Hardening Effects in Superhard Transition-Metal Borides
Hardening Effects in Superhard Transition-Metal Borides
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DOI：
10.1021/accountsmr.1c00192
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发表时间：
2021-12-30
影响因子：
14.6
通讯作者：
Kaner, Richard B.
中科院分区：
文献类型：
--
作者：
Pangilinan, Lisa E.;Hu, Shanlin;Kaner, Richard B.
机械硬度是一种物理属性，用于评估材料在制造和加工行业中的应用。由于其高硬度和耐磨性，超级材料（Vickers Hartness，H-V> = 40 GPA）通常用作切割工具和磨料。尽管钻石是用于工业应用的最难的材料，但其合成需要高压和高温。对超端材料研究领域的兴趣导致寻找具有高硬度和热稳定性的替代方案，以低成本。新颖的超级紧缩的超级智能的发现主要是通过沿两条路径的反复试验而开发的。在一种方法中，研究人员将光元素（例如硼，碳，氮和氧气）结合在一起，通常是在高压下，以复制钻石的高方向，致密，共价键。在第二种方法中，这些光元素（B，C，N和O）与高度不可压缩的，富含电子的过渡金属结合在一起，以在环境压力下形成密集的共价键网络。在此说法中，我们强调了我们在开发Superhard方面的进步过渡金属通过实心溶液效应和晶界强化。我们首先回顾了有助于材料硬度的因素，并在寻找新材料时指导高电子密度和高价值键密度的设计参数。在随后的部分中，我们检查了各种金属硼化物系统，其粘结共价和结构复杂性的增加，从富含金属的单二吡啶和二吡啶并到富含硼的四链球和十二烷。该帐户中讨论的金属硼化物是在环境压力下使用高温固态技术（例如弧熔化和熔融通量合成）形成的。通过通过Vickers硬度测试和高压实验来表征这些材料，我们可以深入了解键合和晶粒形态对机械性能的耦合作用。最后，我们为未来材料的快速发现和可访问的构图提供了前景。我们希望该帐户中讨论的材料和方法为设计和合成下一代工业应用的超级材料提供了新的机会。
Mechanical hardness is a physical property used to gauge the applications of materials in the manufacturing and machining industries. Because of their high hardness and wear resistance, superhard materials (Vickers hardness, H-v >= 40 GPa) are commonly used as cutting tools and abrasives. Although diamond is the hardest known material used for industrial applications, its synthesis requires both high pressure and high temperature. Interest in the field of superhard materials research has led to the search for alternatives with high hardness and thermal stability at low cost. The discovery of novel ultraincompressible, superhard materials has largely developed through trial and error along two paths. In one approach, researchers combine light elements, such as boron, carbon, nitrogen, and oxygen, often at high pressure, to replicate the highly directional, dense, covalent bonds of diamond. In the second approach, these light elements (B, C, N, and O) are combined with highly incompressible, electron-rich transition metals to form dense covalently bonded networks at ambient pressure.In this Account, we highlight our progress in developing superhard transition-metal borides through solid solution effects and grain boundary strengthening. We begin with a review of the factors that contribute to a material's hardness and guide our design parameters of high electron density and high covalent bond density in the search for new materials. In subsequent sections, we examine various metal boride systems with increasing bond covalency and structural complexity, from metal-rich mono- and diborides to boron-rich tetra- and dodecaborides. The metal borides discussed in this Account are formed at ambient pressure using high-temperature solid-state techniques such as arc melting and molten flux synthesis. By characterizing these materials through both Vickers hardness testing and high-pressure experiments, we gain insight into the coupled effects of bonding and grain morphology on mechanical properties. Finally, we provide an outlook into the expedited discovery and accessible compositions for future materials. We hope that the materials and methods discussed in this Account offer new opportunities for the design and synthesis of the next generation of superhard materials for industrial applications.