Dual-Phasic, Well-Aligned, and Strong Flexible Hydrophobic Ceramic Membranes for Efficient Thermal Insulation in Extreme Conditions

The inherent brittleness and hydrophilicity of ceramics pose a great challenge to designing a reliable structure that can resist mechanical loads and moisture in extreme conditions with high temperature and high humidity. Here, we report a two-phase hydrophobic silica–zirconia composite ceramic nanofiber membrane (H-ZSNFM) with exceptional mechanical robustness and high-temperature hydrophobic resistance. For the dual-phasic nanofibers, the amorphous silica blocked the connection of zirconia nanocrystals, and the lattice distortion was observed due to Si in the ZrO 2 lattice. H-ZSNFM has strong strength (5–8.4 MPa), high hydrophobic temperature resistance (450 °C), high porosity (89%), low density (40 mg/cm 3 ), low thermal conductivity (30 mW/m·K), and excellent thermal radiation reflectivity (90%). By simulating the actual high-temperature and high-humidity environment, 10-mm-thick H-ZSNFMs can reduce the heat source from 1365 to 380 °C and maintain complete hydrophobicity even in a water vapor environment of 350 °C. This means that it has superior insulation and waterproof performance even in a high-temperature water environment. For firefighting clothing, H-ZSNFM displayed waterproof and insulation layers, which have excellent thermal protection performance and achieve incompatibility between water and fire, providing valuable time for fire rescue and a safety line of defense for emergency personnel. This design strategy with mechanical robust and hydrophobic temperature resistance applies to the development of many other types of high-performance thermal insulation materials and presents a competitive material system for thermal protection in extreme conditions.