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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°。
The preparation of SiO2 aerogels by atmospheric pressure drying is the key point in this field in recent years. The optimization of process conditions is the key to improve the properties of aerogels. Using tetraethyl orthosilicate as silicon source and methyltriethoxysilane as co-precursor, the sol-gel method was used to combine the secondary surface of the mixed solution of aging and trimethylchlorosilane-n-hexane-absolute ethanol Modification, preparation of hydrophobic SiO2 airgel by atmospheric drying process. The aerogels were characterized by means of BET, FT-IR, SEM, TEM and contact angle test. The effects of hydrolysis time, aging time, aging temperature and modifier dosage on the properties of aerogels were systematically investigated. The results showed that the performance of SiO2 aerogels prepared by hydrolysis for 16 h and aged at 55 ℃ for 48 h followed by 48 h modification with trimethylchlorosilane and tetraethyl orthosilicate in a mixture of 1.56 was the best , The porosity of 92%, the specific surface area of 969m2 / g, the contact angle of 157 °.