Lightweight, high-strength, heat-resistant TiB₂–B₄C-modified phenolic aerogel/carbon fiber composites with excellent thermal stability, oxidation, and ablation resistance for thermal protection

Lightweight ablative materials are commonly utilized as thermal protection materials for hypersonic vehicles. Ceramizable phenolic aerogel/carbon fiber (PA/CF) composites modified with TiB₂ and B₄C were fabricated, which had the characteristics of lightweight, high strength, and low thermal conductivity. The acid-catalyzed phenol-aldehyde polymerization reaction was used to significantly shorten the gelation time, which facilitated the uniform distribution of ceramic fillers. The oxygen-consuming, oxygen-blocking, and carbon-fixing synergistic effects of TiB₂ and B₄C high-temperature ceramic reactions, as well as the multiphase ceramic structure (C-B₂O₃-TiO₂-TiC) formed, conferred excellent thermal stability (the residual weight of 58.8% at 1200 °C), oxidation resistance (the residual strength of 3.44 MPa after static ablation), and ablation resistance (the linear and mass ablation rates as low as 0.045 mm/s and 0.0115 g/s) on the composites. The lightweight, high-strength materials with anti-thermal insulation properties demonstrate significant competitiveness and application potential in the field of thermal protection.