Enhancing Ablation Resistance of C/C-HfC-SiC Composites by In-Situ Growth of HfC Nanowires

ABSTRACT: C/C-HfC-SiC composites are promising ablation-resistant ultra-high temperature thermal protection materials. To further enhance their performance in extreme thermal environments, the introduction of HfC nanowires (HfC_NWs) into the composite has been identified as an effective strategy. The quantity and morphology of the introduced HfC_NWs significantly influence the ablation resistance of the composites. In this study, by controlling the concentration of Ni salt during the hydrothermal synthesis process, the loading amount of Ni catalysts on the surface of carbon fibers was regulated, thereby achieving control over the quantity and structure of HfC_NWs in the C/C-HfC-SiC composites. It was found that a low Ni loading facilitates the growth of sparse and slender HfC_NWs. As the Ni loading increases, the number of HfC_NWs rises, gradually evolving into a high-density, multi-oriented network structure. However, excessive Ni tends to induce short, thick, and clustered growth of the nanowires. Based on this, three types of HfC_NWs-modified C/C-HfC-SiC composites were prepared using the polymer impregnation and pyrolysis (PIP) process. The quantity and diameter of the HfC_NWs significantly affect the ablation resistance of the composites. Among them, the composite prepared with a 4.38 wt% Ni loading exhibited excellent ablation resistance, with mass and linear ablation rates of 0.47 mg·s⁻¹·cm⁻² and 5.50 μm·s⁻¹, respectively. The performance improvement is attributed to the formation of a continuous HfO₂ skeletal structure after the oxidation of an appropriate amount of HfC_NWs. This continuous HfO₂ skeleton significantly enhances the ability of the oxide layer to resist high-speed gas flow erosion and oxygen penetration. This study can provide support for the design of HfC_NWs-reinforced C/C-HfC-SiC composites and promote their engineering application in the field of aerospace thermal protection.