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

该项目的目标是结合英国和德国两个科学小组的专业知识，以推进对纳米复合硬涂层在原子尺度上的基本理解。在工业上，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（其中一微米对应于一毫米的千分之一）。它们必须具有足够的硬度、韧性、耐热性和耐磨性，以便在工业生产中经济可靠地使用。最近，材料研究的重点是通过在比以前精细一千倍的尺度上构建这些材料来改善这些材料的功能性能。超硬或超韧的纳米复合材料由纳米大小的晶体颗粒（其中一纳米是一微米的千分之一）由非晶相分开。迄今为止，纳米复合材料的大部分技术成果都是通过实验研究和大量的试错获得的。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，原子计算机模拟已经成为材料科学和技术领域公认的有价值的预测手段，可以增强实验表征和分析。原子计算机模拟需要了解作用于涂层中原子之间的力。虽然这些原子间作用力在离子体系如岩盐中是众所周知的，但在包括涂层的结晶相和非晶态相的共价碳化物和氮化物体系中，它们的特征却不太明显。牛津大学的这项提议将开发一种新型的原子间势，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特性。我们将使用一个数据库来参数化bop，该数据库对各种不同的晶体结构进行了非常精确但计算要求很高的参考计算。利用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.