Sol-gel formation of gamma-Fe_2O_3/SiO_2 nanocomposites: Effects of different iron raw material

摘要

Silica coated magnetic gamma-Fe_2O_3 nanoparticles were synthesized by the sol-gel method. The crystal phase and magnetic properties of serials of alpha, gamma-Fe_2O_3/SiO_2 from different iron raw materials, submitted to thermal treatment at a temperature of 400 deg 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 deg C in vacuum, the dry gels were sintered at the temperature of 400 deg C to produce the Fe_2O_3 particles. Ferric citrate raw material favored the occurrence of gamma-Fe_2O_3, while ferric chloride gave rise to alpha-Fe_2O_3 formation in SiO_2 matrix.