Effects of Thermal Cycling and Thermal Aging on the Hermeticity and Strength of Silver-Copper Oxide Air-Brazed Seals
Thermal cycle and exposure tests were conducted on ceramic-to-metal joints prepared by a new sealing technique. Known as reactive air brazing, this joining method is currently being considered for use in sealing various high-temperature solid-state electrochemical devices, including planar solid oxide fuel cells (pSOFC). In order to simulate a typical pSOFC application, test specimens were prepared by joining ceramic anode/electrolyte bilayers to washers, of the same composition as the common frame materials employed in pSOFC stacks, using a filler metal composed of 4mol% CuO in silver. The brazed samples were exposure tested at 750°C for 200, 400, and 800hrs in both simulated fuel and air environments and thermally cycled at rapid rate (75°C/min) between room temperature and 750°C for as many as fifty cycles. Subsequent joint strength testing and microstructural analysis indicated that the samples exposure tested in air displayed little degradation with respect to strength, hermeticity, or microstructure out to 800hrs of exposure. Those tested in fuel showed no change in rupture strength or loss in hermeticity after 800hrs of high-temperature exposure, but did undergo microstructural change due to the dissolution of hydrogen into the silver-based braze material. Air brazed specimens subjected to rapid thermal cycling exhibited no loss in joint strength or hermeticity, but displayed initial signs of seal delamination along the braze/electrolyte interface after 50 cycles.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 876946
- Report Number(s):
- PNNL-SA-45923; AA1510100
- Journal Information:
- Journal of Power Sources, 152:97-104, Journal Name: Journal of Power Sources, 152:97-104 Vol. 152; ISSN JPSODZ; ISSN 0378-7753
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
30 DIRECT ENERGY CONVERSION
AGING
BRAZING
CERAMICS
DISSOLUTION
FILLER METALS
HYDROGEN
MICROSTRUCTURE
OXIDES
RUPTURES
SILVER
SOLID OXIDE FUEL CELLS
TESTING
THERMAL CYCLING
air brazing
compressive mica seals
fuel cell
glass
hermeticity
high-temperature applications
joint
metal
silver-copper oxide
thermal aging
thermal cycling