Abstract: At present, the commonly used aerogel gel process is acid-base catalysis, and the hydrolysis time is long and the operation process is cumbersome. In this paper, tetraethyl orthosilicate was used as the silicon source, and the wet gel was prepared by sol-gel method using fluoride ion as the catalyst. After the solvent was replaced by n-hexane solvent and the surface was modified by trimethylchlorosilane, the silica aerogel was prepared by stepwise heating at room temperature. Silica aerogels were studied by means of thermal conductivity analyzer, scanning/transmission electron microscopy and other methods to study the effect of different fluoride ion content on the properties of the prepared aerogels. Experiments show that the aerogel has a minimum density of 0.032 W/(m·K), an average specific surface area of 628.7 m²/g, and an average pore diameter of 17.2 nm. Moreover, with the increase of the amount of fluoride ion, the tetraethyl orthosilicate is more thoroughly hydrolyzed, but it is unfavorable for the surface modification of the wet gel, which leads to a smaller contact angle and an increase in thermal conductivity.

Key words: fluoride ion, silica aerogel, hydrophobic property, microstructure