Berlin 2012 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 49: Nanomaterials II
MM 49.1: Vortrag
Donnerstag, 29. März 2012, 11:45–12:00, H 1029
Control of residual less noble element content during dealloying — •Zhen Qi1 and Jörg Weissmüller1,2 — 1Institut für Werkstoffphysik und Werkstofftechnologie, Technische Universität Hamburg-Harburg, Hamburg, Germany — 2Institut für Werkstoffforschung, Werkstoffmechanik, Helmholtz-Zentrum Geesthacht, Geesthacht, Germany
Nanoporous metal prepared by the corrosion of an alloy can take the form of monolithic, millimeter-sized bodies containing approximately 1015 nanoscale ligaments per cubic millimeter. Applications have been suggested, for instance in catalysis, sensing and actuation. Although the process of dealloying has seen many studies, the underlying processes remain to be clarified in more detail. Here we explore the structure size and residual Ag content in AgAu alloys during electrochemical dealloying. We study different dealloying potentials and a series of alloys including specifically solid solutions that are dilute in Au. A major finding is that nanoporous samples with large content of residual Ag can be prepared. This is surprising in view of the overpotential required for bulk dealloying. The overpotential exceeds the variation of the Ag Nernst potential through the alloy series, suggesting that equilibrium thermodynamics of the bulk alloy alone cannot explain the arrest of the corrosion at finite Ag content. The data set acquired in our study will provide a data base for verifying models of the corrosion process that include capillary terms as well kinetic aspects such as adatom diffusion and vacancy island nucleation.