| 1. |
- Alnegren, Patrik, 1988, et al.
(författare)
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Degradation of ferritic stainless steels under conditions used for solid oxide fuel cells and electrolyzers at varying oxygen pressures
- 2016
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 110, s. 200-212
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Tidskriftsartikel (refereegranskat)abstract
- Four commercial ferritic stainless steels were tested at 850 °C in oxygen pressures ranging from 10-4 to 1 atm, in order to investigate the isolated effect of oxygen pressure on corrosion, in the context of solid oxide electrolysis cells. The oxidation rates of all steels were essentially independent of oxygen partial pressure, which indicates n-type behavior. FIB/SEM analysis revealed that the grain size of the oxides was found to decrease at lower oxygen pressures. Volatile Cr species evaporation in pure oxygen was significantly lower than what has been reported for simulated solid oxide fuel cell environments with humid air.
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| 2. |
- Alnegren, Patrik, 1988, et al.
(författare)
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Severe dual atmosphere effect at 600 °C for stainless steel 441
- 2016
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 301, s. 170-178
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Tidskriftsartikel (refereegranskat)abstract
- AISI 441 foils of 0.2 mm thickness were exposed in a dual atmosphere setup in which one side was exposed to air -3% H2O and the other to Ar -5% H2 - 3% H2O. The experiment was performed at 600 °C and was referenced against exposures in air +3% H2O on both sides. The exposure conditions were chosen to simulate the conditions of an interconnect in intermediate temperature solid oxide fuel cell stacks (IT-SOFC). A strong dual atmosphere effect was observed: local breakaway corrosion was discovered after only 1000 h on samples exposed to dual atmospheres. After 3000 h iron oxide had propagated to cover the entire surface area of the sample. In comparison, the samples exposed in single atmosphere formed thin protective chromia scales on both sides even after 3000 h of exposure.
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| 3. |
- Alnegren, Patrik, 1988, et al.
(författare)
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Temperature dependence of corrosion of ferritic stainless steel in dual atmosphere at 600–800 °C
- 2018
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 392, s. 129-138
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Tidskriftsartikel (refereegranskat)abstract
- The ferritic stainless steel AISI 441 (EN 1.4509) is exposed for 1000 h to air - 3% H2O on one side and to Ar - 5% H2 – 3% H2O on the other at temperatures 600, 700, and 800 °C. Conditions are chosen to mimic the environment of metallic interconnects in an operating solid oxide fuel cell (SOFC). At 600 °C, ∼25 μm thick Fe2O3/(Fe,Cr)3O4 forms on large parts of the air side of the samples. Reference samples exposed to air - 3% H2O on both sides form thin protective layers of (Cr,Mn)3O4/Cr2O3 at the same temperature. At higher temperatures, 700 and 800 °C, all samples form protective layers of (Cr,Mn)3O4/Cr2O3 regardless of exposure to single or dual atmosphere. It is concluded that corrosion resistance in a dual atmosphere has an inverse dependence on temperature. Different hypotheses for the underlying cause for the dual atmosphere effect are discussed and compared to the experimental data.
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| 4. |
- Falk Windisch, Hannes, 1984, et al.
(författare)
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Chromium vaporization from mechanically deformed pre-coated interconnects in Solid Oxide Fuel Cells
- 2015
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 297, s. 217-223
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Tidskriftsartikel (refereegranskat)abstract
- Cathode poisoning, associated with Cr evaporation from interconnect material, is one of the most important degradation mechanisms in Solid Oxide Fuel Cells when Cr2O3-forming steels are used as the interconnect material. Coating these steels with a thin Co layer has proven to decrease Cr vaporization. To reduce production costs, it is suggested that thin metallic PVD coatings be applied to each steel strip before pressing the material into interconnect shape. This process would enable high volume production without the need for an extra post-coating step. However, when the pre-coated material is mechanically deformed, cracks may form and lower the quality of the coating. In the present study, Chromium volatilization is measured in an air-3% H2O environment at 850 C for 336 h. Three materials coated with 600 nm Co are investigated and compared to an uncoated material. The effect of deformation is investigated on real interconnects. Microscopy observations reveal the presence of cracks in the order of several μm on the deformed pre-coated steel. However, upon exposure, the cracks can heal and form a continuous surface oxide rich in Co and Mn. As an effect of the rapid healing, no increase in Cr vaporization is measured for the pre-coated material.
