Fe2O3 particles coated with silica using TEOS

Fine particles of SiO2-coated Fe2O3 were prepared by depositing silica on an iron(III) hydroxide precipitate using tetraethoxysilane (TEOS). The silica deposition proceeded under mild conditions at 20 degreesC; crystallization hardly occurred and silica loading was controlled by the amount of TEOS charged, whereas the precipitate crystallized to a mixture of FeO(OH) and alpha-Fe2O3 under hydrothermal conditions. The specific surface area of the SiO2-coated Fe2O3 increased with silica loading, and exceeded 280 m(2) g(-1) even after calcination at 500 degreesC. The silicate species deposited on the precipitate of iron(III) hydroxide prevented the primary particles from agglomerating during calcination, resulting in the high surface area and hard reducibility of the SiO2-Fe2O3.