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<p>High densification temperature is usually required for high-entropy carbonitride ultra-high temperature ceramics (HECN-UHTCs), which contributes to grain coarsening and deterioration of mechanical properties. Thus, the quest to decrease the densification temperature and simultaneously enhance the mechanical properties of HECN-UHTCs is a crucial issue of wide concern. To achieve this goal, herein, we introduce CrSi<sub>2</sub> as a sintering additive for (Ti, Zr, Hf, Nb, Ta)(C, N), which effectively reduces the densification temperature of (Ti, Zr, Hf, Nb, Ta)(C, N) by 200 °C. Intriguingly, (Ti, Zr, Nb)<sub>2</sub>Cr<sub>4</sub>Si<sub>5</sub> with orthorhombic structure is formed within the framework of (Ti, Zr, Hf, Nb, Ta)(C, N) due to interdiffusion or cation exchange. Apart from high hardness (24.65 ± 0.23 GPa), the dual phase (Ti, Zr, Hf, Nb, Ta)(C, N)/(Ti, Zr, Nb)<sub>2</sub>Cr<sub>4</sub>Si<sub>5</sub> ceramic exhibits a high fracture toughness of 6.03 ± 0.48 MPa m<sup>1/2</sup>, significantly exceeding the values of most reported HECN-UHTCs. The mechanisms for the enhanced mechanical properties include: crack deflection, increase in localized lattice strain, and Cr grain boundary segregation. Furthermore, this liquid phase-assisted low-temperature sintering strategy can be widely applied to other UHTCs.</p>

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Mechanisms for low temperature densification and enhanced mechanical properties of (Ti, Zr, Hf, Nb, Ta)(C, N) using CrSi2 as an additive: formation of (Ti, Zr, Nb)2Cr4Si5 and grain boundary strengthening

  • 期刊论文

  • 发表日期：

    2025年11月21日

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  • Liansen Xia,
  • Shun Dong,
  • Lumeng Wang,
  • Kaixuan Gui,
  • Xinghong Zhang,
  • Yanchun Zhou

摘要

High densification temperature is usually required for high-entropy carbonitride ultra-high temperature ceramics (HECN-UHTCs), which contributes to grain coarsening and deterioration of mechanical properties. Thus, the quest to decrease the densification temperature and simultaneously enhance the mechanical properties of HECN-UHTCs is a crucial issue of wide concern. To achieve this goal, herein, we introduce CrSi2 as a sintering additive for (Ti, Zr, Hf, Nb, Ta)(C, N), which effectively reduces the densification temperature of (Ti, Zr, Hf, Nb, Ta)(C, N) by 200 °C. Intriguingly, (Ti, Zr, Nb)2Cr4Si5 with orthorhombic structure is formed within the framework of (Ti, Zr, Hf, Nb, Ta)(C, N) due to interdiffusion or cation exchange. Apart from high hardness (24.65 ± 0.23 GPa), the dual phase (Ti, Zr, Hf, Nb, Ta)(C, N)/(Ti, Zr, Nb)2Cr4Si5 ceramic exhibits a high fracture toughness of 6.03 ± 0.48 MPa m1/2, significantly exceeding the values of most reported HECN-UHTCs. The mechanisms for the enhanced mechanical properties include: crack deflection, increase in localized lattice strain, and Cr grain boundary segregation. Furthermore, this liquid phase-assisted low-temperature sintering strategy can be widely applied to other UHTCs.