(Ti,Zr,Hf,Ta)CN/SiCN: A new ultrahigh-temperature ceramic nanocomposite with excellent mechanical properties and ablation resistance

Dense monolithic (Ti,Zr,Hf,Ta)CN/SiCN ceramic nanocomposites are prepared via the pyrolysis of novel (Ti-,Zr-,Hf-,Ta)-containing single-source precursors (SSPs) and spark plasma sintering (SPS) with a high heating rate. The synthesis, polymer-to-ceramic transformation, and structural evolution of the nanocomposites are thoroughly investigated. The mechanical properties and air‒plasma ablation resistance of the nanocomposites are also investigated. The results show that the nanocomposites are characterized by multicomponent (Ti,Zr,Hf,Ta)CN nanoparticles uniformly distributed within the SiCN matrix (composed of SiC and/or Si₃N₄). The phase composition and molar ratios of metal elements within the (Ti,Zr,Hf,Ta)CN nanoparticles can be precisely controlled via the molecular design of the SSPs and control of the reaction sequence. The nanocomposites exhibit excellent mechanical properties, with hardness, Young’s modulus, and flexural strength of 35–37, 357–417, and 532–603 MPa, respectively, owing to multicomponent solid solution strengthening and interface strengthening. The linear ablation rate of (Ti_0.1Zr_0.3Hf_0.5Ta_0.1)CN/SiCN with approximately 80 wt% (Ti_0.1Zr_0.3Hf_0.5Ta_0.1)CN at 2200 °C is 0.033 μm/s, which is 2 orders of magnitude lower than those of other multicomponent ultrahigh-temperature ceramics (UHTCs) under similar conditions. The excellent ablation resistance can be attributed to the nanoscale grain size of the multicomponent (Ti,Zr,Hf,Ta)CN phase and its excellent homogeneity within the SiCN matrix, which enables the formation of a continuous and dense oxide layer with a Hf(Zr,Ti)O₂ skeleton filled with SiO₂/Ta₂O₅.