DMREF: Collaborative Research: Accelerated Development of Damage Tolerant and Oxidation Resistant Alumina-Forming MAX Phases

能够承受恶劣环境的材料有可能实现广泛的重要技术。一种称为MAX相的陶瓷碳化物和氮化物材料具有不寻常且通常独特的一系列性能，这些性能结合了陶瓷和金属的一些最佳属性。它们轻，硬，稳定，能够像典型的陶瓷一样抵抗高温，但也具有耐损伤性，在高温下具有延展性，并且像金属一样易于加工。此外，一些MAX相在空气中加热时会形成保护层，这对热冲击、热循环和化学侵蚀具有极强的抵抗力。“革新和工程我们未来的设计材料”（DMREF）奖支持基础研究，以了解MAX阶段这些保护层形成的过程。本研究将结合计算模拟和实验合成与表征，为高温应用中具有优异力学性能的MAX相材料的加速开发和设计建立知识库。该项目的成果将促进MAX相在发电、能源转换、交通、航空航天和国防技术方面的应用。本项目还为研究生和本科生提供综合材料信息学、建模、原子计算和材料设计实验的专业多学科培训。尽管对MAX相进行了20年的实验研究，但设计其最佳组成和微观结构仍然是一个挑战，主要是因为可能的组成和微观结构数量众多，并且缺乏将其组成和微观结构与性能联系起来的可靠物理模型。本研究计划的总体目标是克服这些挑战，并通过以下方式促进高温应用MAX相的设计：(1)开发基于物理的氧化铝保护层形成预测；(2)建立微观力学模型，确定控制固有热力学性能的成分/结构参数；(3)设计贝叶斯标定方案进行参数辨识；(4)实现和部署高效的全局优化协议，以有效地发现具有最佳热力学性能的MAX相；(5)通过材料合成、表征和热力学测试验证所提出的框架。这将为设计用于高温应用的MAX相的最佳组成和微观结构提供指导性的基础知识和协议。

Materials capable of withstanding harsh environments have the potential to enable a wide range of important technologies. A family of ceramic carbide and nitride materials referred to as MAX phases possess unusual and often unique sets of properties that combine some of the best attributes of ceramics and metals. These are light, stiff, stable and able to resist high temperatures like typical ceramics, but also damage tolerant, ductile at high temperatures and as readily machinable as metals. In addition, some of the MAX phases form protective layers when heated in air, that are extremely resistant to thermal shock, thermal cycling and chemical attack. This Designing Materials to Revolutionize and Engineer our Future (DMREF) award supports fundamental research to understand the process by which these protective layers in MAX phases are formed. This research will incorporate computational simulations and experimental synthesis and characterization to build the knowledge base for the accelerated development and design of MAX phase materials with outstanding mechanical properties for high temperature applications. Results of this project will foster application of MAX phases in power generation, energy conversion, transportation, aerospace and defense technologies. This project also provides specialized multidisciplinary training for graduate and undergraduate students on integrating materials informatics, modeling, atomistic computations and experiments in materials design.Despite two decades of experimental studies on MAX phases, designing their optimal composition and microstructure has remained a challenge mainly because of the large number of possible compositions and microstructures, and a lack of robust physical models that relate their composition and microstructure to properties. The overall goal of this research program is to overcome those challenges and foster design of MAX phases for high temperature applications by: (1) developing physics-based predictors for the formation of protective alumina layers; (2) developing micromechanical models and identifying compositional/structural parameters that control intrinsic thermomechanical properties; (3) designing Bayesian calibration protocols for parameter identification; (4) implementing and deploying Efficient Global Optimization protocols for the efficient discovery of MAX phases with optimal thermomechanical properties and; (5) validating the proposed framework through material synthesis, characterization and thermomechanical testing. This will provide guiding fundamental knowledge and protocols to design optimal compositions and microstructures of the MAX phases for high temperature application.