HfO2 Nanocrystal-Reinforced Flexible SiC Nanofibrous Membranes with Excellent Cyclic Bending Durability and Thermal Insulation

Flexible HfO 2 /SiC composite nanofibrous membranes were fabricated via a polymer-derived ceramic strategy by incorporating HfO 2 nanocrystals into a SiC matrix. The optimized membrane exhibits a tensile strength of 1.97 MPa, a static load-bearing capability of approximately 3800 times its own weight, and excellent cyclic bending durability, maintaining Δ R / R 0 below 3% after 1.6 × 10 4 cycles under 180 ° repeated bending. These results demonstrate its robust mechanical stability under both static loading and repeated bending deformation. Concurrently, the membrane achieves a low thermal conductivity of 0.1513 W·m −1 ·K −1 and a high infrared emissivity of ∼0.95. When subjected to direct exposure to a 1200 ° C flame, a 2.5 mm-thick membrane exhibits a backside temperature of only 172.6 ° C. The measured temperature-difference sustainability per unit thickness is 1.19 × 10 5 ° C·s·mm −1 under prolonged thermal exposure, which is 1.6 times that of conventional ceramic, fibrous, and aerogel insulators. Moreover, molecular dynamics simulations provide further evidence that the incorporation of HfO 2 has a reinforcing effect. These results highlight the potential of HfO 2 /SiC nanofibrous membranes for lightweight thermal protection applications under extreme environments.