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This work investigated the effect of ZrB2 content on phase composition, relative density, microstructure, and mechanical performance of Si3N4 ceramics prepared by Si nitridation and hot‐pressing method. Si3N4 ceramics were fabricated using Si powder by nitridation and hot‐pressing process. Results showed that the addition of ZrB2 enhanced the transformation of α‐Si3N4 into β‐Si3N4 phase during nitridation, resulting in a greater fraction of β‐Si3N4 (above 90 wt.%) phase in Si3N4 ceramics with ZrB2 after hot‐pressing. In contrast, ceramics without ZrB2 had a lower ratio of β‐Si3N4 (40.4 wt.%). The use of 2.5 vol.% ZrB2 yielded a significant bimodal microstructure and increased fracture toughness to 5.0 ± 0.2 MPa·m1/2, but decreased Vickers hardness to 16.4 ± 0.5 GPa. However, increasing the ZrB2 content to 5 vol.% and 10 vol.% led to a massive formation of equiaxed coarse β‐Si3N4 grains and a significant decrease in Vickers hardness and fracture toughness. [ABSTRACT FROM AUTHOR]

Currently, previous studies of low‐temperature sintering of high‐entropy carbide ceramics (HECCs) have followed the traditional approach to use the low‐melting‐point metals, such as Co, Ni, and so forth, as sintering additives. However, metallic binders can cause adverse impacts on hardness of HECCs. This study reported an innovation processing method for low‐temperature sintering of HECCs, which involved the use of various contents of CrN as sintering additive and spark plasma sintering at 1600°C to obtain dense HECCs. In comparison to the grain size of pure (Ti, Zr, Nb, Ta, Mo)C bulk sintered at 2000°C (3.29 ± 1.02 μm), the grain size of samples with the addition of 5–15 wt.% CrN sintered at 1600°C was significantly smaller, ranging from 0.32 to 0.48 μm. By using only 5 wt.% CrN, dense (Ti, Zr, Nb, Ta, Mo)C ceramics with a high hardness value of 26.73 ± 0.43 GPa could be obtained. Furthermore, increasing the amount of CrN to 15 wt.% resulted in a fracture toughness of 3.78 ± 0.10 MPa·m1/2. It is anticipated that the (Ti, Zr, Nb, Ta, Mo)C ceramic with an ideally combined hardness and toughness can be achieved at low sintering temperatures by the proper control of CrN content. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the toughening effects of SiC nanowires (SiCnw) and SiC whiskers (SiCw) on high‐entropy carbide based composites prepared at different temperatures (1600°C and 2000°C). At low temperature (1600°C), SiCnw and SiCw maintain their original morphology and properties, and exhibit the good toughening effects. The SiCnw with larger aspect ratio and more curly wires exhibit a much stronger toughening effect on the (Ti0.2Zr0.2Nb0.2Ta0.2Mo0.2)C0.8 composites reinforced with 15 vol.% SiCnw, which shows the highest value of fracture toughness about 6.7 MPa∙m1/2. However, at high sintering temperature (2000°C), SiCnw and SiCw are prone to thermal‐induced damages, which significantly reduces their mechanical properties, and thus, toughening effects on (Ti0.2Zr0.2Nb0.2Ta0.2Mo0.2)C0.8 composites. The addition of SiCw, which have better thermal stability at 2000°C, results in the (Ti0.2Zr0.2Nb0.2Ta0.2Mo0.2)C0.8–15 vol.% SiCw composite exhibiting relatively better fracture toughness, about 3.7 MPa∙m1/2. Based on the results of the current study, the critical influence of SiCnw and SiCw on the toughening of (Ti0.2Zr0.2Nb0.2Ta0.2Mo0.2)C0.8 composites is highly dependent on their high‐temperature thermal stability. [ABSTRACT FROM AUTHOR]