SUMMARY

Nanoporous (NP) metals are three-dimensional (3D) structures with characteristic length-scale of its constituents (ligaments, junctions, and pores) ranging from a few to hundreds of nanometers. Such materials are of great interest for many applications, including catalysis, biological material analogues, and the next generation interconnect materials in electronics packaging. Investigations towards understanding of the mechanical properties of such materials have tried to separate effects of the geometrical arrangement of the 3D network from those due to the nanostructure (abundance of surfaces, presence of grains, and other defects). Traditionally, this has been achieved by assuming that the network is geometrically similar to a macroscopic, low-density metal foam. The goal of this work is to attack the problem using a comprehensive approach that involves isolating the prominent geometry and size scale effects and examining their specific contributions individually for a range of relative densities. Specifically, 3D printed models replicating the geometrical arrangement of a nanoporous metal are used to assess the mechanical properties of the network independently of size effects. Nanoindentation and micropillar compression experiments are used to obtain macroscopic properties of the NP metal, while molecular dynamics (MD) simulations help assess the prevalence, types, and significance of various nanoscale effects. Together, these studies reveal a much more nuanced interaction between geometry and nanoscale effects than previously appreciated. Obtaining a clear understanding of the contribution of geometrical structure on the properties of nanoporous metals will significantly advance our understanding of how to tailor NP metal microstructure such as grains, interfaces, and surfaces to enhance the physical properties of the material. Thus, the findings reported here could inform future studies to maximize the versatility and potential of nanoporous metal structures.