Synthesis of CoFe2O4 nanoparticles embedded in a silica matrix by the citrate precursor technique

A metals-citrate-silica gel was prepared from metallic salts, citric acid and tetraethylorthosilicate by sol-gel method (citrate precursor technique) and it was further used to prepare magnetic nanocomposites. The gel was dried at 100 degrees C and then calcined at temperatures between 600 and 1000 degrees C to obtain powder samples. The nanocomposites were characterized by XRD, IR, VSM and TEM techniques. The diffraction patterns show the formation of a single magnetic phase identified as CoFe2O4. Magnetic nanoparticles with average size less than 50 nm were obtained which are well dispersed in the silica matrix. The combination of different metals concentrations and calcining temperatures allowed obtaining samples with magnetization ranging from 3.6 to 25.3 emu/g. (C) 2005 Published by Elsevier B.V.