Synthesis, Sintering, and Electrical Properties of BaCe0.9−xZrxY0.1O3−δ

BaCe0.9−xZrxY0.1O3−δ powders were synthesized by a solid-state reaction. Different contents of cerium and zirconium were studied. Pellets were sintered using either conventional sintering in air at 1700◦C or the Spark Plasma Sintering (SPS) technique. The density of the samples sintered by SPS is much higher than by conventional sintering. Higher values of ionic conductivity were obtained for the SPS sample

Impedance investigation of BaCe0.85Y0.15O3-delta properties for hydrogen conductor in fuel cells

International audienceThe influence of the sintering conditions on the electrochemical properties of the proton conducting electrolyte BaCe0.85Y0.15O3-delta (BCY15) and Ni - based BCY15 cermet anode for application in high temperature proton conducting fuel cell are investigated by electrochemical impedance spectroscopy. The results show that at lower sintering temperatures due to the formation of parasitic Y2O3 phase an increase of both the electrolyte and electrode resistances is observed. This effect is strongly reduced by enhancement of the sintering temperature. The obtained BCY15 conductivity (sigma = 2.5x10(-2) S/cm at 700 degrees C) is comparable with that of the best proton conducting materials, while the BCY15-Ni cermet (with ASR = 2.5 Omega cm(2) at 700 degrees C) needs further optimization. The results of impedance investigations of BCY15 as proton conducting electrolyte and cermet anode have been applied in development of innovative high temperature dual membrane fuel cell

Retrospective study on the toxicity induced by stereotactic body radiotherapy: overview of the reunion experience on prostate cancer in elderly patients

IntroductionProstate cancer is the fourth most commonly diagnosed cancer among men worldwide. Various tools are used to manage disease such as conventional radiotherapy. However, it has been demonstrated that large prostate volumes were often associated with higher rates of genitourinary and gastrointestinal toxicities. Currently, the improvements in radiotherapy technology have led to the development of stereotactic body radiotherapy, which delivers higher and much more accurate radiation doses. In order to complete literature data about short-term outcome and short-term toxic effects of stereotactic body radiotherapy, we aimed to share our experience about gastrointestinal and genitourinary toxicities associated with stereotactic body radiotherapy in prostate cancer in patients over 70 years old.MethodsWe retrospectively reviewed the medical records of elderly patients with prostate cancer treated between 2021 and 2022. The elderly patients were treated with a non-coplanar robotic stereotactic body radiotherapy platform using real-time tracking of implanted fiducials. The prostate, with or without part of the seminal vesicles, was treated with a total dose of 36.25 Gy delivered in five fractions, each fraction being administered every other day.ResultsWe analyzed a total of 80 elderly patients, comprising 38 low-, 37 intermediate- and 5 high-risk patients. The median follow-up duration was 12 months. We did not observe biochemical/clinical recurrence, distant metastasis, or death. Grade 2 acute genitourinary toxicity was observed in 9 patients (11.25%) and Grade 2 acute gastrointestinal toxicity in 4 patients (5.0%). We did not observe any grade 3 or more acute or late toxicities.ConclusionOver the follow-up period, we noted a low frequency of gastrointestinal and genitourinary toxicities induced by stereotactic body radiotherapy in the context of prostate cancer in elderly patients. Therefore, stereotactic body radiotherapy seems to represent a promising treatment option for elderly patients, with acceptable acute toxicity

Relation structure-dimension des grains monocristallins: Cas d'un materiau polaire, BaTiO_3

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : TD 80907 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Elaboration et caractérisation du matériau d électrolyte pour pile à combustible à conduction protonique (BaCe(0,9-x)ZrxY0,1 O3-delta)

