Gradient C_f/ZrB₂-SiC composites integrating low-density, good mechanical properties and heat-resistant

Ultra-high temperature ceramic composites (UHTCCs) with low density and exceptional heat resistance are essential for hypersonic vehicle applications, enabling increased payload capacity and higher Mach numbers. However, developing a fabrication process that enables UHTCCs with both lightweight and superior thermal protection performance is still a challenge. To tackle this problem, in this study, a combinatorial process of vibration-assisted slurry impregnation and polymer infiltration pyrolysis was developed to fabricate gradient lightweight C_f/ZrB₂-SiC composites, consisting of continuous carbon fiber fabric, ZrB₂-SiC and a carbon aerogels (CAs) layer. The resulting composites exhibit a low density of (0.62–0.96 g cm⁻³) but excellent oxidation and ablation resistance, which can withstand ultrahigh temperatures between 2100 °C and 2500 °C. The porous C_f/CAs layer, with a density of 0.38 g cm⁻³ and specific bending and compressive strengths of 43.47 MPa/(g cm⁻³) and 15.53 MPa/(g cm⁻³), respectively, provides both structural integrity and lightweight properties to the C_f/ZrB₂-SiC composite. Furthermore, the density of the composites can be precisely tailored by adjusting the thickness of the C_f/ZrB₂-SiC layer, allowing for customized fabrication to meet diverse service environment requirements. This flexibility highlights the adaptability of the combined processing techniques. The unique combination of controllable low-density properties and exceptional oxidation and ablation resistance endows gradient lightweight C_f/ZrB₂-SiC composites are promising as lightweight, ultra-high temperature thermal protection systems for hypersonic vehicle applications.