| 1. |
- Alnegren, Patrik, 1988, et al.
(författare)
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Inhibiting chromium evaporation and oxide scale growth on SOFC metallic interconnects by nano coatings
- 2014
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Ingår i: 20th World Hydrogen Energy Conference, WHEC 2014. - 9780000000002 ; 1:2014
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Konferensbidrag (refereegranskat)abstract
- High chromium ferritic steel is today the most commonly considered material for SOFC interconnectors due to many desirable properties, such as matching thermal expansion coefficient with other cell components but most importantly better machinability and price compared to ceramic alternatives. Yet there are some obstacles that need to be addressed before long term stability of a ferritic steel interconnector based fuel cell stack can be realized. First of all the electrical conductivity needs to remain high throughout the fuel cell stack operating life time and thus the formed oxide layers need to be electrically conductive and thin. Secondly, volatilization of chromium from the oxide scale of metallic interconnects causes rapid degradation due cathode poisoning. In the current study both oxidation and chromium evaporation of ferritic steel substrates are investigated in controlled atmospheres that simulates the environments of an operating SOFC stack. Samples coated with nanometer scale dual coatings of Co and Ce were tested. The dual coating substantially increased the performance of the ferritic substrates by i) significantly reducing oxidation rate, ii) increasing scale adherence and iii) diminishing chromium evaporation by 90 % via the formation of a Co-Mn-spinel cap layer.
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| 2. |
- 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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| 3. |
- 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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| 4. |
- Alnegren, Patrik, 1988, et al.
(författare)
-
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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| 5. |
- 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
-
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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| 6. |
- 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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| 7. |
- 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
-
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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| 8. |
- Froitzheim, Jan, 1981, et al.
(författare)
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Investigation of Chromium Volatilization from FeCr Interconnects by a Denuder Technique
- 2010
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 1945-7111 .- 0013-4651. ; 157:9, s. B1295-B1300
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Tidskriftsartikel (refereegranskat)abstract
- A technique is presented for accurate and time-resolved quantification of chromium volatilization from alloys at high temperature. A denuder tube which is coated with Na2CO3 is placed downstream of the samples. CrO2(OH)(2) that evaporated from the samples is collected on the denuder and converted to the thermally stable Na2CrO4. The chromate is then dissolved in water and determined quantitatively. Three commercially available ferritic 22% Cr steels intended for use as solid oxide fuel cell interconnect materials (Sanergy HT, Crofer 22 APU, and ZMG 232) have been investigated with respect to chromium volatilization and oxidation rate. The effect on chromium volatilization of a submicrometer cobalt coating on the steel surface is reported. Comparisons are made with a conventional thick ceramic coating. The experiments are carried out at 850 degrees C in N-2 - 20% O-2 - 3% H2O atmosphere. The submicrometer Co coatings proved to be very efficient, reducing Cr volatilization by 1 order of magnitude. Microscopic studies show that both uncoated steel and steel coated with a submicrometer cobalt film develop two-layered oxide scales with the bottom part consisting of a Cr-rich corundum-type oxide. The uncoated samples develop a top layer consisting of (Cr, Mn)(3)O-4 oxide, whereas the Co-coated samples exhibit a top layer consisting of Co-rich spinel oxide. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3462987] All rights reserved.
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| 9. |
- 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
-
Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 284, s. 321-327
-
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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| 10. |
- Grolig, Jan Gustav, 1986, et al.
(författare)
-
Coated stainless steel 441 as interconnect material for solid oxide fuel cells: Oxidation performance and chromium evaporation
- 2014
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 248, s. 1007-1013
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Tidskriftsartikel (refereegranskat)abstract
- Reactive Element (RE) and RE/cobalt-coated stainless steel AISI 441 was exposed at Solid Oxide Fuel Cell (SOFC) cathode conditions (850 degrees C in air with 3% water content) for up to 500 h. The chromium evaporation was measured by applying the denuder technique. Uncoated material exhibited severe spallation which could be successfully prevented by using cerium or lanthanum coatings. By applying double layer coatings of cerium or lanthanum in combination with cobalt the oxidation rate was decreased and the chromium volatilisation was also about 90% lower than the uncoated material.
