Mechanics, Materials Science & Engineering, April 2017 – ISSN 2412-5954
Structural and Functional Group Characterization of Nanocomposite Fe3O4/TiO2 and Its Magnetic Property40 V. Maria Vinosel1,a, M. Asisi Janifer1, S. Anand1, S. Pauline1 1 – Department of Physics, Loyola College, University of Madras, Chennai, India a – vinovincent90@gmail.com DOI 10.2412/mmse.36.92.83 provided by Seo4U.link
Keywords: Fe3O4, TiO2,XRD, SEM, FTIR, VSM.
ABSTRACT. Nanocomposites of Fe3O4/TiO2 were prepared by non-thermal method in the ratio 1:4. In this method magnetite and TiO2 anatase nanoparticles were prepared individually by hydrothermal and sol-gel respectively. X-ray diffraction analysis (XRD) of the sample reveals that the peaks can be indexed either to Fe3O4 or TiO2. The morphology and phase composition were characterized by High resolution scanning electron microscope (HRSEM) and Energy dispersive X-ray analysis (EDAX). The Fourier transform infrared (FTIR) spectra reveal information about metal oxygen in the composite. The magnetic properties of the sample were determined by Vibrating sample magnetometer (VSM).
Introduction. Titanium dioxide (TiO2) has much attention due to its applications in environmental purification like detoxification of wastewater, luminescent material, solar cells, gas sensors and medical fields. Titanium dioxide is an n-type semiconductor with a wide energy band gap exhibiting photocatalytic activity. This ceramic material has three different structures: rutile, anatase and brookite. Since the energy band gap (3.23 eV) of the anatase phase is wider than that of rutile (3.02 eV) the anatase phase is known to exhibit better photocatalytic behavior [1]. In such semiconductors, photogenerated carriers (electrons and holes) can tunnel to a reaction medium and participate in chemical reactions. The efficiency of photocatalyst is enhanced by the wider separation of an electrons and holes. Titanium dioxide is extensively used in the fabrication of core-shell systems as a photocatalytic agent because of its exceptional properties such as strong oxidation reaction, large effective surface area and low toxicity [2]. Fe3O4 is a magnetic material with wide applications in many areas such as gas sensors, optoelectronic and spintronic devices, biomedicine, etc. Fe3O4 is a kind of functional material and has attractive physical properties such as half-metallic character and strong spin polarization at room temperature. Its magnetic properties can be tuned by size, shape and dimension [3]. The researcher has been investigating on the design of magnetic core TiO2 shell structure for many applications. They have developed several ways to improve the activity of photocatalysts, such as carbon-doped TiO2, carboncoated TiO2, carbon–nanotube–TiO2 and graphene–TiO2 nanocomposites among these graphene TiO2 nanocomposites showed fantastic activity [4]. Fe3O4-TiO2 core–shell nanoparticles were prepared by a homogeneous method. They found, that Fe3O4-TiO2 core–shell nanostructure has higher photocatalytic activity in contrast to TiO2 nanoparticles and plays a crucial role in the field of malignant tumor therapy was reported by He et al [5]. Even though TiO2 has many advantages, there are some basic challenges in the applications of titanium dioxide nanoparticles 1) collecting and retrieving titania nanoparticles from reaction media is impossible, therefore, the nanoparticles used are not accessible anymore and their recycling is not possible 2) recombination of electrons and holes 40
