常压干燥制备疏水SiO2气凝胶的影响因素分析

常压干燥制备SiO2气凝胶是近年来该领域的研究重点,工艺条件的优化是提高气凝胶性能的关键。以正硅酸乙酯为硅源,甲基三乙氧基硅烷为共前驱体,采用溶胶-凝胶法,结合老化和三甲基氯硅烷-正己烷-无水乙醇混合溶液的二次表面改性,通过常压干燥工艺制备疏水SiO2气凝胶。利用BET,FT-IR,SEM,TEM和接触角测试等手段对气凝胶进行表征,系统研究水解时间、老化时间、老化温度和改性剂用量对气凝胶性质的影响。结果表明:水解16h,凝胶于55℃下老化48h后,在三甲基氯硅烷与正硅酸乙酯的摩尔比为1.56的混合液下改性48h制备的SiO2气凝胶的性能最好,其孔隙率92%,比表面积969m2/g,接触角达157°。

Effects of Preparation Conditions on Hydrophobic Silica Aerogels via Ambient Pressure Drying

The preparation of silica aerogel via ambient pressure drying has become of great importance recently.A key to improve the properties of aerogels is to optimize the preparation parameters.Using tetraethoxysiliane(TEOS) and methyltriethoxysilane(MTES) as the silica source and co-precursor,respectively,the hydrophobic silica aerogels via ambient pressure drying process were prepared by sol-gel method with aging and two-step surface modification by trimethylchlorosilane(TMCS)/n-hexane/ethanol(EtOH) solutions.The BET,FT-IR,SEM,TEM and contact angle measurements were used to characterize the structure of silica aerogels.The effects of hydrolyzing time,aging time,aging temperature and surface modification reagents on the properties of silica aerogels were systematically investigated.The results revealed that the silica aerogels prepared using 16 h hydrolyzing time,48 h aging time at 55℃ and surface modified by the molar ratios of TMCS/TEOS being 1.56 for 48 h possessed the best properties.The porosity and specific surface area were 92% and 969m2/g,respectively,with the contact angle of 157°.