ReB2-type hexagonal Osmium diboride (OsB2) has been predicted to exhibit higher hardness than its orthorhombic phase, but hexagonal-orthorhombic phase transformation occurs at temperature higher than 600°C, resulting in the decrease in its hardness. Therefore, ReB2-type hexagonal OsB2 samples with Re addition were produced by a combination of mechanochemical method and pressureless sintering technique, and the effects of Rhenium (Re) addition on phase composition, thermal stability and mechanical properties of OsB2 were investigated in this study. X-ray diffraction (XRD) analysis of the as-synthesized powders by high-energy ball milling indicates the formation of hexagonal Os1-xRexB2 solid solution with Re concentration of 5 and 10 at.% without forming a second phase. After being sintered at 1700°C, part of the hexagonal phase in OsB2 transformed to orthorhombic structure, while Os0.95Re0.05B2 and Os0.9Re0.1B2 maintained their hexagonal structure. This suggests that the thermal stability of the hexagonal OsB2 was significantly improved with the addition of Re. Scanning electron microscopy (SEM) photographs show that all of the as-sintered samples exhibit a homogeneous microstructure with some pores and cracks formed throughout the samples with the relative density >90%. The measurements of micro-hardness, nano-hardness, and Young's modulus of the OsB2 increased with Re addition, and these properties of the sample with 5 at.% addition of Re is higher than that with 10 at.% Re.

中文翻译：

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Re添加对六方OsB2相稳定性和力学性能的影响

据预测，ReB2 型六方二硼化锇 (OsB2) 的硬度高于其正交相，但在高于 600°C 的温度下会发生六方-正交相变，导致其硬度降低。因此，采用机械化学方法和常压烧结技术相结合的方法制备了添加 Re 的 ReB2 型六方 OsB2 样品，并研究了铼 (Re) 添加对 OsB2 的相组成、热稳定性和机械性能的影响。通过高能球磨对合成的粉末进行 X 射线衍射 (XRD) 分析表明，形成了六边形 Os1-xRexB2 固溶体，Re 浓度为 5 和 10 at.%，没有形成第二相。在 1700°C 下烧结后，OsB2 中的部分六方相转变为正交结构，而 Os0.95Re0.05B2 和 Os0.9Re0.1B2 保持其六方结构。这表明六方 OsB2 的热稳定性随着 Re 的加入而显着提高。扫描电子显微镜 (SEM) 照片表明，所有烧结后的样品均呈现出均匀的微观结构，在整个样品中形成了一些孔隙和裂纹，相对密度 >90%。OsB2 的显微硬度、纳米硬度和杨氏模量的测量值随着 Re 的添加而增加，并且添加 5 at.% Re 的样品的这些性能高于添加 10 at.% Re 的样品。这表明六方 OsB2 的热稳定性随着 Re 的加入而显着提高。扫描电子显微镜 (SEM) 照片表明，所有烧结后的样品均呈现出均匀的微观结构，在整个样品中形成了一些孔隙和裂纹，相对密度 >90%。OsB2 的显微硬度、纳米硬度和杨氏模量的测量值随着 Re 的添加而增加，并且添加 5 at.% Re 的样品的这些性能高于添加 10 at.% Re 的样品。这表明六方 OsB2 的热稳定性随着 Re 的加入而显着提高。扫描电子显微镜 (SEM) 照片表明，所有烧结后的样品均呈现出均匀的微观结构，在整个样品中形成了一些孔隙和裂纹，相对密度 >90%。OsB2 的显微硬度、纳米硬度和杨氏模量的测量值随着 Re 的添加而增加，并且添加 5 at.% Re 的样品的这些性能高于添加 10 at.% Re 的样品。