Hydrogenography of MgyNi1−yHx gradient thin films / R. Gremaud in Acta materialia, Vol. 58 N° 2 (Janvier 2010)  

Public ISBD [article]  inActa materialia > Vol. 58 N° 2 (Janvier 2010) . - pp. 658-668 Titre : Hydrogenography of MgyNi1−yHx gradient thin films : interplay between the thermodynamics and kinetics of hydrogenation Type de document : texte imprimé Auteurs : R. Gremaud, Auteur ; C. P. Broedersz, Auteur ; A. Borgschulte, Auteur Article en page(s) : pp. 658-668 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Hydrogen storage Magnesium nickel hydride Mg2NiH4 MgH2 Hydrogenography Index. décimale : 669 Métallurgie Résumé : We monitor the hydrogenation of PTFE/Pd-capped MgyNi1−yHx gradient thin films using the change in optical transmission as a function of time, temperature and hydrogen pressure, to study the relation between kinetics and thermodynamics of hydrogenation of this multiphase hydride system. The interplay between kinetics and thermodynamics is used to extrapolate the hydrogenation equilibrium pressures via the H-absorption rate. Pressure–optical-transmission–isotherms determined independently at different temperatures provide a cross-check for the equilibrium pressure and the enthalpy of H-absorption. We find that the hydrogenation reaction is destabilized with respect to the Mg2Ni → Mg2NiH4 reaction for Mg fractions close to the Mg2Ni–Mg eutectic point. From a comparison with calculated enthalpies obtained from density functional theory, we conclude that the experimentally observed destabilization originates from the well-mixed microstructure around the eutectic point. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235556%23 [...] [article] Hydrogenography of MgyNi1−yHx gradient thin films : interplay between the thermodynamics and kinetics of hydrogenation [texte imprimé] / R. Gremaud, Auteur ; C. P. Broedersz, Auteur ; A. Borgschulte, Auteur . - pp. 658-668. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 2 (Janvier 2010) . - pp. 658-668 Mots-clés : Hydrogen storage Magnesium nickel hydride Mg2NiH4 MgH2 Hydrogenography Index. décimale : 669 Métallurgie Résumé : We monitor the hydrogenation of PTFE/Pd-capped MgyNi1−yHx gradient thin films using the change in optical transmission as a function of time, temperature and hydrogen pressure, to study the relation between kinetics and thermodynamics of hydrogenation of this multiphase hydride system. The interplay between kinetics and thermodynamics is used to extrapolate the hydrogenation equilibrium pressures via the H-absorption rate. Pressure–optical-transmission–isotherms determined independently at different temperatures provide a cross-check for the equilibrium pressure and the enthalpy of H-absorption. We find that the hydrogenation reaction is destabilized with respect to the Mg2Ni → Mg2NiH4 reaction for Mg fractions close to the Mg2Ni–Mg eutectic point. From a comparison with calculated enthalpies obtained from density functional theory, we conclude that the experimentally observed destabilization originates from the well-mixed microstructure around the eutectic point. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235556%23 [...]

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