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| 5. |
- Falk Windisch, Hannes, 1984, et al.
(författare)
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Co- and Ce/Co-coated ferritic stainless steel as interconnect material for Intermediate Temperature Solid Oxide Fuel Cells
- 2017
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 343, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Chromium species volatilization, oxide scale growth, and electrical scale resistance were studied at 650 and 750 °C for thin metallic Co- and Ce/Co-coated steels intended to be utilized as the interconnect material in Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFC). Mass gain was recorded to follow oxidation kinetics, chromium evaporation was measured using the denuder technique and Area Specific Resistance (ASR) measurements were carried out on 500 h pre-exposed samples. The microstructure of thermally grown oxide scales was characterized using Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), and Energy Dispersive X-Ray Analysis (EDX). The findings of this study show that a decrease in temperature not only leads to thinner oxide scales and less Cr vaporization but also to a significant change in the chemical composition of the oxide scale. Very low ASR values (below 10 m? cm2) were measured for both Co- and Ce/Co-coated steel at 650 and 750 °C, indicating that the observed change in the chemical composition of the Co spinel does not have any noticeable influence on the ASR. Instead it is suggested that the Cr2O3 scale is expected to be the main contributor to the ASR, even at temperatures as low as 650 °C.
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| 6. |
- Falk Windisch, Hannes, 1984, et al.
(författare)
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Determination of the oxide scale growth mechanism using 18O-tracer experiments in combination with Transmission Electron Microscopy and nanoscale Secondary Ion Mass Spectrometry
- 2018
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Ingår i: Materials Characterization. - : Elsevier BV. - 1044-5803. ; 136, s. 128-133
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Tidskriftsartikel (refereegranskat)abstract
- Two-stage 18 O 2 / 16 O 2 exposures can be used to investigate the effect that alloying elements, secondary phases, or surface treatments have on the high temperature oxidation behaviour of certain materials. During subsequent exposures to 16 O 2 - and 18 O 2 -rich atmospheres, 16 O- and 18 O-rich layers are formed. Analysis of the layers using Seco ndary Ion Mass Spectrometry (SIMS) depth profiling allows for conclusions to be drawn about the oxide scale growth mechanism. The conclusions are, however, not entirely unambiguous due to the limited lateral resolution of the technology. Rough surface topography and the thickness variation of the oxide scale over the analysed volume add to the ambiguity of the findings. In this study, an Fe-20%Cr alloy was exposed to both 18 O- and 16 O-rich environments at 850 °C. Two methods were used to analyse the thermally grown Cr 2 O 3 scale: (1) traditional SIMS depth profiling and (2) preparation of a cross-sectional lamellae for Transmission Electron Microscopy (TEM), which, subsequently, was analysed in a NanoSIMS. The NanoSIMS 16 O and 18 O elemental maps were then superimposed on the TEM image. In comparison with traditional SIMS depth profiling, the nanoSIMS elemental maps reveal detailed information about local oxide growth in different parts of an oxide scale. Moreover, a clear 16 O/ 18 O interface can be seen in the nanoSIMS maps, which is not the case in the sputter depth profiles. The findings of this study show that the aforementioned issues associated with sputter depth profiling can be eliminated by mapping a cross-section of an oxide scale using high resolution nanoSIMS.
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| 7. |
- Grolig, Jan Gustav, 1986, et al.
(författare)
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Coated stainless steel 441 as interconnect material for solid oxide fuel cells: Evolution of electrical properties
- 2015
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 284, s. 321-327
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Tidskriftsartikel (refereegranskat)abstract
- AISI 441 coated. with a double layer coating of 10 nm cerium (inner layer) and 630 nm cobalt was investigated and in addition the uncoated material was exposed for comparison. The main purpose of this investigation was the development of a suitable ASR characterization method. The material was exposed to a simulated cathode atmosphere of air with 3% water at 850 degrees C and the samples were exposed for up to 1500 h. We compared two methods of ASR measurements, an in-situ method where samples were measured with platinum electrodes for longer exposure times and an ex-situ method where pre-oxidized samples were measured for only very short measurement times. It was found that the ASR of ex-situ characterized samples could be linked to the mass gain and the electrical properties could be linked to the evolving microstructure during the different stages of exposure. Both the degradation of the electric performance and the oxygen uptake (mass gain) followed similar trends. After about 1500 h of exposure an ASR value of about 15 m Omega cm(2) was reached. The in-situ measured samples suffered from severe corrosion attack during measurement. After only 500 h of exposure already a value of 35 m Omega cm(2) was obtained.
