CAREER: Understanding Nanoscale Deformation by Characterizing the Mechanical Behavior of Nanoporous Noble Metals

技术：具有纳米级韧带的纳米多孔金属提供了一个独特的机会来探索高度受限金属体积的变形行为，并了解在纳米尺度上控制机械行为的机制。在纳米晶金属、薄膜和纳米结构材料的研究中，一个长期存在的问题是：位错和其他缺陷在纳米尺度变形中起什么作用？据了解，随着可用变形量的减少，位错的形核和运动受到限制，但目前尚不清楚位错是否能够在几到几十纳米尺寸的金属体积中调节塑性。即使变形过程中涉及位错，其行为也可能受到自由表面和界面存在的严重影响。扩散等其他机制也可能发生。为了正确地解释和模拟纳米晶金属的变形行为，我们必须了解主导变形的实际机制。本CAREER研究计划的目标是：(1)利用原位透射电子显微镜研究纳米孔金、钯和铱的纳米级变形行为；(2)系统地研究了薄膜和块状纳米多孔贵金属的力学性能，并确定了描述这些性能的合适标度定律；(3)评估纳米多孔金属的阻尼行为，与致密或ìm-scale多孔金属相比，纳米多孔金属有望表现出更高的阻尼和非弹性。这个项目的智力价值在于它旨在揭示控制纳米多孔结构力学行为的基本机制。该项目的研究结果将集中在面心立方贵金属上，应该适用于其他纳米多孔金属，并与纳米尺度材料的变形研究相关。非技术：这项研究有很强的基础科学基础，但也将有利于纳米多孔金属的应用，使其机械稳定性得到改善。此外，通过更好地了解纳米多孔结构的力学行为，同行科学家将能够预测和定制特定应用的特性。这项研究的广泛影响将为肯塔基大学材料工程师提供一个独特的出国留学机会，并在德国世界领先的材料实验室进行研究，从而提高他们的本科教育经验。研究生和本科生都将直接参与这项研究。肯塔基大学和卡尔斯鲁厄大学之间的工程学生交换项目一直是PI的重点，他将招募英国本科生与研究生和访问德国的学生一起在他的实验室工作。这种经历将为英国本科生提供国际视野，帮助他们学习如何在全球社会中生活和工作。该项目的结果将在会议上发表，并在科学文献中传播，由每个学生研究小组共同撰写。

TECHNICAL: Nanoporous metals with nanoscale ligaments offer a unique opportunity to explore the deformation behavior of highly confined metallic volumes and understand the mechanisms that govern mechanical behavior at the nm length scale. A persistent problem exists in studies of nanocrystalline metals, thin films and nanostructured materials: what role do dislocations and other defects play in nanoscale deformation? It is understood that constraints on dislocation nucleation and motion arise as the available deformation volume decreases, but it is unclear whether dislocations are able to mediate plasticity in metal volumes that are several to tens of nm in size. Even if dislocations are involved in the deformation process, their behavior is likely to be heavily influenced by the presence of free surfaces and interfaces. Additional mechanisms such as diffusion may also occur. In order to correctly interpret and model the deformation behavior of nanocrystalline metals, we must understand the actual mechanisms that dominate deformation. The objectives of this CAREER research plan are to: (1) investigate nanoscale deformation behavior in nanoporous gold, palladium and iridium, using in situ transmission electron microscopy; (2) systematically study the mechanical properties of thin film and bulk nanoporous noble metals, and determine the appropriate scaling laws that describe these properties; (3) evaluate the damping behavior of nanoporous metals, which are expected to exhibit significantly higher damping and anelasticity versus dense or ìm-scale porous metals. The intellectual merit of this project lies in its aim to uncover the fundamental mechanisms governing the mechanical behavior of nanoporous structures. The results from this project, which will focus on face-centered cubic noble metals, should be applicable to other nanoporous metals and relevant to the study of nanoscale materials subjected to deformation. NON-TECHNICAL: This study has a strong fundamental scientific basis, but will also benefit the application of nanoporous metals by enabling improvements in their mechanical stability. Additionally, by attaining a better understanding of the mechanical behavior of nanoporous structures, fellow scientists will be able to predict and tailor properties for a given application. The broader impact of this research will enhance the undergraduate education experience for materials engineers at the University of Kentucky, by providing them with a unique opportunity to study abroad and perform research in a world-leading materials laboratory in Germany. Both graduate and undergraduate students will be directly involved in this research. The engineering student exchange program between Kentucky and Karlsruhe is a continuing focus of the PI, who will recruit UK undergraduate students to work with graduate students and with visiting German students in his laboratory. This experience will provide UK undergraduates with international exposure and help them learn how to live and work in a global society. The results of this project will be presented at conferences and disseminated in the scientific literature, with joint authorship by each team of student researchers.