Understanding the Mechanical Behavior of Novel High-Strength Nanoscale Structures

纳米结构材料的一个应用是结合到固体表面，以改变这些表面的性质和行为。然而，这些纳米结构在典型应用中遇到的接触应力下通常非常容易变形，这严重限制了它们的耐用性。一种新型的纳米级“核壳”结构最近被发现具有异常高的强度和抗变形能力；然而，导致这种不寻常的机械行为的纳米尺度机制目前尚不清楚。该奖项支持对新型高强度纳米结构的机械行为进行基本理解的研究，以便使用这些结构设计纳米纹理表面以优化机械性能。本研究将为指导微/纳米机电系统（MEMS和NEMS）采用纳米级核壳结构的纳米纹理表面的合理设计提供有价值的信息，并为这个数十亿美元的行业解决磨损和接触力学的困扰问题提供潜在的解决方案。新的纳米级核壳结构概念也可以应用于其他应用，包括磁记录、纳米印迹、表面润湿和生物医学应用，在这些应用中，纳米结构的机械完整性至关重要。将实施全面的教育和推广活动，这将大大激发下一代对纳米材料和纳米力学的兴趣，并将提高美国未来在纳米技术方面的竞争力。该奖项支持桥接材料长度尺度的综合实验和建模方法，以：(1)进行纳米压痕实验，研究核壳材料、核尺寸和微观结构、壳厚度和壳/核体积比对纳米级核壳结构力学行为的影响，包括应变硬化和疲劳；(2)开发并验证分子动力学和耦合原子-连续介质多尺度模拟模型，以了解核/壳界面、核/基板界面、核微观结构、核材料和基板厚度的作用；(3)在模型验证后，通过计算探索一个足够的核/壳参数空间，使模拟提供的基本认识可以指导在原始实验空间之外制造具有最佳行为的纳米级核/壳结构。这项研究将使人们对附着在衬底上的纳米级核壳结构的独特力学行为有一个基本的了解，并确定提供这些结构的新力学行为的机制。该研究还可以产生分子动力学和多尺度模型，这些模型可以用作纳米级核壳结构表面工程的设计工具。

One application of nanostructured materials is incorporation into solid surfaces, to alter the properties and behavior of these surfaces. These nanostructures, however, often deform very easily under contact stresses encountered in typical applications, which severely limits their durability. A novel nanoscale "core-shell" structure was recently discovered to have unusually high strength and deformation resistance; however, the nanoscale mechanisms that contribute to this unusual mechanical behavior are not currently known. This award supports research to gain a fundamental understanding of the mechanical behavior of the novel high-strength nanoscale structures, in order to design nano-textured surfaces using these structures for optimized mechanical performance. This research will provide valuable information to guide the rational design of nano-textured surfaces employing nanoscale these core-shell structures for micro/nano-electro-mechanical systems (MEMS and NEMS), and provide potential solutions for this multi-billion dollar industry to solve plaguing issues of wear and contact mechanics. The novel nanoscale core-shell structure concept can also be applied to other applications, including magnetic recording, nanoimprinting, surface wetting, and biomedical applications, where mechanical integrity of the nanostructures is of paramount importance. Comprehensive education and outreach activities will be implemented which will significantly stimulate the next generation's interest in nanomaterials and nanomechanics and will improve America's future competitiveness in nanotechnology.This award supports an integrated experimental and modeling approach to bridge material length scales, to (1) perform nanoindentation experiments to investigate the effects of core and shell materials, core size and microstructure, and shell thickness and shell/core volume ratio on the mechanical behavior of nanoscale core-shell structures, including strain hardening and fatigue, (2) to develop and validate molecular dynamics and coupled atomistic-continuum multiscale simulation models to understand the role of the core/shell interface, core/substrate interface, core microstructure, core material, and substrate thickness; and determine the mechanisms contributing to the large recoverable deformation and high strength of the nanoscale core-shell structures, and (3) after model validation, to computationally explore a sufficient core/shell parametric space so that the fundamental understanding provided by the simulations can guide the fabrication of nanoscale core-shell structures with optimal behavior, beyond the original experimental space. The research will result in a fundamental understanding of the unique mechanical behavior of nanoscale core-shell structures attached to substrates and identify the mechanisms that provide the novel mechanical behavior of these structures. The research can also result in molecular dynamics and multiscale models that can be used as design tools for surface engineering with nanoscale core-shell structures.