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| 8. |
- Grolig, Jan Gustav, 1986, et al.
(författare)
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Copper Iron Conversion Coating for Solid Oxide Fuel Cell Interconnects
- 2015
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 297, s. 534-539
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Tidskriftsartikel (refereegranskat)abstract
- A conversion coating of iron and copper was investigated with the purpose of increasing the performance of Sanergy HT as a potential SOFC interconnect material. Samples were exposed to a simulated cathode atmosphere (air, 3 % H2O) for durations of up to 1000 h at 850 °C. Their performance in terms of corrosion, chromium evaporation and electrical resistance (ASR) was monitored and compared to uncoated and cobalt-coated Sanergy HT samples. The copper iron coating had no negative effects on corrosion protection and decreased chromium evaporation by about 80%. An Area Specific Resistance (ASR) of 10 mΩcm2 was reached after 1000 h of exposure. Scanning Electron Microscopy revealed well adherent oxide layers comprised of an inner chromia layer and an outer spinel oxide layer.
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| 9. |
- Grolig, Jan Gustav, 1986, et al.
(författare)
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Effect of Cerium on the Electrical Properties of a Cobalt Conversion Coating for Solid Oxide Fuel Cell Interconnects - A Study Using Impedance Spectroscopy
- 2015
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 184, s. 301-307
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Tidskriftsartikel (refereegranskat)abstract
- Coatings of metallic cobalt, which convert into a cobalt manganese spinel oxide are known to improve the properties of interconnects for solid oxide fuel cells (SOFCs). The addition of cerium to the cobalt coating further improves the corrosion properties of the material. For this study traditional four-point DC measurements at high temperatures were combined with impedance spectroscopy at low temperatures in order to investigate the effect of cerium on the electrical properties of a cobalt conversion coating. It was found that combination-coatings of cerium and cobalt exhibit superior electrical properties compared to pure cobalt coatings. Cerium slows down the growth of chromia and prevents the outward diffusion of iron into the cobalt spinel layer. Both effects are beneficial for the electrical properties of the interconnect. Impedance spectroscopy measurements revealed that even after more than 3000 h of exposure the outer cobalt manganese spinel layer still has a higher electrical conductivity when cerium was present.
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| 10. |
- Nugehalli Sachitanand, Rakshith, 1984, et al.
(författare)
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Coatings for SOFC interconnects in fuel side environments
- 2015
-
Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. - 9781607685395 ; 68:1, s. 1575-1580
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Konferensbidrag (refereegranskat)abstract
- This study focuses on examining the effect of PVD coatings on the oxidation performance of interconnects in fuel side environments. The ferritic steels Sanergy HT and AISI 441 were coated with nanoscale thick rare earth oxides of Ce and La. Additionally, Sanergy HT was also coated with Cu, Co and Ce/Co. The samples were exposed at 850°C in Ar-5% H2-3% H2O in a tubular furnace. Chemical analysis on the samples was subsequently performed with SEM/EDX and XRD. It was established that the Ce and La coatings brought about a ≈4x reduction in the oxidation rate while the presence of a metallic phase in the oxide (Cu and Co) negatively affected oxidation performance. Further, the La coating resulted in the formation of a perovskite phase, showing that the intrinsic electronic properties of the oxide can be tailored using coatings.
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| 11. |
- Nugehalli Sachitanand, Rakshith, 1984, et al.
