[en] Nanoporous metal foams synthesized by dealloying inherently undergo dimensional changes (shrinkage). If these changes are unaccounted for in the measurement of relative density, this can be underestimated, causing up to an order of magnitude error in weight-normalized properties. In constrained samples the shrinkage leads to build-up of tensile stress that modifies the porosity and may lead to crack formation. A relationship between shrinkage, relative density and atomic fraction is proposed and experimentally verified.

[en] We synthesize nanoporous platinum (np-Pt) through electrochemical dealloying in aqueous HF from cosputtered Pt_xSi_1-x amorphous films for different initial composition and sputter bias conditions. We demonstrate that, in addition to the expected isotropic open cell np-Pt foam, anisotropic (columnar and Voronoi) np-Pt is obtained. There are two levels of anisotropy: on the micron scale, 100 nm columns or 1 μm Voronoi polygons form. Inside the columnar and Voronoi hyperstructures, the ligaments and pores are anisotropic ranging from 5 to 25 nm. The ligament diameter and grain size is 5 nm for all reported structures. A processing-structure map is developed that correlate np-Pt structures to processing conditions.

[en] We synthesize nanoporous copper (NP Cu) through electrochemical dealloying of amorphous Cu_0.41Si_0.59 under compressive residual stress. Transmission Electron Microscopy reveals that struts are nanocrystalline with grain size equal to the strut thickness. Moreover, a significant population of twins with spacing ∼7 nm is present within each imaged grain. The hardness of this nanocrystalline, nanotwinned NP Cu is approximately one order of magnitude greater than reports on NP Cu in the literature. The yield strength of individual struts inferred through dimensional analysis is approximately an order of magnitude greater than bulk copper and compares well with other nanostructured copper systems