High-entropy boride ceramics demonstrate outstanding high-temperature stability, positioning them as promising candidates for reliable performance in extreme environments. However, their inherent limitation lies in relatively low fracture toughness, coupled with the unclear elucidation of high-temperature tribological behaviors. To address these challenges, high-entropy (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)B₂ (HEB) ceramics are utlized as the matrix material in the current investigation, while hexagonal boron nitride (h-BN) is introduced as a type of toughening and lubricating phase to develop HEB-hBN composite ceramics. The toughening and high-temperature self-lubrication of the composites are achieved by leveraging the high aspect ratio, lamellar microstructure, and interlayer slip characteristics of h-BN. Results indicate that h-BN enhances the fracture toughness of the composite ceramics by nearly 70%, attributed to the optimization of the crack growth path through its lamellar microstructure and facilitating crack deflection and bridging mechanisms due to its high aspect ratio. Moreover, through interlayer slip effects, h-BN collaborates with B₂O₃ and metal oxides generated from high-temperature oxidation, forming a gradient tribofilm in conjunction with other synergistic lubrication mechanisms. This synergistic interaction results in a nearly 40% reduction in the friction coefficient of the composite ceramics, accompanied by an approximately 60% decrease in wear rate under high-temperature friction conditions at 1000 °C. Under extreme friction environments ranging from 1000 °C to 1200 °C, the composite ceramic maintains a friction coefficient consistently below 0.30, with the wear rate stably sustained at an order of magnitude of 10^-5 mm³/(N·m).

High-entropy boride (HEB) ceramics combine ultra-high melting points, superior hardness, and compositional tunability, enabling service in extreme environments; however, difficult densification and limited fracture toughness still constrain their aerospace applications. In this study, metallic Ta was introduced into high-entropy (Ti_0.2Zr_0.2Hf_0.2Nb_0.2Ta_0.2)B₂ as both a sintering aid and a toughening phase. Bulk HEB-Ta composites were fabricated by spark plasma sintering to investigate the effect of Ta content on densification behavior, microstructure, mechanical properties, and high-temperature oxidation resistance. The results show that an appropriate amount of Ta markedly promotes densification; at 10 vol% Ta, the open porosity reaches a minimum of 0.15%. Hardness and fracture toughness exhibit an increase-then-decrease trend with Ta content, attaining maxima at 15 vol% Ta (20.79 ± 0.17 GPa and 4.31 ± 0.12 MPa·, respectively). During oxidation at 800–1400 °C, the extent of oxidation increases with temperature, yet the composite with 10 vol% Ta shows the best oxidation resistance. This improvement arises from the formation of a viscous, protective Ta₂O₅-B₂O₃ glassy layer that effectively suppresses oxygen diffusion and enhances high-temperature stability. Overall, incorporating metallic Ta is an effective route to improve the manufacturability and service durability of HEB ceramics, providing a composition guideline and a mechanistic basis for simultaneously enhancing densification, toughness, and oxidation resistance.

Zr₂Al₄C₅/SiC composite ceramics were successfully fabricated from the powder mixture of Zr, Al, C and SiC by spark plasma sintering method. The composition-dependent densification, phase evolution, microstructure and mechanical properties of the composite ceramics were studied. With increasing the SiC content in the starting powder mixture, the densification behavior of sintered samples was promoted. It is found that the as-sintered products are mainly composed of Zr₂Al₄C₅ matrix and SiC reinforcement, and the fine SiC particles tend to disperse on the matrix grain boundaries. Besides, the addition of SiC particles can evidently hinder the coarsening of Zr₂Al₄C₅ grains. Both the Vickers hardness and Young’s modulus of composites ceramics gradually increase as increasing the SiC content. The fracture toughness of the composites decreases first then increases with the increase in the SiC and the Zr₂Al₄C₅/30vol%SiC sample possesses the maximum value of 4.4MPa·m^1/2.

ZrB₂-SiC-Zr₂Al₄C₅ multi-phase ceramics with uniform structure and high density were successfully prepared through the introduction of in situ synthesized Zr₂Al₄C₅ into ZrB₂-SiC ceramic via SPS at 1800 °C. A systematic analysis and discussion of the experimental results and proposed mechanisms were carried out to demonstrate the composition-dependent sintering properties, mechanical properties and oxidation behavior. The results showed that the in situ synthesized Zr₂Al₄C₅ could be evenly distributed in the ZrB₂-SiC ceramic matrix and inhibited the growth of ZrB₂ grains, which played a positive role in the sintering densification of the composite ceramics. With increasing Zr₂Al₄C₅ content, the Vickers hardness and Young’s modulus of composite ceramics gradually decreased. The fracture toughness showed a trend that first increased and then decreased, and was increased by about 30% compared with ZrB₂-SiC ceramics. The major phases resulting from the oxidation of samples were ZrO₂, ZrSiO₄, aluminosilicate and SiO₂ glass. With increasing Zr₂Al₄C₅ content, the oxidative weight showed a trend that first increased then decreased; the composite ceramic with 30 vol.% Zr₂Al₄C₅ showed the smallest oxidative weight gain. We believe that the presence of Zr₂Al₄C₅ results in the formation of Al₂O₃ during the oxidation process, subsequently resulting in a lowering of the viscosity of the glassy silica scale, which in turn intensifies the oxidation of the composite ceramics. This would also increase oxygen permeation through the scale, adversely affecting the oxidation resistance of the composites with high Zr₂Al₄C₅ content.

How to improve the low temperature performance of asphalt mixture is crucial because low temperature cracking is one of the most common diseases of asphalt pavement. The steel fiber is a effective method in the ordinary asphalt mixture. The effect of steel fiber on the low temperature crack resistance of asphalt concrete is analyzed in cases of different temperatures and contents of steel fiber through the bending test of small beam. It is shown that the flexural tensile strength and the failure strain of the asphalt concrete decreased linearly with the decrease of temperature. Added steel fiber content immensely changed the size of flexural tensile strength(maximum rose to 31.8%). With the increasing of steel fiber content, the flexural tensile strength increases the amplitude showd o rising trend. It is suggested that improved flexural tensile strength and anti-deformability of asphalt concrete after adding steel fiber effectively increase anti-crackingability under low temperature.