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内在物理性质。该项目结合实验和密度泛函计算来确定二元氮化物的固有弹性特性、硬度和抗氧化性值。利用超高真空反应溅射外延技术制备了未探测氮化物的无应力单晶层。测量了固有的机械性能和高温氧化速率，并与第一性原理计算的结果直接相关。根据电子结构和原子键对所有二元过渡金属氮化物进行分类，利用理论计算的各向异性弹性常数和氧替代能量学以及测量的硬度和氧化速率，利用这种相关性建立了完整的属性数据集。二元氮化物的知识被用于开发一个定量模型，该模型将三元氮化物和非化学计量氮化物的组成与机械性能联系起来，使用测量和计算的电子态密度和组成相关的费米能级，后者决定了电荷转移和键的方向性。该项目还通过测量具有相干界面的模型系统的力学性能，并计算两个氮化物边界处的应变相关剪切模量和位错能量，探索了一级微观结构特征。该项目旨在根据过渡金属氮化物的电子结构，系统地了解它们的基本性质。这种理解代表了一种知识基础，有可能通过一种新的涂层设计方法改变价值数十亿美元的硬涂层行业。因此，它为加速发现坚硬、耐磨和耐腐蚀涂层提供了基础，并将保护涂层的不断试验和错误开发转变为基于设计的涂层方法，从而快速部署新型涂层材料，用于新兴应用，包括节油喷气发动机和燃气轮机、环保无润滑油切削工具、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合作研究项目中接受培训，该项目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。提议的工作的一个组成部分是开发一个在线虚拟氮化物性能工具，包括一个研究社区驱动的数据库，用于与硬保护涂层相关的过渡金属氮化物的固有特性。

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.