Synthesis and characterization of Fe2O3/SiO2 nanocomposites

Fe2O3/SiO2 nanocomposites based on fumed silica A-300 (S-BET = 337 m(2)/g) with iron oxide deposits at different content were synthesized using Fe(III) acetylacetonate (Fe(acac)(3)) dissolved in isopropyl alcohol or carbon tetrachloride for impregnation of the nanosilica powder at different amounts of Fe(acac)(3) then oxidized in air at 400-900 degrees C. Samples with Fe(acac)(3) adsorbed onto nanosilica and samples with Fe2O3/SiO2 including 6-17 wt% of Fe2O3 were investigated using XRD, XPS, TG/DTA, TPD MS, FTIR, AFM, nitrogen adsorption, Mossbauer spectroscopy, and quantum chemistry methods. The structural characteristics and phase composition of Fe2O3 deposits depend on reaction conditions, solvent type, content of grafted iron oxide, and post-reaction treatments. The iron oxide deposits on A-300 (impregnated by the Fe(acac)(3) solution in isopropanol) treated at 500-600 degrees C include several phases characterized by different nanoparticle size distributions; however, in the case of impregnation of A-300 by the Fe(acac)(3) solution in carbon tetrachloride only alpha-Fe2O3 phase is formed in addition to amorphous Fe2O3. The Fe2O3/SiO2 materials remain loose (similar to the A-300 matrix) at the bulk density of 0.12-0.15 g/cm(3) and SBET = 265-310 m(2)/g. (C) 2009 Elsevier Inc. All rights reserved.