Highly Oriented SiC@SiO ₂ Ceramic Fiber Aerogels with Good Anisotropy of the Thermal Conductivity and High‐Temperature Resistance

Here electrospinning and freeze-drying techniques are combined to fabricate an anisotropic SiC@SiO₂ ceramic fiber aerogels (A-SiC@SiO₂-FAs). The anisotropic structure of the A-SiC@SiO₂-FAs features aligned layers stacking layer-by-layer with the same direction and highly oriented 1D fibers inside each layer. The A-SiC@SiO₂-FAs exhibit anisotropic thermal properties with an extremely low thermal conductivity of 0.018 W m^-1 K^-1 in the transverse direction (perpendicular to the SiC@SiO₂ nanofibers) and ≈5 times higher thermal conductivity of 0.0914 W m^-1 K^-1 in the axial direction due to the highly oriented SiC@SiO₂ nanofibers. The anisotropy factor of the A-SiC@SiO₂-FAs is as high as 5.08, which exceeds most of the currently reported thermal insulation materials with anisotropic structural design, such as anisotropic wood aerogels, biaxially anisotropic PI/BC aerogels and anisotropic MXene foam, etc. The A-SiC@SiO₂-FAs also have excellent thermal stability, maintaining structural integrity in oxidative environments at temperatures up to 1300^°C. Moreover, these structurally distinct A-SiC@SiO₂-FAs result in superior elastic deformation with a radial recoverable strain exceeding 60% and an axial specific modulus of 5.72 kN m kg^-1. These findings emphasize the potential of SiC nanofiber aerogels in extreme thermal environments and provide valuable insights for designing anisotropic insulation materials.