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533397 
Journal Article 
Surface chemical structure of titania-silica nanocomposite powder 
Wang, LY; Sun, YP; Xu, BS 
2008 
Yes 
Chinese Science Bulletin
ISSN: 1001-6538
EISSN: 1861-9541 
53 
19 
2964-2972 
English 
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 layerrich in O on the topmost surface and the excess O could be attributed to the chem-adsorption of H2O; different composite structures could lead to different contents of Ti/Si suboxides. These results indicated 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+. 
surface structure; titania-silica; sol-gel; suboxide; nanocomposite; visible-light irradiation; sol-gel process; photocatalytic activity; active-sites; mixed oxides; thin-films; tio2; tio2/sio2; microstructure; tio2-sio2