Surface chemistry, skeleton structure and thermal safety of methylsilyl modified silica aerogels by heat treatment in an argon atmosphere

Abstract

In this study, the surface chemistry, skeleton structure and thermal safety of three different methylsilyl modified silica aerogels (SAs) have been explored under heat treatment in an argon atmosphere. With the heat treatment temperature increasing to 700 °C, the secondary particles aggregate, the silica skeletons get denser and the pore volumes diminish. Meanwhile, the excellent thermal insulation performance is still maintained, with the thermal conductivity not exceeding 30 mW⋅m − 1⋅k − 1. It finds the Si-(CH3)3 groups are converted to Si-(CH3)2 groups, and further transformed to Si-CH3 groups. The generated and original Si-CH3 groups can be maintained until 700 °C, which constitutes the chemical basis for the high-temperature hydrophobicity. The improved thermal stability and reduced gross calorific values both verify that the thermal safety of the heat-treated SAs has been obviously enhanced. This study provides an engineering reference for the high-temperature thermal insulation application for hydrophobic SAs.