Material Degradation During Isothermal Ageing and Thermal Cycling of Hybrid Mica Seals under Solid Oxide Fuel Cell Exposure Conditions
Hybrid Phlogopite mica seals with glass interlayers were evaluated in terms of materials degradation in a combined ageing and thermal cycling test. Three glass interlayers were investigated: a standard Ba-Ca-Al silicate glass (G18), a modified Ba-Ca-Al silicate glass with 5% of nucleation agent (G18m), and a borosilicate glass (G6). The hybrid Phlogopite micas were first aged at 800oC for ~500 to ~1000 hrs in a low hydrogen fuel (~2.7% H2/bal. Ar + ~3% H2O), followed by short-term thermal cycling between ~100oC and 800oC. The results of high temperature leak rates showed very poor thermal cycle stability of hybrid micas with G18 glass interlayer after ageing at 800oC for ~1000 hours. Hybrid micas with a borosilicate glass interlayer showed constant leakage during ageing and very good thermal cycle stability with low leakage (< 0.01 sccm/cm @ 0.2psi) after ageing for 508 hours and followed by 56 thermal cycles. Post-mortem analyses showed extensive reaction of G18 with Phlogopite mica, and different fracture path (leak path) for the three hybrid micas. The materials degradation of mica with interlayer glasses was discussed.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1578161
- Report Number(s):
- PNNL-SA-44932
- Journal Information:
- Journal of Power Sources, Vol. 157, Issue 1
- Country of Publication:
- United States
- Language:
- English
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