol amine is used as a core in many of HBPE’s synthesis by AB2 method [15, 16]. Still no work is reported on the use of this molecule in A2+B3 method. Silver nanoparticles were prepared by reductive technique using NaBH4. The antimicrobial activity of silver nanoparticle/ Polyester was tested against E. coli, a gram negative bacterium and S. aureus, a gram positive bacterium.

Experimental. Benzene 1,4 dicarboxylic acids, dimethyl sulfoxide (DMSO), were procured from SD Fine Chemicals. Triethanol amine was procured from Aldrich Chemicals. p-TSA was purchased from Rankem Chemicals. The reagents were of research grade and were distilled before use. Nutrient broth and nutrient agar were from Difco Laboratories, Detroit, 82 MI, USA. Water was purified by using the Milli-Q system (>18M Ώ cm, Millipore).

Methods. Synthesis of Macromolecule.

Polyester was synthesized by melt polycondensation at 120 °C of triethanol amine and benzene 1,4 dicarboxylic acid. The monomers were reacted in 1:1 ratio for 7 hours in a 500 mL four necked flask equipped with N2 inlet, a magnetic stirrer and a drying tube. The reactant mixture was slowly heated and then maintained at 120°C for 7 hours to complete the reaction. The reaction was monitored periodically by checking the acid value of the sample using the titration method and stopped when the acid value was not varied.

Synthesis of silver nanoparticles by reductive technique. Silver nanoparticles in polymer templates were prepared in a two-step process. 3g of Polyester dissolved in 8 mL of DMSO with constant stirring. 2 mL solution of 0.4g of AgNO3 in water was added drop wise with vigorous stirring at room temperature followed by 2 ml solution of 0.2g of NaBH4. The colour of solution turned to deep brown towards the end.

Characterization. FTIR spectra of Polyester were carried out over a wave range of 450-4000cm-1 using JASCO 400 infrared spectrometer. 1H NMR and 13C NMR spectra of Polyester were recorded on a Bruker (400MHz) NMR spectrometer at room temperature using DMSO as the solvent and trimethylsilane as the internal standard. Tetrahydrofuran was used as the eluent and the flow rate was kept at 1mL/min. The absorption spectrum of nanosilver was obtained in ethanol medium using UV visible spectroscope of HITACHI U – 2800 spectrophotometer. . Molecular weight of HBPE was determined using GPC of make, Water-515 referenced with polyethylene as standards. The synthesized samples were analysed for their phase purity by powder X-ray diffractometer of make BRUKER (Germany, D8 Advance diffract meter). The size of the nanosilver particle (2ө=38º) was estimated using Scherrer’s equation 1.

D = 0.9λ/βcosө Where D – crystallite size in nm; λ – radiation wavelength (0.1546 nm for Cu Kα); MMSE Journal. Open Access www.mmse.xyz

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β – band width at half-height; Ө – diffraction peak angle.

Preparation of culture media The culture media was prepared by dissolving 1.3 g of broth powder in 100 mL water. It was sterilized by autoclaving at 15 lbs pressure at 121°C for 15 min. Then it was cooled in a laminar hood, which was disinfected before hand by cleaning thoroughly with absolute alcohol followed by UV irradiation for 20 min. A disinfect wire loop size stock microorganism was transferred in to the cold medium under laminar flow. After transferring the cultured microorganism, the conical flask was replugged and kept in an incubator oven for 24 h at 37 °C. Antimicrobial activity. 3.7 g of nutrient agar powder was dissolved in 100 mL water. The agar solution was sterilized as mentioned above and poured in to petridishes and cooled for sufficient time to solidify the agar medium. 2 mL of the above culture broth was swabbed uniformly in to individual plates using sterile L-rod. Wells of 5 mm diameter were made on nutrient agar plates using sterilized crock borer. Three different samples – silver nitrate/ Polyester nanosilver/ Polyester and pure Polyester were used for analysis. Silver nitrate/ Polyester was prepared as mentioned in the synthesis of nanosilver. Nanosilver/ Polyester is taken for analysis after reducing this solution. Polyester is prepared by dissolving the polymer in DMSO. Using sterile micropipette, 20µlts of these samples were poured on to each of the wells in all the plates. The plates were kept for incubation at 37 ºC for 24 hours.

Results and discussion. Synthesis and characterization of Polyester Both of the two monomer and in the present synthesis are commercially available and their properties are very suitable for preparing polyester used in coatings. As an ordinary dibasic acid, the esterification difficulty degree of benzene 1, 4 dicarboxylic acid is situated between terephthalic acid and phthalic acid. However, polyesters formed from benzene 1, 4 dicarboxylic acid have good chemical stability, mechanical properties, and thermal deformation (Zhang 2010). The synthesis of Polyester from AB2 type monomer is well known. However, most of the AB2- type monomers are unavailable commercially, they are either expensive or have to be synthesized prior to polymerization (). Hence, alternative route based on easily available A2+B3 monomers is preferred for synthesizing Polyester .

The A2+B3 monomer in Polyester synthesis helps in better control over possible premature polycondensation due to much higher shelf life of the monomers. In order to increase the probability that unreacted acid groups reacted with hydroxyl functionality of Polymer skeleton and not with another free monomer, the ratio of benzene 1, 4 dicarboxylic acid was kept as low as possible. The reaction was maintained at relatively low temperature, 120°C, with an optimised time reaction to minimize unwanted side reactions and to avoid gelation. The ester bond was formed from the reaction of COOH of benzene 1, 3 dicarboxylic acid with OH group of triethanol amine. It is well known that direct polycondensation of A2 and B3 monomers generally results in gelation (17). Thus, the crucial problem of this approach is to avoid gelation, and obtain soluble three dimensional macromolecules. The monomer ratio is maintained as 1:1 in the present case. Since theoretically when the ratio of A2 to B3 is 1:1 or less than 1:1, the terminal groups are exclusively B groups.

FTIR analysis. Fig. 1 shows the FTIR spectra of core, chain extender and Polyester. The FTIR spectrum of tri ethanol amine shows an absorption band of 3342 cm-1 due to the presence of the hydroxy group and peak at 2881 cm-1 is due to CH2 stretching. The peak at 1040 cm-1 is due to C-N stretching.

The FTIR spectrum of benzene 1,3 dicarboxylic acid shows an absorptions band at 1691 cm-1 due to the presence of C=O groups and sharp peak at 2881 cm-1 due to the CH stretching group as well as a peak at 732 cm-1 is due to the presence of the aromatic group. The peaks around 1724 cm-1 corresponding to the carbonyl group of ester indicate the formation of Polyester. The peak at 3151 cm- 1 corresponding to carboxylic acid groups and the peaks at 3381 cm-1 could be attributed to the absorptions from hydroxy groups. The stretching of C-O-R is seen at 1183 cm-1 as well as a peak at 732 cm- 1 is due to the presence of the aromatic group. These data indicate that the polymers contain hydroxy MMSE Journal. Open Access www.mmse.xyz

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groups, ester bonds, carboxylic OH and benzene groups, which were in agreement with objective polymers.

Fig. 1. FTIR Spectrum monomer and Polyester.

NMR Analysis. The structures of the synthesized polymers are confirmed by 1HNMR and 13CNMR spectrometry. The 1HNMR spectrum of the core molecule, chain extender and Polyester are shown in Fig. 2. In the 1HNMR spectrum of Polyester (Fig. 2), proton signals for aromatic rings are observed at 7.72-8.3 ppm, CH2COO at 4.43 ppm and proton signals for methylene groups at 2.23-3.35 ppm.

These spectral data support production of the expected Polyester.

Current Data Parameters NAME nmrdata EXPNO 1 PROCNO 1 F2 - Acquisition Parameters Date_ 20121220 Time 12.24 INSTRUM spect PROBHD 5 mm PABBO BB/ PULPROG zg30 TD 65536 SOLVENT DMSO NS 16 DS 2 SWH 8223.685 Hz FIDRES 0.125483 Hz AQ 3.9845889 sec RG 98.85 DW 60.800 usec DE 6.50 usec TE 295.8 K D1 1.00000000 sec TD0 1 ======== CHANNEL f1 ======== NUC1 1H P1 14.25 usec PLW1 14.00000000 W SFO1 400.2604718 MHz F2 - Processing parameters SI 65536 SF 400.2580018 MHz WDW EM SSB 0 LB 0.30 Hz GB 0 PC 1.00

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

-1

-2

ppm

1

Fig. 2. HNMR spectrum of Polyester.

The presence of peak at δ= 150 - 165 ppm of 13CNMR spectrum (Fig. 3) indicates the carbon atoms present in the ester units, peaks at δ= 125 - 145 ppm is due to the aromatic carbons of benzene ring.

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The determination of degree of branching (DB) of the hyperbranched polymers is very important when it comes to synthesis of nanometals. The degree of branching is calculated using Frey equation (2).

Current Data Parameters NAME PD40313 EXPNO 4 PROCNO 1 F2 - Acquisition Parameters Date_ 20130307 Time 14.13 INSTRUM spect PROBHD 5 mm PABBO BB/ PULPROG zgpg30 TD 65536 SOLVENT CDCl3 NS 1024 DS 4 SWH 24038.461 Hz FIDRES 0.366798 Hz AQ 1.3631488 sec RG 199.6 DW 20.800 usec DE 6.50 usec TE 297.4 K D1 2.00000000 sec D11 0.03000000 sec TD0 1 ======== CHANNEL f1 ======== NUC1 13C P1 9.80 usec PLW1 58.00000000 W SFO1 100.6550182 MHz ======== CHANNEL f2 ======== CPDPRG[2 waltz16 NUC2 1H PCPD2 90.00 usec PLW2 14.00000000 W PLW12 0.35097000 W PLW13 0.28428999 W SFO2 400.2596010 MHz F2 - Processing parameters SI 32768 SF 100.6449540 MHz WDW EM SSB 0 LB 1.00 Hz GB 0 PC 1.40

200

180

160

140

120

100

80

60

40

20

0

ppm

Fig. 3. 13CNMR Spectrum of Polyester đ??ˇđ??ľ = 2đ??ˇ/(2đ??ˇ + đ??ż)

(2)

Where D and L refer to the number of dendritic, and linear units in the structure of the polymer, respectively.

It is worth noting that the Frey equation, which has been established for polymers prepared from AB2type monomers, does not really apply for A2+B3 type hyperbranched polymers. Since there is no ready way to determine the DB of A2+B3 type polymers, a number of authors still use it (18). The percentage of dendritic and linear units present in aromatic/aliphatic HBPEs was calculated from the integral area ratios of aromatic and ester carbon zone of 13CNMR spectra. Degree of branching is observed to be 0.46 in the present case.

Other properties. The solubility of polyester was investigated as 0.01g of polymeric sample in 2 mL of solvent. The polymer was found to be highly soluble in several organic polar solvent such as THF, DMSO and several alcohols due to its highly polar nature resulting from large number of hydroxyl end groups. However it exhibits poor solubility in most of the non-polar solvents.

Nanosilver/ Polyester. Silver nanoparticles were formed by the reduction of Ag+ in to Ag0 using Polyester as scaffold. Due to the highly branched structure of the Polyester, the silver ions gets well dispersed in the matrix before reduction. This results in well dispersed nanosilver in Polyester on reduction. During the synthesis the silver nitrate solution turned in to dark brownish colour indicating the formation of silver nanoparticles. An intense band is obtained in the UV-Visible spectrum at 421 nm (Fig. 4).

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60 C

Abs 2.0 A b s o r b a n c e

1.5 1.0 0.5

400

500

600

700

800

Wave length (nm)

nm

Fig. 4. UV

spectrum of nanosilver/ Polyester.

Fig. 5 illustrates a typical X-diffaratogram of the silver nanoparticles showing four prominent peak at 2ө values of about 38.3°, 44.3°, 64.3° and 77°, which is well in agreement with the literature values of silver nanoparticles (Monti et al., 2004). These peaks are indexed to the (111) (200) (220) and (311) planes representing Braggs reflections for face-centered cube (FCC) symmetry of silver. The particle sizes of silver nanoparticles were calculated using Scherrer equation and the average value was found to be around 13.4 nm.

