Resolving Elementary Steps of Vapor-Phase Dealloying via In Situ Transmission Electron Microscopy

Nanopores evolve in dealloying to dictate alloy corrosion while enabling the creation of functional metallic nanomaterials. Yet, the nanoscale dynamics of the porosity evolution have long eluded experimental characterizations. With aberration-corrected transmission electron microscopy, we reveal the evolution of nanoporous Co from the vapor phase dealloying (VPD) of γ-CoZn across scales. The in situ characterization confirms key aspects of the dealloying mechanism based on macroscopic characterizations and simulations, including dissolution by repeated step flow and vacancy-cluster nucleation as well as ligament and pore bifurcation. It also separates the step flow kinetics from that of VPD, revealing that a bond energy difference between the alloy constituents can determine the dealloying kinetics and affect the morphology. The findings refine the classic dealloying theory for potentially new fabrications.