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

这项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。该项目使用实验和密度泛函计算相结合的方法来确定二元氮化物的本征弹性性质、硬度和抗氧化性。利用超高真空反应溅射外延技术沉积了未探索氮化物的无应力单晶层。测量了本征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。这种关联性被用来建立所有二元过渡金属氮化物的完整性质数据集，方法是根据它们的电子结构和原子键将它们分类，使用理论计算的各向异性弹性常数和氧取代能以及测量的硬度和氧化速率。利用二元氮化物的知识开发了一个定量模型，该模型将三元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以及决定电荷转移和键方向性的与组成有关的费米能级。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个氮化物之间的边界上与应变有关的剪切模数和位错能学来探索第一级微结构特征。该项目预计将根据它们的电子结构提供对所有过渡金属氮化物的基本性质的系统了解。这种理解代表了知识基础，它有可能用一种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，并将保护涂层的不断试验和错误开发转变为按设计涂层的方法，从而为新兴应用快速部署新的涂层材料，包括节能型喷气发动机和燃气轮机、环保型无润滑剂刀具、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协作研究计划中接受培训，该计划将两个研究小组联系在一起，在两个机构具有互补的实验和计算专业知识。拟议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，其中包括一个由研究界驱动的数据库，用于研究与硬质防护涂层有关的过渡金属氮化物的内在性能。

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.