800

(111)

700

Intensity (a.u)

600 500 400

(200)

300 200

(220) (311)

100 0 20

30

40

50

60

70

2(degree)

Fig. 5. XRD spectrum of nanosilver/ Polyester.

Antimicrobial activity in silver nanoparticles

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The antibacterial efficacy of nanosilver/ Polyester against microbes was tested based on zone of inhibition tests. Fig. 6 (a) and (b) details the relative retention of activity (zone of inhibition) of nanosilver/ Polyester against Gram positive bacteria (S. aureus) and Gram negative bacteria (E. coli). After 24 hours of incubation, the zones of inhibition of nanosilver/ Polyester against E. coli was observed to be 12 mm. In the case of S. aureus, the zone of inhibition was found to be 11 mm. These were much higher than the zone of inhibition of silver nitrate/HBPE against E. Coli (7 mm) and S. Aureus (8 mm). Surface area involves the increase of contact surface, which is an important condition for the effects of silver nanoparticles. Though the mode of action of nano silver and Ag+ were similar, the effective concentration of nano silver and Ag+ ions were at nanomolar and micromolar levels respectively (19-26]. This may be the reason for the better antibacterial property of nano silver compared to silver ions i.e., silver nitrate/ Polyester. Similar trend has been reported by many researchers [27-30].

Silver nitrate/ Polyester

Polyest er

Nanosilver/Polyester

a) Silver nitrate/ Polyester

Polyester

Nanosilver/Polyester

b) Fig. 5. The zone of inhibition of the samples (a) E.coli bacteria (b) S.aureus bacteria.

Summary. Novel aromatic/aliphatic Polyester with good branching was successfully synthesized from benzene 1, 4 dicarboxylic acid and tri ethanol amine via A2+B3 approach. Silver nanoparticles

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were prepared using these Polyester A well dispersion of globular nanometals were obtained in Polyester. FTIR spectra indicated that interaction between silver nanoparticles and aliphatic/aromatic Polyester play a crucial role on the stability of silver nanoparticles. The fabricated silvernano/ Polyester was evaluated as an antimicrobial agent and showed good efficacy against S.aureus and E.coli.

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[2] Shahverdi, A.R., Fakhimi, A., Shahverdi, H.R., & Minaian,S. (2007). Synthesis and effect of silver nanoparticles on the antibacterial activity of different antibiotics against Staphylococcus aureus and Escherichia coli. Nanomedicine, 3, 168-71. DOI 10.1016/j.nano.2007.02.001.

[3] Baker, C., Pradhan, A., Pakstis, L., Pochan, D.J., & Shah, S.I. (2005). Synthesis and Antibacterial Properties of Silver Nanoparticles. Journalof Nanoscience and Nanotechnology, 5,244–249. DOI 10.1166/jnn.2005.034.

[4] Zhu, Z., Kai, L. & Wang, Y.(2006). Synthesis and Applications of Hyperbranched Polyesters Preparation and Characterization of Crystalline Silver Nanoparticles. Materials Chemistryand Physics, 96, 447–453. DOI 10.1016/J.MATCHEMPHYS.2005.07.067.

[5] Sun, R., Zhao, H., Luo, Y., & Liu, Y. (2011). Methoxy Carbonyl- Terminated Hyperbranched Poly (amine ester) as Templates for Synthesis of Silver Nanoparticles. Journal of Nanopartical Research, 13,1133–1138. DOI 10.1007/s11051-010-0105-1.

[6] Voit, B. (2000) New Developments in Hyperbranched Polymers. Journal of Polymer Science Part A: Polymer Chemistry, 38, 2505–2525. DOI: 10.1002/1099-0518(20000715.

[7] Yates, C.R & Hayes, W. (2004). Synthesis and applications of hyperbranched polymer, European Polymer Journal, 40, 1257–1281. DOI 10.1016/J.EURPOLYMJ.2004.02.007.

[8] Zhang, X. (2010). Synthesis and characterization of hyperbranched polyesters based on isophthalic acid and trimethylolpropane. Journal Macromolecular Science Part A: Pure. Applied Chemistry, 48, 128-134. DOI 10.1080/10601325.2011.537505.

[9] Xiuxia ,W., Lai, G., Jiang, Z., & Zhang, Y. (2006). Synthesis of water soluble HBPs and its application in acrylates.

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DOI 10.1016/j.eurpolymj.2005.08.001 [10] Cheng, K.C., Chuang, T.H., Tsai, T.H., Guo, W. & Su, W.F. (2008) Model of hyperbranched polymers formed by monomers A2 and Bg with wnd-capping molecules. European Polymer Journal, 44, 2998-3004. DOI 10.1016/J.EURPOLYMJ.2008.06.019.

[11] Mahapatra, S.S. & Karak, S.N. (2008). Silver nanoparticle in hyperbranched polyamine: Synthesis, characterization and antibacterial activity. Materials Chemistry and Physics, 112, 11141119. DOI 10.1016/J.MATCHEMPHYS.2008.07.047.

[12] Liu, S., Wei, L. & Hao, L.(2009). Sharper and faster Nano darts kill more bacteria: a study of antibacterial activity of individually dispersed pristine single-walled carbon nanotube. ACS Nano,3, 3891–3902. DOI: 10.1021/nn901252r.

[13] Rayman, M.K., Lo, T.C., & Sanwal, B.D. (1972). Transport of succinate in Escherichia coli. II. Characteristics of uptake and energy coupling with transport in membrane preparations. Journal of Biological Chemistry, 247, 6332–6339.

[14] Schreurs, W.J. & Rosenberg, H. (1982). Effect of silver ions on transport and retention of phosphate by Escherichia coli. Journal of Bacteriology, 152, 7-13.

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[15] Goswami, A. & Singh, A.K(2004). Hyperbranched Polyester Having Nitrogen Core: Synthesis and Applications as Metal Ion Extractant. Reactive and Functional Polymer, 61, 255–263 . DOI 10.1016/J.REACTFUNCTPOLYM.2004.06.006.

[16] Kavitha C. & Priya Dasan, K.(2013). Hyperbranched polyester based on 2,2,'2” nitrilotriethanol Synthesis and characterisation. Chimica oggi/Chemistry Today, 31, 46-49.

[17] Malmstrom, E., Johansson, M. & Hult, A. (1995). Hyperbranched aliphatic polyester.

Macromolecules, 28, 1698-1703. DOI 10.1021/ma00109a049.

[18] Voit, B.I. & Leader, A.(2009). Hyperbranched and highly branched polymer. Chemical Review, 109, 5924-73. DOI: 10.1021/cr900068q.

[19] Gao, C., & Yan D. (2004). Hyperbranched polymers: from synthesis to applications. Progress in Polymer Science, 29, 183-275. DOI 10.1016/j.progpolymsci.2003.12.002.

[20] Maruyama, K., Kudo, H., Ikehara,T., Ito, N. & Nishikubo, T. (2005). Synthesis of photocrosslinkable hyperbranched polyesters and their film properties. Journal of Polymer Science Polymer Chemistry, 43, 4642-4653. DOI 10.1002/pola.20957.

[21] Murali, M. & Samui, A. B. (2006). Photoactive, liquid-crystalline, hyperbranched benzylidene polyesters: Synthesis and characterization. Journal of Polymer Science Part A: Polymer Chemistry, 44, pp. 53–61. DOI 10.1002/pola.21118.

[22] Komber, H., Voit, B., Monticelli, O. & Russo, S. (2001). H-1 and C-13 NMR spectra of a hyperbranched aromatic polyamide from p-phenylenediamine and trimesic acid. Macromolecules, 34, 5487-5493. DOI 10.1021/ma002223f.

[23]Uhrich, K.E., Hawker, C., Frechet, J.M.J. & Turner, S.R. (1992). One-pot synthesis of hyperbranched polyethers. Macromolecules, 25, 4583–7. DOI 10.1021/ma00044a019.

[24] Monti, O. L. A., Fourkas, J. T., & Nesbitt, D. J. (2004). Diffraction-limited photogeneration and characterization of silver nanoparticles. Journal of Physics and Chemistry B, 108, 1604–1612. DOI 10.1021/jp030492c.

[25] Konwar U., Karak N. & Mandal, M. (2010). Vegetable oil based highly branched polyester/clay silver nanocomposites as antimicrobial surface coating materials. Progress Organic Coating, 8, 265273. DOI 10.1016/j.porgcoat.2010.04.001.

[26] Russell, A.D., & Hugo, WB. (1994). Antimicrobial Activity and Action of Silver. Progress in Medicinal Chemistry, 31, 351–370.

[27] Lok, C.N., Ho, C.M., Chen, R., He, Q.Y., Yu, W.Y., Sun, H., Tam, P.K.H., Chiu, J.F., &Che, C.M.(2006). Proteomic Analysis of the Mode of Antibacterial Action of Silver Nanoparticles. Journal of Proteome Research, 5, 916–924. DOI 10.1021/pr0504079.

[28] Morones, J.R., Elechiguerra, J.L., Camacho, J.A., Holt, K., Kouri, J., Ramirez, J.T. & Yacaman, M.J. (2005). The bactericidal effect of silver nanoparticles. Nanotechnology, 16, 2346-2353. DOI 10.1088/0957-4484/16/10/059.

[29] Dibrov, P., Dzioba, J., Gosink, K. K. & Hase, C.C. (2002). Chemiosmotic mechanism of antimicrobial activity of Ag+ in Vibrio cholera. Antismicrobial Agents. Chemotherapy, 46, 26682670. DOI 10.1128/AAC.46.8.2668-2670.2002.

[30] Panacek, A., Kvitek, L., Prucek, R., Kolar, M., Vecerova, R., Pizurova, N., Sharma, V.K., Nevecna, T.J. & Zboril, R. (2006). Silver colloid nanoparticles: synthesis, characterization, and their antibacterial activity. Journal of Physics and Chemistry B, 110, 16248-16253. DOI 10.1021/jp063826h

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II. Mechanical Engineering & Physics M M S E J o u r n a l V o l .

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Part 1. Numerical Integration over a Family of Quadrilateral Elements for Elliptic Partial Differential Equations by Galerkin Finite Element Method 1

K. T. Shivaram1, G. Manjula1, K. Lakshminarayanchari2 1 â&#x20AC;&#x201C; Department of Mathematics, Dayananda Sagar College of Engineering, Bangalore, Karnataka, India 2 â&#x20AC;&#x201C; Department of Mathematics, Sai Vidya Institute of Technology, Rajanukunte, Bangalore, Karnataka, India a â&#x20AC;&#x201C; shivaramktshiv@gmail.com DOI 10.2412/mmse.70.58.771 provided by Seo4U.link

Keywords: mesh generation, explicit integration, PDE, square, parabolic arc.

ABSTRACT. A finite element approach for solving elliptic partial differential equations over curved and rectangular domains are presented by domain discretisation method and discretised into family of linear quadrilateral elements. The performances of the method is illustrated with numerical examples.

Note. 2010 Mathematical Subject Classification: 65M50

Introduction. The problem considered in this paper is the numerical solution of Poisson equation đ?&#x203A;ť 2 â&#x2C6;&#x2026; = đ?&#x2018;&#x201C;(đ?&#x2018;Ľ, đ?&#x2018;Ś) in đ??ś1

(1)

Subject to boundary condition â&#x2C6;&#x2026; = 0 on đ?&#x153;&#x2022;đ??ś1 Where đ??ś1 â&#x20AC;&#x201C; region of the domain; đ?&#x153;&#x2022;đ??ś1 â&#x20AC;&#x201C; is the boundary region.

