SiBCN–ZrO2 aerogel-modified carbon-bonded carbon fiber composite with enhancement of in-plane thermal conductivity for thermal protection applications

Hypersonic vehicles operate under conditions of extreme aerodynamic heating, which presents significant challenges for the design of thermal protection system (TPS). Carbon-bonded carbon fiber (CBCF) composites, known for their exceptional thermal stability, lightweight and oxidative resistance, are highly desirable materials for TPS; nevertheless, their inherent anisotropy in thermal conductivity constrains the efficiency of in-plane heat transfer under severe thermal gradients. Herein, we developed an innovative CBCF composite impregnated with SiBCN–ZrO 2 aerogels (CBCF/SiBCN–ZrO 2 ), which establishes a synergistic architecture to enhance the efficiency of in-plane heat dissipation, thereby mitigating temperature gradients and improving thermal management. The precursor aerogel intended for the matrix was primarily investigated. The CBCF/SiBCN–ZrO 2 composite was synthesized through a solvothermal reaction following infiltration. Microscopic morphology analysis revealed that the aerogel matrix effectively encapsulated and filled the interior of the modified CBCF framework. The lightweight CBCF/SiBCN–ZrO 2 composite exhibited a density of 0.25–0.26 g/cm 3 , with compressive strengths of 2.82–3.19 MPa and 1.30–1.39 MPa in the in-plane (IP) and through-the-thickness (TTT) directions, respectively. The dual functionality of both thermal insulation and in-plane conduction was characterized and verified through quantitative thermal conductivity testing, as well as qualitative assessments of its insulation and in-plane heat‑leading properties. The sample with a single 0.2 mm-thick heat‑leading layer exhibited thermal conductivities of 29.35 W/(m·K) in the IP direction and 0.075 W/(m·K) in the TTT direction. This nearly 400-fold anisotropic difference endows the sample with highly efficient thermal management capabilities, potentially addressing the critical requirements for multifunctional TPS in aerospace applications.