Date of Graduation
Statler College of Engineering and Mineral Resources
Mechanical and Aerospace Engineering
Bruce S. Kang.
In recent years the operating temperature of the SOFC has been reduced to ~800C, making it possible to use silver in the fabrication of the cell stack. Silver is attractive due to its high conductivity, ductility and the fact that it does not form non-conductive scales that could reduce the performance of the fuel cell stack. This research focuses on the development and testing of candidate materials, utilizing silver, in a simulated cathode environment using a simple tube furnace and air supply. Test specimens were fabricated using simple powder metallurgy techniques or by the oxidation of specific alloys to create desired characteristics. Samples are examined using scanning electron microscopy to evaluate microstructure, as well as energy dispersive spectroscopy to evaluate material composition.;Sterling silver was chosen as the material of primary interest due to its favorable composition and low-cost. Sterling silver is a 7.5% Cu-Ag alloy by weight. When exposed in an oxidizing environment the copper in the alloy will oxidize forming copper-oxide which is meant to protect the silver from air exposure and reduce the rate of silver evaporation. The sterling silver samples were compared to pure silver samples in terms of evaporation rate and surface microstructure changes.;Testing showed that the sterling silver samples exhibited a higher rate of evaporation than the pure silver samples tested under the same conditions. Scanning electron microscopy showed a much higher rate of silver faceting at the surface of the pure silver samples than the sterling silver samples indicating that the evaporation rate could be influenced by the silver surface orientation. Microstructure analysis also indicated that copper-oxide may be too volatile for use as a protective oxide due to its high volatility causing particle migration and agglomeration.
Sakacsi, John, "Evaluation of sterling silver as a contacting material for the cathode chamber of the solid-oxide fuel cell" (2006). Graduate Theses, Dissertations, and Problem Reports. 1743.