| 1. |
- Gagliani, Luca, 1991, et al.
(författare)
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The Influence of Humidity Content on Ferritic Stainless Steels Used in Solid Oxide Fuel Cell under Dual Atmosphere Conditions at 600 C
- 2021
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Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 103:1, s. 1809-1815
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Konferensbidrag (refereegranskat)abstract
- In Solid Oxide Fuel Cells (SOFC), interconnects are simultaneously exposed to dual atmosphere conditions in a range of temperature between 600 and 900 C. The presence of dissolved hydrogen in the steel can cause accelerated corrosion on the side exposed to air compared to exposures in air only. Moreover, the interconnect is subject to different humidity levels on the fuel side depending on fuel utilization. It has been already observed that a protective layer of chromia (Cr2O3) at the fuel side can mitigate the dual effect at the airside acting as a barrier for hydrogen permeation into the material. In this work, AISI 441 and Crofer 22 APU samples were exposed to dual atmosphere at 600 C under controlled humidity levels at the fuel side (20% vs. dry). Analysis performed showed how the humidity content on the fuel side largely affects the breakaway corrosion of the samples at the airside.
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| 2. |
- Goebel, Claudia, 1988, et al.
(författare)
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Long-term (4 year) degradation behavior of coated stainless steel 441 used for solid oxide fuel cell interconnect applications
- 2020
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 449
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Tidskriftsartikel (refereegranskat)abstract
- The present work aims to investigate the long-term stability of Ce/Co coated AISI 441 used as an interconnect material in solid oxide fuel cells (SOFC). Being a commercially available alloy the use of AISI 441 would greatly reduce the cost of SOFCs in comparison to tailor-made interconnect materials such as Crofer 22 APU. To analyze the long-term stability Ce/Co coated AISI 441 is exposed in air at 800 °C for up to 38 000 h. Mass gain values are recorded continuously. After 7 000, 23 000, and 35 000 h area specific resistance (ASR) measurements are performed, and cross-sections are prepared and analyzed using scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) spectroscopy. Cr-evaporation measurements are conducted on samples exposed for up to 38 000 h.
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| 3. |
- Goebel, Claudia, 1988, et al.
(författare)
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Self-healing properties of Ce/Co-coated stainless steel under simulated intermediate temperature solid oxide fuel cell conditions
- 2021
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Ingår i: Surface and Coatings Technology. - : Elsevier BV. - 0257-8972. ; 428
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Tidskriftsartikel (refereegranskat)abstract
- The interconnects used in solid oxide fuel cells (SOFC) are usually shaped into a corrugated form that creates gas channels. Coatings are applied onto an interconnect to increase its longevity by reducing Cr(VI) evaporation and oxide scale growth. To date many manufacturers first deform the interconnect and then apply the coating. However, the reverse (hereinafter termed pre-coating) would be more cost-effective, because large-scale roll-to-roll coating processes could then be used instead of batch coating processes. The drawback of this method is that cracks are introduced into the coating during deformation. The present work shows that the cracks heal after relatively short exposure times for the often-used Ce/Co coating (10 nm Ce and 640 nm Co) even at low operating temperatures (650 °C and 750 °C). The Cr evaporation rate of pre-coated deformed Ce/Co-coated AISI 441, even though slightly elevated in the beginning of the exposure, decreases and stabilizes to rates that are comparable to that of undeformed Ce/Co-coated AISI 441. SEM micrographs show that the cracks introduced during the shaping of the interconnect heal after roughly 70 h of exposure at 750 °C and 360 h of exposure at 650 °C.
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| 4. |
- Gündüz, Kerem, 1985, et al.
(författare)
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The effect of hydrogen on the breakdown of the protective oxide scale in solid oxide fuel cell interconnects
- 2021
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 179
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the effect of hydrogen, on the degradation of AISI 441 interconnect, under solid oxide fuel cell operating conditions was investigated between 500−800 °C for 336 h. As a new hypothesis, it is concluded that, hydrogen impedes Cr diffusion, probably in the grain boundaries, leading to the breakdown of the protective oxide scale. This effect is most severe at 600 °C, while at lower or higher temperatures the effect is attenuated. Cr diffusion is enhanced at high temperatures, whereas protective scales can be obtained at low temperatures with a lower amount of Cr.
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| 5. |
- Reddy, Mareddy, 1993, et al.
(författare)
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Evaluating candidate materials for balance of plant components in SOFC: Oxidation and Cr evaporation properties
- 2021
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 190
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Tidskriftsartikel (refereegranskat)abstract
- Balance of plant (BOP) components made of metallic materials in solid oxide fuel cells are subject to high-temperature corrosion and are a significant source of volatile chromium species. Prospective Fe and Ni-base alloys, AISI 441, AISI 444, a FeCrAl alloy A197/Kanthal® EF101, alloy 600, and alloy 800H are investigated for their suitability to BOP components. Oxidation kinetics and chromium evaporation were employed to study the selected alloys at 650 °C and 850 °C for 500 h. A197 performed the best while AISI 441 and AISI 444, performed the worst. Pre-oxidation significantly improved the performance of the alloys at 650 ⁰C.
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| 6. |
- Reddy, Mareddy, 1993, et al.
(författare)
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Reevaluating the Cr Evaporation Characteristics of Ce/Co Coatings for Interconnect Applications
- 2021
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Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 103:1, s. 1899-1905
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Konferensbidrag (refereegranskat)abstract
- Cathode poisoning by chromium evaporation from the interconnects is one of the major degradation mechanisms in SOFC. Coatings have proved to be very effective in suppressing chromium evaporation on interconnects. The quantification of chromium evaporation is important for determining the chromium consumption in the interconnect and predicting the lifetime of the interconnect. Chromium evaporation of uncoated and Ce/Co coated Crofer 22 APU is reevaluated at 800 C. The chromium evaporation of Ce/Co coatings on steel sheets and precut steels is studied. Coupons cut from Ce/Co coated sheets have uncoated edges, which influence the chromium evaporation measurements. The true chromium evaporation of the coated interconnects is evaluated. The PVD Ce/Co coatings on Crofer 22 APU reduce the chromium evaporation by at least 60 times compared to the uncoated at 800 C.
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