(författare)
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The Oxidation of Coated SOFC Interconnects in Fuel Side Environments
- 2016
-
Ingår i: Fuel Cells. - : Wiley. - 1615-6846 .- 1615-6854. ; 16:1, s. 32-38
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on examining the effect of PVD coatings on the oxidation performance of interconnects in fuel (anode) side environments. A Fe-22Cr ferritic steel was coated with (i) Ce 10nm (ii) La 10nm and (iii) Co 600nm. The samples were exposed at 850 degrees C in Ar-5% H-2-3% H2O in a tubular furnace over 500 h. Additionally, the effect of a pre-oxidation step was investigated by exposure in air prior to the simulated fuel gas environment. Chemical analysis on the samples was subsequently performed with SEM/EDX and XRD. It was established that the Ce and La coatings brought about a factor 2-3 reduction (k(p)values of 2.16x10(-14)+/- 3.6x10(-15)g(2)cm(-4)s(-1) for the La 10nm coated steel compared to 7.72x10(-14)+/- 5.86x10(-15)g(2)cm(-4)s(-1) for the uncoated steel) in the oxidation rate while the Co coating disintegrated into metallic islands in and on the thermally grown oxide after exposure. Additionally, the La coating resulted in the formation of a continuous perovskite layer by reaction with the thermally grown oxide.
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| 12. |
- Sattari, Mohammad, 1981, et al.
(författare)
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The effect of Ce on the high temperature oxidation properties of a Fe-22% Cr steel: microstructural investigation and EELS analysis
- 2015
-
Ingår i: Materials at High Temperatures. - : Informa UK Limited. - 0960-3409 .- 1878-6413. ; 32:1-2, s. 118-122
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Tidskriftsartikel (refereegranskat)abstract
- The effect of a 10 nm Ce coating layer on long term oxidation behaviour (up to 3000 hours) of a Fe-22% Cr ferritic stainless steel for solid oxide fuel cell (SOFC) interconnect application is investigated. Scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) analysis showed segregation of Ce to the grain boundaries of Cr, Mn spinel layer adjacent to the scale-gas interface. The findings in this study are in line with the grain boundary blocking model for the Ce effect mechanism. However, segregation of Ce was observed at the grain boundaries of the (Cr, Mn) spinel in the vicinity of the scale-gas interface. No evidence of Ce segregation was found in the grain boundaries of the chromia layer, neither any Ce rich particle was observed in the chromia layer after longer exposure times.
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| 13. |
- Falk Windisch, Hannes, 1984, et al.
(författare)
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Metallic thin-film Co- and Ce/Co-coated steels as interconnect material in IT-SOFC
- 2017
-
Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. - 9781607685395 ; 78:1, s. 1607-1614
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Konferensbidrag (refereegranskat)abstract
- Cr vaporization, oxide scale growth, and the electrical scale resistance (ASR) were studied at 650°C on coated interconnects intended for IT-SOFC applications. The custom-made SOFC interconnect steel Sanergy HT was coated with thin-film Co- and Ce/Co-coatings and compared to the less expensive substrate steel AISI 441 which was coated with Ce/Co and a 15-20 μm thick commercial MCO-coating. All coated materials mitigated Cr vaporization, and due to the very thin chromia scales formed at the low exposure temperature, ASR values below 10 mΩcm 2 were measured for all materials after 500 h at 650°C. The results in this study show that thin-film metallic Co- and Ce/Co-coated steels show excellent properties as interconnect materials for IT-SOFCs. Thick MCO-coatings can also be used at low temperatures; however, the coating method might be a critical issue for lowtemperature applications.
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| 14. |
- Falk Windisch, Hannes, 1984, et al.
(författare)
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Pre-coated Ce/Co-coated steel: Mitigating Cr vaporization, increasing corrosion resistance at competitive cost
- 2015
-
Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. - 9781607685395 ; 68:1, s. 1617-1623
-
Konferensbidrag (refereegranskat)abstract
- Cr vaporization and oxide scale growth are probably the two most detrimental degradation mechanisms associated to Cr2O3-forming alloys as interconnect material in SOFC. Both issues can be improved by the application of coatings. However, the use of coatings increase material cost. To reduce coating costs it is suggested that large amounts of steel can be coated before shaping the pre-coated material into an interconnect. The present study investigates the effectiveness of thin Ce and Co coatings on the cost effective steel AISI 441 with respect to Cr vaporization and corrosion resistance. Furthermore, the effect of mechanical deformation of the coated steel is examined. The results revealed that when the pre-coated steel is deformed, large cracks are formed. However, upon exposure those cracks can heal forming a continuous surface oxide rich in Co and Mn. As an effect of the rapid healing, no increase in Cr vaporization was measured.
