Ag-Cu-Ti braze materials for sealing SOFCs

作者:Kobsiriphat Worawarit*; Barnett Scott
来源:Journal of Fuel Cell Science and Technology, 2008, 5(1): 011002.
DOI:10.1115/1.2784279

摘要

Two Ag-Cu-Ti brazing alloy compositions were studied as gas seals for solid oxide fuel cells (SOFCs). Yttria-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 degrees C for up to 100 h in air or while separating H(2) and air atmospheres. After annealing in air for 0 100 h at 700 C, degradation in microstructure and hermeticity was more pronounced in Cusil-ABA. However in H(2)-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.