Seven equimolar, five-component, metal diborides were fabricated via high-energy ball milling and spark plasma sintering. Six of them, including (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)B2, (Hf0.2Zr0.2Ta0.2Mo0.2Ti0.2)B2, (Hf0.2Zr0.2Mo0.2Nb0.2Ti0.2)B2, (Hf0.2Mo0.2Ta0.2Nb0.2Ti0.2)B2, (Mo0.2Zr0.2Ta0.2Nb0.2Ti0.2)B2, and (Hf0.2Zr0.2Ta0.2Cr0.2Ti0.2)B2, possess virtually one solid-solution boride phase of the hexagonal AlB2 structure. Revised Hume-Rothery size-difference factors are used to rationalize the formation of high-entropy solid solutions in these metal diborides. Greater than 92% of the theoretical densities have been generally achieved with largely uniform compositions from nanoscale to microscale. Aberration-corrected scanning transmission electron microscopy (AC STEM), with high-angle annular dark-field and annular bright-field (HAADF and ABF) imaging and nanoscale compositional mapping, has been conducted to confirm the formation of 2-D high-entropy metal layers, separated by rigid 2-D boron nets, without any detectable layered segregation along the c-axis. These materials represent a new type of ultra-high temperature ceramics (UHTCs) as well as a new class of high-entropy materials, which not only exemplify the first high-entropy non-oxide ceramics (borides) fabricated but also possess a unique non-cubic (hexagonal) and layered (quasi-2D) high-entropy crystal structure that markedly differs from all those reported in prior studies. Initial property assessments show that both the hardness and the oxidation resistance of these high-entropy metal diborides are generally higher/better than the average performances of five individual metal diborides made by identical fabrication processing.
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机译:通过高能球磨和火花等离子体烧结制备了七个等摩尔,五组分,金属二硼化物。其中六个包括(Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)B2,(Hf0.2Zr0.2Ta0.2Mo0.2Ti0.2)B2,(Hf0.2Zr0.2Mo0.2Nb0.2Ti 0.2 < / sub>)B 2 sub>,(Hf 0.2 sub> Mo 0.2 sub> Ta 0.2 sub> Nb 0.2 sub > Ti 0.2 sub>)B 2 sub>,(Mo 0.2 sub> Zr 0.2 sub> Ta 0.2 sub> Nb 0.2 sub> Ti 0.2 sub>)B 2 sub>和(Hf 0.2 sub> Zr 0.2 sub> Ta < sub> 0.2 sub> Cr 0.2 sub> Ti 0.2 sub>)B 2 sub>,实际上具有六方AlB 2 sub>结构。修订后的休ume-罗西大小差异因子用于合理化这些金属二硼化物中高熵固溶体的形成。通常已经使用从纳米级到微米级的基本上均匀的组成实现了大于92%的理论密度。进行了像差校正扫描透射电子显微镜(AC STEM),具有高角度环形暗场和环形亮场(HAADF和ABF)成像和纳米级成分映射,以确认二维高熵的形成金属层,由刚性二维硼网隔开,沿c轴没有任何可检测到的分层偏析。这些材料代表了一种新型的超高温陶瓷(UHTC)以及一类新的高熵材料,它们不仅是第一批制造的高熵非氧化物陶瓷(硼化物)的例证,而且还具有独特的立方(六方)和层状(准2D)高熵晶体结构与先前研究中报道的所有晶体明显不同。初始性能评估表明,这些高熵金属二硼化物的硬度和抗氧化性通常都比通过相同制造工艺制造的五种单独的金属二硼化物的平均性能更高/更好。
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