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Effect of Mg–Nb oxides addition on hydrogen sorption in MgH2

Rahman, M. W. and Castellero, Alberto and Enzo, Stefano and Livraghi, Stefano and Giamello, Elio and Baricco, Marcello (2011) Effect of Mg–Nb oxides addition on hydrogen sorption in MgH2. Journal of Alloys and Compounds, Vol. 509 (Supplement 1), S438-S443. ISSN 0925-8388. Article.

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DOI: 10.1016/j.jallcom.2011.02.064

Abstract

H2 absorption and desorption reactions in MgH2 promoted by ball-milling with 1 mol% MgNb2O6, Mg4Nb2O9 and Mg3Nb6O11 have been investigated. MgH2 was milled with the bare oxides for 12 h under a high purity Ar atmosphere. Absorption and desorption reactions in the ball-milled samples were studied by in situ X-ray diffraction (XRD) in isothermal conditions with Anton Paar XRK 900 reaction chamber. XRD patterns for absorption were recorded at 573 K under hydrogen pressure of 0.9 MPa and for desorption at 623 K in vacuum. Experimental data were analysed according to the Rietveld method. Ball-milled samples showed the presence of a mixture of β and γ allotropes of MgH2, with significantly broadened diffraction peaks due to reduced crystallite size and strain, together with bare additives. The presence of Mg-Nb oxides significantly accelerates the hydrogen absorption and desorption processes. The amount of hydrogen absorbed in the presence of Mg-Nb-O phases is lower than the maximum stoichiometric capacity, because of the presence of a non-reactive MgO layer on the surface of the powders or at the grain boundaries. Experimental results are discussed on the basis of thermodynamic and kinetic arguments.

Item Type:Article
ID Code:5748
Status:Published
Refereed:Yes
Uncontrolled Keywords:Hydrogen storage materials, high-energy ball milling, x-ray diffraction
Subjects:Area 03 - Scienze chimiche > CHIM/02 Chimica fisica
Divisions:001 Università di Sassari > 01 Dipartimenti > Chimica
Publisher:Elsevier Science
ISSN:0925-8388
Copyright Holders:© 2011 Elsevier
Additional Information:Paper presented at the 17h International Symposium on Metastable, amorphous and nanostructured materials, July 4-9, 2010, Zurich, Switzerland
Deposited On:11 May 2011 11:06

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