酸催化二氧化硅溶胶粒径和稳定性的研究

摘要

Silica sols have been prepared by acid-catalyzed hydrolysis and condensation reactions of tetraethylorthosilicate (TEOS). The FTIR spectrum of silica sol, the influences of reactant proportion and reaction temperature on the silica sol sizes, and the stability of the silica sol during aging process were investigated. The results show that the condensation reactions take place before the complete hydrolysis of TEOS, and TEOS hydrolysis is incomplete. The HNO3/TEOS molar ratio has less influence on the sol size while H2O/TEOS molar ratio has greater influence. As the molar ratios of HNO3/TEOS and H2O/TEOS,and the reaction temperature increase, the prepared sol sizes increase step by step. The sol sizes decrease with the increase of EtOH/TEOS molar ratio. During the aging process, the particle size and density of silica sol have unconspicuous change and the sol is relatively stable before the viscosity of silica sol sharply increases. Low aging temperature can prolong the stable time of the silica sol.%以正硅酸乙酯(TEOS)、水、乙醇(EtOH)为原料,HNO3为催化剂,制备了纳米二氧化硅溶胶.研究了二氧化硅溶胶的红外光谱、反应物的配比和反应温度对二氧化硅溶胶粒径的影响及二氧化硅溶胶在陈化过程中的稳定性.实验结果表明,二氧化硅的缩聚反应在TEOS完全水解前就已开始,TEOS水解不完全;HNO3/TEOS摩尔比对二氧化硅溶胶粒径的影响较小,H2O/TEOS摩尔比对溶胶粒径的影响较大.随着HNO3/TEOS摩尔比、H2O/TEOS摩尔比的增加和反应温度的升高,二氧化硅溶胶的粒径增大;随着EtOH/TEOS摩尔比的增加,二氧化硅溶胶的粒径减小.溶胶在陈化过程中,在体系的粘度发生急剧变化之前,二氧化硅溶胶的粒径和密度变化极小,二氧化硅溶胶是相对稳定的.低温陈化有利于延长溶胶的稳定时间.