Hydrophobic SiO_2 Aerogels Dried at Subcritical Condition

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 surfacal 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.