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| 15. |
- Falk Windisch, Hannes, 1984, et al.
(författare)
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The Effect of Metallic Co-Coating Thickness on Ferritic Stainless Steels Intended for Use as Interconnect Material in Intermediate Temperature Solid Oxide Fuel Cells
- 2018
-
Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 89:1-2, s. 233-250
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Tidskriftsartikel (refereegranskat)abstract
- The effect of metallic Co-coating thickness on ferritic stainless steels is investigated. This material is suggested to be used as interconnect material in intermediate temperature solid oxide fuel cells. Uncoated, 200-, 600-, 1000-, and 1500-nm Co-coated Sanergy HT is isothermally exposed for up to 500 h in air at 650 A degrees C. Mass gain is recorded to follow oxidation kinetics, and area-specific resistance (ASR) measurements are conducted on samples exposed for 168 and 500 h. The microstructure of the thermally grown oxide scales is characterized utilizing scanning electron microscopy and energy-dispersive X-ray analysis on broad ion beam-milled cross sections. A clear increase in ASR as a function of Co-coating thickness is observed. However, the increase in ASR, as an effect of a thicker Co-coating, is correlated with thicker (Cr,Fe)(2)O-3 scales formed on these materials and not to an increase in Co spinel top layer thickness.
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| 16. |
- Falk Windisch, Hannes, 1984, et al.
(författare)
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The effect of temperature on chromium vaporization and oxide scale growth on interconnect steels for Solid Oxide Fuel Cells
- 2015
-
Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 287, s. 25-35
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Tidskriftsartikel (refereegranskat)abstract
- Chromium vaporization and oxide scale growth are probably the two most important degradation mechanisms associated with the interconnect in Solid Oxide Fuel Cells (SOFCs) when Cr2O3-forming alloys are used as the interconnect material. This study examines the influence of temperature on both mechanisms. Two commercially available steels; Crofer 22 H and Sanergy HT, were isothermally exposed at 650, 750 and 850 °C in an air-3% H2O atmosphere with a high flow rate. Volatile chromium species were collected using the denuder technique. The microstructure of thermally grown oxide scales was characterized using Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Analysis (EDX) and X-Ray Diffraction (XRD). The findings of this study show that although Cr evaporation is reduced with lower temperature, its relative importance compared to oxide scale growth is greater.
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| 17. |
- Goebel, Claudia, 1988, et al.
(författare)
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Does the conductivity of interconnect coatings matter for solid oxide fuel cell applications?
- 2018
-
Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 383, s. 110-114
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Tidskriftsartikel (refereegranskat)abstract
- The present work aims to quantify the influence of typical interconnect coatings used for solid oxide fuel cells (SOFC) on area specific resistance (ASR). To quantify the effect of the coating, the dependency of coating thickness on the ASR is examined on Crofer 22 APU at 600 °C. Three different Co coating thicknesses are investigated, 600 nm, 1500 nm, and 3000 nm. Except for the reference samples, the material is pre-oxidized prior to coating to mitigate the outward diffusion of iron and consequent formation of poorly conducting (Co,Fe) 3 O 4 spinel. Exposures are carried out at 600 °C in stagnant laboratory air for 500 h and subsequent ASR measurements are performed. Additionally the microstructure is investigated with scanning electron microscopy (SEM). On all pre-oxidized samples, a homogenous dense Co 3 O 4 top layer is observed beneath which a thin layer of Cr 2 O 3 is present. As the ASR values range between 7 and 12 mΩcm 2 for all pre-oxidized samples, even though different Co 3 O 4 thicknesses are observed, the results strongly suggest that for most applicable cases the impact of the coating on ASR is negligible and the main contributor is Cr 2 O 3 .
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| 18. |
- Goebel, Claudia, 1988, et al.
