Abstract: Crack-free and hydrophobic SiO₂ aerogels were repeatedly obtained at subcritical condition dried with iso-butanol, which were modified by TMCS. The microstructure
and properties of the silica aerogel were measured by pore size distribution, SEM, IR, contact angle and BET techniques. The results show that the SiO₂
aerogels prepared at subcritical conditions have classical nano microstructure(mean particle size: 10nm; mean pore radius: 14.5nm), large specific surface area about 708.3m²/g). Because of the significant reduction of drying pressure from
6.4MPa to 2.3MPa, the manufactory price of the silica aerogels can be reduced. On the other hand, it is hydrophobic, which can be used widely. So it is more
suitable for large scale production and application.

Key words: sol-gel, SiO₂ aerogel, nanoporous microstructure, hydrophobic, subcritical drying