In general â&#x2C6;&#x2026;(đ?&#x2018;Ľ, đ?&#x2018;Ś), is represented as displacement of a membrane and đ?&#x2018;&#x201C;(đ?&#x2018;Ľ, đ?&#x2018;Ś) as external force, In heat transfer problem â&#x2C6;&#x2026;(đ?&#x2018;Ľ, đ?&#x2018;Ś) is represented as temperature of a plate and đ?&#x2018;&#x201C;(đ?&#x2018;Ľ, đ?&#x2018;Ś) as external heat source, and in fluid flow problem â&#x2C6;&#x2026;(đ?&#x2018;Ľ, đ?&#x2018;Ś) represents a potential function.

Numerical solution of eqn. (1) in triangle, rectangular, square domain are discussed in [1-4], numerical solution of elliptical partial differential equations by recursive subdivision method are carried out in [5], two dimensional elliptical partial differential are computationally approximated by finite element and finite difference method in irregular and regular domain [6], solving elliptical partial differential equations in curved boundaries by using higher order curved triangle elements in [7]. In this paper, to generate a quadrilateral mesh in regular and irregular domain and approximate the elliptical partial differential equation by Galerkin weighted residual finite element method Quadrilateral mesh generation.

11

Š 2018 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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Quadrilateral mesh generation is based on triangle mesh generator, every triangle is discretised into three quadrilaterals, centroid of triangle is joins with midpoint of its sides, finally generate a quadrilateral meshes in regular and irregular polygonal domain.

Mesh 1

Mesh 2

Mesh 3

Mesh 4

Mesh 5

Mesh 6

Fig. 1. Quadrilateral mesh generation.

Formulation of integrals over quadrilateral elements.

Numerical integration of arbitrary function over quadrilateral element is of the form

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1

𝐼 = ∫−1 ∫−1 𝑓(𝑥(𝜉, 𝜂), 𝑦(𝜉, 𝜂)) 𝐽 𝑑𝜉 𝑑𝜂

(2)

An arbitrary four noded quadrilateral element is mapped into 2-square region. The transformation from (x, y) plane to (𝜉, 𝜂) is given by (𝑦𝑥 ) = ∑4𝑘=1 (𝑦𝑥𝑘 ) 𝑁𝑘 (𝜉, 𝜂) 𝑘

(3)

Where 𝑁𝑘 (𝜉, 𝜂) – be the shape function of quadrilateral element and 1

𝑁𝑘 (𝜉, 𝜂) = 4 (1 + 𝜉𝑘 𝜉)(1 + 𝜂𝑘 𝜂)

(4)

Where ( (𝜉𝑘 , 𝜂𝑘 ), 𝑘 = 1,2,3,4) = ((-1,-1),(1,-1),(1,1),(-1,1)) From the eqn.(3) and eqn.(4), we have

𝜕𝑥 𝜕𝜉 𝜕𝑥 𝜕𝜂 𝜕𝑦 𝜕𝜉 𝜕𝑦 𝜕𝜂

= ∑4𝑘=1 𝑥𝑘

𝜕𝑁𝑘

= ∑4𝑘=1 𝑥𝑘

𝜕𝑁𝑘

𝜕𝜉

𝜕𝜂

= ∑4𝑘=1 𝑦𝑘

𝜕𝑁𝑘

= ∑4𝑘=1 𝑦𝑘

𝜕𝑁𝑘

𝜕𝜉

𝜕𝜂

1

= 4 [(− 𝑥1 + 𝑥2 + 𝑥3 − 𝑥4 ) + (𝑥1 − 𝑥2 + 𝑥3 − 𝑥4 ) 𝜂] 1

= 4 [(− 𝑥1 − 𝑥2 + 𝑥3 + 𝑥4 ) + (𝑥1 − 𝑥2 + 𝑥3 − 𝑥4 ) 𝜉] 1

= 4 [ (−𝑦1 + 𝑦2 + 𝑦3 − 𝑦4 ) + (𝑦1 − 𝑦2 + 𝑦3 − 𝑦4 ) 𝜂 ] =

1 4

[ (−𝑦1 − 𝑦2 + 𝑦3 + 𝑦4 ) + (𝑦1 − 𝑦2 + 𝑦3 − 𝑦4 ) 𝜉 ]

𝜕(𝑥,𝑦)

𝜕𝑥 𝜕𝑦

𝐽 = 𝜕(𝜉,𝜂) = 𝜕𝜉

𝜕𝜂

𝜕𝑥 𝜕𝑦

− 𝜕𝜂

𝜕𝜉

= 𝛼 + 𝛽𝜉 + 𝛾 𝜂

Where 1

𝛼 = 8 [( 𝑥4 − 𝑥2 )(𝑦1 − 𝑦3 ) + (𝑥3 − 𝑥1 )(𝑦4 − 𝑦2 )] 1

𝛽 = 8 [( 𝑥4 − 𝑥3 )(𝑦2 − 𝑦1 ) + (𝑥1 − 𝑥2 )(𝑦4 − 𝑦3 )] 𝛾=

1 8

[( 𝑥4 − 𝑥1 )(𝑦2 − 𝑦3 ) + (𝑥3 − 𝑥2 )(𝑦4 − 𝑦1 )]

Then equation (3) reduces to

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(5)

Mechanics, Materials Science & Engineering, Vol. 15 2018 â&#x20AC;&#x201C; ISSN 2412-5954 1

1

đ?&#x2018;&#x203A; đ??ź = â&#x2C6;Ťâ&#x2C6;&#x2019;1 â&#x2C6;Ťâ&#x2C6;&#x2019;1 đ?&#x2018;&#x201C;(đ?&#x2018;Ľ(đ?&#x153;&#x2030;, đ?&#x153;&#x201A;), đ?&#x2018;Ś(đ?&#x153;&#x2030;, đ?&#x153;&#x201A;)) đ??˝ đ?&#x2018;&#x2018;đ?&#x153;&#x2030; đ?&#x2018;&#x2018;đ?&#x153;&#x201A; = â&#x2C6;&#x2018;đ?&#x2018;&#x161; đ?&#x2018;&#x2013;=1 â&#x2C6;&#x2018;đ?&#x2018;&#x2014;=1 đ?&#x2018;&#x201C; (đ?&#x2018;Ľ(đ?&#x153;&#x2030;đ?&#x2018;&#x2013; , đ?&#x153;&#x201A;đ?&#x2018;&#x2014; ), đ?&#x2018;Ś(đ?&#x153;&#x2030;đ?&#x2018;&#x2013; , đ?&#x153;&#x201A;đ?&#x2018;&#x2014; )) Ă&#x2014; đ??˝ Ă&#x2014; đ?&#x2018;¤đ?&#x2018;&#x2013; Ă&#x2014; đ?&#x2018;¤đ?&#x2018;&#x2014; (6)

Where đ?&#x153;&#x2030;đ?&#x2018;&#x2013; , đ?&#x153;&#x201A;đ?&#x2018;&#x2014; â&#x20AC;&#x201C; are sampling points; đ?&#x2018;¤đ?&#x2018;&#x2013; , đ?&#x2018;¤đ?&#x2018;&#x2014; â&#x20AC;&#x201C; are corresponding weights are calculated of order N=5 by using Gauss Legendre quadrature rule Finite Element formulation in regular and irregular geometry Using Galerkin weighted residual finite element method. The numerical solution of eqn.(1) as expressed as [đ??ž]đ?&#x2018;&#x20AC; Ă&#x2014; đ?&#x2018;&#x20AC; {đ?&#x2018;&#x2C6;}đ?&#x2018;&#x20AC;Ă&#x2014;1 = {đ??š}đ?&#x2018;&#x20AC;Ă&#x2014;1

(7)

Where đ??žđ?&#x2018;&#x2013;,đ?&#x2018;&#x2014; = â&#x2C6;Źđ??ś 1

1

đ?&#x153;&#x2022;đ?&#x2018; đ?&#x153;&#x2022;đ?&#x2018; đ?&#x2018;&#x2014;

1 đ?&#x2018;&#x153;đ?&#x2018;&#x; đ??ś2

đ?&#x153;&#x2022;đ?&#x2018; đ?&#x2018;&#x2013; đ?&#x153;&#x2022;đ?&#x2018;Ł

đ??žđ?&#x2018;˘,đ?&#x2018;˘ = â&#x2C6;Ťâ&#x2C6;&#x2019;1 â&#x2C6;Ťâ&#x2C6;&#x2019;1 ( 1

đ?&#x153;&#x2022;đ?&#x153;&#x2030; đ?&#x153;&#x2022;đ?&#x153;&#x201A;

( đ?&#x153;&#x2022;đ?&#x2018;˘đ?&#x2018;&#x2013; +

đ?&#x153;&#x2022;đ?&#x2018;˘

đ?&#x153;&#x2022;đ?&#x2018; đ?&#x2018;&#x2013; đ?&#x153;&#x2022;đ?&#x2018;Ł đ?&#x153;&#x2022;đ?&#x153;&#x201A; đ?&#x153;&#x2022;đ?&#x153;&#x2030;

+

đ?&#x153;&#x2022;đ?&#x2018; đ?&#x2018;&#x2013; đ?&#x153;&#x2022;đ?&#x2018; đ?&#x2018;&#x2014; đ?&#x153;&#x2022;đ?&#x2018;Ł đ?&#x153;&#x2022;đ?&#x2018;Ł

) đ?&#x2018;&#x2018;đ?&#x2018;Ľ đ?&#x2018;&#x2018;đ?&#x2018;Ś = đ??žđ?&#x2018;˘,đ?&#x2018;˘ + đ??žđ?&#x2018;Ł,đ?&#x2018;Ł

đ?&#x153;&#x2022;đ?&#x2018; đ?&#x2018;&#x2014; đ?&#x153;&#x2022;đ?&#x2018;Ł

)â&#x2C6;&#x2014; (

đ?&#x153;&#x2022;đ?&#x153;&#x2030; đ?&#x153;&#x2022;đ?&#x153;&#x201A;

+

(8)

đ?&#x153;&#x2022;đ?&#x2018; đ?&#x2018;&#x2014; đ?&#x153;&#x2022;đ?&#x2018;Ł 1 đ?&#x153;&#x2022;đ?&#x153;&#x201A; đ?&#x153;&#x2022;đ?&#x153;&#x2030;

) đ?&#x2018;&#x2018;đ?&#x153;&#x2030; đ?&#x2018;&#x2018;đ?&#x153;&#x201A; đ??˝

1

đ?&#x153;&#x2022;đ?&#x2018; đ?&#x2018;&#x2014; đ?&#x153;&#x2022;đ?&#x2018;˘ đ?&#x153;&#x2022;đ?&#x2018; đ?&#x2018;&#x2014; đ?&#x153;&#x2022;đ?&#x2018;˘ 1 đ?&#x153;&#x2022;đ?&#x2018; đ?&#x2018;&#x2013; đ?&#x153;&#x2022;đ?&#x2018;˘ đ?&#x153;&#x2022;đ?&#x2018; đ?&#x2018;&#x2013; đ?&#x153;&#x2022;đ?&#x2018;˘ đ??žđ?&#x2018;Ł,đ?&#x2018;Ł = â&#x2C6;Ť â&#x2C6;Ť ( + )â&#x2C6;&#x2014; ( + ) dđ?&#x153;&#x2030; dđ?&#x153;&#x201A; đ?&#x153;&#x2022;đ?&#x153;&#x2030; đ?&#x153;&#x2022;đ?&#x153;&#x201A; đ?&#x153;&#x2022;đ?&#x153;&#x201A; đ?&#x153;&#x2022;đ?&#x153;&#x2030; đ?&#x153;&#x2022;đ?&#x153;&#x2030; đ?&#x153;&#x2022;đ?&#x153;&#x201A; đ?&#x153;&#x2022;đ?&#x153;&#x201A; đ?&#x153;&#x2022;đ?&#x153;&#x2030; đ??˝ â&#x2C6;&#x2019;1 â&#x2C6;&#x2019;1

1

1

đ??šđ?&#x2018;&#x2013; = â&#x2C6;Ťâ&#x2C6;&#x2019;1 â&#x2C6;Ťâ&#x2C6;&#x2019;1 đ?&#x2018;&#x201C;(đ?&#x2018;˘(đ?&#x153;&#x2030;, đ?&#x153;&#x201A;), đ?&#x2018;Ł(đ?&#x153;&#x2030;, đ?&#x153;&#x201A;)) đ??˝ đ?&#x2018; đ?&#x2018;&#x2013; (đ?&#x153;&#x2030;, đ?&#x153;&#x201A;) đ?&#x2018;&#x2018;đ?&#x153;&#x2030; đ?&#x2018;&#x2018;đ?&#x153;&#x201A;

(9)

Numerical examples Consider the Poisson equation đ?&#x203A;ť 2 â&#x2C6;&#x2026; = đ?&#x2018;&#x201C;(đ?&#x2018;Ľ, đ?&#x2018;Ś) đ?&#x153;&#x2022;â&#x2C6;&#x2026;

If đ?&#x2018;&#x201C;(đ?&#x2018;Ľ, đ?&#x2018;Ś) = â&#x2C6;&#x2019;2, subject to the boundary condition â&#x2C6;&#x2026; = 0 on the line đ?&#x2018;Ľ = 1 and đ?&#x2018;Ś = 1, đ?&#x153;&#x2022;đ?&#x2018;Ľ = 0 on the đ?&#x153;&#x2022;â&#x2C6;&#x2026;

line đ?&#x2018;Ľ = 0, đ?&#x153;&#x2022;đ?&#x2018;Ś = 0 on the line đ?&#x2018;Ś = 0 where C1 is the region bounded by đ?&#x153;&#x2022;đ??ś1 as shown in Figure 1, a.

