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Titania-silica (TS) nanocomposite powder with three different composite structures, containing 10―30 mol% SiO2 in each structure, have been prepared by sol-gel processes. The surface characteristics of these titania-silica samples have been investigated by X-ray photo-emission spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM). The study for all TS oxides annealed at 773 and 1173 K showed: an abnormal surface enrichment in Si increased with increasing annealing temperature; the Ti3+, Ti2+, Si3+ and Si2+ oxides coexisted with Ti4+ and Si4+ oxides, and the contents of these Ti/Si suboxides increased with increasing SiO2 content and annealing temperature; there was a layer rich in O on the topmost surface and the excess O could be attributed to the chemadsorption of H2O; different composite structures could lead to different contents of Ti/Si suboxides. These results indi- cated that the surface of TS oxide powder derived by sol-gel process was a double layer with enriched O first and then SiOx/TiOy (x, y<2). Ti/Si suboxides could result from the thermal diffusion of Ti4+ and Si4+, which might be induced by the strong interaction between Ti4+ and Si4+.
Titania-silica (TS) nanocomposite powders with three different composite structures, containing 10-30 mol% SiO 2 in each structure, have been prepared by sol-gel processes. The surface characteristics of these titania-silica samples have been investigated by X-ray The study for all TS oxides annealed at 773 and 1173 K showed: an abnormal surface enrichment in Si increased with increasing annealing temperature; the Ti3 +, Ti2 +, Si3 + and Si2 + oxides coexisted with Ti4 + and Si4 + oxides, and the contents of these Ti / Si suboxides increased with increasing SiO2 content and annealing temperature; there was a layer rich in O on the topmost surface and the excess O could be attributed to the chemadsorption of H2O ; different composite structures could lead to different contents of Ti / Si suboxides. These results indi- cated that the surface of TS oxide powder derived by sol-gel process was a double laye r with enriched O first and then SiOx / TiOy (x, y <2). Ti / Si suboxides could result from the thermal diffusion of Ti4 + and Si4 +, which might be induced by the strong interaction between Ti4 + and Si4 +.