A novel silica aerogel/porous Si3N4 composite prepared by freeze casting and sol-gel impregnation with high-performance thermal insulation and wave-transparent

•A new method was developed for preparing silica aerogel/porous Si3N4 composite.•The silica aerogel/porous Si3N4 composite possesses nanometer pore structures.•The composite has both low thermal conductivity and dielectric loss tangent.•The thermal insulation and wave-transparent functional integration was implemented.•The composite can be made into complex shapes.

A novel silica aerogel/porous Si3N4 composite with high-performance thermal insulation and wave-transparent has been prepared by freeze casting and sol-gel impregnation. The morphology, microstructure and properties of the composite were investigated. After impregnating of silica aerogel, the composite has nanometer porous structures. The results of performance test show that the room-temperature thermal conductivity remarkably decreased and the compressive strength increased while impregnating porous Si3N4 with silica aerogel. The composite exhibits low thermal conductivity (0.043 Wm−1K−1), low dielectric constant (~1.6) and loss tangent (~0.0018). The silica aerogel/porous Si3N4 composite can be suitable for use in thermal insulation and wave-transparent functional integration material.