Preparation of silica aerogels with high temperature resistance and low thermal conductivity by monodispersed silica sol

Abstract

Silica aerogels with different particle size were prepared by monodispersed silica sol for the first time. The properties of the silica aerogels under normal and high temperature were systematically studied. Among the four different particle size aerogels, the SA-2 sample consisted of 20.31 ± 1.21 nm particles with narrow size distribution had high temperature resistance and low thermal conductivity. Compared with the traditional acid-base two-step prepared silica aerogels, the monodisperse silica aerogels can significantly increase the temperature resistance while maintaining a low thermal conductivity (0.02723 W·m−1·K−1). The sturdy skeleton structure formed by the interconnection of large particles can effectively inhibit the viscous flow between aerogel particles and avoid pore collapse caused by skeleton failure which can maintain a stable structure until 900 °C and retain a relatively complete structure at 1000 °C with only about 35% volume shrinkage after 2 h heat treatment. At 1100 °C, the viscous flow between aerogel particles and pore collapse cannot be effectively suppressed, and the pure silica aerogels can only be used during a short period at 1100 °C. The results will be meaningful for the design of super thermal insulation materials with high temperature resistance and low thermal conductivity.