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| 11. |
- Grolig, Jan Gustav, 1986, et al.
(författare)
-
Copper based conversion coatings on ferritic stainless strip steel as solid oxide fuel cell interconnects: Oxidation performance and chromium evaporation
- 2013
-
Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 57:1, s. 2339-2347
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Konferensbidrag (refereegranskat)abstract
- Ferritic stainless steels such as Crofer 22 H or Sanergy HT have been proven to be effective interconnect materials when additionally coated. These coatings, mainly based on cobalt spinels, successfully prevent chromium evaporation and are stable for long exposure times. A new approach is using copper based spinel coatings which are promising concerning price, conductivity and stability. This investigation is dedicated to a selection of copper spinel conversion coatings, their stability and ability to prevent chromium evaporation. Chromium release was monitored in humidified air (at 850 °C) using the denuder technique. The coatings were post analysed utilizing electron microscopy.
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| 12. |
- 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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| 13. |
- Grolig, Jan Gustav, 1986, et al.
(författare)
-
Effect of Cerium on the Electrical Properties of a Cobalt Conversion Coating for Solid Oxide Fuel Cell Interconnects - A Study Using Impedance Spectroscopy
- 2015
-
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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| 14. |
- 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
-
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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| 15. |
- Nugehalli Sachitanand, Rakshith, 1984, et al.
(författare)
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Evaluation of the oxidation and Cr evaporation properties of selected FeCr alloys used as SOFC interconnects
- 2013
-
Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 38:35, s. 15328-15334
-
Tidskriftsartikel (refereegranskat)abstract
- In recent years, a number of ferritic interconnect materials for use in solid oxide fuel cells (SOFC) have been developed and are now commercially available. Although similar, there are substantial variations in minor alloying elements. This study compares the oxidation performance of five such interconnect materials: Crofer 22 H, Crofer 22 APU (ThyssenKrupp VDM), Sanergy HT (Sandvik Materials Technology), ZMG232 G10 (Hitachi Metals) and E-Brite (ATI Allegheny Ludlum). 1000 h exposures have been carried out in tubular furnaces at 850 degrees C, with 6 l/min airflow and 3% H2O to simulate the air side atmosphere in an SOFC. In addition to the oxidation tests, time resolved in-situ chromium evaporation measurements have been carried out using a novel denuder technique. It was found that higher Mn concentrations in the alloy lead to lower Cr evaporation. Nonetheless, all steels exhibit substantial Cr volatilization and coatings are needed for most SOFC applications. Furthermore, this study demonstrates that the mass gain data alone can be misleading, and the mass loss due to Cr volatilization needs to be taken into account. Neglecting Cr evaporation results in an underestimation of the oxidation rate by between 15% and 200% for the studied steel grades.
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| 16. |
- 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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| 17. |
- 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
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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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| 18. |
- Alnegren, Patrik, 1988, et al.
(författare)
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Degradation of Ferritic steel interconnects in SOEC environments
- 2013
-
Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 57:1, s. 2261-2270
-
Konferensbidrag (refereegranskat)abstract
- This study investigates the corrosion performance of selected ferritic steels in simulated solid oxide electrolysis cell (SOEC) environments for exposure times up 500 h. Ferritic steels have many properties that are desirable for interconnects but suffer from oxidation and chromium evaporation over time. Four different FeCr alloys have been exposed in different concentrations of dry O2 (anode side) and in 34 % H2O -3 % H2-Ar (cathode side) at 850 °C and gravimetrical measurements have been performed to study oxidation rates. Chromium evaporation has been measured and compared for the oxygen containing environments. Chromium evaporation was found to vary largely with oxygen partial pressure, while the oxidation rate of the steels did not vary substantially in the different oxygen partial pressures. Differences in oxidation behavior of the steels were observed between the exposures in dry O2 and in 34 % H2O -3 % H2 -Ar. Both reduced and increased oxidation rates were observed in the cathode side atmosphere compared to the oxygen side atmosphere for different materials.
