Nanostructured pure γ-Fe2O3 via forced precipitation in an organic solvent

Pure maghemite, gamma-Fe2O3, was prepared as ultra fine particles in the nanometer-sized range via the forced precipitation method in an organic solvent. The precipitation of iron(III) ions, from iron(III) chloride in 2-propanol led selectively to highly dispersed particles of ferrihydrite, which upon treatment with temperatures higher than 200degreesC under dynamic vacuum resulted in high-surface-area particles of gamma-Fe2O3. Precipitation in water also led to ferrihydrite, but the final product, after heating at 300degreesC, contained a mixture of gamma-Fe2O3 and alpha-Fe2O3 (hematite). The precipitation from iron(III) nitrate in water resulted in goethite which was converted to hematite upon heating. On the other hand, the final product in 2-propanol was a mixture of maghemite and hematite. The products were characterized by FTIR, TGA, XRD, and gas sorption analysis. Nitrogen gas adsorption studies for the pure gamma-Fe2O3 samples revealed mesoporous particles with high surface areas in the range of 70-120 m(2) g(-1) after heat treatment at 300degreesC. The gamma-Fe2O3 particles retained their gamma-phase as well as their mesoporous structure at relatively high temperatures, as high as 400degreesC.