Nanoparticle-induced phase transformation boosts mechanical and ablation performance of C/C–ZrC–SiC composites

The intrinsic brittleness and strong chemical bonds in ceramics are persistently challenging and hinder dislocation nucleation and atomic slip to accommodate strains. This characteristic impedes plastic deformation for ceramic matrix composites when withstanding dynamic mechanical loading and intense scouring in severe thermal environments. To address these challenges, a nanodispersion-strengthening strategy is used for the C/C–ZrC–SiC composites through a meltable organic–inorganic hybrid infiltration. The introduction of organic-derived ZrC nanoparticles increased dislocation nucleation via pinning effects and enhanced atomic slip by inducing phase transformation, thereby improving the plasticity of both the matrix and the oxide layer. The optimal composite, with a volume ratio of organic zirconium acetylacetonate to inorganic Si–Zr melt (2 : 1), P2S1, exhibited the best comprehensive performance, achieving a flexural strength of 207.5±2.3 MPa, fracture toughness of 7.1±0.1 MPa·m^1/2, and a linear ablation rate of 0.15 μm·s⁻¹ under plasma ablation. This enhancement is achieved through tailored ZrC nanoparticle-induced 3C → 6H-SiC phase transformation in the matrix and the subsequent ZrO₂ nanoparticle-induced martensitic transformation in the dense oxide film. This study presents an effective way to enhance plasticity in ceramics and develop advanced nanodispersion-strengthened ceramic matrix composites with excellent mechanical and ablation resistance in extreme thermal environments.