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°.