Research Papers

Ag–Cu–Ti Braze Materials for Sealing SOFCs

[+] Author and Article Information
Worawarit Kobsiriphat, Scott Barnett

 Northwestern University, 2220 Campus Drive, Evanston, IL 60208

J. Fuel Cell Sci. Technol 5(1), 011002 (Jan 16, 2008) (7 pages) doi:10.1115/1.2784279 History: Received November 09, 2005; Revised July 11, 2006; Published January 16, 2008

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°C for up to 100h in air or while separating H2 and air atmospheres. After annealing in air for 100h at 700°C, degradation in microstructure and hermeticity 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.

Copyright © 2008 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.



Grahic Jump Location
Figure 4

Graph of log pressure (Pa) obtained by vacuum pumping a PSZ pellet sealed to a tube using either Cusil-ABA or Ag-Cusil. Aged samples were subjected to 50h at 700°C in air or H2-air atmosphere.

Grahic Jump Location
Figure 1

Schematics showing test geometry for (a) H2-air atmosphere aging experiments and (b) open-circuit voltage tests on PSZ-supported SOFCs (figures not to scale)

Grahic Jump Location
Figure 2

Structure and x-ray maps of PSZ-PSZ joint brazed with (a) Cusil-ABA and (b) Ag-Cusil at 880°C for 30min

Grahic Jump Location
Figure 3

X-ray diffraction patterns obtained from as-brazed samples of (a) Cusil-ABA and (b) Ag-Cusil

Grahic Jump Location
Figure 5

SEM images and corresponding x-ray maps of PSZ-PSZ joint aged in air at 700°C for 100h: (a) Cusil-ABA and (b) Ag-Cusil

Grahic Jump Location
Figure 6

SEM images and x-ray maps of joints aged in H2-air atmosphere for 100h at 700°C: (a) Cusil-ABA and (b) Ag-Cusil

Grahic Jump Location
Figure 7

XRD data obtained from the surface, middle, and bottom parts of Cusil-ABA on PSZ after aging for 100h at 700°C in H2-air atmosphere

Grahic Jump Location
Figure 8

Interconnected pores formed in a region of Ag-Cusil braze layer after aging in H2-air atmosphere for 100h at 700°C

Grahic Jump Location
Figure 9

Open-circuit voltage (Voc) versus time for fuel cell sealed with Cusil-ABA and Ag-Cusil tested at 700°C for a total of 100h

Grahic Jump Location
Figure 10

SEM micrographs of post-cell test samples: (a) Cusil-ABA and (b) Ag-Cusil



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In