Synthesis and Characterization of CoFe2O4 particle by PVA sol ...
Advanced Materials Research Vols. 93-94 (2010) pp 659-663 © (2010) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.93-94.659
Synthesis and Characterization of CoFe2O4 particle by PVA sol-gel method A. Hunyeka, C. Sirisathitkulb, P. Hardingc Molecular Technology Research Unit, School of Science Walailak University, Nakon Si Thammarat, 80160, Thailand *E-mail: [email protected] [email protected] [email protected]
Keywords: Cobalt ferrites, Sol-gel method, XRD, Magnetic properties. Abstract. Cobalt ferrite (CoFe2O4) is a soft magnetic material that can be used as fillers in polypropylene. This magnetic polymer composite is studied for its electromagnetic wave absorbing property. To synthesize CoFe2O4 by the polyvinyl alcohol (PVA) sol-gel method, PVA powder was dissolve in distilled water with 5%, 10% and 15% weight per volume. The solution was stirred and regulated at temperature between 60-80°C until turning into PVA gel. Fe and Co powder of atomic ratio 2:1 were then added to the PVA gel with the metal weight per gel volume 1:6, 1:10 and 1: 12. After sintering at 800°C, phases of the synthesized powder were identified by X-ray diffraction (XRD). Magnetic properties of CoFe2O4 were characterized in order to select the appropriate synthesis condition for electromagnetic wave absorbers Introduction Cobalt ferrites (CoFe2O4) are well-known magnetic ceramics used in electrical equipment and microwave devices. When used in high frequency inductors or transformers, the core loss of ferrites is minimal because of their high electrical resistivity and magnetic softness [1]. With good mechanical hardness and chemical stability, they are also candidates as fillers in microwave absorbing polymer composites [2]. Such properties arise from their inverse spinel structure with a nearly close-packed cubic crystal structure. In each unit cell, interstitial sites are occupied by cobalt cations (Co2+) resulting in net magnetic moments of ferrites [1]. CoFe2O4 can be synthesized by various methods such as solid state raction [3], microemulsion [4], chemical co-precipitation [5], hydrothermal method [5], microwave synthesis [6] and sol–gel method [7]. The sol-gel method, a wet chemical process, is efficient for preparing high quality ceramics. The attraction of the gel reaction prevents atom from breaking out, while the chelating gel is dried by heat treatments [8]. Since it can be consistently controlled, the homogeneity on a molecular level can be obtained. The objective of this research is to synthesize CoFe2O4 by the sol-gel method using polyvinyl alcohol (PVA) as a chelating agent. In the characterization stage, structural properties of ferrites were characterized by an X-ray diffraction (XRD) technique and their magnetic moments were measured by a fluxmeter. These properties were analyzed as functions of the sol-gel compositions in order to find an optimum synthesis condition. Experimental The PVA gel was prepared by dissolving PVA powders in distilled water (5%, 10% and 15% w/v) at temperatures between 70 and 80°C. The PVA powders were slowly sprinkled under constant stirring in order to avoid clumping of the material in the water. The PVA solution was kept at temperatures between 70 and 80°C for 5-7 hours or until the solution became clear. Cobalt nitrate (Co(NO3)2⋅6H2O) and iron nitrate (Fe(NO3)3⋅9H2O) powders were then mixed with the PVA solution. The sol-gel reaction was continued about 3 hours and the temperature was then increased to 80°C for 10-12 hours or until the gel was dried. Samples with 3 different ratios of cobalt nitrate weight: iron nitrate weight: gel volume, i.e. 1:2:6, 1:2:10 and 1:2:12, were prepared. All samples All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of the publisher: Trans Tech Publications Ltd, Switzerland, www.ttp.net. (ID: 111.235.71.20-11/12/09,02:51:05)
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Functionalized and Sensing Materials
were sintered at 800°C for 4 hours. In the structural characterization, the X-ray diffractometer (Rigaku model TTRAXIII) uses a copper target in the X-ray source (K α , wavelength=1.54058°A) with 40 kV between the cathode and the copper target. The measurement was performed in the range of 2θ angles from 10 to 80 degrees with each rotating step 0.02 degree. To study the effect of synthesis condition on magnetic properties, the samples were filled in standard 500 mg-drug capsules. The magnetic moment in each capsule were then measured by placing it in a Helmholtz coil (Lake Shore FH-2.5) connected to a fluxmeter (Lake Shore 480).
Figure 1 A fluxmeter connected to a Helmholtz coil in the magnetic moment measurement.
