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采用3种溶胶凝胶工艺制得钛包硅、硅包钛及钛硅均匀混合3种结构的钛硅纳米复合氧化物粉体,每个结构的SiO2摩尔分数分别为10%~30%.利用X射线光电子能谱(XPS)及高分辨透射电子显微镜(HRTEM)对样品表面的化学结构进行表征.对所有经773和1173K热处理的样品表面研究表明:有相当数量的Si原子在表面富集,其含量随热处理温度升高而增加;表面Ti3+,Ti2+,Si3+,Si2+低价氧化物与Ti4+和Si4+氧化物共存,随热处理温度升高和SiO2含量增大,表面低价钛氧化物和低价硅氧化物含量增大;钛硅复合氧化物表面的浅表层为富氧层,多余的氧可能来自化学吸附水.复合结构不同导致表面各种价态的钛氧化物和硅氧化物含量不同.这些结果表明溶胶凝胶法制得的钛硅纳米复合氧化物粉体表面为双层结构,即第一层为富氧层,第二层为SiOx/TiOy(x,y<2)层.钛和硅的低价氧化物可能是由Ti4+和Si4+的热扩散引起的,而这种热扩散可能与Ti4+和Si4+之间的强相互作用有关.
The three kinds of titanium-silicon nanocomposite oxide powders were prepared by three kinds of sol-gel processes, including Ti-Si, Si-Ti and Ti-Si. The mole fractions of SiO2 in each structure were 10% ~ 30% XPS and HRTEM were used to characterize the chemical structure of the sample surface.All the surface properties of all the samples treated by heat treatment at 773 and 1173K showed that a considerable amount of Si atoms were enriched on the surface, The contents of Ti3 +, Ti2 +, Si3 + and Si2 + are coexistent with Ti4 + and Si4 + oxides. With the increase of heat treatment temperature and the increase of SiO2 content, the contents of low-cost titanium oxide and low- The content of silicon oxide increases; the superficial layer of the surface of the titanium-silicon composite oxide is oxygen-rich layer, and the extra oxygen may come from the chemical adsorption water. The content of titanium oxides and silicon oxides of various valence states on the surface is different due to the composite structure. These results indicate that the surface of the titanium-silicon nanocomposite oxide obtained by the sol-gel method has a bilayer structure, that is, the first layer is an oxygen-rich layer and the second layer is a SiOx / TiOy (x, y <2) The silicon suboxide may be thermally diffused by Ti4 + and Si4 + , And this thermal diffusion may be related to the strong interaction between Ti4 + and Si4 +.