Synergistic Design of High‐Emittance Ceramicizable B ₄ C ‐ LaB ₆ /Silicone Rubber Thermal Protection Coatings and Their Ultra‐High‐Temperature Ablation‐Radiation Coupling Mechanism

ABSTRACT Aerodynamic heating threatens hypersonic vehicles, making lightweight, flexible thermal protection coatings essential. This paper designs and prepares a multifunctional B ₄ C‐LaB ₆ /silicone rubber high‐emissivity ceramicizable thermal protection coating. By incorporating chopped high‐silica silica fibers and aramid fibers as ablation‐resistant fillers into the silicone rubber matrix, and combining them with the high‐emissivity functional components B ₄ C and LaB ₆ , a coating material with both ablation protection and radiative heat dissipation capabilities was achieved. Research indicates that the synergistic effect of B ₄ C‐LaB ₆ significantly enhances the thermal stability and thermal insulation performance of the composite coating: At a B ₄ C:LaB ₆ ratio of 20:20, the coating's mass retention rate at 1000°C increased from 43.45% to 80.68%, with an average infrared emissivity reaching 0.947. Concurrently, the coating exhibited lower linear ablation rates and a denser ceramic layer structure. This research offers new insights for multifunctional silicone rubber thermal protection coatings, showing potential for hypersonic vehicles.