If đ?&#x2018;&#x201C;(đ?&#x2018;Ľ, đ?&#x2018;Ś) = â&#x2C6;&#x2019;10(2đ?&#x2018;Ľ â&#x2C6;&#x2019; 8đ?&#x2018;Ś â&#x2C6;&#x2019; 10đ?&#x2018;Ľ 2 + 12đ?&#x2018;Ľđ?&#x2018;Ś â&#x2C6;&#x2019; 10đ?&#x2018;Ś 2 + 12đ?&#x2018;Ľ 3 + 60đ?&#x2018;Ľđ?&#x2018;Ś 2 + 12đ?&#x2018;Ś 3 â&#x2C6;&#x2019; 36đ?&#x2018;Ľ 3 đ?&#x2018;Ś â&#x2C6;&#x2019; 36đ?&#x2018;Ľđ?&#x2018;Ś 3 Subject to the boundary condition â&#x2C6;&#x2026; = 0, where C2 is the region bounded by đ?&#x153;&#x2022;đ??ś2 as shown in Figure 2, b.

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a)

b)

Fig. 2. Schematic of physical configuration. a) Square region, b) Region with parabolic arc.

Integrals of Eq. 3, a-c are calculated for each quadrilateral elements by Gauss Legendre quadrature rule and assembling is performed to add the effect of all quadrilateral elements into account with boundary condition, finding all unknown of u in eq. [7] and these are contour plotted in Fig. 3, a-b

a)

b)

Fig. 3. Contour plot of stress function â&#x2C6;&#x2026; (x, y)in the region C1 and C2 Mesh -1 and Mesh -5.

Summary. A numerical solution of linear partial differential equation in regular and curved parabolic are presented by domain discretization method in order to increase the quadrilaterals to get better approximate solution comparing with triangle mesh.

Reference [1] O. C. Zienkiewicz, R.L. Taylor and J.Z. Zhu (2005), The Finite Element Method: Its Basis and Fundamentals, 6th ed., Elsevier, Oxford.

[2] M. A. Bhatti (2005), Fundamental Finite Element Analysis and Applications, John Wiley and Sons, Inc., New York.

[3] J. N. Reddy (2005), An Introduction to the Finite Element Method, 3rd ed., Tata McGraw-Hill.

[4] H.T. Rathod, Md. Shajedul Karim (2002), An Explicit Integration Scheme Based on Recursion for the Curved Triangular Finite Elements, Comput. Struct., vol. 80, 43- 76.

[5] Ribbens and J. Calvin (1987), A Fast Grid Adaption Scheme for Elliptic Partial Differential Equations, Computer Science Technical Reports. Paper 589.

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[6] G. Papanikos, Maria, G. Koutita (2015), A Computational Study with Finite Element Method and Finite Difference Method for 2D Elliptic Partial Differentialm Equations, Applied Mathematics, 2104-2124.

[7] K. V. Nagaraja, V. Kesavulu naidu, P. G. Siddheshwar (2014), Optimal Sub parametric Finite Elements for Elliptic Partial Di_erential Equations Using Higher-Order Curved Triangular Elements, International Journal for Computational Methods in Engineering Science and Mechanics, 15, 83-100.

[8] G. Manjula, K.T. Shivaram and N.G. Vignesham Finite element mesh generation for complex geometry, Journal of Mathematical and Computational science, vol.5, 943-952, 2016 [9] K.T. Shivaram and A.M. Yogitha (2016), Numerical Integration of Arbitrary Functions over a Convex and non convex polygonal domain by quadrature method, Journal of Mathematical and Computational Science, 6, 1177-1186.

[10] K.T. Shivaram (2013), Generalised Gaussian Quadrature rules over an arbitrary tetrahedron in Euclidean three dimensional space, International Journal of Applied Engineering Research, 13, 15331538 [11] K.T. Shivaram, H.T. Prakasha (2016), Numerical integration of Highly oscillating functions using quadrature method, Global Journal of Pure and Applied Mathematics, 12, 2683- 2690

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Innovative Approach for Preparation of Skilled Engineers 1

K.A. Ziborov, T.O. Pismenkova, S.O. Fedoriachenko, A.V. Merkulova, I.K. Ziborov 1 – National Mining University, Ukraine, Dnipro DOI 10.2412/mmse.57.30.812 provided by Seo4U.link

Keywords: artistic and aesthetic abilities engineer designer, more competence, training content design engineer.

ABSTRACT. The purpose of the work is to reveal the content of the professional competencies of the modern engineerdesigner in the aspect of artistic and aesthetic abilities. The acquisition of which should be foreseen in the formation of educational programs for the training of applicants for higher education in the engineering field, as a condition for the preparation of a competitive specialist. The paper proposes the basics of designing mechanisms and machines, the educational program of training engineers specializing in "Industrial Aesthetics and Certification of Industrial Equipment" in the specialty "Materials Science" allows preparing specialists who have not only the necessary knowledge of the engineer-designer, but also know how to develop this technology. Create an artistic image of industrial products of a diverse range.

Introduction. The modern educational paradigm is based on a life-long learning strategy. This is due to the rapid development of society. In geometric progression the volume of information increases, technologies are improved, new professions appeared.

The national economy demands from the higher school the solution of new tasks - the correspondence of high school graduates with the challenges of the government requirements [1].

National Mining University today has a leading position in Ukraine in terms of training specialists in engineering specialties. The training of specialists in NMU takes into account the requirements of the industries and is carried out on the basis of a competent approach.

The purpose of the work is to reveal the content of the professional competencies of the modern engineer-designer in the aspect of artistic and aesthetic abilities. The acquisition of which should be foreseen in the formation of educational programs for the training of applicants for higher education in the engineering field, as a condition for the preparation of a competitive specialist.

As one should know, designing is the creative process of creating an optimal variant of a machine in documents based on theoretical calculations, design, technological and operational experience.

Construction of machines is carried out in several stages, established by state standards. For unit production it is: • Development of a technical task and a technical proposal; • Development of a sketch project; • Development of a technical project; • Development of a working project.

Today, all these stages of creating a new industrial design is impossible to imagine without the stage of artistic design, which ensures not only high reliability, efficiency and product quality, but also the aesthetic appearance of the subject of design.

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The overall successful design result depends on the knowledge of the methods by which you can create not only a functional, but also an attractive thing. At the final stage engineer should be acting like a designer to demonstrate the developed product for the consumer in the realistic environment in order to be positively esteemed by the potential final customer. Therefore, to acquire a high school skills of an industrial designer will enable him not only to become a competent specialist in the creation of a new product, but also to increase his competitiveness in the labor market.

When creating a new sample of any machine-building product, spatial representations play an important role, which should accumulate and develop throughout the applicant's training period. Spatial representations are inherent in any person, but in the design engineer, they must be developed for a broader, more detailed vision of the end product result with the peculiarities of its functioning. Images of memory should preserve the shape, size, material, color and texture of a large number of surrounding objects and means of labor, machines and mechanisms. At the same time, it is equally important to associate spatial characteristics with the conditions and place of exploitation of these objects (mechanisms and machines).

Such disciplines as descriptive geometry, engineering and computer graphics, the theory of mechanisms and machines, parts of machines were and still are the basis of engineering training. Today, the content of disciplines allows you to form a future specialist engineering competence as a basis for his professional activities. After receiving the appropriate training, it is possible to carry out in the future in the professional activity any tasks, including tasks related to the aesthetic component of the projected product.

Industrial design is closely linked to 3D modeling, which made it easier to create concepts and prototypes. Visualization of variants of products helps to preview the industrial design, and in the prototype to identify possible disadvantages.

In order to create a product sketch, industrial design involves not only artistic and analytical activities, but also number of graphic applications: AutoCAD, Compass, 3D Studio Max, SolidWorks, Pro/Engineer, as well as programs for automation of industrial design and CAD programs develop product visualisation.

Creation of functional and ergonomic objects, aesthetical appearance of the product, increased energy and resource conservation in the production and use of the object, the design of safe and the environmentally friendly forms, creating intuitively easy to use equipment - all these criteria of the new product demand from modern engineer not only professional skills, but also a broad imagination and a subtle aesthetic vision. In addition, it must be taken into account that the finished product must meet the needs of a specific target audience.

For example, in 2017, the Mini-Electric Halo City assembly scooter (Figure 1) became the winner of the Red Dot Design Awards in the Design-Concept nomination.

Having analyzed the product, its components - the system of forming elements, it is possible to establish a list of competencies necessary for its creation.

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Fig. 1. Design concept of Halo City mini electric assembly scooter.

The system of assembly of "lever type" - the task of structural synthesis of mechanisms for the theory of mechanisms and machines - that allows you to quickly and compactly collect a scooter, moving in a assembled form in a car or, if necessary, in any public transport.

Magnesium alloy, carbon fiber, high-quality composite materials - the task of materials science and technology of structural materials - not only that reduce the weight of the scooter, ensuring its durability, but also suitable for reuse, which is favorable for environmental sustainability.

Ecologically pure lithium battery, intelligent battery management system, high-speed brushless motor, sinusoidal controller, - tasks in the field of electric drive and automation and control of technological processes.

Intelligent modules that allow you to display information related to current traffic flows, track the vehicle's location in real time from anywhere with gadgets, using theft protection feature, etc.

Two years of research and development, 98% of original details, 13 national patents - an example of creating a modern product of industrial design, in accordance with the developed concept [2].

As you can see, industrial design, as a kind of activity, includes not only elements of art, mechanics and technology. It covers a wide range of issues, from the choice of aesthetic models to high-tech, high-tech calculations. Intellectual property rights to objects developed within the framework of industrial design must be protected by a patent for an invention. After all, plagiarism in our time is not uncommon for a long time. And creating inventions, including, offering its new properties, improves not only functional qualities, but also external dignity, you need to be sure that no one steals your idea.

All competencies required to create a modern functional product are provided by educational programs in higher education.

Today, when constructing (in the framework of educational programs) and new and well-known (with the stereotyped forms) of the machine-building products, students of the department on the basis of designing mechanisms and machines are included, including, in addition to the classical tasks of training engineer-mechanics and tasks of artistic and aesthetic perfection created product.

