Influence of calcination temperature on structural and magnetic properties of nanocomposites formed by Co-ferrite dispersed in sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate as precursor |
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Authors: | Mehrnaz Gharagozlou |
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Institution: | (1) Department of Nanotechnology and Nanomaterials, Institute for Color Science and Technology, P.O. Box 16765-654, Tehran, Iran |
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Abstract: | Effects of calcination temperatures varying from 400 to 1000°C on structural and magnetic properties of nanocomposites formed
by Co-ferrite dispersed in the sol-gel silica matrix using tetrakis(2-hydroxyethyl) orthosilicate (THEOS) as water-soluble
silica precursor have been investigated. Studies carried out using XRD, FT-IR, TEM, STA (TG-DTG-DTA) and VSM techniques. Results
indicated that magnetic properties of samples such as superparamagnetism and ferromagnetism showed great dependence on the
variation of the crystallinity and particle size caused by the calcination temperature. The crystallization, saturation magnetization
Ms and remenant magnetization Mr increased as the calcination temperature increased. But the variation of coercivity Hc was not in accordance with that of Ms and Mr, indicating that Hc is not determined only by the crystallinity and size of CoFe2O4 nanoparticles. TEM images showed spherical nanoparticles dispersed in the silica network with sizes of 10-30 nm. Results
showed that the well-established silica network provided nucleation locations for CoFe2O4 nanoparticles to confinement the coarsening and aggregation of nanoparticles. THEOS as silica matrix network provides an
ideal nucleation environment to disperse CoFe2O4 nanoparticles and thus to confine them to aggregate and coarsen. By using THEOS as water-soluble silica precursor over the
currently used TEOS and TMOS, the organic solvents are not needed owing to the complete solubility of THEOS in water. Synthesized
nanocomposites with adjustable particle sizes and controllable magnetic properties make the applicability of Co-ferrite even
more versatile. |
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