Preparation and ablation behavior analysis of non-equimolar C_f/(Hf_1/2Zr_1/3Ti_1/6)C composites under oxyacetylene flame with different heat fluxes

In this study, the synthesis of C_f/(Hf_1/2Zr_1/3Ti_1/6)C non-equimolar middle-entropy composites was reported through precursor infiltration and pyrolysis processing for the first time. The pyrolysis process of the (Hf_1/2Zr_1/3Ti_1/6)C precursor was examined by XRD, while the resultant ceramic was characterized by SEM, EDS, and TEM. The results showed that precursor-derived (Hf_1/2Zr_1/3Ti_1/6)C powders were characterized by single-phase and uniformly distributed elements from microscale to nanoscale. The C_f/(Hf_1/2Zr_1/3Ti_1/6)C composites exhibited a density of 2.741 g/cm³ and a porosity of 11.49 vol%. The various elements were uniformly distributed throughout the material. It also demonstrated outstanding mechanical properties, with a flexural strength of 219.34 MPa and a modulus of 24.82 GPa. At the heat flux of 3 MW/m², the oxides after ablation were inadequate to fully envelop the substrate. When the heat flux increased to 4 MW/m², a dense Hf-Zr-Ti-O multiphase oxide layer was formed on the surface of the sample, providing the internal C_f/(Hf_1/2Zr_1/3Ti_1/6)C composites against further ablation. At the heat flux of 5 MW/m², (Hf, Zr)TiO₄ was severely consumed. Our research expands the application scope of non-equimolar middle-entropy composites in the domain of ultra-high temperature ablation resistance.