Mechanical properties of unidirectional nanoporous gold under compression

Dealloyed nanoporous (NP) metals are expected to be stronger by more than one order of magnitude than conventional porous metals of same porosity. However, the strengths of random-structured NP metals in practice are limited by the low mechanical efficiency of their network structure. In this paper, we report that an anisotropic nanoporous gold (NPG) with unidirectional pore channels can also be self-organized in dealloying. This material combines a mechanically efficient topology structure with ultra-strong nanoscale solid skeleton. In consequence, its out-of-plane mean strength (461 ± 52 MPa) is more than twice that of the strongest NPGs reported in previous studies. Because of the structural anisotropy, unidirectional NPGs deform by the formation and expansion of kink bands under compression, unlike the uniform densification of most previous NPGs. The pore-channel misalignment and other defects such as the voids in pore walls may have reduced macroscopic strength, which accounts for a large scatter in the measured strength and a gap between theoretical and experimental data. We anticipate that the structure and mechanical properties of unidirectional NPGs will be further improved in the future by optimizing dealloying parameters. A combination of high strength, unidirectional pore channels, and excellent thermal and electrical conductivity of metallic pore-wall phase might enable novel applications of this material in many areas.