Nanoporosity evolution during dealloying: Interplay between chemical dissolution, material defects, coarsening and local structural rearrangements over long timescales

Abstract Selective dissolution/dealloying of metal alloys is commonly used to synthesize nanoporous structures. During dealloying, the morphological evolution over minutes timescales involves an interplay between chemical dissolution, ligament formation, coarsening of ligaments, local collapse within ligaments, and material defect formation. Ligament relaxation (collapse, defect-formation, etc.) events happen at picosecond-nanosecond timescales, whereas dissolution events proceed at seconds timescales. To resolve the underlying materials phenomena in unprecedented detail, we introduce a novel multiscale framework that combines lattice kinetic Monte Carlo (KMC) and molecular dynamics (MD) with an appropriate handshaking algorithm. Our algorithm exploits the underlying separation of timescales to capture several key features: (i) no breakage of ligaments occurs during dissolution, (ii) coarse ligaments with diameter ~10 times larger than the ones from standard KMC models are obtained, (iii) a maximum in surface area is observed at 50-60% dissolution, (iv) particle shrinkage happens due to ligament collapse, (v) constant porosity is obtained beyond ~50% dissolution, and (vi) dislocation density increases as more electroactive atoms are dissolved. The effect of particle size, temperature, alloy composition, and overpotential are also captured. This study underscores the need to incorporate continuous ligament relaxation while modeling selective dissolution of metal alloys.