Influence of aging conditions on textural properties of water-glass-based silica aerogels prepared at ambient pressure

The experimental results of aging time and temperature on the textural properties of water-glass (sodium silicate)-based silica aerogels are reported and discussed. Aging of the hydrogel for different times and temperatures led to an ability to increase the stiffness and strength of the networks. These improvements enabled the gel to withstand ambient pressure drying (APD) and, consequently, preserve the highly porous silica network without collapse. The pore size and volume increased with increasing aging temperature and time, while the specific surface area decreased. Monolithic aerogels with extremely low bulk density (similar to 0.069 g/cm(3)), high specific surface area (820 m(2) g(-1)), large cumulative pore volume (3.8 cm(3) g(-1)), and high porosity (similar to 96%) were obtained by aging at 60 degrees C for 18 hours. Therefore, easy synthesis of monolithic silica aerogels at ambient pressure is achievable using a relatively inexpensive silica precursor (sodium silicate).