80 research outputs found
Electronic Structure and Formation Enthalpy of Hydroaluminates and Hydroborates
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Complex Hydrides. A collection of Density Functionale studies
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45154_comphy.pdf (Publisher’s version ) (Open Access)Radboud University Nijmegen, Faculteit NWI, 28 augustus 2008Promotor : Groot, R.A. de184 p
Donkere schaduw over de eeuwwisseling. Recensie van: H. Beliën, M. Bossenbroek en G.J. van Setten (ed.), In de vaart der volken. Nederlanders rond 1900 (Amsterdam 1999)
No full textFirst-principles calculations of the crystal structure, electronic structure, and thermodynamic stability of Be(BH4)(2)
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72422.pdf (Publisher’s version ) (Open Access)7 p
Lightweight sodium alanate thin films grown by reactive sputtering
No full textWe report the preparation of sodium alanate, a promising hydrogen storage material, in a thin film form using cosputtering in a reactive atmosphere of atomic hydrogen. We study the phase formation and distribution, and the hydrogen desorption, with a combination of optical and infrared transmission spectroscopy. We show that the hydrogen desorption, the phase segregation, and the role of the dopants in these complex metal hydrides can be monitored with optical measurements. This result shows that a thin film approach can be used for a model study of technologically relevant lightweight metal hydrides.DelftChemTechApplied Science
Donkere schaduw over de eeuwwisseling. Recensie van: H. Beliën, M. Bossenbroek en G.J. van Setten (ed.), In de vaart der volken. Nederlanders rond 1900 (Amsterdam 1999)
No full textAb initio study of Mg(AlH4)2
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33314.pdf (Publisher’s version ) (Open Access
Electronic structure and optical properties of lightweight metal hydrides
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34825.pdf (Author’s version preprint ) (Open Access
Hydrogenography of MgyNi1-yHx gradient thin films: Interplay between the thermodynamics and kinetics of hydrogenation
No full textWe 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. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved
Optical response of the sodium alanate system: GW0-BSE calculations and thin film measurements
No full textWe calculate from first principles the optical spectra of the hydrides in the sodium alanate hydrogen storage system: NaH, NaAlH4, and Na3AlH6. In particular we study the effects of systematic improvements of the theoretical description. To benchmark the calculations we also measure the optical response of a thin film of NaH. The simplest calculated dielectric functions are based upon independent electrons and holes, whose spectrum is obtained at the G0W0 level. Successive improvements consist of including partial self-consistency (so-called GW0) and account for excitonic effects, using the Bethe-Salpeter equation (BSE). Each improvement gives a sizable blue shift or red shift of the dielectric functions, but conserves the trend in the optical gap among different materials. Whereas these shifts partially cancel at the highest (GW0-BSE) level of approximation, the shape of the dielectric functions is strongly modified by excitonic effects. Calculations at the GW0-BSE level give a good agreement with the dielectric function of NaH extracted from the measurements. It demonstrates that the approach can be used for a quantitative interpretation of spectra in novel hydrogen storage materials obtained via, e.g., hydrogenography.ChemE/Chemical EngineeringApplied Science
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