Multiphase Symbiotic Engineered Elastic Ceramic‐Carbon Aerogels with Advanced Thermal Protection in Extreme Oxidative Environments

Abstract Elastic aerogels can dissipate aerodynamic forces and thermal stresses by reversible slipping or deforming to avoid sudden failure caused by stress concentration, making them the most promising candidates for thermal protection in aerospace applications. However, existing elastic aerogels face difficulties achieving reliable protection above 1500 °C in aerobic environments due to their poor thermomechanical stability and significantly increased thermal conductivity at elevated temperatures. Here, a multiphase sequence and multiscale structural engineering strategy is proposed to synthesize mullite‐carbon hybrid nanofibrous aerogels. The heterogeneous symbiotic effect between components simultaneously inhibits ceramic crystalline coarsening and carbon thermal etching, thus ensuring the thermal stability of the nanofiber building blocks. Efficient load transfer and high interfacial thermal resistance at crystalline‐amorphous phase boundaries on the microscopic scale, coupled with mesoscale lamellar cellular and locally closed‐pore structures, achieve rapid stress dissipation and thermal energy attenuation in aerogels. This robust thermal protection material system is compatible with ultralight density (30 mg cm^–3), reversible compression strain of 60%, extraordinary thermomechanical stability (up to 1600 °C in oxidative environments), and ultralow thermal conductivity (50.58 mW m^–1 K^–1 at 300 °C), offering new options and possibilities to cope with the harsh operating environments faced by space exploration.