Collaborative Research: Strengthening Metallic Nanofoams Through Ligament Scale Materials Design

纳米级的金属泡沫显示出几个显著的特性。目前最常见的纳米结构泡沫是由纯金属制成的，它们在催化、电池和光学等领域显示出优异的性能。然而，这些金属泡沫通常是易碎的，很难整合到工程应用中。到目前为止，机械强化泡沫以制造坚固材料的能力仅限于纯金属。该奖项支持旨在创造一种新型材料--复合纳米泡沫塑料--的研究，这种材料表现出与纯金属泡沫塑料相同的显著性能，但结构完整性显著增强。通过这项工作设计的新材料将允许研究人员和工程师开发独特的性能，而不会在机械操作或维修过程中发生故障。本研究所获得的基础知识可用于设计和制造低成本、高强度的催化剂、容量更大、充电时间更快的燃料电池、抗疲劳性高的生物医学植入物，以及更轻、更坚固的储氢单元。克拉克森和普渡两所大学的一组研究人员将开展这项工作，让两所学校的学生接触到推进研究所需的日益常见的远程合作。研究小组将把原子和介观尺度(分子动力学和有限元分析)的材料工程计算方法与制造和表征复合纳米结构泡沫的实验方法结合起来。工作假设是，在单个泡沫韧带上涂上纳米结构的多层膜将导致形成更强的泡沫。为了制造这些材料，铜和镍将被电镀，以在电纺聚合物的纸状垫子的模板上形成核壳层，这些模板将被氧化，然后被还原以形成纳米级的铜金属线。利用脉冲激光热弹性激发来确定泡沫的色散和振动共振，以获得泡沫的整体弹性性质。这些结果将直接与复合材料的有限元模拟进行比较，以隔离几何和韧带属性的影响。泡沫强度将基于韧带的分子动力学模拟进行预测，这将为有限元模型提供信息，并最终与使用平板冲头几何形状的纳米压痕进行屈服强度的实验研究进行比较。这项工作的智力意义将是在计算材料工程的指导下开发一类新的材料，以及开发制造和测试纳米级金属泡沫的新技术。

Nanoscale metal foams exhibit several remarkable properties. The most common nanostructured foams are currently made of pure metals, and they demonstrate exceptional performance in areas such as catalysis, batteries, and optics. These metal foams are, however, often fragile and difficult to integrate into engineering applications. The ability to mechanically strengthen foams to create robust materials has heretofore been limited in pure metals. This award supports research aimed at creating a new class of materials - composite nano foams - which display the same remarkable properties as pure metal foams, but with significantly enhanced structural integrity. The new materials designed through this work will allow researchers and engineers to exploit unique properties without suffering failure during mechanical handling or service. The fundamental knowledge gained from this research may be used in designing and manufacturing catalysts with low cost and high strength, fuel cells with higher capacity and faster charging times, biomedical implants with high fatigue resistance, and lighter and stronger hydrogen storage units. A team of researchers at two universities, Clarkson and Purdue, will carry out this work, exposing students at both schools to the increasingly common long-distance collaborations needed for advancing research. The research team will couple computational methods of materials engineering at the atomistic and mesoscopic scales (molecular dynamics and finite element analysis) to experimental methods of manufacturing and characterizing composite nanostructured foams. The working hypothesis is that coating individual foam ligaments with nanostructure multilayers will result in the formation of stronger foams. To create these materials, copper and nickel will be electroplated to form core-shell layers on templates of paper-like mats of eletrospun polymers, which will be oxidized and then subsequently reduced to form nanoscale copper metal wires. Pulsed-laser thermoelastic excitation will be used to determine the dispersion and vibrational resonance to obtain the foam's bulk elastic properties. These results will be compared directly to finite element simulations of the composite to isolate the effects of geometry and ligament properties. Foam strength will be predicted based on molecular dynamics simulations of the ligaments, which will provide information to feed into the finite element models, and finally compared to experimental studies of the yield strength using nanoindentation with a flat punch geometry. The intellectual significance of this work will be the development of a new class of materials guided by computational materials engineering, and the development of novel techniques for manufacturing and testing nanoscale metallic foams.