0000000001077911
AUTHOR
Sébastien Fontana
Scale composition and oxidation mechanism of the Ti–46Al–8Nb alloy in air at 700 and 800 °C
It is known that the oxide scale formed on TiAl alloys is generally composed of a mixture of alumina (Al2O3) and titania (TiO2). The presence of niobium changes the activities of Ti and Al and influences the kinetics of oxidation and oxide layer composition. In this work, the Tie46Ale8Nb alloy was subjected to cyclic oxidation in air at 700 � C (for 2 and 24 h) and 800 � C (for 300 h). Scale composition was analyzed by means of different techniques including X-ray photoelectron spectroscopy, X-ray diffraction and secondary ion mass spectroscopy. The scale consisted of several layers. The outer layer was built of alumina (amorphous or with very fine grains), whereas the inner layer e mainly …
Metallic interconnects for solid oxide fuel cell: Effect of water vapour on oxidation resistance of differently coated alloys
International audience; The need of interconnect to separate fuel and oxidant gasses and connect individual cells into electrical series in a SOFC stack appears as one of the most important point in fuel cell technology. Due to their high electrical and thermal conductivities, thermal expansion compatibility with the other cell components and lowcost, ferritic stainless steels (FSS) are nowconsidered to be among the most promising candidate materials as interconnects in SOFC stacks. Despite the formation at 800 ◦C of a protective chromia Cr2O3 scale, it can transform in volatile chromium species, leading to the lost of its protectiveness and then the degradation of the fuel cell. A previous…
OXYDATION D'INTERCONNECTEURS METALLIQUES DE PILE A COMBUSTIBLES DE TYPE SOFC SOUS HYDROGENE ENRICHI EN VAPEUR D'EAU
Les interconnecteurs représentent une pièce maîtresse des piles à combustibles à oxyde solide (Solid Oxide Fuel Cells : SOFCs) car ils sont chargés de collecter et de délivrer le courant produit par la pile. Les matériaux d'interconnecteurs sont à la fois en contact avec l'anode et la cathode et doivent donc être parfaitement stables dans l'air (côté cathodique) et dans l'hydrogène enrichie en vapeur d'eau (côté anodique). Les matériaux métalliques les plus prometteurs sont les chromino-formeurs. Ces alliages sont choisis car, à haute température, ils forment une couche de chromine, Cr2O3, protectrice vis-à-vis des conditions corrosives de fonctionnement de la pile. Cependant, cette couche …
INTERCONNECTEURS METALLIQUES DE PILES A COMBUSTIBLES DE TYPE SOFC : EFFET DE LA VAPEUR D'EAU SUR LA RESISTANCE A LA CORROSION
Les interconnecteurs représentent une pièce maîtresse des piles à combustibles à oxyde solide (Solid Oxide Fuel Cells : SOFCs) car ils sont chargés de collecter et de délivrer le courant produit par la pile. Les matériaux d'interconnecteurs sont à la fois en contact avec l'anode et la cathode et doivent donc être parfaitement stables dans l'air (côté cathodique) et dans l'hydrogène enrichie en vapeur d'eau (côté anodique). Les matériaux métalliques les plus prometteurs sont les chromino-formeurs. Ces alliages sont choisis car, à haute température, ils forment une couche de chromine, Cr2O3, protectrice vis-à-vis des conditions corrosives de fonctionnement de la pile. Cependant, cette couche …
Metallic interconnects for solid oxide fuel cell: Performance of reactive element oxide coating during long time exposure
One of challenges in improving the performance and cost-effectiveness of SOFCs (solid oxide fuel cells) is the development of suitable interconnects materials. Chromia-forming alloys and especially ferritic stainless steels, like Crofer22APU, are considered to be among the most promising candidate materials as interconnects in SOFC stacks. However, the performance of chromia-forming materials can be limited by the low electronic conductivity of the oxide scale (high ASR – area specific resistance – value). Such degradation are unacceptable regarding the long-term operation (>40 000 h). A previous study 1 demonstrated that in air, the addition of a nanometric reactive element oxide (La2O3) l…
Evaluation of Haynes230 for Solid Oxide Fuel Cell Interconnect Application
National audience; Abstract - Interconnects are among the most critical parts for commercialization of SOFCs. They separate the fuel and oxidant gases and provide electric connection between the anode and cathode of adjacent cells. A Ni-based alloy, Haynes230 alloy, was evaluated in this work as a candidate material for SOFC interconnects application. During operation, a scale of chromia forms on Haynes230. Unfortunately, this scale can degrade the fuel cell performances. Thus, protective coatings are required to increase long-term stability. In this study, a nanometric layer made of reactive element oxide (La2O3, Nd2O3 and Y2O3) was applied on alloy surface by MOCVD. Perovskite oxides, suc…
On the Effect of Surface Treatment to Improve Oxidation Resistance and Conductivity of Metallic Interconnects for SOFC in Operating Conditions
International audience; Due to the reduction of operating temperature from 1000°C to 800°C, chromia forming alloys are the best candidates for interconnects in Solid Oxide Fuel Cells (SOFCs). These interconnects have to be operational in service conditions, at 800°C in air (cathode side) and in humidified hydrogen (anode side). The performance of the interconnect stainless steels is limited by the oxide scale formation (chromia), the low electronic conductivity of this scale and the possible volatility of chromium oxides. In the field of high temperature oxidation of metals, it is well known that the addition of a nanometric layer made of reactive element oxide such as, La2O3, Nd2O3 and Y2O…
Interconnecteurs métalliques de piles à combustibles de type SOFC : effet d'un traitement de surface par MOCVD.