(författare)
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Influence of pre-oxidation on dual atmosphere effect on AISI 441 interconnects for solid oxide fuel cell applications
- 2017
-
Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 78:1, s. 1559-1563
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Konferensbidrag (refereegranskat)abstract
- In previous studies an extreme dual atmosphere effect on the airfacing side of AISI 441 at 600°C was observed. However indications showed that pre-oxidation of the material might have a beneficial effect on the corrosion resistance in dual atmosphere. To examine this further we pre-oxidized AISI 441 samples for 0 min, 11 min, 45 min, 180 min and 280 min and subsequently exposed these at 600 °C for 500 h under dual atmosphere conditions. Photographs of the air-facing sides were taken throughout exposure to monitor the corrosion behavior. SEM analysis was performed on all samples after exposure.
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| 19. |
- Goebel, Claudia, 1988, et al.
(författare)
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Long term (4 years) performance of Co/Ce coated 441 for SOFC interconnect applications
- 2017
-
Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 78:1, s. 1675-1679
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Konferensbidrag (refereegranskat)abstract
- Co/Ce coated 441 samples were exposed at 800°C in laboratory air for up to 37 000 h and subsequently characterized using different techniques. Mass gain data of all samples were recorded throughout exposure. Cr-evaporation measurements were conducted and compared with unexposed Co/Ce coated AISI 441 as well as unexposed and uncoated AISI 441. Furthermore SEM analysis on BIB cross-sections was performed on 7 000 h, 23 000 h and 35 000 h exposed Co/Ce coated 441.
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| 20. |
- Goebel, Claudia, 1988, et al.
(författare)
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The effect of pre-oxidation parameters on the corrosion behavior of AISI 441 in dual atmosphere
- 2018
-
Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 43:31, s. 14665-14674
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Tidskriftsartikel (refereegranskat)abstract
- Dual atmosphere conditions have been shown to be detrimental for the ferritic stainless steel interconnects used in solid oxide fuel cells (SOFC) under certain conditions. In the present work, we analyze the influence of pre-oxidation on corrosion resistance in dual atmosphere with regard to two parameters: the pre-oxidation time and the pre-oxidation location (pre-oxidation layer on the air-facing side or the hydrogen-facing side). The steel AISI 441 is investigated and pre-oxidation is achieved in air at 800 °C. To examine the influence of pre-oxidation time on corrosion behavior, five different pre-oxidation times are used: 0, 11, 45, 180, and 280 min. The samples are exposed discontinuously to dual atmosphere for 1000 h at 600 °C. Photographs, taken throughout the exposure, show that the pre-oxidation time correlates with the onset of breakaway corrosion. To analyze the influence of pre-oxidation location on corrosion behavior, the samples are pre-oxidized for 180 min, and then a pre-oxidation layer is removed from one side of the sample. Subsequent dual atmosphere exposure at 600 °C for 500 h shows that the pre-oxidation layer on the hydrogen-facing side is more important for corrosion resistance in dual atmosphere than the pre-oxidation layer on the air-facing side.
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| 21. |
- Goebel, Claudia, 1988, et al.
(författare)
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The influence of different factors on the dual atmosphere effect observed for AISI 441 interconnects used in solid oxide fuel cells
- 2019
-
Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 91:1, s. 2261-2266
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Konferensbidrag (refereegranskat)abstract
- Interconnects used in solid oxide fuel cells are subjected to dual atmosphere corrosion at 600 °C. In this work we show that the dual atmosphere effect is dependent on the thickness of the steel sheet. For this AISI 441 with varying thicknesses was exposed to dual atmosphere at 600 °C for 336 h. Before and after exposure photographs were taken to analyze the progress of corrosion on the air-facing side of the steel samples. Additionally, scanning electron microscopy and energy dispersive x-ray diffraction (SEM/EDX) analysis was conducted on all exposed samples. It was found that thinner samples showed increased breakaway oxidation than thicker samples.
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| 22. |
- Magraso, A., et al.
