Preparation and characterization of porous ultrafine Fe2O3 particles

Porous ultrafine Fe2O3 particles were prepared by homogeneous precipitation method. Fe3+ and urea were chosen as starting materials and anionic surfactant as the template. It is shown that the reaction results in the precipitation of a gelatinous hydrous iron oxide/surfactant mixture, which gives ultrafine Fe2O3 particles after drying and calcinations. The products were characterized by XRD, TEM, TG/DTA and BET. Conventional XRD patterns show that the products are mixture of γ-Fe2O3 and α-Fe2O3 phase after being sintered at 350 °C, and γ-Fe2O3 transforms entirely to α-Fe2O3 when sintered at 650 °C. The low-angle XRD patterns indicate that the mesostructure can only exist between 350 and 400 °C. TEM results show that the Fe2O3 particles have diameters of about 30 nm and lengths ranging from 100 to 120 nm; in each particle, there are several vermiculate-like mesopores with diameter of about 20–25 nm. The BET surface areas in excess of 50 m2/g are obtained after calcinations at 350 °C. The BJH desorption average pore width is around 22 nm, which is in agreement with the TEM results. The results show that anionic surfactant and sintering temperature are important to obtain this special morphology.