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

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 degrees 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 center dot m (1)center dot 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 degrees 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.

Automated summary

In this study, the surface chemistry, skeleton structure, and thermal safety of three different methylsilyl modified silica aerogels (SAs) were investigated under heat treatment in an argon atmosphere. Increasing the heat treatment temperature to 700 degrees C resulted in the aggregation of secondary particles, densification of silica skeletons, and reduction in pore volumes. Despite these changes, the thermal insulation performance remained excellent, with a thermal conductivity below 30 mW center dot m (1) center dot k (1). The study also confirmed the conversion of Si-(CH3) (3) groups to Si-(CH3) (2) groups and their further transformation to Si-CH3 groups. The presence of these generated and original Si-CH3 groups up to 700 degrees C contributes to the high-temperature hydrophobicity. Additionally, the enhanced thermal stability and reduced gross calorific values of the heat-treated SAs demonstrate the improved thermal safety. This research provides valuable engineering insights for the high-temperature thermal insulation application of hydrophobic SAs.