Les performances des alliages chromino-formeurs, utilisés comme interconnecteurs de piles à combustibles sont limitées par la formation d'une couche de chromine qui a une conductivité électrique faible et par la volatilisation des oxydes de chrome qui polluent la pile, et par conséquent détériorent son comportement. La réalisation d'une couche nanométrique d'oxydes d'éléments réactifs (La2O3, Y2O3, Nd2O3) par MOCVD permet d'améliorer la résistance à la corrosion à 800°C des alliages chromino-formeurs. Ces revêtements ont été réalisés sur l'alliage Crofer22APU dans le but de former des oxydes de type pérovskite tels que LaCrO3, NdCrO3 et YCrO3 lors de l'oxydation et qui possèdent une meilleu…
Metallic interconnects for SOFC: Characterisation of corrosion resistance and conductivity evaluation at operating temperature of differently coated alloys
Abstract One of challenges in improving the performance and cost-effectiveness of solid oxide fuel cells (SOFCs) is the development of suitable interconnect materials. Recent researches have enabled to decrease the operating temperature of the SOFC from 1000 to 800 °C. Chromia forming alloys are then among the best candidates for interconnects. However, low electronic conductivity and volatility of chromium oxide scale need to be solved to improve interconnect performances. In the field of high temperature oxidation of metals, it is well known that the addition of reactive element into alloys or as thin film coatings, improves their oxidation resistance at high temperature. The elements of …
Investigation of La2O3 and/or (Co,Mn)3O4 deposits on Crofer22APU for the SOFC interconnect application
International audience; Chromia forming alloys (stainless steels) are among the best candidates for SOFC interconnects. However, problems of decreasing electronic conductivity during high temperature service and volatility of chromium oxide scales need to be solved. Electronically conductive surface coatings, which also reduce oxide scale growth and chromium volatility, are needed to improve stainless steel interconnects. The goal of this study is to investigate combinations of lanthanum oxide (La2O3) and cobalt manganese oxide ((Co,Mn)3O4) coatings on Crofer22APU stainless steel. Thin film coatings of La2O3 (~200 nm) and Co,Mn (1:1) (~2 mm) were deposited via metal organic chemical vapor d…
Metallic interconnects for SOFC: competitive effect of water vapour and oxygen on the oxidation behaviour of ferritic stainless steel.
Due to their low environmental impact, their high efficiency and their fuel flexibility, Solid Oxide Fuel Cells are studied for many years in order to supply electricity without fossil sources. The need of interconnect to create a stack (providing electrical connection between anode and cathode) and seal every single cell (having to avoid any contact between air and fuel) appears as a crucial point. Ferritic Stainless Steel (FSS) like Crofer22APU are considered as good candidates for interconnects. These chromia forming alloys have to be operational in the service conditions: 800°C in air (cathode side) and in humidified hydrogen (anode side). The performance of the interconnect stainless s…
Metallic interconnects for SOFC: effect of water vapour on oxidation resistance of differently coated alloys.
The need of interconnect to separate fuel and oxidant gasses and connect individual cells into electrical series in a SOFC stack appears as one of the most important point in fuel cell technology. Due to their high electrical and thermal conductivities, thermal expansion compatibility with the other cell components and low cost, Ferritic Stainless Steels (FSS) are now considered to be among the most promising candidate materials as interconnects in SOFC stacks. Despite the formation at 800°C of a protective chromia Cr2O3 scale, it can transform in presence of water vapour in volatile chromium species leading to the lost of its protectiveness and then the degradation of the fuel cell. A prev…