Carbon fiber–reinforced ultra-high-temperature ceramic matrix composites (C_f/UHTCs) suffer from limited structural continuity, regional protection mismatch, and unstable failure mechanisms in oxidative plasma ablation environments above 2500 °C, where single-phase UHTC systems (e.g., HfC or HfB₂) fail to maintain wide-temperature synergistic stability. To address this ablation-limit imbalance, a dual-UHTC-phase C_f–HfC–HfB₂–SiC composite is designed, achieving a wide-temperature synergistic protection effect. The composite exhibits an ultra-low linear ablation rate of 1.88 × 10⁻⁴ mm/s at 2600 °C for 1500 s, increasing only slightly to 2.32 × 10^-4 mm/s at 2700 °C. Structural analyses reveal a stable triple-layer oxidation architecture consisting of a dense HfO₂ outer layer, an HfO₂–SiO₂ intermediate layer, and a porous inner buffer layer with spatially partitioned responses. First-principles calculations show that the HfC–HfB₂ interface facilitates the formation of a continuous oxygen coordination network, supporting the evolution of a continuous protective oxide scale. These findings suggest a zonal synergistic protection behavior associated with the cooperative evolution of different ablation regions under non-uniform ultra-high-temperature environments.

Finding the optimum balance between strength and toughness, as well as acquiring reliable thermal shock resistance and oxidation resistance, has always been the most concerned topic in the discussion of ultra-high temperature ceramic composites. Herein, PyC modified 3D carbon fiber is used to reinforce ultra-high temperature ceramic (UHTC). The macroscopic block composite with large size is successfully fabricated through low temperature sintering at 1300 ℃ without pressure. The prepared PyC modified 3D C_f/ZrC-SiC composites simultaneously possess excellent physical and chemical stability under the synergistic effect of PyC interface layer and low temperature sintering without pressure. The fracture toughness is increased in magnitude to 13.05 ± 1.72 MPa·m^1/2 accompanied by reliable flexural strength of 251 ± 27 MPa. After rapid thermal shock spanning from room temperature (RT) to 1200 ℃, there are no visible surface penetrating cracks, spalling, or structural fragmentation. The maximum critical temperature difference reaches 875 ℃, which is nearly three times higher than that of traditional monolithic ceramics. The haunting puzzle of intrinsic brittleness and low damage tolerance are resolved fundamentally. Under the protection of PyC interface layer, the carbon fibers around oxide layer and matrix remain structure intact after static oxidation at 1500 ℃ for 30 min. The oxide layer has reliable physical and chemical stability and resists the erosion from fierce oxidizing atmosphere, ensuring the excellent oxidation resistance of the composites. In a sense, the present work provides promising universality in designability and achievement of 3D carbon fiber reinforced ceramic composites.