It is precisely within the framework of the professional component of the educational program in the specialty "Materials Science" specialization "Industrial Aesthetics and Certification of Industrial Equipment" by the staff of the Department of Fundamentals of Designing Mechanisms and Machines of the State Higher Educational Institution "National Mining University" a series of academic disciplines is proposed: Computer Technologies in Designing, Artistic Designing and Virtual simulation of equipment, Hybrid modeling in CAD systems, Industrial art and design, Ergonomics and technical aesthetics, Fundamentals of creating a company Metrology and Standardization, Production Equipment Certification, Organization and Testing Technology, Qualimetry and Quality MMSE Journal. Open Access www.mmse.xyz

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Management, which complement and distribute the learning outcomes received in the first year [3].

It allows not only to form future specialists with additional competencies of the modern engineerdesigner, in the aspect of artistic and aesthetic abilities, but also to master modern tools that will protect their own intellectual development.

For example, let consider the task of creating a steering wheel of a car. As you know, the steering wheel is used in most modern terrestrial vehicles, including all mass production vehicles, light and heavy trucks. Steering wheel is part of a control system directly influenced by the driver [4].

From the moment of its appearance in the device, the steering wheel changed significantly: the diameter, angle of inclination, the thickness of the rim and the number of knitting needles, the number of revolutions from the stop to the stop. Improved ways to transfer effort from steering wheel to wheel, appeared hydrologic booster, and then - and electric actuator drive. The main principle of driving a car still unchanged the steering wheel is rotating. Moreover, paying attention to engineering management issues, the majority of automanufactures left the design of the steering wheel at the backstages.

At present, design requirements related to the safety and ease of management (Fig. 2, a), the maximum viewing area of the instrument panel through the steering wheel (Fig. 2, b) remain unchanged.

However, do not forget to appeal to the feelings of the future customer, to his/her emotional response [5].

a)

b)

Fig. 2. Different position of the driver's hands while driving.

Therefore, within the framework of the set conditions, the student solves the problem of design, but the classical sequence of stages (see above), while being modified (Fig. 3). Initially, the stage of the artistic design analysis of existing solutions is carried out, then the stage of artistic and design synthesis and only then the design of the product directly.

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Fig. 3. Stages of the artistic and design process.

Almost all stages are carried out using computer simulation tools in a virtual environment. The objects of virtual reality are not subject to the laws of the physical world, open to direct intervention of designer. The most important quality of the created models is their artistic expressiveness, which is determined by the infinite variety of visual possibilities. Images (render) obtained as a result of visualization can be associatively transferred to a projected design object after some compositional or color correction. It is obvious that one and the same element can and should even have many fundamentally different forms, each of which emphasizes the mood and complements the composition. Modeled by the artist image of a certain mechanism (details), dictates their requirements to the appearance, because, only based on the vision of the result, it is possible to create a coherent picture (Fig. 4).

Below are some renders made by students of technical specialties, the emotional perception of the design steering wheel design.

Fig. 4. Design of the steering wheel of the car.

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Fig. 5. Option number 1. Cozy.

For amateurs of autumn, warm bulky sweaters and large cups of tea. The wheel's (fig. 5) lunch looks like a weaving thread in a knitted sweater, thus follows the driver into memories of golden autumn and snowy winters, in the comfort and warmth of home furnishings. However, at the same time association with the "dangerous" period of driving - the wet slippery road, forcing to be especially attentive while driving.

Fig. 6. Option number 2. Marine.

For those who love the whole sea with the heart. The shape of the wheel (fig. 6) resembles a shell, which is included in one associative row with a leave. A holiday, as you know, is a period of unhurried, measured life, so you can forget about the speeding on the way to work you can forget forever. Similarly, this model can be called Fibonacci.

Particular attention should be paid to the functionality of this model: it is provided with additional areas for the arrangement of control buttons. Which is very convenient for safe driving, and for people with disabilities.

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Fig. 7. Option number 3. Romantic.

Suitable for sensitive romantic individuals who dreams of living surrounded by blossoming flowers, butterflies, and emotional individuals who are passionate about sports cars.

This model is asymmetric, which will wake up the thought of a creative person. And also, to emphasize the rebel character of the driver of such a steering wheel.

The ability to visualize information not only accelerates the process of work, but also eliminates the barriers of individual perception, helping all project creators come to a single vision of the end result at an early stage of design. Under such conditions, an enterprise is able to implement a project in a more qualitative and shorter timeframe, to find errors before the production of prototype samples, since fixing various disadvantages at the design stage costs hundreds of times cheaper than at the production stage.

Thus, a modern student, receiving special knowledge in the field of design, must be simultaneously both an engineer and an artist, combining the functionality and aesthetic appeal of the product.

Summary. Proposed basics of designing mechanisms and machines, the educational program of training engineers specializing in "Industrial Aesthetics and Certification of Industrial Equipment" in the specialty "Materials Science" allows you preparing specialists who have not only the necessary knowledge of the engineer-designer, but also know how to develop this technology. Create an artistic image of industrial products of a diverse range.

An important component of the educational process is not only the technical but also methodological training of specialists – mastering the psychologists with the methods of studying various phenomena of social life, including in the field of psychology of art, the development of visual culture and the ability of visual perception, therapy artistic visual visual means.

Disciplines of engineering direction are formed by students of competence, allowing to effectively design different products; systems of knowledge about the modern principles of the creation of these products with the use of industrial design. Such disciplines are designed to teach the applicant when designing a chain of product life cycle to take into account his relationship with marketing, sociology, psychology, having professional competencies using the research method of activity as an effective means of enhancing creative abilities and the formation of professional skills.

References [1] Law of Ukraine “On higher education” since 01.07.2014, №1556-VII, retrieved from http://vnz.org.ua/zakonodavstvo/111-zakon-ukrayiny-pro-vyschu-osvitu

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[2] Iftikhar B. Abbasov, V’iacheslav V. Orekhov (2016). Conceptual Model of “Lapwing” Amphibious Aircraft. Mechanics, Materials Science & Engineering, Vol 7.

DOI 10.13140/RG.2.2.12856.14081 [3] Iftikhar B. Abbasov, V'iacheslav V. Orekhov (2017). Computational modeling of the cabin interior of the conceptual model of amphibian aircraft “Lapwing”, Advances in Engineering Software, Elsevier, vol 114, 227-234, DOI 10.1016/j.advengsoft.2017.07.003

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III. Electrical Complexes and Systems M M S E J o u r n a l V o l . 1 5

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Improved Design of Low-speed Inductor Generator for Wind Turbines with Vertical Axis of Rotation 1

Shkrabets F.P.1, Tsyplenkov D.V.2, a, Kolb A.A.2, b, Grebenuk A.N.2, c, Panchenko V.I.2 1 – Head of the Renewable Energy Department, Dr. Sci. (Tech.), National Mining University, Dnipro, Ukraine 2 – Associate professor of the Renewable Energy Department, Ph.D., National Mining University, Dnipro, Ukraine a – tsyplenkov.d.v@nmu.one b – kolb.a.a@nmu.one c – hrebeniuk.a.m@nmu.one DOI 10.2412/mmse.51.33.453 provided by Seo4U.link

Keywords: induction generator, stator, rotor, wind energy.

ABSTRACT. This paper considers the design of the end generator of wind turbines. Relationships for the estimated power of a new design inductor generator are obtained. The possibilities of increasing this power are shown. The modified generator design is given. Calculation of current loads of the stator winding is made. The indicators of the inductor generator with twice the number of longitudinal rows of packets of the stator, allowing an increase in estimated power relative to the baseline design, are analyzed.

Introduction. Generally, wind power plant engines are slow-speed; therefore, the use of traditional synchronous generators for production of electric voltage with frequency of 50Hz requires mechanical speed-up units resulting in plant design complication, weight increase and operational reliability degradation. Alternatively, it is possible to use low-speed synchronous generators, but in order to produce voltage with frequency of 50Hz, they must have a large number of poles, which would also result in size and weight increase.

Low-speed induction generators for the wind power plants. Conventional synchronous generators with the electromagnetic excitation have a brush assembly with the sliding contacts for direct current supply to excitation winding, which complicates their design and reduce operational reliability.

Multipolarity is relatively simply implemented in the designs of induction generators [1] being a kind of classic synchronous machines. Such generators are non-contacting (excitation winding is stationary), simple in design and more reliable as compared with other types. Estimated power of induction generator is determined according to following formula [2]:

Pi  0,164i K f Kr K B AD2l n , where  і – is estimated pole overlap coefficient; Kf

, K r – are magnetic excitation flux shape coefficient and winding coefficient, respectively;

K – is magnetic excitation flux leakage coefficient;

1

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(1)

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B – is maximum value of magnetic induction within the air gap; A – is linear load of stator winding; n is rotor rotation frequency.

Active materials (windings copper and magnetic core electrotechnical steel) utilization efficiency is characterized by the specific coefficient, of which expression results from (1):

KA 

P D2l

 0,164i K f K r K B A

(2)

In the conventional induction generator designs, value B is limited by the magnetic saturation of stator teeth and does not exceed 0.9T, and value A is limited by the cooling conditions and stator winding insulation thermal endurance. In case of air-cooled machines A  5  104 A/m. The value K for the conventional induction generators makes 0,4  0,45 . It is apparent that the value K A and therefore generator power within the set dimensions could be increased by the proper affecting values K , B i A . Let us consider induction generator design [3], which provides the increase of values B and A . The longitudinal generator section is shown in Fig.1.

Cylindrical rotor bushing 3 is fixed on shaft 1 by means of disks 2; toothed radial packages 4 and 5 assembled of the insulated electrotechnical steel laminations are mounted on the bushing external surface with mutual axial displacement. Packages teeth are mutually circumferentially displaced by the geometrical angle  , where z2 is number of teeth per package. Stator is made with magnetic z2 core in form of separate longitudinal packages 6 located circumferentially outside the rotor teeth.

Packages are assembled of the radially directed electrotechnical steel laminations. Ends of packages 6 are pressed by clamps 7 against the external surfaces of cylindrical laminated packages (yokes) 8 and 9. Coils 10 of upper and lower stator winding portions are located on the packages 6 portions projecting outside the rotor. In the height wise midportion of generator, longitudinal packages are bonded to each other by non-magnetic alloy filled in the gaps between them. In case of three-phase generator, number of longitudinal packages is set according to formula: z1  2 z2  K , where K  1, 2,3... and z1 must be multiple of three. In gaps between the rotor toothed packages, toroidal excitation winding 11 is located with its external surface attached to the longitudinal packages 6. Both stator winding portions along with the respective yokes and portion of longitudinal packages are placed in the closed casings 12 and 13 filled with the dielectric liquid. External surfaces of casings can be provided with the cooling devices, as necessary.

When direct current is supplied to excitation winding and wind engine rotates the rotor, teeth of packages 4 and 5 continuously change their positions in relation to the internal surfaces of longitudinal stator packages causing change of magnetic flux size and direction in the latter ones.

These fluxes link the coils of both stator winding portions causing development of electromotive force (EMF) with frequency f  z2 n .

60 We determine generator estimated power according to formula:

P  mE1I1 , where m – is number of phases;

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E1I1 – is EMF and current of stator winding phase.

Fig. 1. Longitudinal and cross-sectional view of the generator.

Coils at the ends of each longitudinal stator package are related to one of winding phases. Taking into account that EMFs of these coils are antiphased, these are connected in series opposition, and their resulting EMF En is related to one stator package. Number of longitudinal packages per phase zф  z1 m , hence, the phase EMF:

E1  z ph Ec K r 

z1Ec K r , m

(4)

where K r – is distribution coefficient taking into account a relative phase shift of EMF vectors of different packages of the same phase.

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Relative arrangement of stator packages 6 and teeth of rotor packages 4 and 5 is schematically shown in Fig. 2 for some initial moment of time (Fig. 2, a) and after rotor circumferential displacement by distance of pole pitch   t z1 (Fig.2, b) where t z1 is stator slot pitch.

Fig. 2. Schematic relative arrangement of stator packages and rotor teeth.