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excited by ultraviolet radiation would easily take place that reduces the photocatalytic activity of TiO2. In order to overcome these problems, titanium dioxide was supplemented with magnetite nanoparticles (Fe3O4) to increase the photocatalytic activity as well as their recyclability with the help of an external magnetic field [6]. The magnetite was used to enhance separation properties of the photocatalyst from the treated water, whereas the titanium dioxide was useful for the degradation of organic contaminants. In the present study, nanocomposite of Fe3O4/TiO2 was synthesized by non-thermal method. The magnetite and TiO2 anatase nanoparticles were prepared individually by hydrothermal and sol-gel methods respectively. A. Hasanpour et al [7] reported TiO2 shell coating on Fe3O4 core nanoparticles by novel non-thermal method. Experimental. Preparation of Fe3O4 nanoparticles. In a typical procedure, 2M of FeCl2 and 4M of NaOH was dissolved in 40 ml of distilled water. The aqueous solution of NaOH was added drop by drop into the above solution under the vigorous stirring for 20 min. Then the solution was transferred into the autoclave for heat treatment at 180°C for 12 h. It was allowed to cool down to room temperature after the reaction. The precipitate was washed several times with ethanol and acetone by centrifugation. The final product was dried at 50°C for 12 h. Preparation of TiO2 nanoparticles. In the present study, TiO2 nanoparticles were prepared by Solgel method. 100 ml of isopropyl alcohol was added to 15 ml of Titanium (IV) isopropoxide (TTIP). The mixture was stirred for 25 min then 10 ml of water was added drop by drop to the above solution for hydrolysis reaction. It was continuously stirred for 2 h. After an aging period it gets transformed to gel. Then it is filtered and dried in vaccum oven at 80°C for 3 h. The obtained TiO2 was calcinated at 550°C for 4 h. Preparation of Fe3O4/TiO2 nanocomposite. To prepare the nanocomposite of Fe3O4/TiO2 the as prepared magnetite and TiO2 was dispersed in 40 ml of deionised water and kept under ultrasonication for about 30 min. TiO2 nanoparticles was added into Fe3O4 solution. Molar ratio of Fe3O4 to TiO2 was kept at 1:4. The mixture solution was then kept under sonication for about 1 h. Then the solution was centrifuged and precipitate was dried at 300°C for 12 h. The final product was Fe3O4/TiO2 nanopowder. Result and Discussion X-ray diffraction analysis. Fig.1 shows the XRD pattern of Fe3O4/TiO2 nanocomposite. Diffraction peaks corresponding to both Fe3O4 (JCPDS 85-1436) and TiO2 (JCPDS 21-1272) are clearly observed in the coupled diffraction pattern. For pure Fe3O4, the diffraction peaks are located at 2Ө = 35.53°, 30.20°, 43.05°, 57.48°, 62.69° are associated with [220], [311], [400], [511], [440] planes respectively. This pattern has been indexed as magnetite phase with lattice constants a=b=c=8.381 Å. The observed diffraction peaks of TiO2 at 2Ө = 25.4°, 37.9°, 48.1°, 53.9°, 62.8° are associated with [101], [004], [200], [105], [204] planes respectively, which can be assigned to be anatase phase with the lattice parameters of a=b= 3.785 Å c=9.513 Å. From the XRD diffraction peak it is found that the intensities of Fe3O4 have been decreased by TiO2. At the interface between titania and magnetite there is no new phase formation that indicates absence of extra peaks. There is no chemical reaction between Fe3O4 and TiO2 in non-thermal mechanism. The crystallite size of the sample was calculated by Debye Scherrer formula.
d =
Ө
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where is the average crystallite size (nm), is the grain shape factor (0.9), is the X-ray wavelength (nm), is the full width at half maximum in radians and Ө is the Bragg diffraction angle of the 2Ө peak. The average crystalline size was estimated to be 21 nm.
Fig. 1. XRD pattern of Fe3O4/TiO2 nanocomposite. Fourier Transform Infrared (FT-IR) analysis. Helin Niu et al [8] have reported similar absorption peaks observed in the synthesis of Fe3O4/TiO2 visible light active and magnetically recyclable nanocomposite. The FTIR transmission spectra of Fe3O4/TiO2 nanocomposite are shown in Fig. 2. The strong band at 620 cm-1 was assigned to the Ti–O metal oxygen bond. The Fe3O4 high intensity band at 585 cm-1 has been weakened. The broad band around 3432 cm-1 is the asymmetric and symmetric stretching vibrations of O-H group, whereas the band around 1630 cm-1and 2919 cm-1 is the H-O-H bending vibrations of the coordinated water. The Fe3O4 surfaces are linked with hydroxyl group it also enhances the affinity between Fe3O4 and TiO2 nanoparticles.
