Sol-gel route to synthesize titania-silica nano precursors for photoactive particulates and coatings

Nano titanium dioxide sols containing silica in the range 5-50 mol% have been synthesized using sol-gel route starting from titanyl sulphate with a view of developing antisoiling surfaces. The titania sol had an average particle size of similar to 30 nm while the average size of titania-silica sol was 61 nm. The influence of silica addition on the phase transition and grain growth of nanocrystalline titania has been investigated. The effect of calcination temperature on the photocatalytic activity of nano titania has been reported. A titania-silica composition containing 30 mol% SiO2 (TS-30), annealed at 700 A degrees C has shown the highest photoactivity. While the 30% silica composition retained 100% anatase phase up to 800 A degrees C, the pure titania has started transformation to rutile at 600 A degrees C. Commercial glazed ceramic tiles, coated with titania-silica precursor sols and annealed at 700 A degrees C, have been found to be photoactive. The addition of silica has enhanced the photoactivity while suppressing the phase transformation of titania from anatase to rutile.