Low‐Cost, Large‐Scale Nanoporous Metals by Mechanical Alloying, Oxide Reduction, and Dealloying of Powders

Nanoporous (np) metals are increasingly diverse in alloy options and more sophisticated in control of pore characteristics. The aspects of simplicity and scalability of precursor alloy synthesis and pore formation are less developed. Powder metal processes are commercially practiced, and some aspects have been applied to np metals. Mechanical alloying is highly capable of producing unique, nonequilibrium alloys and nanostructured composites, and the powder precursors can often be readily scaled. Pore formation processes can be aided by enhanced accessibility to the bulk of the material, which is made possible with hierarchical porosity. Therefore, a powder precursor with multistage pore formation has the potential to efficiently provide nanoscale porosity at scale. The feasibility of this process pathway is highlighted here using Ag–Cu and Ag–CuO powder precursors that are produced through high‐energy ball milling. These two powder types are then made np by traditional dealloying and by a hybrid oxide reduction/dealloying protocol, respectively, and both methods result in nanoscale porosity. The hybrid process leads to some phase separation in the highly insoluble Ag–Cu alloy, but it also reduces overall particle size, increases the rate of dealloying, and produces a more open structure with smaller ligaments on average and lower residual Cu content.