Gradient Lamellar SiC Nanowire Networks with Dense Coating for High-Performance Reusable Thermal Protection Materials

As space exploration advances, reusable thermal protection materials are essential for spacecraft that must withstand extreme aerodynamic heating during reentry. SiC nanowire aerogels offer a combination of ultralow density, excellent thermal insulation, and inherent oxidation resistance, but their application is limited by insufficient thermal stability above 1200 °C in oxygen-rich environments. In this study, a layered SiC nanowire network was fabricated by hot-pressing to enhance nanowire cross-linking and reduce pore size. A dense SiC coating was subsequently introduced via chemical vapor infiltration (CVI), forming a gradient structure with nanowire diameters decreasing from surface to core. This design yields a low density of 640 mg·cm^-3, high compressive strength of 10.1 MPa, and exceptional ablation resistance. During 60 s of oxyacetylene torch ablation at 1800 °C, the material exhibited a negative mass ablation rate of -0.02 mg·s^-1 and a negative linear ablation rate of -1.05 μm·s^-1. These results demonstrate a promising structural strategy for enhancing the mechanical and thermal robustness of ceramic aerogels, advancing their application in extremely high-temperature environments.