Abstract: By pre-hydrolysis of TEOS, TiO₂/SiO₂ composites with homogeneous texture were prepared by a
sol-gel process. These composite powders were characterized by UV/Vis spectra, FT-IR, TEM, XRD, and BET techniques. It was found that the
growth and anatase-to-rutile transformation of titania nanocrystals in the composite were retarded significantly in the presence of small
amount of silica. Mesoporous TiO₂ with high specific surface area and crystalline framework was obtained by selective dissolving of silica
in composite. The fact that more than 90% of silica was removed after selective dissolving and the resulting TiO₂ was mesoporous with mean pore size about
4nm suggested the network of ultrafine silica was continuous and uniform.

Key words: titanium dioxide, transformation, growth of nanocrystals, silica