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

技术支持：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的金属体积的变形行为，并了解在纳米长度尺度上控制机械行为的机制。在纳米金属、薄膜和纳米结构材料的研究中，存在一个长期存在的问题：位错和其他缺陷在纳米级变形中起什么作用？应当理解，随着可用变形体积的减小，对位错成核和运动的约束出现，但尚不清楚位错是否能够介导尺寸为几至几十nm的金属体积中的塑性。即使位错参与变形过程，它们的行为也可能受到自由表面和界面存在的严重影响。还可能出现扩散等其他机制。为了正确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）使用原位透射电子显微镜研究纳米多孔金、钯和铱的纳米级变形行为;（2）系统地研究薄膜和块状纳米多孔贵金属的机械性能，并确定描述这些性能的适当标度律;（3）评估纳米多孔金属的阻尼行为，预期纳米多孔金属相对于致密或微米级多孔金属表现出显著更高的阻尼和滞弹性。这个项目的智力价值在于它的目的是揭示纳米多孔结构的机械行为的基本机制。该项目的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，并与变形纳米材料的研究有关。非技术性：这项研究有很强的基础科学依据，但也将有利于纳米多孔金属的应用，使其机械稳定性的改善。此外，通过更好地理解纳米多孔结构的机械行为，其他科学家将能够预测和定制特定应用的性能。这项研究的更广泛的影响将提高材料工程师在肯塔基州大学的本科教育经验，为他们提供一个独特的机会，出国留学，并在德国的世界领先的材料实验室进行研究。研究生和本科生都将直接参与这项研究。肯塔基州和卡尔斯鲁厄之间的工程学生交流计划是PI的持续关注，PI将招募英国本科生与研究生和访问德国的学生在他的实验室工作。这一经历将为英国本科生提供国际视野，并帮助他们学习如何在全球社会中生活和工作。该项目的成果将在会议上提出，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.