Mean value of EMF developed in the left coil of upper longitudinal package (Fig. 2):

Еc '  wc1

2Ф Ф1  wc1 c1  4 fwc1Фc1 , t 0.5T

where wc1 – is number of coil turns; Ф1  2Фc1 – is magnetic flux change across the coil for period t  0.5T corresponding to the

rotor displacement by distance  ;

Фk1 – is coil flux at the package 6 and tooth 4 axes alignment; T – is EMF period; f – is EMF frequency.

Similarly, the EMF of right coil of upper package (Fig. 2):

Еc ''  4 fwc 2Фc 2

,

where wc 2 – is number of coil turns; Фc 2 – is coil flux under conditions specified for flux Фc1 .

Let us consider the case that number of turns is the same in both coils, that is, wc1  wc2  wc . Then resulting package EMF will be:

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



Eres  Еc ' Еc ''  4 fwc Фc1  Фc2 .

According to schematic (Fig. 2), magnetic flux directed from the rotor tooth 4 to the package 6:

Фz  Фc1  Фc2  Ф12

,

(5)

where Ф12 – is flux going from the longitudinal stator package to the slot of adjacent circular rotor package.

According to (5), Фc1  Фc2  Фz  Ф12 , and therefore

Eres  4 fwc Фz  Ф12  .

(6)

Ratios for the magnetic fluxes in the above formula:

Фz 

0 F S z 0 F S12 ; Ф12  1 2

where 0 – is magnetic constant;

F – is magneto-motive force (MMF) of excitation winding per air gap;

1 ,  2 – are air gaps between the stator package and rotor tooth and slot, S z , S12 – are areas linked by the respective fluxes:

S z  bz1lz 2 ; S12  bg 2lg 2 where bz1 – is stator package circumferential width; bg 2  1, 2bz1 is rotor slot estimated width; l z 2 is rotor package thickness.

After plugging the Фz and Ф12 expressions in formula (6), we obtain following formula for the actual value of the package EMF:

 1, 21  Еп  kф Eres  4 fKф wc B lz 2bz1 1    2 f  p Kф Kn wk B l  , 2  

where B 

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p 

bz1



Kn  1 

– is coefficient; 1,21

2

– is magnetic flux leakage coefficient;

K ф – magnetic flux form factor; l  2lz 2 – magnetic core active length.

Let us write expression for the total current of single stator winding coil:

I1wk  ja Sc wc  ja Sd  lc hc Kd ja

,

(8)

where ja – is current density;

Sc – is coil wire cross-sectional area; Sd – is coil copper cross-sectional area; hc , lc – is coil thickness and axial length;

K d – is coefficient of coil cross-section filling with copper.

Stator winding circumferential linear load:

A

2hc lc K d ja . t z1

(9)

By comparing the expressions (8) and (9), we obtain:

I1wc  0.5 At z1 , from where I1 

At z1 .

2wc

We plug expressions (7) and (10) in formula (3), taking into account (4) and following ratios:

f  pn

60 ,

where p – is number of pairs of poles, p  z2 .

  D 2 p

,

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(10)

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where D – is diameter of circumference, around which stator packages are positioned (bore diameter).

Eventually, we obtain: P  8.22 102  p Kф K p Kn B AD2l n .

(11)

We analyze constituents of the above formula.

For coefficient K n , we define:  2  1  hz 2 , where hz 2 is rotor tooth height; according to 1,2 recommendation [1], hz 2  151 , then expected value K n  1   0,925 .

16 Let us have a closer look at the ratio  p 

bz1

. We designate gap between the stator packages around  the circumference of diameter D as nominal slot width bn1 . This gap contains two coils of thickness 

hk each. We assume bg1  2hc (limiting case). On the other side, bg1  t z1  bz1  t z1 1  

bz1   . Stator t z1 

slot pitch:

t z1 

D z1



D 2 z2 

k z2



D  k  z2  2   z2  

tz2



2

K z2

,

where t z 2 – is slot pitch of rotor with t z 2  2 .

Since z2  k , then t z1   Taking into account the above correlations, we write expression for product  p A from formula (11) in following form

 p A   p 1   p  lc Kd ja .

Maximum value of this product and therefore generator estimated power would be at  p  0,5 .

Coefficient of distribution for the EMF fundamental harmonic is determined according to formula:

Kp 

1  300 2аb sin   аb 

,  

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where ab 

z1 – is number of stator packages, of which coils form one branch of phase winding km

(coefficient k is taken from formula z1  2 z1  k ).

There are no teeth in the magnetic core of generator stator [3] in principle, therefore, value of magnetic induction B is only limited by the magnetic saturation of electrotechnical steel of stator packages and iron of rotor bushing, and could make up to 1.8T. Generator design involves cooling of stator winding coils by means of dielectric liquid, which allows increasing of value of current density in winding, and therefore, linear load up to twice as much as that in the case of winding air cooling. Moreover, generator allows increasing of linear load by means of variation of coil length lk , which could be set to at least 8 10 hc .

We compare estimated powers of conventional induction generator Pi and generator [3] P at the same D , l , kô and following indices: a)

induction –  i  0,9 ; Kr  0,92 ; K  0, 4 ; B  0,8 T; A  4  104 A ; м

b)

generator as per [3] – К р  0,95 ;  р  0,5 ; K n  0,925 ; B  1,6 T; A  8104 A . м

Ratio: P 8,22  102  0,5  0,95  0,925  1,6  8  104   2,65 Pi 0,164  0,9  0,92  0,4  0,8  4  104

which supports possibility of considerable increase in estimated power of generator [3] as compared with the conventional induction generator.

Analysis of the formula (11) demonstrates the possibility of increase in estimated power of generator [3] due to increase in relative width of stator package  p  bz1  . However, at the unchanged bore diameter, slot width and therefore winding coils thickness and linear load would be reduced. The situation could be maintained by the extension of coil length, but this would result in the machine axial length extension, which is undesirable. It is proposed to address this problem by means of the generator design modification [3] as shown in Fig.3.

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Fig. 3. Longitudinal and cross-sectional view of the improved inductor generator Elements of the same purpose in Fig.1 and Fig.3 are marked by the identical numbers. Unlike the generator (Fig. 1), proposed design provides shortening of longitudinal packages 6 in the machine midportion, and addition of second (external) row of packages 14 in number of z1 , which are positioned around the circumference of greater diameter D3  D  and connected with the radial laminated packages 15 in the first row. Midportions of external packages are pressed by the clamp 16 against the laminated ring yoke 8; stator winding coils 10 are attached to the longitudinal packages of external row on both sides of yoke. Winding coils along with magnetic core portion are placed in the closed casing 12 filled with the dielectric liquid. New design rotor remains unchanged. Design (Fig.3) has a considerably lesser axial dimension, but some greater diameter as compared with (Fig.1).

Slot pitch for the position diameter of external stator packages of external row:

t3 

D3 z1

 t z1

D3 .

D

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Thicknesses of packages around the circumferences of both diameters are the same, therefore, t з  bz1  bnз where bz1   pt z1 , bnз is gap between packages around the circumference of diameter

D3 . Obviously: bnз  2hk1 , where hk1 is thickness of new design winding coil. We write following relations:

 pt z1  bпз  t z1

Dз D  , bпз  2hk1  t z1  з   р  .

D D 

(12)

 2D  From where, at  ð  0,5 we obtain: hk1  hk  3  1 .  D 

Hence, coil thickness (at specified  p ) and therefore winding linear load according to (9) could be increased due to longitudinal stator packages positioning around the circumference of larger diameter: this would result in respective increase in copper consumption for winding making. On the other side, generator design (Fig.3) allows increasing of the value  ð due to the respective alteration of stator package width. From the structural considerations, we specify maximum permissible value  p .

Reasonable rotor tooth width to stator package thickness ratio:

bz 2  1,2 , from where bz 2  1,2bz1 . bz1

bn 2  1,2  1,3bz 2 .

Rotor slot pitch: t z 2  2  bn 2  bz 2  2,2  2,3bz 2  1,22,2  2,3bz1  2,6  2.8bz1 .

From where b  p  z1  0,76  0,72 . We assume  p  0,75 . In order to avoid increased stator winding copper  consumption as compared with the generator shown in Pic.1, winding coils thickness remains unchanged, that is, hk  0,5bn1  0,25t z1 . Then specified  p would be reached at the ratio: Rotor

slot

width

D3   p  0,5  1,25 D

Due to the increase in  p from 0.5 to 0.75, generator estimated power would be increased by factor of 1.5. From physical standpoint, it is attributed to the increase in magnetic excitation flux, which enters the stator packages and links stator winding coils. However, it would result in some increase in electrotechnical steel consumption.

Summary. 1. The formula is derived for the estimated power of new design induction generator.

Possibilities to increase this power amount are shown.

2. The analysis is conducted of induction generator parameters with the doubled number of longitudinal stator packages rows, which allows increase in estimated power as compared to the baseline design.

References [1] Ivanov O., Shkrabets F., Zawilak J. Tsyplenkov D. (2011). Electrical generators driven by renewable energy systems. Wroclaw University of Technology, 169 pp.

[2] Tsyplenkov D.V., Ivanov A.B., Kuvayev Y.V., Ed. by Shkrabets F.P. (2008). Design of electric machines. NMU, 325 pp.

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[3] Golubenko М.С., Vyshnevetsky P.O., Dovgalyuk S.I. et al. (2009). UA Patent 86650. Alternator.

“Promyslova vlasnist”, No.9

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VI. Environmental Safety M M S E J o u r n a l V o l . 1 5

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Study Impact of Different Natural Factors to Agricultural Vegetation Development by Using Modis Images and Geobia Method (caSe of Syr-Darya Province, Uzbekistan) 1

Shamshodbek Bakhtiyarovich Akmalov1,a, Aybek Mukhamedjanovich Arifjanov2,b, Luqmon Nayimovich Samiev3,c, Tursunoy Ubaydullaevna Apakxo’jaeva4 1 – assistant Department of Hydralogy and Hydrogeology, of Tashkent Institute of Irrigation and Agricultural Mechanization Engineers.

2 – Head of the department, Department of Hydraulics and Hydroinformation, Doctor technical sciences, professor, Tashkent Institute of Irrigation and agricultural mechanization engineers.

3 – Senior researcher, Department of Hydraulics and Hydroinformation, Tashkent Institute of Irrigation and agricultural mechanization engineers.

4 – assistant, Department of Hydraulics and Hydroinformation, Tashkent Institute of Irrigation and agricultural mechanization engineers. a – shamshodbekjon@mail.ru b – obi-life@mail.ru c – luqmonsamiev@mail.ru DOI 10.2412/mmse.49.23.625 provided by Seo4U.link

Keywords: agriculture, MODIS (Moderate-resolution Imaging Spectroradiometer), RS (Remote Sensing), NDVI (Normalised Difference of Vegetation Index), Syr-Darya, GEOBIA (Geographic Object Based Image Analyse), eCognition, Irrigation, Vegetation.

ABSTRACT. In the study, natural and anthropogenic effects on vegetation are discussed and the degree of their influence is analysed in the Syr-Darya province (Uzbekistan) by using MODIS (Moderate-resolution Imaging Spectroradiometer) RS (Remote Sensing) images and meteo and hydro data. MODIS NDVI (Normalised Difference of Vegetation Index) images have been analysed by using GEOBIA (Geographic Object Based Image Analyse) method via eCognition software. In this article was investigated 2 novelty: 1) finding optimal Segment parameters for MODIS NDIVI images segmentation and 2) study different factors on agriculture, for understanding why agricultural land goes out of the agricultural balance and organizing future sustainable agricultural activities. In accordance with results of these analyses, in Syr-Darya province the vegetation development depends on air temperature, indeed, it is a natural phenomenon, because the vegetation period occurs during the hot term of the year. Unfortunately, in this period, the water amount decreases and vegetation withers and dies as a result of water shortage, besides, that land becomes saline. In analysis of vegetation periods, RS images play an important role. In this article we will review the possibilities of RS and OBIA in middle resolution image analysis.

