Synthesis and Characterization of Alumina Zirconia Composite Material Doped with Silica

Article

Synthesis and Characterization of Alumina Zirconia Composite Material Doped with Silica Manas Ranjan Majhi1, S Viswakarma2, NS Meheta3, K Sauravh4, S Singh5

Abstract Present research work deals with synthesis of alumina zirconia silica Composite material by mixed powder composed of varying weight percentage of alumina and silica with fixed 30% weight composition of zirconia. The characteristics such as bulk density, apparent porosity, linear shrinkage and weight loss behaviour, XRD, bending strength and micro structures of different samples were analysed comparatively with gradual increment of silica content from 0 to 4wt% into base composition. After sintering at 1200°C, samples shows significant change in its physical and microstructural properties such as densification and reduction in apparent porosity, XRD pattern reveal zirconium aluminium oxide phase with conversion of monoclinic zirconia to tetragonal phase and bending strength ware also improved apparently. Micro structure analysis of sintered composite gives relative grain sizes and phases present in different samples which shows improved bonding between the matrixes with silica addition.

Keywords: Alumina Zirconia, Silica, XRD pattern Introduction There are some common refractories which are commonly used in composites for their property of withstanding high temperature without showing any sign of melting or deformation also with better mechanical and physical properties.1 The composites made using these ceramic materials are widely used in industrial applications.

Specifically, they are used in the steel industry, cement industry, glass industry etc. Refractory materials with ZrO2 contents ranging from 30 to 42wt % are manufactured by melting and casting, and are characterized by high corrosion resistance toward several types of aggressive environments.2,3 However it was seen experimentally, the presence of ZrO2 in AZS refractories causes a significant change in volume of about 3-5% above 1000°C due to tetragonal to monoclinic phase transformation in ZrO2, which corresponds to a martensitic transformation.4-5 During cooling of the material, the martensitic transformation causes the formation of micro cracks and porosity, with a decrease in mechanical strength, associated with a reduction in its Young‘s modulus.7,8 The present work deals with improving mechanical and physical properties with silica addition.9,10

1,2,3,4,5

Department of Ceramic Engineering, Indian Institute of Technology (BHU), Varanasi, Uttar Pradesh, India.

Correspondence: Mr. Manas Ranjan Majhi, Indian Institute of Technology (BHU), Varanasi, Uttar Pradesh, India.

E-mail Id: mrmajhi.cer@itbhu.ac.in Orcid Id: http://orcid.org/0000-0001-9081-0469 How to cite this article: Majhi MR, Viswakarma S, Meheta NS et al. Synthesis and Characterization of Alumina Zirconia Composite Material Doped with Silica. J Adv Res Glass Leath Plast Tech 2017; 2(1&2): 18-24.

© ADR Journals 2017. All Rights Reserved.

J. Adv. Res. Glass Leath. Plast. Tech. 2017; 2(1&2)

Majhi MR et al.

Experimental Procedure

Sample Characterization

Composition of Material

After preparation and sintering the sample were characterized i.e. Bulk density, apparent density, linear shrinkage, weight loss. Phase determination by XRD analysis the main aim of project is to improve the properties of material after adding 2%, 4% of silica as an additive.

Table 1.Batch Composition

Sample No. 1 2 3

Alumina (wt. %) 70 68 66

Zirconia (wt %) 30 30 30

Silica (wt %) 0 2 4

Results and Discussion

Experimental Procedure

Bulk Density Measurement

Al2O3 (70wt %) + ZrO2 (30wt %) <100gm> mix with 2wt%, 4wt% of silica with additive of 2% PVA which act as binder. Mix powder press in steel die (1.5cm) by hydraulic pressure at 15tonn/sq. inch, for making powder in pellet form, all pellets pressed at constant rate of load as 1 minute time (holding time).

Bulk density of all the sintered samples were determined and analysed comparatively for their values. The bulk density of the composite continuously increases with increased silica content which are listed below.

Table 2.Bulk Density of Different Samples

These pellets are sintered at a temperature of 1200°C. Fired at required temperature with shocking time period of 30 min. measured weight loss, linear shrinkage properly using veneer scale before and after sintering. Determine the behaviour of bulk density, weight losses, linear shrinkage, and apparent porosity

Sample No. 1 2 3

Bulk density (gm/cc) 1.61 1.71 1.85

Figure 1.Bulk Density vs. Silica wt%

Measurement of Apparent Porosity Apparent porosity of all sintered samples is determined and analysed comparatively for their values. The apparent porosity of the composite continuously increases with decrease bulk density.

The apparent porosity of the composite continuously decreases with increased silica content which are listed below:

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Table 2.Apparent porosity of different samples Sample No. Apparent porosity (%) 1 19.03 2 10.62 3 6.84 A graph plotted between bulk density values with increasing silica composition which is given below:

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J. Adv. Res. Glass Leath. Plast. Tech. 2017; 2(1&2)

20 18 16 14 12 Apparent porosity10 8 (in %) 6 4 2 0 Silica 0%

Silica 2%

Silica 4%

Figure 2.Apparent Porosity vs. silica %

The densification of Alumina zirconia silica composite material was confirmed, apparent porosity decreased with the increase of silica content but bulk density increases. Increased densification with increased silica due to the presence of discrete secondary zirconia phase. Retarded grain growth did not allow pores to become trapped within the grains. As a result the pores did not grow in size but were eliminated from the surface of the grains. This phenomenon led to

decreased porosity and improved densification of the Alumina zirconia silica composite material.

Weight Loss Calculation Weights of all samples are taken before and after sintering, hence giving the percentage of weight loss in different compositions which are given below in table.

