Preparation of Various Composite TiO 2 /SiO 2 Ultrafine Particles by Vapor-Phase Hydrolysis

Ultrafine TiO 2 /SiO 2 composite particles were prepared by vapor-phase simultaneous hydrolysis of titanium tetraisopropoxide (TTIP) and tetraethoxyorthosilicate (TEOS). The various modes of TiO 2 /SiO 2 composite particles, including both core-shell and mixed-type structures, were prepared according to the methods of reactant mixing. They differed considerably in morphology, size, chemical composition, and crystal structure evolution by heat treatment. In a mixed-type composite of TiO 2 and SiO 2 , SiO 2 inhibited both the growth of the particles and the anatase-to-rutile transformation of TiO 2 .