TiO_2/蒙脱石纳米复合物中TiO_2的结构相变

Phase Transition of TiO_2 in TiO_2/Montmorillonite Nanocomposites

以钛酸丁酯和季铵盐改性有机蒙脱石为原料,采用原位水解法和原位脱羟法制备了TiO2/蒙脱石纳米复合物。采用X射线衍射(XRD)、拉曼光谱(Raman)表征了不同焙烧温度下TiO2/蒙脱石纳米复合物中TiO2的结构相变,并与不同焙烧温度下纯TiO2的结构相变进行对比。结果发现TiO2/蒙脱石纳米复合物中TiO2从锐钛矿相开始转变为金红石的最低温度要比纯TiO2从锐钛矿开始相转变为金红石的最低温度高200℃,且在焙烧温度1 200℃时还存在锐钛矿相,而纯TiO2在焙烧温度800℃时就全部转换为金红石相。TiO2/蒙脱石纳米复合物中TiO2和纯TiO2的平均晶粒度都随焙烧温度升高而增大,但TiO2/蒙脱石纳米复合物中TiO2的平均晶粒度要小于相同温度下焙烧纯TiO2的平均晶粒度。表明蒙脱石结构层的硅氧结构抑制了TiO2晶型由锐钛矿相向金红石相的转变,进而使相变温度升高,同时阻碍了晶体的生长。

The TiO2/montmorillonite composites were prepared by in-situ hydrolyzing reaction and in-situ dehydrating reaction of tetrabutyl titanate-hexadecyl trimethyl ammonium bromide intercalated montmorillonite.The structural phase transition of TiO2 in TiO2/montmorillonite composites calcined at different temperatures was characterized by using X-ray diffraction（XRD） and Fourier transform Raman spectroscopy（Raman）,and the results were compared with that of the product obtained from tetrabutyl titanate hydrolysis.The results show that the phase-transition temperature from anatase to rutile phase of TiO2 in TiO2 / montmorillonite nanocomposites is 200 ℃ higher than pure TiO2.The anatase phase still exists in TiO2 / montmorillonite nanocomposites at the calcination temperature of 1 200 ℃,but pure TiO2 is all converted to rutile at the calcination temperature of 800 ℃.The average crystal size of TiO2 in TiO2/ montmorillonite nanocomposites and pure TiO2 both increase with the calcination temperature.The average grain size of TiO2 in TiO2/montmorillonite nanocomposites is less than that of pure TiO2 at the same calcination temperature.The results also show that the silicon-oxygen structure in layered montmorillonite structure can effectively depress the phase transformation from anatase to rutile,thus enhancing the transition temperature and inhibitting the growth of anatase crystals.