PHYSICAL MATHEMATICS SEMINAR TOPIC: NATURE OF THE DISSOLUTION FRONT DURING ELECTROCHEMICAL FORMATION OF NANOPOROUS METAL SPONGES SPEALER: DR. JONAH ERLEBACHER Division of Engineering and Applied Science Harvard University ABSTRACT: Selective electrochemical etching of one component of a binary alloy often leaves the remaining component in the form of a topologically complex, bulk three-dimensional nanoporous sponge. This behavior has long been known to occur in corrosion-related contexts where it can lead to problems such as stress-corrosion cracking in metals. Lately, however, de-alloying has been receiving new attention as a powerful method to texture and pattern structures on extremely small length scales, a context where de-alloyed materials have potential application as filters, catalytic surfaces, etc. In this talk I will present results of kinetic Monte Carlo simulations we developed in order to examine the origin of pore formation during electrochemical dissolution on the microscopic level of individual atoms. Particular attention is paid to the morphological evolution of the interfacebetween de-alloyed and bulk material (the dissolution front), which is inaccessible in experiment. We have found that a simulation model that incorporates only (1) diffusion of all species and (2) dissolution of the less noble species exhibits the entire range of (macroscopic) current/voltage behavior seen in real experiments. Furthermore, the model exhibits the same porosity-forming morphological evolution as seen in real systems. DATE: TUESDAY, NOVEMBER 9, 1999 TIME: 2:30 PM LOCATION: Building 2, Room 338 Refreshments will be served at 3:30 PM in Building 2, Room 349 Massachusetts Institute of Technology Department of Mathematics Cambridge, MA 02139