Title page for ETD etd-10262003-200453


Type of Document Dissertation
Author Dursun, Aziz
Author's Email Address adursun@vt.edu
URN etd-10262003-200453
Title Nanoporosity Formation in Ag-Au Alloys
Degree PhD
Department Materials Science and Engineering
Advisory Committee
Advisor Name Title
Corcoran, Sean Gerald Committee Chair
Reynolds, William T. Jr. Committee Co-Chair
Farkas, Diana Committee Member
Kampe, Stephen L. Committee Member
Marand, Hervé L. Committee Member
Keywords
  • selective dissolution
  • porous metals
  • dealloying critical potential
  • small angle neutron scattering
  • coarsening
  • surface diffusion
Date of Defense 2003-05-13
Availability unrestricted
Abstract
Selective dissolution also known as dealloying is a corrosion process in which one component of a binary alloy system is selectively removed through an electrochemically controlled process which leads to the formation of a porous metal "sponge" with a porosity that is completely interconnected and random in direction.

Nanoporous metals are desirable since they have larger surface areas than an equal volume of non-porous material. Because of their enormous surface area per volume, these highly porous metal electrodes are superior materials for high surface area applications such as in biomedical devices, microfilters and catalysts.

Understanding the kinetic processes governing the development of porosity during dealloying and having ability to change the electrochemical conditions will allow us to better control over the average ligament size and distribution in porosity. The basic kinetic processes involved in the formation of these structures are related to such issues as environmental effects and electrochemical conditions on diffusion, microscopic coarsening phenomenon at room temperature and elevated temperatures, alloy passivation, and Gibbs-Thomson effects.

The average pore size and distribution was found to depend on the electrolyte composition, dealloying rate, applied potential and time. The porosity was found to significantly coarsen at room temperature during the dealloying process and this coarsening was highly dependent on the applied potential.

It is showed that the commonly accepted measurement of the critical potential for alloy dissolution calculated based on extrapolation of anodic polarization data results in an overestimation of this quantity. A series of constant applied potential experiments prove to be a more accurate method for critical potential determination.

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