Results and discussion The XRD patterns in figure 2 indicate that samples prepared from 5% PVA powder (A, B, C) contain both CoFe2O4 and Fe2O3 phases. In samples prepared from 10 and 15% PVA powder (D, E), however, Fe2O3 peaks disappear and only CoFe2O4 peaks are identified. In the case of 15% PVA, CoFe2O4 peaks are exceptionaly sharp. It follows that the degree of crystallization in this sample is high and the magnetic moment is reduced as shown in table 1.
Advanced Materials Research Vols. 93-94
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Figure 2 XRD patterns of ferrite products from varying sol-gel components. Data between 32 and 34 degree are magnified to compare the Fe2O3 peak.
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Functionalized and Sensing Materials
Table 1 Magnetic moment of samples with different synthesis condition.
Sample
% PVA powder in water (w/v)
A B C D E
5% 5% 5% 10% 15%
cobalt nitrate: iron nitrate: PVA gel 1:2:6 1:2:10 1:2:12 1:2:12 1:2:12
Magnetic moment (µWb⋅cm) 2.626 2.084 1.685 2.772 1.758
Magnetic behaviors of samples are confirmed by the measurement of magnetic moment which is related to the saturation magnetization. In table 1, the magnetic moments are shown with the variation of sol-gel compositions. Polymerized by heating, the PVA powders become high density network polymers and the amount of PVA powder in the distill water regulates the viscosity of the gel. The function of gel is to cleave metal atoms during the water evaporation. When the sol-gel composition in table 1 is 1:2:12, 10% PVA powder gives rise to the highest magnetic moment. The lowest viscosity in this experiment obtained from 5% PVA powder is still enough to keep metal atoms from breaking out. While the viscosity depends on the density of the PVA powder in the distilled water at any temperature, the degree of reaction is controlled by the ratio of cobalt and iron nitrate per gel. The high density network structure results in more reactive powders. According to table 1, the magnetic moment was increased with increasing ratio of cobalt and iron nitrate per gel. The increased amount of gel improves the degree of crystallization of ferrite products [9]. In the case of high degree of crystallization of CoFe2O4 powders, the response of magnetization to the external magnetic field is lowered and the magnetic moments are therefore decreased. Conclusions Five sets of ferrites were produced by the sol-gel method with PVA as a chelating agent of different sol-gel compositions. When 5% PVA powder in the distilled water was used, the ferrite products clearly consisted of CoFe2O4 and Fe2O3. However, only sharp CoFe2O4 peaks were exhibited in samples prepared from 10 and 15% PVA powder. The contents of PVA powder also influenced the viscosity of the gel and and the magnetic moment of ferrite products. The magnetic moment was increased with increasing ratio of cobalt and iron nitrate per gel. From this experiment, the appropiate synthesis condition for CoFe2O4 used as fillers in polypropylene composites for electromagnetic wave absorber can be selected. Acknowledgments This work is supported by Molecular Technology Research Unit, School of Science, Walailak University and Industry/University Cooperative Research Center (I/U CRC) in HDD Component Faculty of Engineering, Khon Kaen University, Thailand. X-ray diffraction was carried out at National Metal and Materials Technology Center (MTEC). References [1] C. Robert and O’Handley: Modern Magnetic Materials:Principles and Applications (A WileyInterscience Publication, USA 2000). [2] W. Fu, S. Liu, W. Fan, H. Yang, X. Pang, J. Xu and G. Zou: J. Magn. Magn. Mater. Vol. 316 (2007), p. 54–58 [3] A. Rafferty, T. Prescott and D. Brabazon: Ceram Int. Vol. 34 (2008), p.15
Advanced Materials Research Vols. 93-94
663
[4] E.J. Choi, Y. Ahn, S. Kim, D.H. An, K.U. Kang, B.G. Lee, K.S. Baek and H.N. Oak: J. Magn. Magn. Mater. Vol. 262 (2003), p. 198–202 [5] M. Bradiceanu, P. Vlazan, S. Novaconi, I. Grozescu and P.Barvinschi: Chem. Bull. “Politehnica” Univ. Vol. 52 (2007), p.141 [6] F. Bensebaa, F. Zavaliche, P. L’Ecuyer, R.W. Cochrane and T. Veres: J. Colloid and Interface Sci. Vol. 277 (2004), p. 104–110 [7] J.G. Lee, J.Y. Park and C.S. Kim: J. Mater. Sci. Vol. 33 (1998), p. 3965 [8] L.A. Garcia-cerda, M.U. Escareno-castro and M. Salazar-Zertuche: J. Non-Cryst. Solids Vol. 353 (2007), p.808 [9] R. Qin, F. Li, L. Liu and W. Jiang: J. Alloys Comp. Vol. 482 (2009), p.509
