Facile fabrication of machinable low-density moisture-resistant silica aerogels

Low-density moisture-resistant silica aerogels with enhanced mechanical strength were obtained by combining with the aging of the teteraehoxysilane (TEOS)-based alcogels in the TEOS/ethanol solution and the modification in the hexamethyldisilazane (HMDS)/ethanol solution. This route introduced less organic impurities into as-prepared aerogels and their mechanical strength was also enhanced. The linear volume shrinkage of the modified wet gels reached as low as 3.6% during supercritical drying. Thus, the aerogels had appropriate mechanical strength to be adapted the requirements of applications with various shapes. Moreover, the densities of silica aerogels maintained stable after modification by high concentration HMDS, suggesting excellent moisture resistance.