高温稳定TiO_2 -SiO_2 复合粉体的两步水热法制备

以钛酸丁酯和硅酸乙酯为原料,通过两步水热法制备了具有高光催化活性的高温稳定TiO_2-SiO_2复合粉体. 采用动态光散射粒度分析仪、差示扫描量热仪、傅里叶变换红外光谱仪、透射电子显微镜和X射线衍射仪等对TiO_2-SiO_2复合粉体进行了表征. 粒度分析表明,复合粉体分散良好, 颗粒大小为10～30nm,颗粒分布较窄. 热分析表明,SiO_2的加入能显著提高TiO_2的热稳定性.物相分析表明:复合粉体中SiO_2含量越高,锐钛矿型TiO_2的高温稳定性越好;TiO_2/SiO_2摩尔比为1: 1的复合粉体在1200℃处理2h后仍保持锐钛矿晶型. 红外分析表明,800℃处理2h前后的复合粉体中均无 Ti-O-Si 键. TiO_2-SiO_2复合粉体在紫外光作用下使甲基橙水溶液降解的实验表明:未经热处理的复合粉体的光催化性能和商品P25 TiO_2粉体相似;800℃和1000℃热处理2h后的复合粉体的光催化性能保持良好, 远高于相同条件处理过的P25;1200℃处理2h后的复合粉体只有微弱的光催化活性.

Preparation of TiO_2-SiO_2 Composite Powders Stabilized at High Temperature by Two-Step Hydrothermal Method

TiO_2-SiO_2 composite powders stabilized at high temperature with high photocatalytic activity were prepared using a two-step hydrothermal method, with tetrabutyl titanate and tetraethyl orthosilicate as the materials. The powders were then characterized by means of dynamic light-scattering size analysis, DSC, FT-IR, TEM and XRD. The results of particle size analysis indicate that the composite powders disperse well in a size range of 10～30nm with narrow distribution. DSC results show that the addition of silica greatly improves the high-temperature stability of titania dioxide. Phase analysis results demonstrate that the high-temperature stability of anatase titania becomes better with the increase of SiO_2 content, and that the composite powders with a TiO_2/SiO_2 molar ratio of 1: 1 maintain as anatase phase after being treated at 1200℃ for 2h. FT-IR spectra show that there is no Ti-O-Si bonds in the TiO_2-SiO_2 composite powders before and after the treatment at 800℃ for 2h. Moreover, according to the degradation of aqueous methyl orange by TiO_2-SiO_2 composite powders under UV irradiation, it is found that (1) the photocatalysis of the composite powders without heat treatment is similar to that of commercial P25 TiO_2 powders;(2) the photocatalytic activity of the composite powders after the heat treatment at 800 and 1000℃ for 2h is much higher than that of P25;and (3) after the heat treatment at 1200℃ for 2h, the photocatalytic activity of the composite powders becomes poorer.