SiO_2表面上制备纳米TiO_2中水量对TiO_2含量和形貌的影响

INFLUENCE OF WATER CONTENT ON CONTENT AND CHARACTERISTIC OF TiO_(2) DURING PREPARATION OF TiO_(2) NANOPARTICLES ON SiO_(2) SURFACE

利用吸附相反应技术在SiO2表面原位制备了纳米TiO2,研究水的加入量对TiO2粒子制备的影响.用分光光度法测定乙醇体相中Ti含量随反应时间的变化,发现Ti含量呈现先快后慢的变化趋势,且水量在1.0～1.1 mL时Ti含量出现急剧变大.Ti含量的这一突变区域通过电子色散能谱仪对载体SiO2表面Ti含量的测定得到了进一步地确定.由透射电子显微镜观察到SiO2表面TiO2粒子存在着两种不同的形貌:覆盖在SiO2表面黑色区域和直径在1 nm左右的单一小粒子.X射线衍射分析表明:TiO2晶粒粒径随着水量的增加而变大.实验结果发现:在不同的水量下,钛酸丁酯能够与吸附层和乙醇体相中的水以及SiO2表面羟基发生水解缩合反应.3种反应的不同反应速率导致了Ti含量曲线中的不同斜率,另外钛酸丁酯在醇体相中的水解也导致体系中Ti含量的急剧变大.

TiO2 nano-particles were prepared on an SiO2 surface by the adsorption phase reaction technique, and the influence of water content added on the preparation of TiO2 nano-particles in the adsorption phase nanoreactor was investigated. The changes of Ti content with the reaction time in ethanol bulk during the reaction were determined by spectrophotometry. The results show that the change of Ti content is rapid at the beginning then becomes slow. When the water volume is 1.0-1.1 mL, the Ti content in bulk jump, which is in correspondence to a similar phenomena of the Ti content on the SiO2 surface from energy dispersive X-ray microanalysis. Two different morphologies on the SiOs surface were observed for TiO2 particles by transmission electron microscopy, i.e. black regions covered the silica, and there were few single particles with 1 nm in diameter. X-ray diffraction result shows that the grain size of TiO2 particles increases with the increase of water volume. It was found that tetrabutyl titanate can be hydrolyzed with tbe water in the adsorption layer and in bulk, as well as the hydroxyl group on the SiO2 surface. The different reaction rates with water and hydroxyl group lead to the different slope in Ti content curves. The hydrolysis reaction of tetrabutyl titanate in ethanol bulk causes a sharp decrease in the Ti content curve.