Phase-separation induced synthesis of superhydrophobic silica aerogel powders and granules

Abstract

A phase-separation induced (PSI) method of synthesizing superhydrophobic silica aerogel powders and granules is developed by direct hydrophobilization of silica alcogels in diluted trimethylchlorosilane organic solution and followed by ambient pressure drying (APD). It’s interesting to observed that after the successful hydrophobilization of the alcogels, phase-separation occurred and the gels are dispersed in the organic solvent layer while ethanol and HCl forming another layer. Therefore the gels could be facilely collected and dried under ambient pressure, without the essential solvent-exchange step that frequently employed in the traditional APD methods. The silica aerogel powders and granules synthesized by the PSI method possess specific surface areas up to 756.0 m2/g, thermal conductivity down to 0.0164 W/m·K, and variable densities from 47.6 to 120.0 mg/cm3. Besides, the appearance of the silica aerogels could be well-controlled to be highly transparent powders or granules. In sum, the PSI method provide a simple method to synthesize high quality silica aerogel powders and granules in an economic way, and the aerogels may find valuable applications in thermal insulation, environmental remediation and adsorption, etc.