Nanoporous Au: A high yield strength material

Abstract

The plastic deformation of nanoporous Au under compressive stress was studied by depth-sensing nanoindentation combined with scanning electron microscope characterization. The nanoporous Au investigated in the current study exhibits a relative density of 42%, and a spongelike morphology of interconnecting ligaments on a length scale of ∼100nm. The material is polycrystalline with a grain size on the order of 10–60nm. Microstructural characterization of residual indentation impressions reveals a localized densification via ductile (plastic) deformation under compressive stress and demonstrates the ductile behavior of Au ligaments. A mean hardness of 145(±11)MPa and a Young’s modulus of 11.1(±0.9)GPa was obtained from the analysis of the load-displacement curves. The hardness of investigated np-Au is ∼10 times higher than the hardness predicted by scaling laws of open-cell foams thus potentially opening a door to a class of high yield strength—low-density materials.