(författare)
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Reduced long term electrical resistance in Ce/Co-coated ferritic stainless steel for solid oxide fuel cell metallic interconnects
- 2015
-
Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 40:27, s. 8579-8585
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Tidskriftsartikel (refereegranskat)abstract
- The present study is focused on the influence of selected coatings on a ferritic stainless steel (Sanergy HT (TM), Sandvik) on the evolution of the area specific resistance (ASR) as a function of time at high temperature. The samples are exposed in humidified air at 850 degrees C for up to 4200 h. It combines long-term ASR measurements with the thermogravimetric behavior and microstructural analysis of the cross sections by scanning electron microscopy. The results show that uncoated and Co-coated Sanergy HT (TM) exhibit similar oxidation kinetics and comparable ASRs, while a combined Ce/Co coating improves oxidation resistance and, consequently, reduces the ASR significantly. Other reports have earlier shown that Co- (and Ce/Co)-coated Sanergy HT (TM) reduces the evaporation of volatile chromium species. Overall, the study indicates that Ce/Co-coatings will render substantially improved performance for ferritic steel interconnects for solid oxide fuel cells.
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| 23. |
- Nugehalli Sachitanand, Rakshith, 1984, et al.
(författare)
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The Influence of Cr Evaporation on Long Term Cr Depletion Rates in Ferritic Stainless Steels
- 2015
-
Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 84:3-4, s. 241-257
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Tidskriftsartikel (refereegranskat)abstract
- It is shown that well defined flow rates are an essential parameter in oxidation experiments influenced by scale volatilisation. The 22 % Cr ferritic steel Sanergy HT, intended for use as an SOFC interconnect material, was exposed discontinuously over 3100 h at 850 °C in air + 3 % H2O @ 6000 sml min−1 (27 cm s−1) and stagnant conditions in a tubular reactor. Time resolved isothermal Cr evaporation measurements over 1000 h were also performed in the 6000 sml min−1 case while the stagnant exposure environment was saturated in Cr(VI) species to suppress any evaporation reactions. Mass balances based on oxidation and evaporation data were in good agreement with SEM/EDX bulk Cr concentration measurements. The time to a bulk concentration of 15 wt% Cr increased by ≈2× from ≈3000 to ≈5500 h when evaporation was suppressed. Further, it was established that a suppressed evaporation reaction affected not just the magnitude of Cr depletion in the steel but even its long term depletion rate.
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| 24. |
- Sudireddy, B. R., et al.
(författare)
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Development of Robust Metal-Supported SOFCs and Stack Components in EU METSAPP Consortium
- 2017
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Ingår i: Fuel Cells. - : Wiley. - 1615-6846 .- 1615-6854. ; 17:4, s. 508-516
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Tidskriftsartikel (refereegranskat)abstract
- The potential of MS-SOFCs was demonstrated through the previous EU METSOFC project, which concluded that the development of oxidation resistant novel metal-supported solid oxide fule cell (MS-SOFC) design and stack is the requirement to advance this technology to the next level. The following EU METSAPP project has been executed with an overall aim of developing advanced metal-supported cells and stacks based on a robust, reliable and up-scalable technology. During the project, oxidation resistant nanostructured anodes based on modified SrTiO3 were developed and integrated into MS-SOFCs to enhance their robustness. In addition, the manufacturing of metal-supported cells with different geometries, scalability of the manufacturing process was demonstrated and more than 200 cells with an area of approximate to 150 cm(2) were produced. The electrochemical performance of different cell generations was evaluated and best performance and stability combination was observed with doped SrTiO3 based anode designs. Furthermore, numerical models to understand the corrosion behavior of the MS-SOFCs were developed and validated. Finally, the cost effective concept of coated metal interconnects was developed, which resulted in 90% reduction in Cr evaporation, three times lower Cr2O3 scale thickness and increased lifetime. The possibility of assembling these cells into two radically different stack designs was demonstrated.
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| 25. |
- Tomas, Matthieu, 1993, et al.
(författare)
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Cu-based coatings for IT-SOFC applications
- 2019
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Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 91:1, s. 2291-2298
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Konferensbidrag (refereegranskat)abstract
- Cu and Ce/Cu coated Sanergy HT samples were exposed at 650 °C and 850 °C for 500 h in air + 3 % water vapor and characterized. Mass gain data of all samples were measured throughout exposure. Cr-evaporation measurements were conducted and compared with uncoated Sanergy HT materials. Furthermore, SEM analysis on BIB cross-sections were performed on exposed samples. Results have shown higher mass gain for samples exposed at 850 ºC than 650 ºC as well as higher Cr evaporation. Microstructural analysis shows thinner oxide scales for samples coated with reactive elements.
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