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| 19. |
- Canovic, Sead, 1979, et al.
(författare)
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Oxidation of Co- and Ce-nanocoated FeCr steels: A microstructural investigation
- 2013
-
Ingår i: Surface and Coatings Technology. - : Elsevier BV. - 0257-8972. ; 215, s. 62-74
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Tidskriftsartikel (refereegranskat)abstract
- The effect of novel Co and Ce nanocoatings on oxidation behaviour and chromium volatilization from a commercial Fe-22Cr steel (Sanergy HT) developed for solid oxide fuel cell interconnect applications is investigated. Three different coatings (10 nm Ce, 640 nm Co and 10 nm Ce + 640 nm Co) are studied. Uncoated and nanocoated samples are exposed isothermally at 850 C in the air with 3% H2O for 168 h. The detailed microstructure of the different coatings is investigated. The surface morphology and microstructure of the oxide scales are characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and energy dispersive X-ray analysis (EDX). Cross-section TEM thin foils are prepared by using a combined FIB/SEM (focused ion beam/scanning electron microscope) instrument. A 640 nm cobalt coating strongly inhibits Cr volatilization but has only minor effects on oxidation rate. In contrast, a 10 nm Ce coating decreases the oxidation rate but has no significant effects on chromium volatilization. Combining the two coatings, i.e., applying a 640 nm Co coating on top of the 10 nm Ce, effectively reduces Cr evaporation and slows down the rate of alloy oxidation.
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| 20. |
- Chyrkin, Anton, 1984, et al.
(författare)
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Effect of Hydrogen on the Internal Oxidation of a Pd–Cr Alloy in Dual-Atmosphere Conditions
- 2022
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Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 97:5-6, s. 527-538
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Tidskriftsartikel (refereegranskat)abstract
- The effect of hydrogen on oxygen permeability has been studied in a diluted Pd–Cr alloy in dual- and single- atmosphere conditions between 600 and 950 °C. The 0.3 mm thick Pd–1.5Cr foil was exposed in dry and humid air as well as in dual-atmosphere conditions, with one sample surface being exposed to air and one to hydrogen, as encountered in solid oxide fuel cells. At all temperatures, Cr oxidized internally forming internal oxidation zones which were measured in metallographic cross sections. Below 800 °C, an external layer of PdO formed on the surface decreasing the internal oxidation kinetics. No measurable effect of hydrogen on the internal oxidation of Cr in Pd has been detected.
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| 21. |
- Chyrkin, Anton, 1984, et al.
(författare)
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High-temperature oxidation behavior of additively manufactured IN625: Effect of microstructure and grain size
- 2022
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Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 205
-
Tidskriftsartikel (refereegranskat)abstract
- High-temperature oxidation of additively manufactured (AM) Ni-base alloy IN625 has been studied in air and Ar-5%H2-3%H2O at 900–1000 °C. AM material is found to oxidize faster than the conventionally manufactured (CM) IN625 due to severe intergranular oxidation observed in the former. The AM IN625 was heat treated at 1100–1250 °C and hot rolled at 980 °C in order to modify the AM microstructure, primarily grain size, and analyze its role in alloy oxidation behavior. Grain size is shown to affect overall oxidation kinetics but not the intergranular oxidation morphology.
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| 22. |
- Chyrkin, Anton, 1984, et al.
