Nickel ferrite on silica nanocomposites prepared by the sol-gel method

Nanocomposites with nickel ferrite nanoparticles uniformly dispersed in silica matrix were successfully synthesized using tetraethoxysilane as a precursor of silica and metallic nitrates as precursors of ferrite. The obtained (NiFe2O4)(X)SiO2(1-x) (0.05 less than or equal to X less than or equal to 0.55) samples were investigated by X-ray diffraction, differential scanning calorimetry, infrared spectroscopy, transmission electron microscopy and vibration sample magnetometer. The results show that for X less than or equal to 0.15 the materials have an amorphous character and for 0.15 less than or equal to X less than or equal to 0.50 the crystalline sizes ranging from 2 to 25 nm increase with increasing concentration, while at higher concentrations, a decrease in the crystalline sizes is observed. The magnetic properties exhibit a strong dependence on the crystalline size, M-s values increase with the crystalline size ranged from 3.7 to 11 emu/g and coercivity can get value as high as 313 Oe, which is more than four times higher than the coercivity of bulk nickel ferrite. (C) 2004 Elsevier B.V. All rights reserved.