Chromium Vapor Species over Solid Oxide Fuel Cell Interconnect Materials and Their Potential for Degradation Processes

Hilpert, K.; Das, Debarati; Miller, M.; Peck, Dong‐Hyun; Weiss, Robin

doi:10.1149/1.1837264

Cited by 554 publications

(353 citation statements)

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“…Since the AL453 steel is exposed to both air and a reducing (H 2 -H 2 O) atmosphere at the predicted IT-SOFC operation temperature of about 1,073 K, surface modification is required in order to improve the electrical conductivity of the chromia scale or the chromia-rich sublayer [5]. The second issue encountered with chromia is their potential transformation into volatile chromium species such as CrO 2 (OH) 2 , leading to the loss of their protective properties and the poisoning of the cathode material, and the subsequent degradation in the electrochemical performance of the cell, irrespective of the type of steel used for the construction of SOFC steel interconnects [8,9]. One way to effectively reduce such adverse effects is to deposit active protective and conductive coatings of several conducting perovskite [10][11][12] or spinel [13][14][15][16] layers on the surface of ferritic steels.…”

Section: Introductionmentioning

confidence: 99%

Mn–Co spinel protective–conductive coating on AL453 ferritic stainless steel for IT-SOFC interconnect applications

Kruk

Stygar

Brylewski

2012

J Solid State Electrochem

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This paper presents research on the synthesis and properties of the Mn 1.5 Co 1.5 O 4 (MC) spinel powder, as well as its application for the preparation of a MC thick film on the AL453 steel to be used for metallic interconnect material in IT-SOFCs. In order to prepare the MC micropowder with excellent homogeneity of the chemical and phase compositions, EDTA gel processes were utilized. In order to improve the contact electrical resistance between an AL453 steel interconnect and the La 0.8 Sr 0.2 FeO 3 (LSF) cathode and protect the cathode from Cr poisoning, the surface of the AL453 steel was coated with a protective manganese cobaltite spinel matrix using screen printing in combination with an appropriate heat treatment. The oxidation of the AL453/MC composite layer carried out in the air-H 2 O gas mixture at 1,073 K for 55 h showed that the spinel coating may serve as an effective barrier against outward Cr diffusion from the AL453 steel and, therefore, significantly inhibit the formation of volatile Cr vapors from the chromia scale. The contact ASR study of the interconnect-cathode interface in the AL453/MC/LSCM/LSF/LSCM/MC/AL453 system carried out in the range of 723−1,073 K in air showed a very large drop in ASR compared to the resistance of the AL453/LSCM/LSF/LSCM/AL453 system without the spinel coating.

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Section: Introductionmentioning

confidence: 99%

Mn–Co spinel protective–conductive coating on AL453 ferritic stainless steel for IT-SOFC interconnect applications

Kruk

Stygar

Brylewski

2012

J Solid State Electrochem

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“…This degradation mechanism is of great importance on the cathode-side of solid oxide fuel cell (SOFC) interconnects, where deposition of Cr at triple-phase points can degrade the fuel cell. [1][2][3][4] It may also be important as a long-term degradation mechanism in the steam side of advanced coal power plants.…”

Section: Introductionmentioning

confidence: 99%

Calculation of Reactive-evaporation Rates of Chromia

Holcomb

2008

Oxid Met

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A methodology is developed to calculate Cr evaporation rates from Cr 2 O 3 with a flat planar geometry. Variables include temperature, total pressure, gas velocity, and gas composition. The methodology was applied to solid oxide fuel cell conditions for metallic interconnects and to advanced steam turbines conditions. The high velocities and pressures of the advanced steam turbine led to evaporation predictions as high as 5.18 × 10 -8 kg/m 2 /s of CrO 2 (OH) 2 (g) at 760°C and 34.5 MPa. This is equivalent to 0.080 mm per year of solid Cr loss. Chromium evaporation is expected to be an important oxidation mechanism with the types of nickel-base alloys proposed for use above 650°C in advanced steam boilers and turbines. It is shown that laboratory experiments, with much lower steam velocities and usually much lower total pressure than found in advanced steam turbines, would best reproduce chromium evaporation behavior with atmospheres that approach either O 2 +H 2 O or Air+H 2 O with 57% H 2 O.

