Thermal cycle stability of a novel glass–mica composite seal for solid oxide fuel cells: Effect of glass volume fraction and stresses

Chou, Yeong‐Shyung; Stevenson, Jeffry W.; Singh, Prabhakar

doi:10.1016/j.jpowsour.2005.03.213

Cited by 54 publications

(29 citation statements)

References 16 publications

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“…The contact strength decreases as the CTE of the resulting material decreased relative to the original asjoined state [20]. This also caused the increase of leakage rate for glass/mica composite compressive seals [21]. Even though the braze sealant also experienced substantial CTE mismatch upon cooling (a anode ∼ 10.5 × 10 −6 K −1 , a SS430 ∼ 12.5 × 10 −6 K −1 , a silver ∼ 22.5 × 10 −6 K −1 ), the ductile sealant could be plastically deformed.…”

Section: Resultsmentioning

confidence: 99%

Effective Ag–CuO sealant for planar solid oxide fuel cells

Shen

Zhu

et al. 2010

Journal of Alloys and Compounds

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Section: Resultsmentioning

confidence: 99%

Effective Ag–CuO sealant for planar solid oxide fuel cells

Shen

Zhu

et al. 2010

Journal of Alloys and Compounds

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“…Moreover, precipitation of sheet-like silicates from liquids composed of TEOS and surfactants [16], and O-barrier effects of silica coatings prepared from liquids by layer-by-layer deposition methods (although without artificially applied stress) [17] have been reported. If these assumptions of 'tension induced layerlike microscopic structures' are valid, then the silica matrix observed here also could have been mechanically strengthened to some extent, because it is well known that layer-like structures are usually tough toward fracturing across the layer [18].…”

Section: Presence and Effects Of Stressmentioning

confidence: 91%

Crack formation, exfoliation, and ridge formation in 500°C annealed sol–gel silica coatings on stainless steel SUS304: Part II Spectroscopic and mechanical analyses and insights into mechanisms controlling coating characteristics

Takemori

2009

Ceramics International

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“…The temperature profiles for the thermal cycling are given in Ref. 11 and 12. The sample was aged for an additional 1000 h in the second stage and thermally cycled for 30 times.…”

Section: Methodsmentioning

confidence: 99%

Material Degradation during Isothermal Aging and Thermal Cycling of Hybrid Mica Seal with Ag Interlayer under SOFC Exposure Conditions

Chou

Stevenson

Hardy

et al. 2006

J. Electrochem. Soc.

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Hybrid phlogopite mica seals with silver interlayers were evaluated in terms of material degradation in a combined isothermal aging and thermal cycling test. The hybrid mica was composed of a phlogopite mica paper sandwiched between two Ag foils. The hybrid micas were first aged at 800°C for ϳ1000 h in a low hydrogen fuel ͑ϳ2.7% H 2 /bal.Ar + ϳ 3% H 2 O͒, followed by short-term thermal cycling between ϳ100 and 800°C. The combined test was repeated three times for a total of 4000 h aging at 800°C and 119 thermal cycles. The results of high-temperature leak rates showed very good thermal stability and thermal cycle stability with 800°C leak rates of ϳ0.02-0.03 sccm/cm. The hybrid mica was also tested in a high-water-content fuel ͑30 vol % H 2 O/70 vol % H 2 ͒ and demonstrated similar leakage during the isothermal aging and the subsequent thermal cycles. Postmortem analyses showed no extensive reaction of Ag with phlogopite mica as well as the mica degradations. The issues of volatility of Ag and mica in the solid oxide fuel cell ͑SOFC͒ environments were discussed. Simple models were simulated to estimate the effect of leakage on the open-circuit voltage and the total fuel loss at various SOFC stack sizes. The results showed very minute fuel loss for the current hybrid micas and demonstrated it to be a good candidate for SOFC sealing.It is recognized that sealing of solid oxide fuel cell ͑SOFC͒ stacks is one of the most challenging tasks for advancing SOFC technologies. The sealing material has to survive hundreds to thousands of thermal cycles in the harsh SOFC environments, i.e., oxidizing, wet, and reducing, at elevated temperatures during routine operations. The sealant not only needs to maintain hermetic or low leak rates during numerous thermal cycles, but it also needs to exhibit long-term ͑e.g., 40,000 h͒ mechanical, thermal, chemical, and electrical stability during SOFC operations.To date, there are several different approaches to SOFC seal development: rigid glass and/or glass-ceramics seals, 1-4 compressive seals, 5-7 and metallic active brazes. 8 Each approach has its own advantages as well as disadvantages, as discussed in the review article by Fergus. 9 The very uniqueness of compressive mica seal is that no close coefficient of thermal expansion ͑CTE͒ match is required as contrast to the other approaches. In this paper we report our recent progress in the development of compressive mica seals, particularly in the material degradation during combined long-term aging and thermal cycling. In our earlier studies, we have identified the major leak paths of conventional compressive mica seals to be at the interfaces between the mating materials and the mica sheet, not through the mica seal itself. 5,6 Based on the findings, the "hybrid" mica was proposed by adding two extra interlayers at these interfaces ͑Fig. 1͒. The high-temperature leak rates were reduced by 2-3 orders of magnitude as compared to the conventional mica seal. 5,6 The phlogopite micas were also found to have reasonable thermal stability i...

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Thermal cycle stability of a novel glass–mica composite seal for solid oxide fuel cells: Effect of glass volume fraction and stresses

Cited by 54 publications

References 16 publications

Effective Ag–CuO sealant for planar solid oxide fuel cells

Effective Ag–CuO sealant for planar solid oxide fuel cells

Crack formation, exfoliation, and ridge formation in 500°C annealed sol–gel silica coatings on stainless steel SUS304: Part II Spectroscopic and mechanical analyses and insights into mechanisms controlling coating characteristics

Material Degradation during Isothermal Aging and Thermal Cycling of Hybrid Mica Seal with Ag Interlayer under SOFC Exposure Conditions

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