(författare)
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High temperature oxidation of AISI 441 in simulated solid oxide fuel cell anode side conditions
- 2022
-
Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 203
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigates the corrosion of AISI 441 in simulated anode conditions of solid oxide fuel cells (SOFCs). Several parameters such as temperature, humidity, surface condition, pre-oxidation temperature and environment, were investigated. Samples pre-oxidized at 800 ºC were protective at 550–900 ºC, while as-received samples showed protective behavior only at 900 ºC. Additional exposures performed at 600 ºC revealed the negative effect of increasing steam concentration, the beneficial effect of grinding, while pre-oxidation at 600 ºC did not improve the protectiveness. The role and the interplay of the aforementioned factors are discussed.
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| 23. |
- Chyrkin, Anton, 1984, et al.
(författare)
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Intergranular oxidation of additively manufactured Ni-base alloy 625: The role of Si
- 2023
-
Ingår i: Corrosion Science. - 0010-938X. ; 219
-
Tidskriftsartikel (refereegranskat)abstract
- Additively manufactured (AM) Ni-base alloy 625 exposed in air and H2/H2O at 900 °C has been shown to suffer from intergranular oxidation attack unlike its conventionally manufactured (CM) variant. Modification of the AM microstructure via hot-rolling and heat-treatment did not alter the oxidation pattern. Detailed analysis of minor differences in chemical composition of AM and CM exposed the critical role of Si in oxidation protection of alloy 625. Experiments with model alloys as well as diffusion modeling confirmed the crucial role of a minimum Si concentration to form a SiO2 subscale preventing thereby intergranular oxidation attack.
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| 24. |
- Chyrkin, Anton, 1984, et al.
(författare)
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Internal Oxidation of a Fe-Cr Binary Alloy at 700-900 degrees C: The Role of Hydrogen and Water Vapor
- 2022
-
Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 98:3-4, s. 273-289
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Tidskriftsartikel (refereegranskat)abstract
- Internal oxidation of Fe-2.25Cr has been studied in Fe/FeO Rhines pack (RP) and H-2/H2O gas mixtures at 700-900 degrees C. A novel exposure technique allowing RP experiments in dual atmosphere conditions was developed. No measurable effect of hydrogen on lattice oxygen permeability in ferrite could be detected: neither in single nor in dual atmosphere conditions. The H-2/H2O atmosphere was found to induce stronger oxidation attack at alloy grain boundaries resulting in a morphology similar to intergranular stress corrosion cracking often reported in nuclear technology. The intergranular oxidation attack was demonstrated to be independent of the dual atmosphere effect, i.e., hydrogen dissolved in the alloy.
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| 25. |
- Falk Windisch, Hannes, 1984, et al.
(författare)
-
Influence of chromium evaporation and oxidation on interconnect steels at 650-850°C
- 2013
-
Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 57:1, s. 2225-2233
-
Konferensbidrag (refereegranskat)abstract
- Chromium evaporation and oxide scale growth are two important degradation mechanisms in SOFCs when chromia-forming alloys are used as the interconnect material. In this paper the influence of temperature on both mechanisms were studied. Isothermal exposures were carried out for 24, 168 and 500h at 650, 750 and 850°C in an air-3%H2O atmosphere. In the second part uncoated and metallic nano-coated samples were exposed for 3000h. This study clearly points out the relevance of Cr-evaporation at reduced temperatures and the importance of high quality coatings not only to protect the cell from cathode poisoning but also to reduce the risk of Cr-depletion within the interconnect steel.
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| 26. |
- Falk Windisch, Hannes, 1984, et al.
(författare)
-
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
-
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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| 27. |
- Falk Windisch, Hannes, 1984, et al.
(författare)
-
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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| 28. |
- Falk Windisch, Hannes, 1984, et al.
(författare)
-
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
-
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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| 29. |
- Falk Windisch, Hannes, 1984, et al.
(författare)
-
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
-
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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| 30. |
- Froitzheim, Jan, 1981, et al.
