Effect of solvent exchange on silica aerogel properties via ambient pressure drying

Abstract

Abstract Silica aerogel has been widely used in aerospace, energy construction, petrochemical industry, etc. Its physicochemical properties strongly correlate to the modification methods, such as aging and surface hydrophobicity treatments. Among these methods, solvent exchange plays a key role in synthesizing silica aerogel by ambient pressure drying. In order to facilitate the ambient pressure drying preparation of silica aerogel for industrial application, we designed an efficient automatic solvent exchange device for silica wet gels, and systematically studied the influence of solvent exchange on the physicochemical properties of silica aerogel via ambient pressure drying. After aging and surface hydrophobic modification, the silica wet gels undergo solvent exchange at different temperatures and times. The results show that with the increase of temperature and time, the moisture content of solvent in silica wet gel, as well as the bulk density and thermal conductivity of silica aerogel decrease. Moreover, we studied the effect of solvents with different surface tensions on the physicochemical properties of silica aerogels. The use of solvents with low surface tension can produce silica aerogels with lower bulk density and thermal conductivity, while the specific surface area, pore diameter and pore volume increase. These findings emphasize the importance of solvent exchange to improve the ability of gel particle network skeleton to withstand irreversible pore collapse via ambient pressure drying.