Synthesis and Characterization of CoFe2O4 particle by PVA sol-gel method A. Hunyeka, C. Sirisathitkulb, P. Hardingc Molecular Technology Research Unit, School of Science Walailak University, Nakon Si Thammarat, 80160, Thailand *E-mail: [email protected] [email protected] [email protected]
Keywords: Cobalt ferrites, Sol-gel method, XRD, Magnetic properties. Abstract. Cobalt ferrite (CoFe2O4) is a soft magnetic material that can be used as fillers in polypropylene. This magnetic polymer composite is studied for its electromagnetic wave absorbing property. To synthesize CoFe2O4 by the polyvinyl alcohol (PVA) sol-gel method, PVA powder was dissolve in distilled water with 5%, 10% and 15% weight per volume. The solution was stirred and regulated at temperature between 60-80°C until turning into PVA gel. Fe and Co powder of atomic ratio 2:1 were then added to the PVA gel with the metal weight per gel volume 1:6, 1:10 and 1: 12. After sintering at 800°C, phases of the synthesized powder were identified by X-ray diffraction (XRD). Magnetic properties of CoFe2O4 were characterized in order to select the appropriate synthesis condition for electromagnetic wave absorbers Introduction Cobalt ferrites (CoFe2O4) are well-known magnetic ceramics used in electrical equipment and microwave devices. When used in high frequency inductors or transformers, the core loss of ferrites is minimal because of their high electrical resistivity and magnetic softness [1]. With good mechanical hardness and chemical stability, they are also candidates as fillers in microwave absorbing polymer composites [2]. Such properties arise from their inverse spinel structure with a nearly close-packed cubic crystal structure. In each unit cell, interstitial sites are occupied by cobalt cations (Co2+) resulting in net magnetic moments of ferrites [1]. CoFe2O4 can be synthesized by various methods such as solid state raction [3], microemulsion [4], chemical co-precipitation [5], hydrothermal method [5], microwave synthesis [6] and sol–gel method [7]. The sol-gel method, a wet chemical process, is efficient for preparing high quality ceramics. The attraction of the gel reaction prevents atom from breaking out, while the chelating gel is dried by heat treatments [8]. Since it can be consistently controlled, the homogeneity on a molecular level can be obtained. The objective of this research is to synthesize CoFe2O4 by the sol-gel method using polyvinyl alcohol (PVA) as a chelating agent. In the characterization stage, structural properties of ferrites were characterized by an X-ray diffraction (XRD) technique and their magnetic moments were measured by a fluxmeter. These properties were analyzed as functions of the sol-gel compositions in order to find an optimum synthesis condition. Experimental The PVA gel was prepared by dissolving PVA powders in distilled water (5%, 10% and 15% w/v) at temperatures between 70 and 80°C. The PVA powders were slowly sprinkled under constant stirring in order to avoid clumping of the material in the water. The PVA solution was kept at temperatures between 70 and 80°C for 5-7 hours or until the solution became clear. Cobalt nitrate (Co(NO3)2⋅6H2O) and iron nitrate (Fe(NO3)3⋅9H2O) powders were then mixed with the PVA solution. The sol-gel reaction was continued about 3 hours and the temperature was then increased to 80°C for 10-12 hours or until the gel was dried. Samples with 3 different ratios of cobalt nitrate weight: iron nitrate weight: gel volume, i.e. 1:2:6, 1:2:10 and 1:2:12, were prepared. All samples All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of the publisher: Trans Tech Publications Ltd, Switzerland, www.ttp.net. (ID: 111.235.71.20-11/12/09,02:51:05)
660
Functionalized and Sensing Materials
were sintered at 800°C for 4 hours. In the structural characterization, the X-ray diffractometer (Rigaku model TTRAXIII) uses a copper target in the X-ray source (K α , wavelength=1.54058°A) with 40 kV between the cathode and the copper target. The measurement was performed in the range of 2θ angles from 10 to 80 degrees with each rotating step 0.02 degree. To study the effect of synthesis condition on magnetic properties, the samples were filled in standard 500 mg-drug capsules. The magnetic moment in each capsule were then measured by placing it in a Helmholtz coil (Lake Shore FH-2.5) connected to a fluxmeter (Lake Shore 480).
Figure 1 A fluxmeter connected to a Helmholtz coil in the magnetic moment measurement.