Fig. 2. FTIR spectrum of Fe3O4/TiO2 nanocomposite.
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Scanning electron microscopy (SEM) analysis. Using electron microscope the surface structure of the as prepared sample was probed. Fe3O4/TiO2 composites were investigated by High resolution scanning electron microscopy (HR-SEM). Fig. 3 shows SEM images for different magnification. The morphology of the as synthesized nanocomposite was spherical in shape and uniform sizes of nanoparticles with strong agglomeration. A. Banisharif et al. [9] reported the similar nanospheres morphology for Fe3O4/TiO2 nanocomposite synthesized by ultrasonic- assisted deposition precipitation method.
Fig. 3. SEM micrographs of Fe3O4/TiO2 nanocomposite. Energy dispersive X-ray (EDX) analysis. Energy dispersive X-ray (EDX) spectra revealed the presence of stoichiometric proportion of Fe, Ti and O elements without extra signals confirms the pure phase of Fe3O4/TiO2 nanocomposite.
Fig. 4. EDX spectrum of Fe3O4/TiO2 nanocomposite. Vibrating sample magnetometer (VSM) analysis. Chu- Ling Zhu et al [3] have reported similar magnetization for Fe3O4/TiO2 nanotubes prepared by wet chemical method. The magnetic behavior MMSE Journal. Open Access www.mmse.xyz 164
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of the sample was investigated using M-H curve from VSM analysis. Fig.5 shows the hysteresis loop of Fe3O4/TiO2 nanocomposite. For Fe3O4/TiO2 nanocomposite saturation magnetization (Ms), remanant magnetization (Mr), coercivity (Hc) was estimated to be 16.80 emu/g, 3.723 emu/g, 181.35 Oe, respectively. The narrow magnetic hysteresis loop with extremely small coercivity and remanence values indicates a near superparamagnetic behavior of Fe3O4/TiO2 nanocomposite. Taking into account the sample contains 20% of Fe3O4 nanoparticle. The Ms is much lower than that of the corresponding bulk Fe3O4 (92 emu/g), which may be due to the small size of the Fe3O4 nanoparticles. The lower values are attributed by the presence of non-magnetic TiO2.
Fig. 5. M-H curve of Fe3O4/TiO2 nanocomposite. Summary. In summary, the crystalline Fe3O4/TiO2 nanocomposites were synthesized by non-thermal method. Each were individually prepared by hydrothermal and sol-gel methods. The X-ray diffraction confirms the pure phase of Fe3O4/TiO2 nanocomposites. The FTIR spectrum reveals the formation of metal oxygen bonds without interactions. The absorption band at 584 cm-1 is assigned to Fe-O stretching band and the strong band at 620 cm-1 was assigned to be Ti-O stretching bands. SEM indicates the formation of agglomerated uniform nanospheres. EDAX confirms the stiochiometric proportion of elements. The magnetic behavior of the sample was analysed by VSM. The Fe3O4/TiO2 nanocomposite exhibits ferromagnetic behavior at room temperature. The as prepared sample has excellent magnetic property it can be used for photocatalytic application using magnetic separation method in various environmental and medical fields. References [1] A.V. Murugan, V. Samuel, V. Ravi, Synthesis of nanocrystalline anatase TiO2 by microwave
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Cite the paper V. Maria Vinosel, M. Asisi Janifer, S. Anand, S. Pauline (2017). Structural and Functional Group Characterization of Nanocomposite Fe3O4/TiO2 and Its Magnetic Property. Mechanics, Materials Science & Engineering, Vol 9. doi:10.2412/mmse.36.92.83
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