Fast and one-pot synthesis of silica aerogels via a quasi-solvent-exchange-free ambient pressure drying process

A very fast (less than 2 h) and one-pot synthetic strategy was developed for the synthesis of silica aerogels . Organic silica gel was first formed under basic condition by adding a predetermined amount of hexane to a freshly prepared silica sol. After aging at elevated temperature for several minutes, the organogel was mechanically crushed and vigorously stirred in a mixture of trimethylchlorosilane and hexane . Finally, silica aerogel was produced by drying the hydrophobized organogel at temperatures higher than 180 °C. The effects of gelation conditions, amount of modification agents, and drying temperatures on the physical properties of the silica aerogels were investigated. The N 2 adsorption and desorption measurements indicated that high BET surface areas (up to 725.8 m 2 /g) could be obtained for the aerogels sintering at 350 °C, while that of the silica aerogels dried at 180 °C were relative lower (from 379.4 to 564.8 m 2 /g based on the modification conditions). Similar trend was also found in the thermal conductivities of the aerogels, e.g., lower values of thermal conductivity (∼0.025 W/mK) were obtained for the sintering samples, while that of the samples without sintering were relative higher (∼0.034 W/mK). In summary, a fast ambient pressure drying method has been developed, which show a great potential to synthesize silica aerogels in the industrial scale.