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

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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.