DMREF/Collaborative Research: Nitride Discovery - Creating the Knowledge Base for Hard Coating Design

本研究计划的主要目标是开发一种系统的方法来确定过渡金属氮化物的固有物理性质。该项目采用实验和密度泛函计算相结合的方法，以确定二元氮化物的固有弹性特性，硬度和抗氧化性值。使用超高真空反应溅射外延沉积未探测氮化物的无应力单晶层。内在的机械性能和高温氧化率的测量和直接相关的第一原理计算的结果。这种相关性是用来开发一个完整的属性数据集的所有二元过渡金属氮化物，通过分类它们根据它们的电子结构和原子键合，使用理论计算的各向异性弹性常数和氧置换能量和测量的硬度和氧化速率。从二元氮化物的知识是用来开发一个定量模型，涉及的三元和非化学计量的氮化物的机械性能的组合物，使用测量和计算的电子态密度和组合物相关的费米能级，它决定了电荷转移和键的方向性。该项目还通过测量具有共格界面的模型系统中的机械性能，并计算两种氮化物之间边界处的应变相关剪切模量和位错能量，探索第一级微观结构特征。该项目预计将基于电子结构对所有过渡金属氮化物的基本性质提供系统的理解。这种理解代表了知识基础，有可能通过新的涂层设计方法改变数十亿美元的硬涂层行业。因此，它为加速发现坚硬、耐磨和耐腐蚀的涂层提供了基础，并将保护涂层的渐进式试错开发转变为涂层设计方法，从而快速部署用于新兴应用的新涂层材料，包括燃油效率高的喷气发动机和燃气轮机、环保无润滑切削工具、高温聚光太阳能发电厂、和风力涡轮机。研究生和本科生在这个跨学科的合作研究计划中接受培训，该计划将两个研究小组与两个机构的互补实验和计算专业知识联系起来。所提出的努力的一个组成部分是开发一个在线虚拟氮化物属性工具，包括一个研究社区驱动的数据库，用于与硬质保护涂层相关的过渡金属氮化物的固有属性。

The primary objective of this research program is to develop a systematic method to determine the intrinsic physical properties of transition metal nitrides. The project uses a combination of experiments and density functional calculations, to determine intrinsic elastic properties, hardness, and oxidation resistance values for binary nitrides. Stress-free single crystal layers of unexplored nitrides are deposited using ultra-high vacuum reactive sputter epitaxy. Intrinsic mechanical properties and high temperature oxidation rates are measured and directly correlated to results from first-principles calculations. This correlation is used to develop a complete property dataset for all binary transition metal nitrides by classifying them according to their electronic structure and atomic bonding, using theoretically computed anisotropic elastic constants and oxygen replacement energetics and measured hardness and oxidation rates. The knowledge from binary nitrides is used to develop a quantitative model that relates composition of ternary and off-stoichiometric nitrides to mechanical properties, using both measured and calculated electron density of states and the composition-dependent Fermi level, which determines charge transfer and bond directionality. The project also explores first-level microstructural features by measuring mechanical properties in a model system with coherent interfaces and calculating strain-dependent shear moduli and dislocation energetics at the boundary between two nitrides.This project is expected to provide a systematic understanding of the fundamental properties of all transition metal nitrides, based on their electronic structure. This understanding represents the knowledge base that has the potential to transform the multi-billion-dollar hard coating industry with a new coatings design approach. Thus, it provides the basis to accelerate discovery of hard, wear and corrosion resistant coatings and transform the evolutionary trial-and-error development of protective coatings into a Coatings-by-Design approach, resulting in rapid deployment of new coating materials for emerging applications including fuel-efficient jet engines and gas turbines, environmentally-friendly lubricant-free cutting tools, high-temperature concentrating solar power plants, and wind turbines. Graduate and undergraduate students are trained in this interdisciplinary collaborative research program which links two research groups with complementary experimental and computational expertise at two institutions. An integral part of the proposed effort is the development of an online virtual nitride-property tool including a research-community-driven database for intrinsic properties of transition metal nitrides relevant to hard protective coatings.