Abstract: The rapid preparation of high-performance carbon-based composites that integrate competitive mechanical strength and outstanding ablation resistance is of particular importance for their application under extreme conditions. Herein, we report for the first time a molten salt-assisted spark plasma melt infiltration strategy that enabled efficient incorporation of ultra-high-temperature ceramics into a lightweight carbon preform within just 90 min, significantly shorter than conventional precursor impregnation pyrolysis (several weeks) or reactive melt infiltration (~24 h). This approach leverages the synergistic effects of molten salt-mediated fluidization and external pressure-driven infiltration, achieving rapid densification, mitigating fiber erosion, and forming a hierarchical ceramic structure with nanoscale-to-micron-scale grains at the ceramic/carbon interface. These features facilitate load transfer, delivering a compressive strength of 264.91 ± 3.28 MPa and a flexural strength of 174.67 ± 7.53 MPa. Furthermore, the multi-scale ceramic grains effectively improve ablation resistance by establishing a dual-scale oxygen diffusion barrier, yielding a low linear ablation rate (-0.26 μm s^-1) and mass loss rate (0.43 mg s^-1) under cyclic oxyacetylene torch testing (120 s × 3). This work not only demonstrates the fastest-known preparation route for high-performance modified carbon-based composites reported to date but also offers a scalable pathway for the development of advanced ultra-high-temperature composites.

Key words: Carbon-based composites, Ultra-high temperature ceramics, Rapid preparation, Ablation resistance