Linking Fundamental Structural and Physical Properties of the MAX Phases at Finite Temperatures through Synergetic Experimental and Computational Research

通过协同实验和计算研究将有限温度下 MAX 相的基本结构和物理特性联系起来

• 批准号: 1410983
• 负责人: Raymundo Arroyave
• 金额: $ 44.01万
• 依托单位: Texas A&M Engineering Experiment Station
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-01 至 2018-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1410983&HistoricalAwards=false
• 关键词: Linking; Fundamental; Structural; Physical; Properties

NON-TECHNICAL DESCRIPTION: Recently, a new class of nanolayered carbides and nitrides, commonly referred to as MAX phases, has attracted considerable attention as potential multi-functional/structural materials for harsh environments since they combine some of the best attributes of ceramics (high-temperature stability and strength) and metals (high thermal conductivity and resistance to fracture). MAX phases are an exciting, and technologically important class of high-temperature materials but much remains to be understood, especially about the influence of chemistry on their properties, and their transition from brittle to ductile behavior (at elevated temperatures). This project addresses this challenge by synergistically combining experiments and computer simulations. A better understanding of the relationship between chemistry and mechanical stability may enable the faster deployment of MAX phases in technologies that benefit from higher operating temperatures, making it possible to develop more reliable and efficient power generation (and propulsion) systems. In addition to contributions to the science and technology of MAX phases, the project supports activities related to curriculum development, K-12 outreach, high school teacher training, mentoring and contributing to the professional training and development of undergraduate and graduate student researchers.TECHINCAL DETAILS: The overall goal of this project is to investigate the finite-temperature structural and thermo-mechanical properties of MAX phases (comprised of an early transition metal (M), an A-group element and X which is either carbon and/or nitrogen) and their solid solutions through high-throughput experimental and computational approaches. Computations are being used for the rapid screening of materials while high-throughput synthesis allows the fine exploration of alloying effects on the thermal, mechanical and structural properties of a wide range of MAX structures. The project's major scientific goal is to elucidate the microscopic mechanisms responsible for the ductile-to-brittle transition in these materials under the hypothesis that the anharmonic nature of the motion of the M and A layers in the structures drives the onset of mechanical instability. Conventional electronic structure calculations and ab initio molecular dynamics will be used to investigate the ground state and anharmonic properties of MAX phases while spark plasma sintering will be used for the high-throughput synthesis of compositional variants of MAX compounds pre-screened by computations. The project addresses fundamental questions related to the compositional stability of MAX phases, the effect of composition and structure on their finite-temperature mechanical properties as well as the microscopic basis for the brittle-to-ductile transition. Understanding of the influence of chemistry on thermo-mechanical stability of these materials will enable their faster deployment in important technologies.

非技术描述：最近，一类新的纳米层状碳化物和氮化物，通常称为MAX相，作为用于恶劣环境的潜在多功能/结构材料已经引起了相当大的关注，因为它们结合了陶瓷（高温稳定性和强度）和金属（高导热性和抗断裂性）的一些最佳属性的联合收割机。MAX相是一种令人兴奋的、技术上重要的高温材料，但仍有许多问题有待了解，特别是化学对其性能的影响，以及它们从脆性到韧性的转变（在高温下）。该项目通过协同结合实验和计算机模拟来解决这一挑战。更好地理解化学和机械稳定性之间的关系，可以使MAX阶段在受益于更高工作温度的技术中更快地部署，从而有可能开发更可靠和更有效的发电（和推进）系统。除了对MAX阶段的科学和技术做出贡献外，该项目还支持与课程开发、K-12推广、高中教师培训、指导和促进本科生和研究生研究人员的专业培训和发展相关的活动。本计画的主要目的是研究MAX相的有限温度结构与热机械性质（由前过渡金属（M）、A族元素和为碳和/或氮的X组成）及其固溶体。计算被用于快速筛选材料，而高通量合成允许精细探索合金化对各种MAX结构的热，机械和结构性能的影响。该项目的主要科学目标是阐明这些材料中韧脆转变的微观机制，假设结构中M和A层运动的非谐性质驱动机械不稳定性的发生。传统的电子结构计算和从头算分子动力学将用于研究MAX相的基态和非谐性质，而放电等离子体烧结将用于高通量合成MAX化合物的组成变体，这些变体通过计算预先筛选。该项目解决了与MAX相的组成稳定性、组成和结构对其有限温度力学性能的影响以及脆韧性转变的微观基础相关的基本问题。了解化学对这些材料的热机械稳定性的影响将使它们能够更快地部署在重要技术中。