Introduction. Syr-Darya province is the main province in Uzbekistan which situated most part of agricultural field. There are 13 Province in the Republic, Area of all irrigated fields 4.2 mln. ha from this 0.3 mln.ha situated in Syrdarya provice. In 2014, all Republic profit of the farmland consisted 25156.2 billion sum (http://www.stat.uz/statinfo/dinamicheskie-ryady; Last acces 22/11/2016), from this sum share of the Syr Darya was 1451.3 billion sum (http://sirdaryo.uz/viloyat-iqtisodiyoti/; Last access: 22/11/2016) Agricultural lands are also very important for the Syr-Darya province, because this region has the biggest agricultural farms and most part of the population is engaged with agriculture (more then 11

© 2018 The Authors. Published by Magnolithe GmbH. This is an open access article under the CC BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/

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70%). The main products of agriculture of the province are melon, watermelon, cotton, wheat and barley. But recently, owing to natural and anthropogenic factors, the agricultural lands are in danger.

It is observed that many fields quit the agricultural circle because of different factors [25, 12, 18].

Extinction of plants occurs in some agricultural fiends.

The cause of this problem is the existing unstable agricultural activity, water waste and the destruction of drainage systems [25, 12, 18], the second group of scientists explains it as caused by climatic changes and decrease of precipitations [8, 15, 16, 22, 23]. Others appoints to the partition of the SyrDarya river, this river is the only water resource for the Syr-Darya province and closed by the upstream countries by water reservoirs in order to receive electric energy during vegetation periods [1, 11, 17, 26]. By studies, we can conclude that each factor has a share in the ecologic deterioration.

Especially, climate change, decrease of precipitations and the change of river flow regime are problems of global importance. What effect has this on vegetation development? To which of these factors should the agriculture be more adapted to in future? Which factor is the most important? How do we study the vegetation development and the connection between these factors? This article will help to find the answers to these questions. With the finding answer to questions above, on can try to save agriculture unexpected losses and give instruction for adaptation.

However, the area of the province are very large and all this area covered with agricultural fields. In addition, factors can effect different part of this are. For this reason, it is important to study all the territory of province and analyse all fields. Analysis in different branches and in huge scale requires recourses and time. Except this, the connection between vegetation period and natural factors can be found by long-term research. For this, it is obligatory to choose the natural condition. For example, a year with rich precipitation and a year with poor precipitation; the hottest summer and a year with the lowest temperature; a year with a big volume of water and a year with small. This period should be taken to study the vegetation development in all areas of the province, gather the information and analyse it. Many years and seasons must be taken to increase the accuracy. It is difficult to realize such a large scale research requiring many years. But RS (Remote sensing) images will help to realize it. Remote sensing technologies include the study of land surface and the environment at a distance, theories, instruments, methods, interpreting means which help to collect, re-use data and create new information [5]. This is put in force by taking images of land by active or passive sensors that are placed on board of planes or in satellites.

Nowadays, satellite remote sensing is widely used in studying land surface, environmental protection and ecologic monitoring. With this data, it is possible to observe the ecologic processes as anthropogenic effects, land covering and land use, natural resources on a large scale [10]. According to Gyuris [10], Giniyatullina [7], using RS in ecology helps us to solve the following difficulties and necessities, presented in traditional ecologic analysing methods: a) It is possible to study different fouler and natural objects on large scale. With RS development, it has become possible to take data on global, regional and local scales. b) It is possible to analyse the duration and repetition processes for a long time. (Because, the satellites send images from one point in a certain period. For example, MODIS arrives at the same point every 16 days and sends the image of the very area. In accordance with Gyuris’ [10] conclusion, it is possible to observe the development period of any natural object or process gradually because of these features of the satellites). c) It prevents from increasing the range errors of analysis, as different climates do not have effect on satellites. d) It is possible to analyse the same data in different ways. Many sciences used NDVI (Normalized Difference of Vegetation Index) layer of satellite images for analyse vegetation development.

In accordance with much research work, the red zone of the sun’s spectrum (0.62-0.75 mkm) is absorbed by chlorophylls the most, and intensity of this process expresses the rate and extent of a plant’s photosynthesis [20]. Because of the high photosynthetic activeness, the amount of radiation absorbing to chlorophylls grows, and this process is expressed in photosynthetic active radiation share [14]. The near red zone of the sun’s spectrum (0, 75-1.3 mkm) returns through the plant’s leaf.

Counting the NDVI is based on this very process [14]. Rouse’s et. al. [21] experiments studied the MMSE Journal. Open Access www.mmse.xyz

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spectral essence of photosynthetic biomass in laboratory on tomato plants, they started first counting NDVI. NDVI is expressed mathematically in the following way: NDVI=(NIR+R)/(NIR-R) where R – red band of satellite image, NIR – Near Infrared band of satellite image.

Calculating vegetation indiceses by satellite was started by installing AVHRR equipment into NOAA platform flying the satellite Nimbus (Сhoudgury, Tucker) into space in 1964. It was possible to take a photograph of the earth’s red, close red and heat spectral distanced surfaces. NASA started to put the program Earth Resources Technology Satellite (ERTS) in force simultaneously while Landcat program started. So, monitoring the global and regional vegetation had started at the same time.

Nowadays have satellites which installed special NDVI platform.

To analyse the vegetation development intensity, we use NDVI layer of MODIS Terra images. The benefits of using MODIS Terra images in the analysis:  MODIS Terra scanner has NDVI layers, which save time in calculations and increase the accuracy of them;  MODIS Terra scanner is the only satellite, which has been importing images to Earth incessantly since 2000, every 16 day. Other existing satellites sometimes deviated from schedule due to technical disrepairs and other reasons, and other satellites have been launched just in recent years.

The other remaining satellites have low resolution images. Change of vegetation layer occurs in short period andits data should be collected incessantly and MODIS is a perfect satellite for it (glovis.usgs.gov); 

Images of MODIS have been used widely by the scientists of Uzbekistan;



MODIS images are easily accessible;

 MODIS takes large scale images which cover wide areas (250 m/pixel) and it gives an opportunity to make analyses on large scales;  Agricultural fields of Sirdarya province are large, and the low resolution of MODIS helps to merge them into 1 or several pixels. As a result, 1 pixel includes NDVI information on one type of vegetation field approximately, thus the work will be simplified (Klein et al., 2012);  MODIS images have been used frequently in GEOBIA analyses widely. So, our work can contribute to enrich this field of science [6].

MODIS images covers large scale surface, that’s why storage of this images are very high. In this article planned to analyse data from long time. It is very difficult gathering this very high storage data and analyse it fast and accurate. In that case GEOBIA method helps us [6]. That’s why we choose eCognition Developer 9 software which works according to GEOBIA method. We analyzed the connection of meteorological and hydraulic factors with average vegetation intensity with MODIS NDVI images. We use the correlation coefficient: the factor with the highest correlation coefficient with vegetation activation means that it has the biggest influence.

METHOD AND MATERIALS. Case of study. The research area of the thesis is Syr-Darya province. Syr-Darya is one of the regions of Uzbekistan, which was established on 16 February 1963.

The Syr-Darya area is located in the east of the country, on the left riverside of Syr-Darya River, on the output of the Fergana valleys. Latitude is 40°30'42"N, Longitude is 69°00'38"E. In the north, the Province borders the Kazakhstan Republic, in the east it borders the Toshkent Province, in the south the Tajikistan Republic and in the west the Jizzakh Province. The area of the Province is 5.3 thousand MMSE Journal. Open Access www.mmse.xyz

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square kilometres or 0.9% of the total territory of the Republic. Syr-Darya province consists of 9 districts (Bayavut, Gulistan, Mehnatabad, Mirzabad, Oqoltin, Sayxunabad, Sirdarya, Xovos and Sardoba), 5 cities (Gulistan, Bakht, Sirdarya, Shirin and Yangiyer), 6 towns (Bayavut, Dehkanabad, Dustlik, Pakhtabad, Saykhun and Khovos) and 75 villages (2004). Gulistan city is the center of the Province (Fig. 1) [27].

Fig. 1. Situation map of research area (Changed after: http://www.indiana.edu/~afghan/maps.html.

Last access 11/10/2016).

The climate of the area is sharply continental, with comparatively cold winters and long-lasting hot summers. The average annual temperature in Syr-Darya city is + 14.75 C°, in Yangier it is + 15.86 C°. The most hot month is July. The average maximum and minimum temperature in Syr-Darya city are + 29.90 C°, minimum is -10.20 C°. In Yangier city it is accordingly +33.86 C° and -8.00 C°.

Ground in daylight-savings time warms up until 38-40 °С and during winter temperatures is lowered to -10 C° (UzGidroMet data, 2000-2012).

Usually, hot summer winds drain the soil and harm the plants. The vegetation period is 218 days.

Because of intense evaporation in summer, salinization occurs on the surface of the field (Sharof Rashidov, Oqoltin, Gulistan districts). The speed of “Bekabad wind” that occurs often in November, reaches to 20-25 meter/second (it is 40 m/s in Bayavut district). Sometimes these kinds of winds harm the cotton plants in spring. Recently enclosing gardens have been built [27]. The precipitation falls out beside 340 mms, 80%, which accounts for winter-spring time. Relative moisture of the air at wintertime forms 74-78%, but during the year - 29-31%, at average annual importance 56%. Annual evaporability is 1500 mms [19].

In Syr-Darya area there are no natural water resources except the Syr-Darya River. Transboundary river water flowing through Syr-Darya is 240 m3/s. The main presence of water in the territory of the area are the South Golodnostep channel and channel Dustlik [19].

Collector-drainage water, forming on territory of the area, in volume from 1.8 before 2.1 km3 are conducted in river Syr-Darya and Arnasay. Themain collectors in this zone are: Shuruzyak, Main Caught collector (MCC) and Central Golodnostep collector (CGC). According to reports of MMSE Journal. Open Access www.mmse.xyz

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“Suvokova”, water supplement of the region is 78 %. The site sewage network and clearing the sewages in region is absent [27].

Most of the territory of Syr-Darya provice is occupied with agricultural lands. Agriculture is specialized in cotton production, grain cultivation, fruit-growing, vegetable-farming and livestock breeding. There are 6170 farms and 30 shirkat companies in Syr-Darya province (2004). The total agricultural field of the region is 245.0 thousand hectares, 115.3 thousand hectares of which is planted with cotton, 86.3 thousand hectares for grain, 6.0 thousand hectares is for rice, 1.9 thousand is for vegetables, 2 thousand is for cultivation of melons and cucumbers, 450 hectares is for potatoes and 19.5 hectares is for fodder. 1233 hectares is for gardening and vineyards. Besides, alfalfa, chickpea, mung bean, sesame, bean and sunflower are cultivated in irrigating fields. Gulistan and Hovvos districts are the main vegetable-farming areas (2004) [27].

Collected data. Meteo data. Some natural factors were selected in order to measure the correlation with MODIS NDVI value in the analysis. This data was taken from UzGidroMet center of Uzbekistan, from the meteo and hydro stations which situated in Syr-Darya Province, and calculated average monthly values of this numbers. By using the value of these factors we have created a graphic of the monthly change of metrological and hydraulic conditions in the province. The data which were used are the following: air temperature; soil temperature; speed of wind; runoff value of Syr-Darya River and rainfall. All the taken information is collected between 2000 and 2012. MODIS data collection. This analysis was performed using Terra MODIS (VI) products. The VI images were obtained every 16 days at a spatial resolution of 250 meters at the Sinusoidal projection. The 16-day period of Terra image capturing starts from day 001. The VI products consist of Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), and four spectral bands: Blue (459–479 nm), Red (620–670 nm), Near Infrared (841–876 nm), and Shortwave Near Infrared (SWIR-2) (2105–2155 nm) [6]. From the VI products above, we have used NDVI for analysis.

Because this layer is much used for vegetation analysis and gives good results [24]. There were 154 images collected during the period of 2000 to 2012. The images were taken in sequence of one image per month. The parameters of the Terra scanner that were used in the analysis are the following (MxD13Q1): Horizontal Tile Number-23; Vertical Tile Number-4; Latitude-45.0; Longitude-77.8.

