A compressible, highly elastic anisotropic SiC/SiO2 composite aerogel for thermal-insulated building materials

Ceramic aerogels feature extremely low thermal conductivity, low density, and high-temperature stability, making them suitable for construction, industry, and aerospace vehicles. However, achieving high elasticity in aerogels based on ceramic components remains a significant challenge. In this work, we prepared SiC/SiO2 composite aerogels with anisotropic porous structures via the oriented ice templating method. This anisotropic porous microstructure enables simultaneous improvement in mechanical properties and thermal insulation. On the one hand, the micron-scale cell walls in the anisotropic porous structure enhance the mechanical properties along the pore-aligned direction, thereby increasing the modulus and strength. On the other hand, heat transfer in anisotropic structures helps reduce the heat flux perpendicular to the growth direction of cell walls. This uneven thermal diffusion increases the heat flow in the direction with high thermal conductivity while decreasing it in the direction with low thermal conductivity, thereby enhancing the overall thermal insulation performance. The results show that the SiC/SiO2 composite aerogels exhibit high stiffness along the axial direction (with a high specific modulus of 27.0 kN m/kg) and high elasticity in the radial direction, capable of withstanding 100 cycles of compression tests without obvious plastic deformation, demonstrating excellent mechanical properties. In addition, the SiC/SiO2 composite aerogels have a thermal conductivity of 22.4 mW/m−1 K−1 along the radial direction, can withstand high temperatures of ∼1100 °C, and exhibit excellent thermal stability. These results demonstrate the innovative advantages of anisotropic porous structures in directional thermal insulation.