Preparation and Properties of Iron Oxide Doped Mesoporous Silica Systems

Abstract

In present paper synthetic conditions and properties of mesoporous silica materials containing magnetic iron oxides (γ-Fe2O3, Fe3O4) have been studied. Two synthetic routs have been considered in detail. The first sample series has been prepared by template hydrothermal synthesis via co-condensation of silica and iron oxide (HT). The second sample series has been prepared via intercalation of γ-Fe2O3 nanoparticles into an MCM-48 silica matrix (PM). For these materials specific surface, pore volume, pore and particle sizes have been determined. The relationship of the synthetic method, [Si]/[Fe] ratio, phase composition of the materials and their textural and structural characteristics has been established. Phase composition of the samples was determined by X-ray diffraction (XRD) method. In the samples of FexOy–SiO2 with the component ratios [Si]/[Fe] = 0.4–0.6 synthesized by the HT method, maghemite (γ-Fe2O3) has been found to be the main phase of iron oxide component. For preparation of these samples a solution of FeSO4 and FeCl3 with a molar ratio of 1:1 was used as an iron oxide precursor. According to XRD data γ-Fe2O3 phase is present in all the samples of FexOy–SiO2, obtained by the PM method. Magnetic properties of the both sample series have been studied in the temperature range 4–300 K. According to the hysteresis curves, the sample FexOy–SiO2 ([Fe]/[Si] = 0.6), obtained by the HT method, has been found to be a typical ferromagnetic. The sample with the same oxide ratio obtained by the PM method demonstrated a ferrimagnetic behavior.