167 research outputs found

    A MACROSCOPIC MODEL OF THE THERMO-CHEMO-MECHANICAL BEHAVIOUR OF MIXED IONIC AND ELECTRONIC CONDUCTORS

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    International audienceThis paper suggests a macroscopic model describing the thermo-chemo-mechanical behaviour of ceramic dense membrane for oxygen separation application. This work takes in account to oxygen permeation and strain induced by stoichiometry variation with working conditions. This model, developed within the traditional framework of phenomenological approach, is based on the assumption of strain partitions and requires only three state variables: oxygen activity, temperature and total strain. Oxygen bulk diffusion and surface exchanges are described thanks to the thermodynamic approach developed by Onsager. While many works focused on semi-permeation induced strain, the proposed model also includes the temperature effect on chemical expansion. Strains predicted by the proposed model are validated thanks to experimental test on La0.8Sr0.2Fe0.7Ga0.3O3-ÎŽ. Implemented in F.E.A code Abaqus, this model permits studying the design and the process management effects such as chemical shocks on the membrane reliability

    MODELISATION DU TRANSPORT DE L'OXYGENE A TRAVERS UN OXYDE CONDUCTEUR MIXTE

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    National audienceLa production actuelle d'oxygĂšne pure est rĂ©alisĂ©e essentiellement par cryogĂ©nie (-180 °C). Or de nombreux procĂ©dĂ©s industriels, comme le reformage du mĂ©thane, utilisent ce gaz Ă  haute tempĂ©rature (entre 650 et 1000 °C suivant le procĂ©dĂ©). Il en rĂ©sulte une perte Ă©nergĂ©tique importante. Une des solutions envisagĂ©es est la sĂ©paration de l'oxygĂšne contenu dans l'air Ă  haute tempĂ©rature via une membrane cĂ©ramique dense prĂ©sentant des propriĂ©tĂ©s de conduction mixte. Ces membranes ont une structure pĂ©rovskite sous-stoechiomĂ©trique, qui induit la formation de lacune d'oxygĂšne favorisant une conduction ionique d'oxygĂšne. De plus, la structure pĂ©rovskite implique un nombre important de cations favorisant une conduction Ă©lectrique. À haute tempĂ©rature, lorsque la membrane est soumise Ă  un gradient de pression partielle d'oxygĂšne, les anions d'oxygĂšne diffusent Ă  travers celle-ci. Les Ă©lectrons diffusent dans le sens opposĂ©, afin d'assurer l'Ă©lectroneutralitĂ©. Cela est dĂ» Ă  la propriĂ©tĂ© de semi-permĂ©ation de l'oxygĂšne qui correspond Ă  l'ensemble des mĂ©canismes de transport Ă  travers la membrane (en surface et en volume). La structure cristalline n'est toutefois pas modifiĂ©e par cette migration d'espĂšces. Pour la majoritĂ© des conducteurs mixtes, la semi-permĂ©ation induit des dĂ©formations dites chimiques du mĂȘme ordre de grandeur que la dilatation thermique. Ainsi pour Ă©valuer les contraintes que subit la membrane au sein d'un rĂ©acteur en fonctionnement, un modĂšle thermo-chimio-mĂ©canique contenant une modĂ©lisation complĂšte de la semi-permĂ©ation est indispensable. AprĂšs avoir dĂ©crit les phĂ©nomĂšnes de la semi-permĂ©ation mis en jeu, plusieurs modĂšles d'Ă©changes ioniques en surfaces seront Ă©tudiĂ©s. Finalement, un nouveau modĂšle sera proposĂ©

    Etude et modĂ©lisation du comportement thermo‐chimio-­mĂ©canique des oxydes conducteurs mixtes

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    National audienceLa sĂ©paration de l'oxygĂšne de l'air est couramment rĂ©alisĂ©e par distillation cryogĂ©nique. Depuis un peu plus de 30 ans, les oxydes conducteurs mixtes semblent constituer une alternative intĂ©ressante pour la production d'oxygĂšne ultra pur. L'oxygĂšne est sĂ©parĂ© de l'air, Ă  haute tempĂ©rature, par conduction ionique Ă  travers une membrane cĂ©ramique dense. Tous les procĂ©dĂ©s nĂ©cessitant de l'oxygĂšne (oxycombustion, mĂ©tallurgie, domaine mĂ©dical, ...) sont des applications possibles de cette technologie. Les conducteurs mixtes sont des matĂ©riaux cĂ©ramiques dans lesquels deux espĂšces chimiques se dĂ©placent : une espĂšce ionique et une espĂšce Ă©lectronique. Le rapport des conductivitĂ©s Ă©lectroniques et ioniques est tel que la neutralitĂ© Ă©lectrique est conservĂ©e. Cette propriĂ©tĂ© est obtenue par dopage d'une cĂ©ramique (le plus souvent de structure perovskite) qui gĂ©nĂšre la prĂ©sence de dĂ©fauts, notamment des lacunes d'oxygĂšne. Le composĂ© est alors qualifiĂ© de sous-stƓchiomĂ©trique en oxygĂšne. Les Ă©carts Ă  la stƓchiomĂ©trie sont fonction de l'oxyde de dĂ©part, de la tempĂ©rature et de l'activitĂ© chimique des composĂ©s. En service, la fluctuation de la stoĂ©chiomĂ©trie, rĂ©sultant du chargement thermique et du flux des ions oxygĂšne Ă  travers la membrane, occasionne des dĂ©formations du rĂ©seau cristallin qui se traduisent macroscopiquement par une dĂ©formation de la membrane et une modification (faible) des propriĂ©tĂ©s mĂ©caniques. Afin de confirmer le rĂŽle de ces dĂ©formations dites "chimiques" dans la rupture des membranes et d'Ă©tudier l'influence de paramĂštres telles que la gĂ©omĂ©trie (scellement cĂ©ramique/mĂ©tal) ou les conditions opĂ©ratoires, un modĂšle macroscopique du comportement thermo-chimio-mĂ©canique de ces cĂ©ramiques a Ă©tĂ© dĂ©veloppĂ© et implĂ©mentĂ© dans le logiciel Abaqus. La modĂ©lisation est relativement complĂšte, tant du point de vue du comportement de la membrane que des sollicitations : la dĂ©formation chimique est prise en compte par l'intermĂ©diaire d'un comportement thermomĂ©canique dĂ©diĂ© ; le transport ionique de l'oxygĂšne est Ă©galement reproduit via une loi de transport dĂ©diĂ©e, en lien avec l'Ă©volution du champ de tempĂ©rature. La simulation d'essais de dilatomĂ©trie sous diffĂ©rentes atmosphĂšres contrĂŽlĂ©es permet d'illustrer les capacitĂ©s actuelles du modĂšle ainsi que ses limites. Enfin, ce modĂšle a permis de simuler les diffĂ©rentes phases de fonctionnement d'un rĂ©acteur pilote, dĂ©veloppĂ© par Air Liquide. Les prĂ©visions obtenues sont pertinentes et mettent en lumiĂšre l'origine de certaines des difficultĂ©s actuelles de transfert de la technologie Ă  l'Ă©chelle industrielle

