CoFe2O4/SiO2 nanocomposites by thermal decomposition of some complex combinations embedded in hybrid silica gels

The study reports the preparation of CoFe2O4/SiO2 nanocomposites by a new modified sol-gel method starting from cobalt nitrate, iron nitrate, and diols: 1,2-ethanediol (EG), 1,3-propanediol (1,3PG), and tetraethylorthosilicate (TEOS), for final compositions of 30 %CoFe2O4/70 %SiO2 and 50 %CoFe2O4/50 %SiO2. The method is based on the formation of a Co(II), Fe(III)-carboxylate precursors mixture, during the redox reaction between the NO (3) (-) ion and the diol (similar to 140 A degrees C) within the silica gels. The thermal decomposition of these complex combinations takes place at similar to 300 A degrees C leading to the corresponding amorphous metal oxides within the pores of the hybrid gels. Depending on the subsequent thermal treatment, CoFe2O4 can be obtained as single phase or in a mixture with Co2SiO4. The CoFe2O4 crystallites sizes are in the nanometer range (3-10 nm). The obtained nanocomposites have a hard magnet behavior, as a result of the high anisotropy of CoFe2O4 having large hysteresis cycles.