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-...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+.展开更多
基金Supported by the National Natural Science Foundation of China (Grant Nos. 20776091 and 90306014)
文摘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+.