Results and discussion The XRD patterns in figure 2 indicate that samples prepared from 5% PVA powder (A, B, C) contain both CoFe2O4 and Fe2O3 phases. In samples prepared from 10 and 15% PVA powder (D, E), however, Fe2O3 peaks disappear and only CoFe2O4 peaks are identified. In the case of 15% PVA, CoFe2O4 peaks are exceptionaly sharp. It follows that the degree of crystallization in this sample is high and the magnetic moment is reduced as shown in table 1.
Advanced Materials Research Vols. 93-94
661
Figure 2 XRD patterns of ferrite products from varying sol-gel components. Data between 32 and 34 degree are magnified to compare the Fe2O3 peak.
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Functionalized and Sensing Materials
Table 1 Magnetic moment of samples with different synthesis condition.
Sample
% PVA powder in water (w/v)
A B C D E
5% 5% 5% 10% 15%
cobalt nitrate: iron nitrate: PVA gel 1:2:6 1:2:10 1:2:12 1:2:12 1:2:12
Magnetic moment (µWb⋅cm) 2.626 2.084 1.685 2.772 1.758
Magnetic behaviors of samples are confirmed by the measurement of magnetic moment which is related to the saturation magnetization. In table 1, the magnetic moments are shown with the variation of sol-gel compositions. Polymerized by heating, the PVA powders become high density network polymers and the amount of PVA powder in the distill water regulates the viscosity of the gel. The function of gel is to cleave metal atoms during the water evaporation. When the sol-gel composition in table 1 is 1:2:12, 10% PVA powder gives rise to the highest magnetic moment. The lowest viscosity in this experiment obtained from 5% PVA powder is still enough to keep metal atoms from breaking out. While the viscosity depends on the density of the PVA powder in the distilled water at any temperature, the degree of reaction is controlled by the ratio of cobalt and iron nitrate per gel. The high density network structure results in more reactive powders. According to table 1, the magnetic moment was increased with increasing ratio of cobalt and iron nitrate per gel. The increased amount of gel improves the degree of crystallization of ferrite products [9]. In the case of high degree of crystallization of CoFe2O4 powders, the response of magnetization to the external magnetic field is lowered and the magnetic moments are therefore decreased. Conclusions Five sets of ferrites were produced by the sol-gel method with PVA as a chelating agent of different sol-gel compositions. When 5% PVA powder in the distilled water was used, the ferrite products clearly consisted of CoFe2O4 and Fe2O3. However, only sharp CoFe2O4 peaks were exhibited in samples prepared from 10 and 15% PVA powder. The contents of PVA powder also influenced the viscosity of the gel and and the magnetic moment of ferrite products. The magnetic moment was increased with increasing ratio of cobalt and iron nitrate per gel. From this experiment, the appropiate synthesis condition for CoFe2O4 used as fillers in polypropylene composites for electromagnetic wave absorber can be selected. Acknowledgments This work is supported by Molecular Technology Research Unit, School of Science, Walailak University and Industry/University Cooperative Research Center (I/U CRC) in HDD Component Faculty of Engineering, Khon Kaen University, Thailand. X-ray diffraction was carried out at National Metal and Materials Technology Center (MTEC). References [1] C. Robert and O’Handley: Modern Magnetic Materials:Principles and Applications (A WileyInterscience Publication, USA 2000). [2] W. Fu, S. Liu, W. Fan, H. Yang, X. Pang, J. Xu and G. Zou: J. Magn. Magn. Mater. Vol. 316 (2007), p. 54–58 [3] A. Rafferty, T. Prescott and D. Brabazon: Ceram Int. Vol. 34 (2008), p.15
Advanced Materials Research Vols. 93-94
663
[4] E.J. Choi, Y. Ahn, S. Kim, D.H. An, K.U. Kang, B.G. Lee, K.S. Baek and H.N. Oak: J. Magn. Magn. Mater. Vol. 262 (2003), p. 198–202 [5] M. Bradiceanu, P. Vlazan, S. Novaconi, I. Grozescu and P.Barvinschi: Chem. Bull. “Politehnica” Univ. Vol. 52 (2007), p.141 [6] F. Bensebaa, F. Zavaliche, P. L’Ecuyer, R.W. Cochrane and T. Veres: J. Colloid and Interface Sci. Vol. 277 (2004), p. 104–110 [7] J.G. Lee, J.Y. Park and C.S. Kim: J. Mater. Sci. Vol. 33 (1998), p. 3965 [8] L.A. Garcia-cerda, M.U. Escareno-castro and M. Salazar-Zertuche: J. Non-Cryst. Solids Vol. 353 (2007), p.808 [9] R. Qin, F. Li, L. Liu and W. Jiang: J. Alloys Comp. Vol. 482 (2009), p.509
