MIRE Group

Madrid, Spain

MIRE Group

Madrid, Spain

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Barawi M.,MIRE Group | Granero C.,MIRE Group | Diaz-Chao P.,National Engineering School of Caen | Manzano C.V.,Imm Institute Microelectronica Of Madrid Cnm Csic | And 5 more authors.
International Journal of Hydrogen Energy | Year: 2014

Nanocrystalline Mg films with thicknesses between 45 and 900 nm were prepared by e-beam on fused-SiO2 substrates and hydrogenated at 280 °C to investigate the H-absorption/desorption process. Films were characterized by XRD, RBS, Raman, FEG, "in situ" optical measurements and TPD-MS. Whereas practically full conversion into MgH2 is observed in thinner films (d < 150-200 nm), higher amount of hydrogen is not absorbed by thicker films (d > 200-250 nm) that is attributed to the formation of Mg2Si-MgO phases (observed by RBS and Raman) as well as the slow kinetics of MgH2 formation. H-desorption process is controlled by a nucleation and growth process and hydrogen is released at lower desorption temperatures (Td = 425 °C) than bulk MgH2. T d are slightly lower (ΔT ∼ 25 °C) in thickest hydrogenated films (d > 200-250 nm) suggesting an influence of Mg 2Si and MgO phases, formed during hydrogenation. Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.


Ares J.R.,MIRE Group | Leardini F.,University of Rome La Sapienza | Diaz-Chao P.,National Engineering School of Caen | Ferrer I.J.,MIRE Group | And 2 more authors.
International Journal of Hydrogen Energy | Year: 2014

Nanocrystalline Pd-capped Mg films were prepared by e-beam evaporation and hydrided/deuterated in order to investigate the hydride decomposition mechanism. To that aim, different techniques were used (XRD, FEG, TPD-MS, isotope exchange and "in situ" desorption optical measurements). Obtained results show that hydride films decomposed at T = 165 C by a process controlled by the Mg/MgH2 interface reaction with an activation energy Ea = 136 ± 5 kJ/mol H2. Interface is located into each MgH 2 nanocrystallite according to RBS (Rutherford Backscattering) and ERDA (Elastic Recoil Detection Analysis) measurements performed during hydride decomposition. Moreover, RBS and ERDA spectra also show the formation of a MgxPdy intermixed region. This intermixed region does not modify the type of control mechanism but increases the activation energy of the desorption process and slows down further hydrogenation events. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.

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