Ambient pressure dried shape-controllable sodium silicate based composite silica aerogel monoliths

Abstract

The shape-controllable sodium silicate based fiber reinforced silica aerogel monoliths with excellent integrity and thermal insulating property were prepared by ambient pressure drying. The non-woven silica fiber up to 17.5 wt% could be uniformly distributed and well incorporated into the three-dimensional silica network since the fiber introduced and silica precursor could simultaneously react with methyltriethoxysilane (MTES) and trimethylchlorosilane (TMCS) during the two-step surface modification. The densities and porosities of the composite silica aerogel monoliths were 0.104–0.146 g/cm3 and 93%–95%, respectively, with the thermal conductivities of 21–31 m W/(m K) and the average modulus of 323–535 kPa. The characteristic linear and zigzag responses were observed from the compression stress–strain curves. Incomplete modification due to a large amount of fiber incorporation led to severe volume shrinkage during ambient pressure drying.