Le composé BaCe(0,9-x)ZrxY0,1 O3-delta (x=0 ; 0,3 ; 0,7 et 0,9) est étudié en tant que matériau d électrolyte de pile à combustible à conduction protonique (PCFC). Des pastilles denses ont été fabriquées à partir de poudres synthétisées par chamottage, puis frittées à 1700C. Elles ont été caractérisées chimiquement par ICP AES, morphologiquement par MEB, structuralement par DRX et Raman et mécaniquement par dilatométrie. L insertion de protons après traitement sous atmosphère humide a été mise en évidence par profilométrie SIMS, XPS et DRX. La quantification des défauts protoniques entre 400C et 600C par mesure de la prise en eau a montré l augmentation de la concentration protonique avec le taux de cérium et lorsque la température diminue. Grâce à des mesures en courant continu sous atmosphère humide, la conductivité totale a été décomposée en deux termes : une contribution de type p aux fortes pressions partielles en oxygène et une contribution ionique. L étude de l effet isotopique a révélé une contribution protonique significative à 500C et 600C. Lorsque le taux de cérium augmente, l énergie d activation, déterminée d après les courbes d Arrhenius obtenues par spectroscopie d impédance, augmente et la résistivité des joints de grains par rapport au volume diminue. Une optimisation du procédé de mise en forme et de contrôle de la microstructure permettrait l amélioration de ces résultats déjà prometteurs. Des tests de frittage par Spark Plasma Sintering (SPS) ont été réalisés sur des échantillons sans cérium, lesquels présentent des valeurs de conductivité plus importantes que les échantillons frittés conventionnellement.BaCe(0.9-x)ZrxY0.1 O3-delta (x=0, 0.3, 0.7 et 0.9) compounds have been studied as electrolyte material for protonic ceramic fuel cell (PCFC). The powders were synthesized by a solid state reaction, and sintered to form dense pellets at 1700C. Chemical, morphological, structural and mechanical characterizations were performed on the samples, using respectively ICP AES, SEM, XRD, Raman and dilatometry. SIMS, XPS and XRD studies showed the insertion of protonic species in the samples, when treated in a moisturized atmosphere. Water uptake experiments provided quantification of the proton content between 400C and 600C: the protonic concentration increases with increasing cerium content and with decreasing temperature. The DC conductivity measured in wet atmosphere can be expressed as the sum of a p-type component, prominent at high oxygen partial pressure, and an ionic contribution. A study of the conductivity isotope effect revealed a significant protonic conductivity at 500C and 600C. When the cerium content increases, the activation energy, determined with the Arrhenius plots of the conductivity, increases and the resistivity of grain boundaries decreases compared to that of the bulk. An optimisation of the fabrication process and the control of the microstructure would improve these promising results. Spark Plasma Sintering (SPS) experiments have been performed on BaZr0.9Y0.1O3-delta samples, which exhibit higher conductivity values than the conventional sintered samples.DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

Metallic interconnects for solid oxide fuel cell: Effect of water vapour on oxidation resistance of differently coated alloys

International audienceThe 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 study demonstrated that in air, the application by metal organic chemical vapour deposition (MOCVD) of a nanometric layer of reactive element oxides (La2O3, Y2O3, Nd2O3) on FSS improved both the electrical conductivity and the oxidation resistance. The beneficial effect of this type of coating on FSS on oxidation resistance in H2/H2O (anode side) is not yet completely understood. So, the goal of this study is to apply reactive element oxide coating (La2O3, Y2O3, Nd2O3) on two FSS (a commercial, Crofer22APU, and a model, Fe30Cr) and to perform oxidation tests in H2/10%H2O. Kinetics was registered for 100 h at 800 ◦C and the corrosion products were characterized by SEM, EDX, TEM, SIMS and XRD

Interconnecteurs métalliques de piles à combustible de type SOFC (résistance à la corrosion et conductivité électrique à haute température)

