Sol–gel formation of γ-Fe2O3/SiO2 nanocomposites: Effects of different iron raw material

Silica coated magnetic γ-Fe2O3 nanoparticles were synthesized by the sol–gel method. The crystal phase and magnetic properties of serials of α, γ-Fe2O3/SiO2 from different iron raw materials, submitted to thermal treatment at a temperature of 400 °C were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), Fourier-transform IR spectroscopy and magnetometry. Different amounts of TEOS, ethanol, water (media), and the different sources of iron, including ferric citrate (adjusting pH with citric acid), ferric chloride (adjusting pH with HCl), ferric nitrate (adjusting pH with nitrate) as raw material were mixed to form sol, and then gel. After drying at 60 °C in vacuum, the dry gels were sintered at the temperature of 400 °C to produce the Fe2O3 particles. Ferric citrate raw material favored the occurrence of γ-Fe2O3, while ferric chloride gave rise to α-Fe2O3 formation in SiO2 matrix.