FRG: M_n+1AX_n Phase Solid Solutions: Unique Opportunities at Engineering Bulk and Surface Properties

非技术描述：一个由德雷克塞尔大学和罗文大学的研究人员组成的重点研究小组(FRG)将对一系列新兴的无机纳米层压工程化合物的性质进行研究。这些通式为Mn1AXn(其中n=1至3，M是早期过渡金属，A是A族(主要是IIIA和IVA)元素，X是C和/或N)的材料及其被称为所谓的MAX相的固溶体合金具有独特的化学、物理、电子和机械性能。它们具有极好的可加工性和极低的摩擦系数，尽管它们是极其坚硬的材料。这种性能的结合将金属和陶瓷的一些杰出性能连接在一种材料类别--MAX相中。这些特性使Max Phas成为许多领域的理想选择，例如航空航天、电子产品、工具和消费品中需要低磨损、高温应用的领域。该计划的努力包括广泛的实验和理论模拟工具和资源，用于表征、建模、预测和操纵特性。该项目代表了授予博士学位的德雷克塞尔大学与罗文大学的合作，罗文大学是一所四年制本科大学，有着优秀的本科生研究的强大传统。来自两个机构的学生、教师和资源的联系将使本科生和研究生在一个跨学科的环境中聚集在一起，提供更广泛的教育和研究经验，发展重要的分析技能，通过直接相互作用加强他们对材料的知识，并进一步激发积极参与和有才华的本科生在科学和工程学科继续研究生学习的兴趣。技术细节：MAX相是少数几种通过扭结和剪切带形成的组合以及单个颗粒内的分层而变形的多晶固体之一。这种不寻常的性质组合可以追溯到它们的层状结构，MX键的金属共价性质非常强，以及M-A键相对较弱，特别是在剪切方面。虽然选择的Mn1AXn相用于高温结构应用的潜力开始被认识到，但人们对如何有效地调整其热、电子和机械性能以在其固溶体中产生新的和意想不到的性能组合知之甚少。在这里，我们建议通过组合材料合成、电子性质的第一性原理计算和最大相固溶体的晶格动力学计算来探索新材料。随着块体和薄膜分析实验技术已被证明在表征这些相方面取得了成功，有效覆盖成分和合成工艺参数空间将能够快速识别具有吸引人的、很可能是新颖的性质组合的固溶体。表征将包括纳米摩擦学测量，如通过变温扫描探针显微镜进行局部摩擦和表面能量耗散；通过纳米压痕进行局部应力-应变分析；通过原位拉曼散射将晶格动力学与机械性能联系起来；以及探测块体和薄膜的电子、光学和磁性。

NON-TECHNICAL DESCRIPTION: The properties of an emerging family of inorganic, nano-laminate engineered compounds will be investigated by a focused research group (FRG) of investigators from Drexel and Rowan Universities. These materials with the general formula Mn+1AXn (where n = 1 to 3, M is an early transition metal, A is an A-group (mostly IIIA and IVA) element and X is either C and/or N) and their solid solution alloys known as the so-called MAX phases feature unique chemical, physical, electronic and mechanical properties. They possess superb machinability and extremely low friction coefficients despite being extremely stiff materials. This combination of properties bridges some of the outstanding properties of metals and ceramics within one class of material, the MAX phases. These properties make MAX phases an ideal choice in many areas, for example those requiring low-wear, high-temperature application in aerospace, electronics, tools and consumer goods. The efforts in this program encompass a broad range of experimental and theoretical simulation tools and resources for the characterization, modeling, prediction and manipulation of properties. This program represents a partnership of Drexel, a Ph.D.-granting university, with Rowan, a four-year undergraduate university with a strong tradition of undergraduate research excellence. The linking of students, faculty and resources from both institutions will bring undergraduates and graduate students together in an interdisciplinary environment to provide broader educational and research experiences, to develop important analytical skills, to reinforce their knowledge of the materials through direct interactions, and to further stimulate interest among actively participating and talented undergraduates to pursue graduate studies in a science and engineering discipline.TECHNICAL DETAILS: The MAX phases are among the few polycrystalline solids that deform by a combination of kink and shear band formation, together with delaminations within individual grains. The unusual combination of properties is traceable to their layered structure, the metallic-covalent nature of the MX bonds that are exceptionally strong, together with M-A bonds that are relatively weak, especially in shear. While the potential of select Mn+1AXn phases for high temperature structural applications is beginning to be realized, little is understood about how their thermal, electronic and mechanical properties can be effectively tuned to produce new and unexpected combination of properties in their solid solutions. Herein we propose to explore new materials using combinatorial materials synthesis along with first-principles calculations of electronic properties and lattice dynamical calculations of MAX-phase solid solutions. With bulk and thin-film analytic experimental techniques that have proven to be successful in characterizing these phases, efficient coverage of the compositional and synthetic processing parameter space will enable rapid identification of solid solutions with attractive, and quite possibly novel, combinations of properties. Characterization will include nano-tribological measurements such as local friction and surface energy dissipation via variable temperature scanning probe microscopy; local stress-strain analysis via nanoindentation; linkage of lattice dynamics with mechanical properties via in situ Raman scattering; and probing of electronic, optical and magnetic properties in bulk and thin films.