| 1. |
- Reddy, Mareddy, 1993, et al.
(författare)
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Experimental review of the performances of protective coatings for interconnects in solid oxide fuel cells
- 2023
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 568
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Tidskriftsartikel (refereegranskat)abstract
- Ferritic stainless steel interconnects are used in solid oxide fuel cells; however, coatings are required to improve their performance. Although several types of coatings have been proposed, they have been scarcely investigated under similar conditions. This study compares the characteristics of uncoated Crofer 22 APU and eight different coatings on Crofer 22 APU for up to 3000 h at 800 °C. The coatings were deposited at various research laboratories around the world, and the experiments were performed at Chalmers University of Technology, Sweden. Cross-sections of the samples were analysed using scanning electron microscopy and energy-dispersive x-ray spectroscopy. The (Co,Mn)-based coated steels showed more than 50-fold lower chromium evaporation and at least 3 times thinner Cr2O3 scale thickness compared to uncoated steel. The coated steel samples showed lower area-specific resistance (ASR) values than the uncoated steel after 3000 h of exposure, irrespective of the coating thickness, composition and deposition method.
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| 2. |
- Talic, Belma, et al.
(författare)
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Correlating Oxygen Electrode Degradation to Cr Vaporization from Metallic Interconnects in Solid Oxide Cell Stacks
- 2023
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Ingår i: Journal of the Electrochemical Society. - 1945-7111 .- 0013-4651. ; 170:12
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Tidskriftsartikel (refereegranskat)abstract
- Symmetrical cells consisting of La0.58Sr0.4Co0.2Fe0.8O3-δ (LSCF) oxygen electrodes screen printed on both sides of a Ce0.9Gd0.1O2-δ (CGO) electrolyte were tested at 800 °C while being held close to a piece of Crofer 22 APU alloy. The alloy was either just pre-oxidized or coated with MnCo2O4 and heat treated prior to the exposure test to elucidate the effects of different Cr vaporization rates. Degradation of the symmetrical cells was monitored by electrochemical impedance spectroscopy, and TOF-SIMS, SEM and EDX analysis were used to examine Cr deposition on the electrodes after the exposure. The results show that the degradation rate of the symmetrical cell is directly proportional to the concentration of gaseous Cr(VI)-species, which had been assessed in a previous experiment. The Cr vaporization rate from Crofer 22 APU with a dense MnCo2O4 coating was measured in moisturized air up with up to 40% H2O and found to be invariant with respect to the steam activity. The degradation rate of symmetrical cells was accelerated by humidity in the air, but, noteworthy, this was found also in the absence of a Cr source.
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| 3. |
- Talic, Belma, et al.
(författare)
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Effect of coating density on oxidation resistance and Cr vaporization from solid oxide fuel cell interconnects
- 2017
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 354, s. 57-67
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Tidskriftsartikel (refereegranskat)abstract
- Manganese cobalt spinel oxides are promising materials for protective coatings for solid oxide fuel cell (SOFC) interconnects. To achieve high density such coatings are often sintered in a two-step procedure, involving heat treatment first in reducing and then in oxidizing atmospheres. Sintering the coating inside the SOFC stack during heating would reduce production costs, but may result in a lower coating density. The importance of coating density is here assessed by characterization of the oxidation kinetics and Cr evaporation of Crofer 22 APU with MnCo1.7Fe0.3O4 spinel coatings of different density. The coating density is shown to have minor influence on the long-term oxidation behavior in air at 800 °C, evaluated over 5000 h. Sintering the spinel coating in air at 900 °C, equivalent to an in-situ heat treatment, leads to an 88% reduction of the Cr evaporation rate of Crofer 22 APU in air-3% H2O at 800 °C. The air sintered spinel coating is initially highly porous, however, densifies with time in interaction with the alloy. A two-step reduction and re-oxidation heat treatment results in a denser coating, which reduces Cr evaporation by 97%.
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