The preparation of dense high-entropy carbide ceramics (HECCs) is extremely challenging owing to their strong covalent bonding and sluggish diffusion associated with high-entropy effects, which necessitate ultrahigh sintering temperatures that in turn cause severe grain coarsening and excessive energy consumption. In this study, a novel low-temperature consolidation route is developed based on Ti₃AlC₂ reactive sintering. Specifically, the reactive precursor Ti₃AlC₂ decomposes into TiC_x and Al during spark plasma sintering. The in situ formed TiC_x accelerates interdiffusion and solid-solution formation among transition-metal carbides, while the released Al effectively activates particle interfaces. This dual-activation mechanism markedly enhances sintering kinetics, enabling the densification of (TiVNbTaMo)C_x ceramics at 1550 °C. The optimized sample achieved a relative density of 98.5%, a Vickers hardness of 22.94 GPa under a load of 9.8 N, a flexural strength of 1018 MPa, and a fracture toughness of 5.67 MPa·m^1/2, showing superior strength and hardness compared with most reported high-entropy carbides while maintaining an acceptable level of toughness. Furthermore, the interfacial modification results in a stable friction coefficient from room temperature to 900 °C, accompanied by nonadhesive wear behavior at elevated temperatures, making the obtained samples promising for high-temperature structural and wear-resistant applications. Therefore, reactive-Ti₃AlC₂ precursor-assisted sintering provides a new pathway for the design and scalable fabrication of advanced dense high-entropy ceramics under low-temperature conditions.

Carbides are considered promising candidates for advanced manufacturing applications due to their superior mechanical properties and excellent thermal stability. However, the requirement for high sintering temperatures remains a significant barrier to achieving dense microstructures with refined grain sizes. In this work, high-entropy (TiVNbTaMo)C_4.5 ceramics with a fine average grain size of ~ 434 nm and high relative density were successfully synthesized at a relatively low temperature of 1550 °C via spark plasma sintering. The pronounced reduction in both sintering temperature and grain size is attributed to the high-entropy effect and the lattice distortion introduced by incorporating multiple principal elements with different crystal structures. The resulting ceramics exhibit a high flexural strength of 813 MPa and a Vickers hardness of 39.19 GPa, without sacrificing fracture toughness, thereby overcoming the typical trade-off between hardness and toughness. The effects of grain refinement and solid–solution strengthening on mechanical properties are systematically investigated using advanced microstructural characterization techniques. This study demonstrates an efficient and cost-effective strategy for the fabrication of high-performance high-entropy (TiVNbTaMo)C_4.5 carbide ceramics.

High-entropy diborides (HEBs) are considered as promising high-temperature structure materials owing to their high melting point and excellent thermal stability. However, the intrinsic brittleness is the main obstacle that seriously limits their practical applications. To overcome with this obstacle, carbon fibers (C_f) with outstanding mechanical properties are used in the present work as a first attempt to improve the damage tolerance of HEBs. The as-prepared C_f/(Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)B₂–SiC composite (C_f/HEB–SiC) shows high relative density (97.9%) and good mechanical properties with flexural strength of 411±3 MPa and fracture toughness of 6.15±0.11 MPa·m^1/2. More importantly, the damage tolerance parameter (D_t) has increased from 0.10 m^1/2 for HEB–SiC to 0.29 m^1/2 for C_f/HEB–SiC. Through microstructural analysis and Vickers indentation of the composite, the toughening mechanisms are disclosed. The carbon fibers coated with carbon coatings demonstrate unique capacity for prolonging the crack propagation path, which promotes the reliability of the composite effectively. Moreover, the C_f/(Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)B₂–SiC composite also exhibits good static oxidation resistance in the temperature range of 1100–1500 ℃ in air due to the formation of the protective oxide layer constituting of multicomponent oxides (Zr)HfTiO₄ and (Zr)Hf₆Ta₂O₁₇ embedded in a continuous SiO₂ glass. These results are promising, and this primary work can be used as a reference to the synthesis of C_f/HEBs for thermal protection materials under high-temperature serving conditions.

High-entropy rare-earth aluminate (Y_0.2Yb_0.2Lu_0.2Eu_0.2Er_0.2)₃Al₅O₁₂ (HE-RE₃Al₅O₁₂) has been considered as a promising thermal protection coating (TPC) material based on its low thermal conductivity and close thermal expansion coefficient to that of Al₂O₃. However, such a coating has not been experimentally prepared, and its thermal protection performance has not been evaluated. To prove the feasibility of utilizing HE-RE₃Al₅O₁₂ as a TPC, HE-RE₃Al₅O₁₂ coating was deposited on a nickel-based superalloy for the first time using the atmospheric plasma spraying technique. The stability, surface, and cross-sectional morphologies, as well as the fracture surface of the HE-RE₃Al₅O₁₂ coating were investigated, and the thermal shock resistance was evaluated using the oxyacetylene flame test. The results show that the HE-RE₃Al₅O₁₂ coating can remain intact after 50 cycles at 1200 ℃ for 200 s, while the edge peeling phenomenon occurs after 10 cycles at 1400 ℃ for 200 s. This study clearly demonstrates that HE-RE₃Al₅O₁₂ coating is effective for protecting the nickel-based superalloy, and the atmospheric plasma spraying is a suitable method for preparing this kind of coatings.

As a kind of high-entropy ceramics, high-entropy boride ceramics have attracted more and more attention because of their excellent high temperature comprehensive mechanical properties and stability. However, there is no review on the research of high entropy boride ceramics. Therefore, the definition of high-entropy ceramics and the preparation methods of high-entropy borides were introduced. The application of first-principles calculations in the study of high entropy borides, the prediction of synthesis of high-entropy borides and the prediction and understanding of properties are summarized. The advantages and disadvantages of various preparation methods of high-entropy boride ceramic powders and bulks were comprehensively evaluated. Taking mechanical properties as the focus, various physical and chemical properties of high-entropy boride ceramics and their influencing factors and mechanisms were analyzed. At the same time, the shortcomings of high-entropy borides in theoretical calculation, preparation and exploration of material properties are summarized, and the possible future research directions were analyzed and prospected.