(författare)
-
Chromium evaporation of Coated and uncoated FE-22CR steels investigated by a novel denuder technique
- 2009
-
Ingår i: 3rd European Fuel Cell Technology and Applications - Piero Lunghi Conference, EFC 2009; Rome; Italy; 15 December 2009 through 18 December 2009. - 9788882862114 ; , s. 77-78
-
Konferensbidrag (refereegranskat)abstract
- The formation of volatile chromium species is a major problem concerning metallic interconnects for Solid Oxide Fuel Cells (SOFC). This problem is known and a number of routes, usually in the form of coatings, has been presented to overcome this problem. This paper investigates the influence of thin metallic films which can be applied by a low cost process. The measurements are carried out by a novel denuder technique where volatile chromium species are collected as sodium chromate. This technique allows the quantification of chromium evaporation in a time resolved manner. Coated and uncoated samples of ferritic steels developed for SOFC applications are investigated at 850°C in a N2-O2-H2O environment.
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| 31. |
- Froitzheim, Jan, 1981, et al.
(författare)
-
Cr evaporation of metallic interconnects: A novel method for quantification
- 2009
-
Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. - 9781566777391 ; 25:2 PART 2, s. 1423-1428
-
Konferensbidrag (refereegranskat)abstract
- Chromium evaporation from metallic interconnects in SOFCs is commonly poisoning the cathode of SOFCs. To reduce chromium evaporation, rather thick coatings have been deposited using various coating techniques. In this study, a 22% Cr ferritic steel has been coated with thin films (
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| 32. |
- Froitzheim, Jan, 1981, et al.
(författare)
-
Long term study of Cr evaporation and high temperature corrosion behaviour of Co coated ferritic steel for solid oxide fuel cell interconnects
- 2012
-
Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 220, s. 217-227
-
Tidskriftsartikel (refereegranskat)abstract
- The oxidation behaviour of the uncoated ferritic Fe-22Cr steel Sanergy HT is compared with an 640 nm Co coated version of the same material. The materials have been subject to corrosion and Cr volatilization measurements in air for up to 3000 h at 850 degrees C. Oxidation tests have been carried out both isothermal and discontinuously. The volatilization measurements were carried out using a recently developed denuder technique, which allows to quantify Cr evaporation in a time resolved manner. The oxidation process is studied from very initial phases (>15 s) to long term behaviour (3000 h). The formed oxide scales are analysed by XRD, SEM/EDX as well as TEM/EDX.The results show that both materials form an oxide scale with an inner layer of Cr2O3 and a spinel layer on top. In the case of the uncoated material, the spinel layer is of (Cr,Mn)(3)O-4 type while in the presence of a Co coating a (Co,Mn,Fe)(3)O-4 is formed. The Cr evaporation measurements show that despite the fact that the Co coating is very thin (640 nm) it effectively blocks Cr evaporation for at least 3000 h. This is in line with TEM analysis showing that after 3000 h there is only a low Cr content in the outer oxide scale. This long term stability indicates the suitability of the coated material as solid oxide fuel cell (SOFC) interconnect.
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| 33. |
- Froitzheim, Jan, 1981, et al.
(författare)
-
Multifunctional Nano-Coatings for SOFC Interconnects
- 2011
-
Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. - 9781607682127 ; 35:1, s. 2503-2508
-
Konferensbidrag (refereegranskat)abstract
- Chromium evaporation from metallic interconnects in SOFCs is commonly poisoning the cathode of SOFCs. To reduce chromium evaporation, rather thick coatings have been deposited using various coating techniques. In this study a 22% Cr ferritic steel has been coated with multilayered nano coatings. The best coatings combine a Cr retention layer (800nm Co) with a 10nm layer of Ce that reduces the corrosion rate of the metallic interconnect. Such coatings might be a cost efficient way to meet the required lifetime targets for SOFC interconnects. The Cr evaporation measurements are carried out with a recently developed denuder technique which allows time resolved quantification of volatile chromium species. Downstream of the samples a denuder tube is placed which collects any CrO2(OH)(2) evaporating from the samples.
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| 34. |
- Froitzheim, Jan, 1981, et al.
