Tailoring thermal transport pathways and ablation-resistant structures in Cf/HfC-SiC composites through processing-induced matrix evolution

Ultra-high temperature ceramic matrix composites (UHTCMCs) are essential for thermal protection in extreme aerospace environments. The role of ultra-high temperature ceramic (UHTC) matrix architecture in governing thermal transport and ablation resistance remains insufficiently understood. In this work, high-thermal-conductivity C f /HfC-SiC composites with distinct matrix structures were fabricated via slurry infiltration (SI) and precursor infiltration and pyrolysis (PIP). The PIP route, enabled by molecular-scale precursor infiltration, yields a uniform HfC dispersion within the SiC matrix, establishing a continuous phonon transport network that delivers an axial thermal conductivity as high as 296 W/(m·K). In contrast, the SI route leads to localized HfC enrichment in inter-bundle pores, which, upon ablation, oxidizes into abundant HfO 2 particles that pin the SiO 2 melt, producing a dense and erosion-resistant oxide scale. Consequently, the SI-HfC composite exhibits a linear ablation rate of 0.042 μm/s and a mass ablation rate of 3.61 mg/s, with only a 9.31% degradation in axial thermal conductivity after 100 s ablation at 4.5 MW/m 2 , suffers less thermal conductivity degradation than the PIP-HfC (11.80%). This work elucidates the processing-microstructure-property correlations in UHTCMCs, providing a quantitative basis for route selection in high-thermal-conductivity thermal protection systems.