DMREF/Collaborative Research: Multiscale Theory and Experiment in Search for and Synthesis of Novel Nanostructured Phases in BCN Systems

非技术描述：超硬材料，如金刚石，立方氮化硼和碳化硼（B4 C）可以表现出高的熔化温度，大的压缩强度，化学惰性和高导热性，使它们在科学和工程应用中具有实际重要性。然而，它们很脆，很容易断裂，这是一个严重的缺陷，阻碍了许多工程应用。将结合计算方法来开发延展性超硬材料，以扩展工程应用。最初，量子力学将用于预测新的韧性超硬材料的最佳候选人，通过分析大量的情况下在硅片。对于最好的预测材料，将采用新的实验方法，其中金刚石砧单元扭曲，同时施加高压，以形成预测的相。然后将测试这些材料的性能。技术说明：我们的目标是推进多尺度理论，建模和实验，足以使一个革命性的新方法来搜索和合成新的纳米结构相的BCN系统。大的塑性剪切变形将与独特的旋转金刚石压砧单元（RDAC）中的高压相结合，以（a）寻找在没有塑性剪切应变的情况下在压力下不能获得的新的纳米结构超硬相，（B）显著降低相变途径到新的和/或已知相所需的压力，以及（c）稳定这些新相以用于在环境压力下加工。重点将放在BCN系统中一些最有前途的材料上：碳超硬相（金刚石、富勒烯、高密度无定形C、纳米管和长程有序无定形簇）、硼、立方cBN和纤锌矿wBN、立方cBC 2N、cBC 4 N、高密度cC 3 N4（预测比金刚石更硬，但从未合成），BCN系统内的纳米结构复合材料，以及这些系统中的其他新相，所有这些都将通过原子模拟来预测。

Non-technical Description: Superhard materials, such as diamond, cubic boron nitride, and boron carbide (B4C) can exhibit high melting temperatures, large compression strengths, chemical inertness, and high thermal conductivity, making them of practical importance for science and engineering applications. However, they are brittle, breaking easily, a serious flaw that prevents many engineering applications. Computational approaches will be combined to develop ductile superhard materials for extended engineering applications. Initially, quantum mechanics will be used to predict the best candidates for new ductile superhard materials by analyzing a large number of cases in silico. For the best predicted materials novel experimental methods will be employed in which diamond anvil cells are twisted while applying high pressure to form the predicted phases. The properties of these materials will then be tested. Technical Description: The goal is to advance multiscale theory, modeling, and experiment sufficiently to enable a revolutionary new approach to search for and synthesize novel nanostructured phases in the BCN system. Large plastic shear deformation will be combined with high pressure in a unique rotational diamond anvil cell (RDAC), to (a) search for new nanostructured superhard phases that cannot be obtained under pressure without plastic shear straining, (b) dramatically reduce pressure required for phase transformation pathways to new and/or known phases, and (c) stabilize these new phases for processing at ambient pressure. The focus will be on some of the most promising materials within the BCN system: superhard phases of carbon (diamond, fullerene, high-density amorphous C, nanotubes, and long-range ordered amorphous clusters), boron, cubic cBN and wurtzitic wBN, cubic cBC2N, cBC4N, high density cC3N4 (predicted to be harder than diamond but never synthesized), nanostructured composites within BCN system, and other new phases in these systems, all of which will be predicted by the atomistic simulations.