Les interconnecteurs représentent une pièce maîtresse des piles à combustibles à oxyde solide (SOFC) car ils sont chargés de collecter et de délivrer les électrons produits lors de la réaction électrochimique du cœur de pile. Les matériaux d interconnecteurs doivent donc être stables sous air et sous H2/H2O. Ce travail vise à étudier l influence d un mince revêtement d oxydes d éléments réactifs (La2O3, Y2O3) réalisé par MOCVD sur le comportement à haute température (800C) de matériaux d interconnecteurs métalliques, tels que les alliages Crofer22APU, Haynes230 et Fe30Cr. La réalisation de tests de longue durée (7 700 et 15 400 heures) s est avérée être riche en enseignements. Le suivi cinétique, la caractérisation des couches d oxyde et la détermination du paramètre ASR ont permis d établir que la présence d oxydes de type pérovskite (LaCrO3, YCrO3), formés lors de l oxydation, permettaient d améliorer sensiblement la conductivité électrique des matériaux d interconnecteurs. Sous atmosphère anodique (H2/10%H2O), même si les éléments réactifs conservent leur effet bénéfique, les cinétiques de corrosion sont plus rapides. L augmentation de la porosité de la couche, l amélioration de l adhérence et la diminution de la taille des grains d oxyde portent à croire que la diffusion anionique devient prépondérante sous vapeur d eau. Enfin, l effet bénéfique d une pré-oxydation courte à 1 000C sur le comportement des alliages revêtus et non revêtus est établi. Des expériences de marquage isotopique sous 16O2/18O2 ont démontré que cette amélioration s explique par un changement du mécanisme de diffusion, la pré-oxydation engendrant une diminution de la contribution cationique.The need of interconnect to connect individual cells into electrical series in a SOFC stack appears as one of the most important point in fuel cell technology. The main important criteria requires for interconnect is an excellent oxidation resistance in air and in H2/H2O. The goal of this study is to determine the influence on corrosion behaviour of a reactive element oxide coating (La2O3, Y2O3) realized by MOCVD on different metallic alloys like Crofer22APU, Haynes230 and Fe30Cr. The realisation of long ageing (7 700 and 15 400 hours) proved to be insightful. The corrosion kinetic experiments, the oxide scale characterisation and ASR measurements established that the presence of perovskite oxides (LaCrO3, YCrO3), formed during oxidation, can significantly improve the electrical conductivity of metallic interconnects. In H2/10%H2O (anode side), the beneficial effect of reactive element oxides is less important than in air. The oxide scales formed in wet hydrogen are more porous and have a smaller grain size; this fact increases the plasticity of the oxide scale and could be explained by an increase of the anionic diffusion. Finally, the study demonstrated that the realisation of a short pre-oxidation at 1,000C on uncoated and coated alloys can improve the oxidation resistance. Two stage oxidation experiments at 800C in 16O2/18O2 demonstrated that this improvement could be explained by a change of the corrosion mechanism; the pre-oxidation decreases the cationic diffusion.DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

Metallic interconnects for SOFC: effect of water vapour on oxidation resistance of differently coated alloys.

International audienc

Evaluation of Haynes230 for Solid Oxide Fuel Cell Interconnect Application

National audienceAbstract - 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, such as LaCrO3, NdCrO3 and YCrO3, are then expected to grow during high temperature oxidation processes, because they present a good conductivity at 800°C in air. The first goal of this study was to perform experiments in air and in H2/10%H2O at 800°C in order to validate the coating influence. The second goal of this study was to determine the influence on oxidation resistance of a pre-oxidation on coated and uncoated Haynes230 at 1000°C for 2 hours in air under atmospheric pressure

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 meilleure conductivité électrique à 800°C que la chromine. L'application d'un fin revêtement de La2O3 permet une amélioration de la tenue à la corrosion sous air, avec une diminution du paramètre ASR. Cependant cette température ne semble pas être toujours suffisante pour garantir la formation de la phase pérovskite. L'objectif de ce travail est donc de réaliser des pré-oxydations à 1000°C pendant 2 heures sous air sur le Crofer22APU revêtu et non revêtu. L'intérêt de ces pré-oxydations consiste notamment à pré-former les phases pérovskites dans le cas des échantillons revêtus. La résistance à la corrosion à 800°C sous air de ces échantillons a été testée. Les produits de corrosion ont été analysés par MEB, EDX, DRX, SIMS. La cinétique d'oxydation du Crofer22APU revêtu et non revêtu pré-oxydé montre une nette diminution de la vitesse d'oxydation (faible prise de masse et faible constante de vitesse parabolique). Les analyses effectuées montrent que lors, de la pré-oxydation sous air à 1000°C pendant 2 h, il se forme une couche d'oxyde très protectrice qui n'évolue quasiment pas pendant les 100 h à 800°C