Structure, magnetic and catalytic properties of SiO2-MFe2O4 (M = Mn, Co, Ni, Cu) nanocomposites and their syntheses by a modified sol-gel method

The structure, magnetic and catalytic properties of silica - ferrite nanocomposites were investigated. A series of SiO2-MFe2O4 (M = Mn, Co, Ni, Cu) composites were synthesized by a sol-gel technique using citric acid and glycerin. The samples were characterized by TGA, XRD, TEM and BET methods. Results of magnetization measurements proved a strong dependence of the saturation magnetization and the blocking temperature on the calcination temperature. The Co-based nanocomposites showed increased coercive field of the magnetic hysteresis loops relative to the other studied nanocomposites. It was also observed that the structural differences of the Cu-based composites subjected to calcination at two temperatures significantly modify the magnetic behavior. The catalytic properties of composites were tested in nitrous oxide decomposition. The conversion of nitrous oxide over the SiO2-MFe2O4 composites increased in the sequence: Mn (39%) < Ni (69%) < Co (76%) = Cu (76%), at temperature 973 K and WHSV = 30000 ml.g(-1).h(-1).