(författare)
-
Nano coated interconnects for SOFC (NaCoSOFC)
- 2013
-
Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 57:1, s. 2187-2193
-
Konferensbidrag (refereegranskat)abstract
- The NaCoSOFC project is focused on the development of nano coatings for SOFC interconnects. The project is sponsored by the Nordic Top Level Research Initiative and has four project partners: Sandvik Materials Technology which is producing coated interconnects, Chalmers University of Technology and the University of Oslo that characterize samples with respect to e.g. corrosion, Cr evaporation and ASR as well as Topsoe Fuel Cell that is testing the developed interconnects in its stacks. The developed coatings are based on a combination of Co with RE elements and exhibit high corrosion resistance, 10 fold decrease in Cr evaporation and ASR values that are approximately 50% of the uncoated material.
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| 35. |
- Froitzheim, Jan, 1981, et al.
(författare)
-
Nanocoatings for SOFC interconnects - Mitigating chromium volatilization and improving corrosion properties
- 2011
-
Ingår i: Materials Science Forum. - 1662-9752 .- 0255-5476. - 9783037852354 ; 696, s. 412-416
-
Konferensbidrag (refereegranskat)abstract
- Two important degradation mechanisms in Solid Oxide Fuel Cells (SOFC) are directly related to the metallic interconnects. The formation of volatile chromium oxides from metallic interconnects commonly causes fast degradation in cell performance due to poisoning the cathode. Secondly is the ability of the metallic interconnect to form a thin protective oxide one of the most important lifetime limiting factors for SOFC. Chromium volatilization of various uncoated steels is studied as a function of temperature by a recently developed denuder technique which allows time resolved quantification of volatile chromium species. The inhibition of Cr evaporation by Co thin film coatings (800nm) is investigated; it will be shown that these coatings are more effective than much thicker ceramic coatings that are commonly used for this purpose. In order to increase the lifetime of the metallic components in SOFC nano-coatings of reactive elements (RE) have been investigated as well. The application of such coatings can reduce the corrosion rates substantially and thus increase the lifetime of the fuel cell stack. It will be shown that it is possible to combine the positive effects of RE with the beneficial effects of a Co coating and thus to obtain an interconnect material with low Cr evaporation and increased oxidation resistance.
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| 36. |
- Gagliani, Luca, 1991, et al.
(författare)
-
The Influence of Humidity Content on Ferritic Stainless Steels Used in Solid Oxide Fuel Cell under Dual Atmosphere Conditions at 600 C
- 2021
-
Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 103:1, s. 1809-1815
-
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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| 37. |
- Goebel, Claudia, 1988, et al.
(författare)
-
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
-
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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| 38. |
- Goebel, Claudia, 1988, et al.
(författare)
-
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
-
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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| 39. |
- Goebel, Claudia, 1988, et al.
(författare)
-
Long-term (4 year) degradation behavior of coated stainless steel 441 used for solid oxide fuel cell interconnect applications
- 2020
-
Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 449
-
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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| 40. |
- Goebel, Claudia, 1988, et al.
(författare)
-
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
-
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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| 41. |
- Goebel, Claudia, 1988, et al.
(författare)
-
Self-healing properties of Ce/Co-coated stainless steel under simulated intermediate temperature solid oxide fuel cell conditions
- 2021
-
Ingår i: Surface and Coatings Technology. - : Elsevier BV. - 0257-8972. ; 428
-
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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| 42. |
- Goebel, Claudia, 1988, et al.
(författare)
-
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
-
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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| 43. |
- Goebel, Claudia, 1988, et al.
(författare)
-
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
-
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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| 44. |
- Gündüz, Kerem, 1985, et al.
