Department of
Materials Science and Engineering
2008 Spring Seminar Series
February 15
The Ag-Au Dealloying Critical Potential
Mr. Davis Eichelberger
MSE Graduate Student
Dealloying is the selective dissolution of the less noble element in an alloy. The process typically results in the production of a nanoporous material of the more noble element(s) with a completely interconnected metal - void structure containing pores as small as 3.5 nm in diameter. The structure can be coarsened to larger length scales; at room temperature pore sizes up to 200 nm can be easily produced and at elevated temperatures structures as large as several micrometers can be achieved. In addition to being an important aspect of many corrosion processes such as stress corrosion cracking in brass, noble metals and stainless steels as well as the accelerated corrosion of 2024 aluminum alloys; various applications have been found for these structures including: Raney catalysts, high surface area electrodes, actuators, skeletal structures for advanced applications and confining structures for studies of superfluid behavior. A key characteristic of a system undergoing dealloying is the critical potential, which marks the transition from passivity to porosity development. Recent work has examined methods of determining the critical potential in the Ag-Au and Cu-Pt systems. The traditional method of evaluation of anodic polarization data is dependent upon experimental conditions such as scan rate and surface preparation. A series of potential hold measurements near the critical potential was shown to accurately determine an intrinsic critical potential, which is 100-200mV below the extrinsic critical potential usually reported. A novel method of rapidly measuring the intrinsic critical potential has been discovered. I present this new method and the critical potential of the Ag-Au alloy in relation to alloy composition and electrolyte activity.
BIO
Davis Eichelberger received a B.S. in Materials Science and Engineering from Virginia Tech in May 1994. He worked for American Research Corporation and Luna Innovations before returning to Virginia Tech. He began graduate school at Virginia Tech in Spring 2003, and is advised by Dr. Sean Corcoran.