All MODIS Terra images were downloaded from website: http://glovis.usgs.gov/.

Used software and analyse steps. We used eCognition Developer 9 program for our analysis. This software was created in Munich Germany in the base of GEOBIA method. Were analysed only NDVI layers of MODIS images. All MODIS NDIVI images Segmented in different SP and the monthly average value of NDVI had been copied from the window of "image object information" and pasted to Excel and the correlation coefficient (R) had been calculated by various statistical formula.

Segmentation. In MODIS images segmentation, the value of scale parameters was very small unlike other H and VHR images segmentation. Because it’s spatial resolution is 250 m/pixel and every pixel can reflect an object or objects. During the all multi resolution segmentation processes the scale of shape and compactness parameters were changed and the most suitable parameter has been selected.

During the analysis, we came across two problems: first is that as a result of raising the scale parameters, unknown areas join the segmented objects. The second problem is the appearance of big segment objects in small scale parameters (The scale parameter has reached just three, but the objects’ quantity is 216 despite the outstanding objects). Because the MODIS resolution is very low, so the pixel indices are very close; besides, its radiometric resolution is also low, that is why the scale parameters appear too different. In Dao & Liou's [6] scientific work about identifying water objects with MODIS images GEOBIA analysis, the conclusion was the following: the resolution of MODIS images covers a very large area. Therefore, we first need to segment it to pixels, and then with region growing segmentation merge it in different scale parameters to homogeneous objects. Therefore, in image segmentation of MODIS data, pixel extraction is more common. Thus, the initial segmentation of "chess board segmentation" had been chosen, this segmentation algorithm extracts the images to pixels. To solve the problems above, images have been segmented until pixel degree with the help of MMSE Journal. Open Access www.mmse.xyz

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Chessboard Segmentation algorithm. Thus, each pixel might participate in further analysis instead of unifying them. This algorithm is the most useful for creating the pixel objects. In our analysis was given 1 for object size to create a pixel object in MODIS image. We created 77400 pixel object, in these objects are no data areas.

Then, we used "Multi resolution segmentation region grow" algorithms. This segmentation is a bottom-up region growing technique beginning with image objects in the size of one pixel and then gradually growing by merging adjacent objects. The assimilation of objects depends on the average heterogeneity of the object weighted by its size and stops when user-defined criteria are reached. The size of the segments is highly dependent on the generated scale. By varying the scale parameter, objects of different sizes with varying homogeneity criteria are produced. The objects of interest typically appear on different scales in an image simultaneously [2, 3, 29].

To avoid mixing them into one, these areas have been divided into a special No Data Class. We have used Assign Algorithm for it, because this algorithm includes the condition of “if…then”. But now we cannot segment the areas with data by multiresolution segmentation because it is an algorithm dividing the common image. But eCognition gives the opportunity to use the algorithm for definite classes: Multiresolution Segmentation region grow algorithm. During the MODIS segmentation process all of the images have got similar weight (=1). The reason is that all of those images form one NDVI band, and are captured in different intervening periods. Moreover, all of them are of equal practical significance for analysis.

Images have been segmented in various scale parameters (SP) with invariable degrees of shape (0.5) and compactness (0.9). Thus, with the changing different scale parameters of the "multiresolution segmentation region grow" algorithm, we created MODIS NDVI objects. NDVI values of these objects have been exported to statistical analysis software and based on this statistical analysis to MODIS images. We found optimal segmentation parameters with a good correlation with natural factors. This resulted in the following segmentation group of objects (Fig. 2):

Fig. 2. Segment object creation value in different Scale Parameter.

If we give attention to this Figure 2 we can see a few changes of objects quantity between SP2 and SP3 segmentation value. When objects get the maximum homogeneity in next step changes not will be more.

Result. Choosing optimal segment parameters for MODIS NDVI image analysis for Syr-Darya province. According to the size of segmented object, after SP3 segment objects start to increase fast.

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After SP=3, size of segmented object not much to size of separate agricultural fields. According to size between SP=1 and SP=3 optimal variant (Figure 3).

Now we will choose optimal SP parameter according to correlation degree. Taking into account the objects created until 7000, we will simplify the correlation degree. We generalized all objects according to their correlation degree (correlated objects > 0,55; Non-correlated objects <= 0,55) (Fig 4).

Fig. 3. Result of segmentation of MODIS NDVI data in different scale.

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According to Segmentation and Correlation results was chosen scale parameter equal to 2 is an optimal segment parameter to study the correlation between MODIS images NDVI of Syr-Darya province and natural factors (Fig. 5).

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Fig. 5. The most optimal scale parameter segment object.

There are many segment objects with a high correlation of NDVI degree and various natural factors in it. And size of segmented objects similar with size of agricultural field area. If we pay attention to the quantitative and the percent index of correlation between segment objects and air temperature.

There are few numbers of non-correlated areas and many objects with a high correlation (see Figures 4). In the SP=2 segmentation map a total of 1856 NDVI objects was created and 64% of them are in strong correlation with temperature in accordance with Syr-Darya hydrostationâ&#x20AC;&#x2122;s information, and the main part belongs to objects nearby Syr-Darya station.

Why SP=2 is optimal and why this scale parameter is helping to get more accurate results in clarifying the correlation between NDVI degree of area with natural factors? Guyet et. al. [9] introduced main content of choosing SP correct in their scientific work about choosing the segment parameters in OBIA analyses of MODIS images. They explain the importance of MODIS segment parameters for the creation of homogeny objects.

Various plants are grown in agricultural fields. Apart from the fact that their NDVI degrees are different in different seasons, they are in different correlation with natural factors. As an example, rice field has a positive correlation with the runoff amount, because it is planted near the river and must be under water all the time. Decrease of runoff volume influences it negatively. Barley is planted during the beginning of a vegetation period and feeds from precipitation during the whole growth period. Thus, its NDVI degree has a positive correlation with precipitation. A few numbers of segment objects which well correlate with natural factors means that different vegetation fields are turned to be mixed. In the result, the NDVI degree of various vegetations in one segment object influences the different correlation and therefore the general index of correlation remains small. A high degree of correlation of MODIS NDVI images means that segmentation has been carried out properly. The existing maximum index of homogeny objects in eCognition Developer 9 shows that fields of one type of vegetation has been segmented to one object. Thus, by right segmentation we have a chance to combine the objects of one type of vegetation by reaching the maximum homogeneity and high correlation. Indeed, it is possible to compare it throughout field experiments.

Correlation results of NDVI with different factors. We have calculated the correlation of the NDVI index with temperature and precipitation in accordance with information received from meteorological station in Province. And these analyses showed that vegetation development is in MMSE Journal. Open Access www.mmse.xyz

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strong positive correlation with change of temperature. This correlation can be seen in Figure 4. In accordance with that information, development of NDVI is not correlated with precipitation. This is caused by all amounts of precipitations falls in autumn and winter season, when vegetation activities are finished (Fig. 6).

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In the province, the main precipitation falls during non-vegetation periods in autumn and winter, and this is the reason of non-correlation of NDVI with precipitation. Thus, precipitation cannot influence the vegetation period (Fig. 6). The province is not located in a mountain area, and there is no point of water creation, as a result the quantity of snow has no effect on the vegetation period. The reason of strong positive correlation of NDVI with air temperature are agricultural activities during the hot season of the year.

The NDVI index of objects in this segmentation and for other parameters with runoff shows a high negative correlation. If we pay attention to vegetation period, we can see that this period occurs in the last months of spring, during summer months and the first months of autumn. In accordance with meteorological research, during this term due to the increase of air temperature, mountain ice begins to melt which results in the increase of runoff in rivers, such as Syr-Darya River. That means that the correlation between the vegetation period and the runoff must be positive. The reason of a negative index is an anthropogenic factor influencing the Syr-Darya River from neighboring countries. The problem is collecting the water of Syr-Darya in reservoirs during periods of full vegetation to produce electricity in the winter season (Fig. 7).

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Upstream of the Syr-Darya River there are two water reservoirs: Tokhtagul reservoir in Kyrgyzstan and Kayrakkum reservoir in Tajikistan. They have been constructed to produce electrical energy. As a result of their activity, water of the Syr-Darya River is collected intensively during the vegetation period and during the non-vegetation period (cold days of autumn and winter) collected water is dropped to the Syr-Darya River to produce electricity. Our statistic research shows a correlation of change of runoff and NDVI has shown negative results. This analysis confirms the information given in literary reviews about the decrease of water volume of the Syr-Darya River caused by collection of water in vegetation periods into water reservoirs by neighboring countries.

Nevertheless, the main part of the Province consists of irrigated agricultural areas and the change of runoff volume of the river only influences the agricultural events. It is difficult to see this in general analyses. Mostly, decrease of water amount during vegetation periods has resulted in the death of plants, which caused a fall in the NDVI degree of the area. Big amount of water during the vegetation period causes better development of agricultural vegetation. Because of water absence for irrigating the vegetation NDVI index has decreased. This figure also shows the most part of province land is an irrigated area, because the water absence in river has decreased the NDVI. Currently, main research in the Republic of Uzbekistan is done with MODIS images. Because these images are easy accessible and it is possible to review the changes of global land surface. Moreover, the low resolution of these images gives good results in pixel based analysis. The main goal of analysis is researching the changes of NDVI indices. The problem of analyzing data of big volume is the chance of wasting much time by reviewing the reliability of the results and the absence of the opportunity to carry out all of them except field experiments. These problems could be solved easily and quickly with eCognition. The segmentation of 154 images has taken 12 minutes.

Summary. Th most optimal Segmentation parameters for Syr-Darya province MODIS NDVI images is SP=2; Shape=0.5 and Compactness=0.9. There are many segment objects with a high correlation of NDVI degree and various natural factors in it. And size of segmented objects similar with size of agricultural field area.

In accordance with analysis results, vegetation development in Province is mainly related to temperature. But, the reason of vegetation destruction is the problem of water shortage in the middle of the vegetation period. This water shortage is created by Tohtagul water reservoir. Because this water reservoir collects water during the vegetation period and drops water during the non-vegetation MMSE Journal. Open Access www.mmse.xyz

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period. It causes vegetation destruction in the hot months of summer because of water shortage in agricultural areas with artificial irrigation (Data UzGidroMetCentr 2000-2012).

The water amount of the Syr-Darya River during the vegetation period has been decreasing every year simultaneously with the rising problem of water shortage in the province. It is seen in the graph made for July (Fig. 7). Therefore, agricultural and water resources management of the province should focus all attention on solving this problem. If this problem between countries will not be solved, agricultural management of Syr-Darya province must adapted to water shortage conditions in the future.

Water lack is a semi-natural process progressing with climatic change which is difficult to avoid. We can only estimate the future impact of it. It is a big problem and the water management of the Republic of Uzbekistan might not solve it. Because the only water resource of the province is the Syr-Darya River streaming down from three republics. Transboundary water problems are international issues requiring global interference. We recommend to continue the current research by gathering all field experiments’ results and to realize the adaptation for future natural changes on the basis of these results.

The use of RS images in analysing the relation between vegetation developments with various natural factors saves time and resources. And the use of MODIS images in global analyses is expeditious.

Besides, MODIS images have a NDVI band which saves us from the difficulties of calculation.

Today, the MODIS images are easy accessible, and the analysis program of eCognition Developer that we have used is much used software. They guarantee high accuracy, which enables detailed and quick analysis. This method is useful for agriculture.

Acknowledgement. The author is grateful to Erasmus Mundus CEA scholarship, Lille1 University Science and technology, Doctoral department SESAM and Laboratory TVES, and Tashkent Institute of Irrigation and Melioration, Head and personnel of departments of Geography and urban planning, Department of International affairs (Lille 1) and Hydromelioration (TIIM), head and personnel of UzGidroMet centre for providing financial and material assistance to carry out this research work, who supported with materials and finance during the writing of this article. The author is especially grateful to their supervisors Olivier Blanpain and Eric Masson.

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