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“…The color of the material loaded with these well dispersed chromate species would appear to be yellow (Figures 4c, 7, and 8). 28 As chromium loading increases, hydroxyl groups diminish and chromate species may form O-Cr-O bonds resulting in polychromated species, and eventually CrO 3 . 44,51 The agglomerated chromate species are minimally anchored to the surface and therefore are minimally stabilized.…”

Section: Resultsmentioning

confidence: 99%

“…Sequence of steps illustrating the formation of CrO 3 on aluminosilicate fibers. Monochromate species form O-Cr-O bonds resulting in polychromated species (r 4 , r 5 ), and eventually CrO 3 . Formation of this species would lend the fibers a brown color.…”

Section: Resultsmentioning

confidence: 99%

XPS Characterization of Aluminosilicate Fibers Post Interaction with Chromium Oxyhydroxide at 100–230°C

Tatar¹,

Gannon²,

Swain³

et al. 2018

J. Electrochem. Soc.

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Chromium containing materials, e.g. stainless steels, are commonly used in high temperature (>500 • C) applications such as solid oxide fuel cell (SOFC) stacks, combustion exhaust systems, and in various chemical process equipment. At these temperatures and in oxidizing atmospheres, chromium oxide (chromia) surface layers form and grow, effectively protecting the underlying alloy. Also known to form under these conditions, however, are volatile chromium species such as CrO 2 (OH) 2 and CrO 3 . Formation of these volatile species may have detrimental effects not only on the source material, but also on surrounding materials in the system which may interact with these species. To better understand how volatile chromium species interact with materials, volatile chromium species were generated from ferritic stainless steel (FSS) T409 at 700 • C and directed into aluminosilicate fibers at 100-230 • C for 150 hours. Post exposure fibers were noted to possess yellow, brown, and/or green stained regions which were isolated and characterized using X-ray photoelectron spectroscopy (XPS). Examination of Cr 2p 3/2 peaks revealed varied Cr(VI) content and Cr(III) multiplet-split components for different discolored regions. Possible explanations for differences in chromium content by discoloration color are discussed. The volatilization of chromium species from chromium containing materials is a well-documented phenomenon which holds consequences for SOFCs, human health, and the environment. Using chromia as an example for a source, in the presence of oxygen and absence of water vapor, the dominant volatilization pathway proceeds according to Reaction 1.If, however, water vapor is present in addition to oxygen, then the dominant volatilization pathway proceeds according to Reaction 2. 1-7The generation of these gas/vapor species is well understood, but the same cannot be said of how they interact with (e.g. condense onto) other materials. This is of great importance for human health and the environment considering that chromium species may take toxic forms (hexavalent) or non-toxic forms (trivalent). This relative dearth of understanding also holds negative implications for SOFCs, and so many investigative efforts have been undertaken to understand how CrO 2 (OH) 2 interacts with ceramic components in SOFCs. Electrochemical reduction of CrO 2 (OH) 2 has often been observed to occur at the triple phase boundary (TPB), where cathode, electrolyte, and gas phase meet. [8][9][10] This electrochemical reaction is not limited to the TPB, however, and can occur away from the TPB given: the formation of a continuous chromia layer for hole transport, a mixed conducting electrolyte, or a mixed conducting cathode. 8 While there is evidence for preferential electrochemical reduction of CrO 2 (OH) 2 , 11,12 open circuit chemical reactions have also been observed with cathodes containing Mn or Sr. 13 It should be noted that Cr transport to lanthanum strontium manganite (LSM) was observed via solid state diffusion, whereas vapor deposition o...

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Chromium Vapor Species over Solid Oxide Fuel Cell Interconnect Materials and Their Potential for Degradation Processes

Cited by 554 publications

References 2 publications

Mn–Co spinel protective–conductive coating on AL453 ferritic stainless steel for IT-SOFC interconnect applications

Mn–Co spinel protective–conductive coating on AL453 ferritic stainless steel for IT-SOFC interconnect applications

Calculation of Reactive-evaporation Rates of Chromia

XPS Characterization of Aluminosilicate Fibers Post Interaction with Chromium Oxyhydroxide at 100–230°C

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