    Low exposure long-baseline neutrino oscillation sensitivity of the DUNE experiment

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    The Deep Underground Neutrino Experiment (DUNE) will produce world-leading neutrino oscillation measurements over the lifetime of the experiment. In this work, we explore DUNE's sensitivity to observe charge-parity violation (CPV) in the neutrino sector, and to resolve the mass ordering, for exposures of up to 100 kiloton-megawatt-years (kt-MW-yr). The analysis includes detailed uncertainties on the flux prediction, the neutrino interaction model, and detector effects. We demonstrate that DUNE will be able to unambiguously resolve the neutrino mass ordering at a 3σ\sigma (5σ\sigma) level, with a 66 (100) kt-MW-yr far detector exposure, and has the ability to make strong statements at significantly shorter exposures depending on the true value of other oscillation parameters. We also show that DUNE has the potential to make a robust measurement of CPV at a 3σ\sigma level with a 100 kt-MW-yr exposure for the maximally CP-violating values \delta_{\rm CP}} = \pm\pi/2. Additionally, the dependence of DUNE's sensitivity on the exposure taken in neutrino-enhanced and antineutrino-enhanced running is discussed. An equal fraction of exposure taken in each beam mode is found to be close to optimal when considered over the entire space of interest

    A Gaseous Argon-Based Near Detector to Enhance the Physics Capabilities of DUNE

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    This document presents the concept and physics case for a magnetized gaseous argon-based detector system (ND-GAr) for the Deep Underground Neutrino Experiment (DUNE) Near Detector. This detector system is required in order for DUNE to reach its full physics potential in the measurement of CP violation and in delivering precision measurements of oscillation parameters. In addition to its critical role in the long-baseline oscillation program, ND-GAr will extend the overall physics program of DUNE. The LBNF high-intensity proton beam will provide a large flux of neutrinos that is sampled by ND-GAr, enabling DUNE to discover new particles and search for new interactions and symmetries beyond those predicted in the Standard Model

    Snowmass Neutrino Frontier: DUNE Physics Summary

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    The Deep Underground Neutrino Experiment (DUNE) is a next-generation long-baseline neutrino oscillation experiment with a primary physics goal of observing neutrino and antineutrino oscillation patterns to precisely measure the parameters governing long-baseline neutrino oscillation in a single experiment, and to test the three-flavor paradigm. DUNE's design has been developed by a large, international collaboration of scientists and engineers to have unique capability to measure neutrino oscillation as a function of energy in a broadband beam, to resolve degeneracy among oscillation parameters, and to control systematic uncertainty using the exquisite imaging capability of massive LArTPC far detector modules and an argon-based near detector. DUNE's neutrino oscillation measurements will unambiguously resolve the neutrino mass ordering and provide the sensitivity to discover CP violation in neutrinos for a wide range of possible values of ÎŽCP. DUNE is also uniquely sensitive to electron neutrinos from a galactic supernova burst, and to a broad range of physics beyond the Standard Model (BSM), including nucleon decays. DUNE is anticipated to begin collecting physics data with Phase I, an initial experiment configuration consisting of two far detector modules and a minimal suite of near detector components, with a 1.2 MW proton beam. To realize its extensive, world-leading physics potential requires the full scope of DUNE be completed in Phase II. The three Phase II upgrades are all necessary to achieve DUNE's physics goals: (1) addition of far detector modules three and four for a total FD fiducial mass of at least 40 kt, (2) upgrade of the proton beam power from 1.2 MW to 2.4 MW, and (3) replacement of the near detector's temporary muon spectrometer with a magnetized, high-pressure gaseous argon TPC and calorimeter

    A Gaseous Argon-Based Near Detector to Enhance the Physics Capabilities of DUNE