(författare)
-
The effect of additive manufacturing on the initial High temperature oxidation properties of RE-containing FeCrAl alloys
- 2021
-
Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 188
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of additive manufacturing on the high temperature oxidation properties of FeCrAl materials was investigated. For this purpose, additively manufactured Kanthal AM100 cut parallel and perpendicular to the building direction and hot-rolled Kanthal AF as a reference were exposed to air at 900 and 1100 °C for 168 h. AM100 performed slightly better than AF in terms of mass gain. Nevertheless, an oxide scale with local differences in thickness formed on AM100 due to the bimodal grain structure of the underlying metal, which was composed of coarse-grained cuboidal repeating units (100 μm wide), separated by fine-grained rims.
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| 45. |
- Gündüz, Kerem, 1985, et al.
(författare)
-
The effect of hydrogen on the breakdown of the protective oxide scale in solid oxide fuel cell interconnects
- 2021
-
Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 179
-
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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| 46. |
|
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| 47. |
- Jonsson, Torbjörn, 1970, et al.
(författare)
-
The influence of KCl on the corrosion of an austenitic stainless steel (304L) in oxidizing humid conditions at 600 ºC: A microstructural study
- 2009
-
Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 72:3, s. 213-239
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of KCl on the corrosion behavior of the austenitic stainless steel 304L was studied at 600 A degrees C in 5% O(2) + 40% H(2)O + N(2). The breakdown of the protective oxide was investigated. This was done through a detailed microstructural characterization of the oxide scales formed after 1, 24 and 168 h. The oxidized samples were investigated by SEM/EDX, FIB and STEM/EDX. The presence of KCl(s) causes a breakdown of most of the protective scale, even though it is not in direct contact with KCl(s) particles, starting after just 1 h exposure. A fast growing porous oxide formed in direct contact with (former) KCl(s) particles and an about 2 mu m thick scale covered most of the surface. Only some regions were covered by a thin scale. K(2)CrO(4) particles were randomly distributed all over the scale after 1 h exposure. The particles are situated above the oxide scale and are not in direct contact with the subjacent metal. The thin scale contains lower Cr levels than has been observed in corresponding scales formed in the absence of KCl. The breakdown of the protective scale is suggested to be caused primarily by the formation of K(2)CrO(4), depleting the protective oxide in chromium. In addition, chromia evaporation contributes to chromia depletion and breakdown of the protective scale. Very little or no transition metal chlorides were found after breakaway oxidation. Cl is suggested to play a minor role in the initial breakdown of the protective scale. The presence of KCl particles caused local rapid oxidation, which results in an outward growing Fe and Fe-Cr rich porous oxide.
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| 48. |
- Magraso, A., et al.
(författare)
-
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
-
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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| 49. |
- Nugehalli Sachitanand, Rakshith, 1984, et al.
(författare)
-
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
-
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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| 50. |
- Reddy, Mareddy, 1993, et al.
(författare)
-
11–23% Cr steels for solid oxide fuel cell interconnect applications at 800 °C – How the coating determines oxidation kinetics
- 2023
-
Ingår i: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 48:34, s. 12893-12904
-
Tidskriftsartikel (refereegranskat)abstract
- The present work investigates the low-cost steels AISI 441, AISI 430, and AISI 444 against the tailor-made high Cr steel Crofer 22 APU (22.9 wt% Cr) at 800 °C in simulated solid oxide fuel cell (SOFC) cathode conditions. Furthermore, a low Cr steel, AISI 409 (11.4 wt% Cr) is included in the study. The oxidation, chromium evaporation, and area-specific resistance (ASR) of the uncoated and Ce/Co-coated steels are studied for up to 3000 h. Ce/Co-coated steels showed significant improvement in behaviour compared to their uncoated counterparts. The oxidation and chromium evaporation behaviour between the uncoated steels varied substantially while the Ce/Co coated steels exhibited highly similar behaviour. The area-specific resistance of the coated low-cost steels was on par with Crofer 22 APU. However, 430 formed a continuous silica layer, resulting in a higher ASR after 3000 h. Cross-sections of the uncoated and Ce/Co-coated steels were analysed using a scanning electron microscope and energy dispersive X-ray spectroscopy.
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