Two Ag-Cu-Ti brazing alloy compositions were studied as gas seals for solid oxide fuel cells (SOFCs). Yttia-stabilized zirconia pellets were bonded using Ag-35.25Cu-1.75Ti (Cusil-ABA) or Ag-20.1Cu-1.0Ti (average composition; Ag-Cusil). Both as-brazed filler metals contained metallic Ag and Cu phases, along with continuous titanium oxide layers at the filler metal-zirconia interfaces. The brazed joints were then aged at 700°C for up to 100 h in air or while separating H2 and air atmospheres. After annealing in air for 100 h at 700°C, degradation in microstructure and hermeticily was more pronounced in Cusil-ABA. However in H2-air atmosphere, Cusil-ABA performed better than Ag-Cusil. Ag-Cusil aged in H2 air delaminated from zirconia and its microstructure showed large interconnected pores in Ag-rich regions. The results were confirmed by single-cell tests using each filler metal as a gas seal. Observations of the post-test Cusil-ABA microstructure revealed little degradation. These results indicate that Cusil-ABA is better suited than Ag-Cusil as a SOFC gas seal.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Energy Engineering and Power Technology
- Mechanics of Materials
- Mechanical Engineering