Coarsening kinetics of alloy-doped nanoporous metals

Abstract

Due to their high surface-to-volume ratios, nanoporous metals are being explored for a range of catalytic and structural applications. However, these materials have thermodynamically unstable morphologies and degrade via coarsening at elevated temperatures. One potential mitigation strategy is to introduce atomic species that inhibit diffusional transport, but there is limited mechanistic understanding. To begin addressing this knowledge gap, the impact of a slow-diffusing dopant on the coarsening behavior of a nanoporous metal is studied using kinetic Monte Carlo simulations. The simulations were analyzed using reaction models and isoconversional analyses to extract constitutive coarsening laws, which confirm a coarsening exponent associated with classical surface diffusion. In addition, a rate equation is derived for the role of alloying dopants. It is found that only a few atomic percent is needed to stymie coarsening over experimentally relevant timescales, which has broad implications for the future design and tailoring of these materials.