High-temperature microtexture, microstructure evolution, and thermal insulation properties of porous Si3N4/silica aerogel composites produced by impregnation

Porous Si 3 N 4 /silica aerogel composites were prepared by sol impregnation with porous Si 3 N 4 as the framework, and the microstructure evolution and properties of the composites were studied in detail at high temperature. Porous Si 3 N 4 had a strong skeleton structure, which effectively inhibited the pore collapse of the aerogel, kept the nanostructure stable to 1100 °C, and significantly improved the temperature resistance of the silica aerogel. Preventing the growth of gel particles and pore collapse at temperatures above 1100 °C was difficult, and the silica aerogel gradually crystallised. When the temperature reached 1300 °C, the aerogel inside was completely crystallised, and the nanopore structure basically disappeared. The specific surface area of the composite decreased with increasing temperature, whereas the pore size and thermal conductivity increased with increasing temperature. The high-temperature thermal insulation performance was tested, and the composite material exhibited low thermal conductivity (0.254 W m −1  K −1 ) at even 1300 °C, which suggests this composite is suitable for thermal insulation use in a high-temperature environment. Graphical abstract