Carbide and nitride nanocomposite coatings: development and application of analytic bond-order potentials

该项目的目标是将英国和德国两个科学小组的专业知识联合收割机，以便在原子尺度上推进对纳米复合硬质涂层的基本理解。在工业中，碳化物和氮化物化合物被广泛用作切削、铣削、车床或拉丝等金属成形工具的涂层。这些涂层具有微米级的多晶结构（其中一微米对应于千分之一毫米）。它们必须具有足够的硬度、坚韧、耐热性和耐磨性，以便在工业生产中经济可靠地使用。最近，材料研究的重点一直是通过将这些材料的结构化到比以前精细一千倍的程度来改善其功能性能。超硬或超韧纳米复合材料是由纳米级晶粒（纳米为千分之一微米）和非晶相组成的复合材料，目前绝大多数纳米复合材料的技术成果都是通过实验研究和大量试错而获得的。对微观机制和过程的科学理解，将界面的微观结构特性与宏观力学特性联系起来，仍然主要是经验性的，还不是很详细。然而，这种理解是控制和优化纳米复合材料合成以提高性能的重要先决条件。如今，原子计算机模拟已成为材料科学和技术领域公认的有价值的和预测性的手段，增强了实验表征和分析。原子计算机模拟需要的知识，在涂层中的原子之间的作用力。尽管这些原子间力在离子体系如岩盐中是众所周知的，但对于包含涂层的结晶和非晶相的共价碳化物和氮化物体系，它们的特征就不那么好了。基于牛津的提议将开发出一类新的原子间势，即所谓的键序势（BOPs），它将能够描述和分析纳米复合材料的结构和性能。我们将使用一个非常精确但计算要求非常高的数据库，对各种不同的晶体结构进行参数化的BOP计算。随着牛津大学开发的潜力，纳米复合材料的原子模拟将与IWM密切合作，并与实验工作进行比较。

The goal of this project is to combine the expertise of two scientific groups in the United Kingdom and Germany in order to advance the fundamental understanding of nanocomposite hard coatings at the atomic scale.In industry, carbide and nitride compounds are widely used as coatings of metal-shaping tools for cutting, milling, lathing, or wire-drawing. These coatings have polycrystalline structures on the micrometer scale (where one micrometer corresponds to one in a thousand parts of a millimeter). They must be sufficiently hard, tough, heat and wear resistant for economical and reliable use in industrial production.Recently, materials research has been focusing on the improvement of the functional performance of these materials by structuring them on a scale that is a thousand times finer than before. Superhard or supertough nanocomposites are composed of nanometer-sized crystalline grains (where one nanometer is one in a thousand parts of a micrometer) seperated by an amorphous phase.Hitherto, most of the technological achievements for nanocomposites have been obtained through experimental research and a large amount of trial and error. The scientific understanding of microscopic mechanisms and processes, which relate the microscopic structural properties of interfaces to the macroscopic mechanical properties, is still mostly empirical and not yet very detailed. However, this understanding is an important prerequisite for the control and optimisation of the synthesis of nanocomposite materials for improved performance. Nowadays, atomistic computer simulations have become well recognised in materials science and technology as valuable and predictive means which augment experimental characterisation and analysis.The atomistic computer simulations require a knowledge of the forces which act between the atoms in the coatings. Whereas these interatomic forces are well-known for ionic systems such as rock salt, they are less well characterized for covalent carbide and nitride systems thatcomprise the cyrstalline and amorphous phases of coatings.The Oxford-based proposal will develop a novel class of interatomic potentials, the so-called bond-order potentials (BOPs), which will be capable of describing and analysing the structures and properties of nanocomposites. We will parameterize the BOPs using a database of veryaccurate but computationally very demanding reference calculations for a wide range of different crystal structures. With the potentials developed at Oxford, atomistic simulations of nanocomposites will then be carried out in close collaboration with IWM and compared to experimental work.