Table 3.Weight loss Percentage

Sample no.

1 2 1 2 1 2

Batch 1 Batch 2 Batch 3

Initial weight 4.503 5.137 3.247 4.125 3.199 3.796

Linear Shrinkage Measurement Linear dimensions such as length, width, thickness are taken before and after sintering. These dimensions

Final weight 4.074 4.654 2.994 3.935 3.026 3.684

Weight loss % 9.53 9.402 7.79 4.606 5.408 2.95

show shrinkage behaviour after sintering because of moisture elimination which was earlier present in green body. Different samples of different batch are dimensionally measured which are obtained as given below:

Table 4.Linear Shrinkage Percentage

Sample no.

1

2

3

Length Width Thickness Length Width Thickness Length Width Thickness

It is found that Shrinkage values for linear dimensions decrease on increasing silica value in the composite

Initial 41.41 10.58 6.1 41.41 10.58 4.31 41.41 10.58 5.07

final 40.6 10.41 6.02 40.77 10.42 4.26 40.84 10.45 5.02

Shrinkage (%) 1.96 1.61 1.31 1.55 1.51 1.16 1.38 1.23 0.99

material. The above tabulated values of shrinkage values graphically represented as below:

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2.5

2

1.5 Length Shrinkage %

Width Shrinkage % 1

Thickness Shrinkage % 0.5

0 Sample No. 1 Sample No 2 Sample No 3

Figure 3.Shrinkage Percentage Values of Different Samples

XRD Analysis XRD Analysis of Base Composition Powder X-ray diffraction patterns are carried out for all compositions using ‘Rigaku High Resolution Powder X-ray Diffractometer’ with Cu Kα1 radiation and Nifilter is employed at room temperature. Fig. shows

the XRD pattern of base composition sintered powder.

Powder X-ray diffraction pattern of the sample show different phases that is because of converting ZrO2 into tetragonal form (t) and there is also a small peak of monoclinic (m) phase is present in the graph. The ZrO2 is stabilized because of alumina presence in composition. All peaks of Zirconium Aluminium oxide phase is matched with JCPDS file no. 820494.

Figure 4.XRD Pattern of Base Composition (Alumina Zirconia Composite)

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The pattern shows no any residual alumina phase. The XRD patterns were recorded in the 2- theta range of 10-80 degree.

XRD Analysis after 2% and 4% Silica Addition It is seen that some unreacted SiO2 remains in the samples as residual form fired at relatively lower temperatures such as 1200°C, since there is no reaction taken place with silica.

Figure 5.XRD Pattern with Silica Addition

But it gives the scope for further phase formation at higher temperature range with increasing values of silica content. In present case phases remains same as obtained earlier. The XRD pattern does not change with slight change of silica addition as from 2% to 4% in base composition of Alumina Zirconia Composite material; however it enhances the mechanical properties as seen previously. The XRD pattern with silica addition is shown in Fig. 5.

Modulus of Rupture/ Flexural Strength Flexural strength or bending strength of different samples of different batch are calculated from three

point bending set up which are tabulated as below: Table 5.Bending Strength Values for Different Samples

Sample No. 1 2 3

Bending Strength (MPa) 59.51 205.60 232.62

These bending strength shows increment in values with increasing silica value in composition. This is because of the fact that content increases mechanical behaviour of composition that is Alumina zirconia composite.

their their silica base

70 60

59.62 51.6

50 Bendin 40 g Strengt h 30 (MPa)

39.51

20 10 0 0 Silica %

2

4

Figure 6.Bending Strength vs. Silica Composition at 1200°C

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Hence, higher densification with increased silica content helps in improving bending strength of Alumina Zirconia Silica composite material. Variation in bending strength has shown graphically as above.

Microstructure Characterization The microstructure of Alumina zirconia silica composite has been examined for each batch composition with slight increment of silica content.

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From sample 1 to 3 due to densification and decrease in porosity value more uniform matrix of the composite material is obtained. It gives clear indication of improvement in mechanical properties such as bending strength because of improved bonding between the matrixes which is lesser in base composition of alumina zirconia composite. It clearly shows changes in its microstructure by following graphs:

Figure 7.Microstructure in Alumina Zirconia Silica Composite

This microscopy can be utilized in finding the length of required phase or voids. Some of the lengths measured in each samples are obtained as below: Table 6.Micro Measurement Data in Different Samples

Measurement Name L1

L2

L3

L4

Sample No. 1 2 3 1 2 3 1 2 3 1 2 3

Length (Micron) 3.530 3.046 1.857 6.746 1.732 2.716 1.500 3.267 3.233 26.072 3.775 0.866

The bulk density of the composite material increase with increase the silica percentage in base composition of alumina zirconia composite material.

Apparent porosity decreases with increasing silica percentage because of retarded grain growth which does not allow pores to become trapped within the grains. As a result, the pores do not grow in size and are also eliminated from the surface of the grains.

Percentage linear shrinkage decreases with increasing silica content. There is slight weight reduction of every sample after sintering at 1200°C. From the XRD analysis, it is confirmed that different phases are developed after sintering. Strength of the material increases with increasing silica content. Bending strength of base composition i.e. alumina zirconia composite is low when there is no presence of silica content in it. Microstructure comparisons of different samples clearly identify the improved physical and mechanical properties.

Conclusions

References

Various tests have been done to study the characteristics of alumina zirconia silica composite material. The tests are the rate of shrinkage measurement, bulk density and porosity percentage measurement, bending strength and weight loss calculations. The entire test was done for sintering temperature of 1200°C with 30 min soaking time. A dimensions change such as length, width and thickness measurements of composite materials has shown reductions after sintering.

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