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Hydrogen sorption properties of a Mg-Y-Ti alloy
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
2010 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 489, no 2, 375-378 p.Article in journal (Refereed) Published
Abstract [en]

The catalytic effect of titanium on the hydrogen sorption properties of a Mg–Y–Ti alloy has been investigated. The alloy is formed by a majority phase Mg24+xY5, a minor phase of solid solution of Y in Mg and Ti clusters randomly dispersed in the sample. During the first hydrogen absorption cycle 5.6 wt.% hydrogen was absorbed at temperatures above 613 K. The alloy decomposed almost completely to MgH2 and YH3. After hydrogen desorption pure Mg and YH2 were formed. For further absorption/desorption cycles the material had a reversible hydrogen capacity of 4.8 wt.%. The MgH2 decomposition enthalpy was determined to −68 kJ/mol H2, and the calculated activation energy of hydrogen desorption of MgH2 was 150(±10) kJ/mol.

Place, publisher, year, edition, pages
2010. Vol. 489, no 2, 375-378 p.
Keyword [en]
Magnesium intermetallics, Hydrides, Hydrogen storage materials, X-ray diffraction.
National Category
Inorganic Chemistry
Research subject
Inorganic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-107390DOI: 10.1016/j.jallcom.2009.09.085ISI: 000273251000014OAI: oai:DiVA.org:uu-107390DiVA: diva2:229063
Available from: 2009-08-11 Created: 2009-08-10 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Light-Metal Hydrides for Hydrogen Storage
Open this publication in new window or tab >>Light-Metal Hydrides for Hydrogen Storage
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Demands for zero greenhouse-gas emission vehicles have sharpened with today’s increased focus on global warming. Hydrogen storage is a key technology for the implementation of hydrogen powered vehicles. Metal hydrides can claim higher energy densities than alternative hydrogen storage materials, but a remaining challenge is to find a metal hydride which satisfies all current demands on practical usability. Several metals store large amounts of hydrogen by forming a metal hydride, e.g., Mg, Ti and Al. The main problems are the weight of the material and the reaction energy between the metal and hydrogen.

Magnesium has a high storage capacity (7.6 wt.% hydrogen) in forming MgH2; this is a slow reaction, but can be accelerated either by minimizing the diffusion length within the hydride or by changing the diffusion properties. Light-metal hydrides have been studied in this thesis with the goal of finding new hydrogen storage compounds and of gaining a better understanding of the parameters which determine their storage properties. Various magnesium-containing compounds have been investigated. These systems represent different ways to address the problems which arise in exploiting magnesium based materials. The compounds were synthesized in sealed tantalum tubes, and investigated by in situ synchrotron radiation X-ray powder diffraction, neutron powder diffraction, isothermal measurements, thermal desorption spectroscopy and electron microscopy.

It is demonstrated that hydrogen storage properties can be improved by alloying magnesium with yttrium or scandium. Mg-Y-compounds decompose in hydrogen to form MgH2 nano-structures. Hydrogen desorption kinetics are improved compared to pure MgH2. The influence of adding a third element, gallium or zinc has also been studied; it is shown that gallium improves hydrogen desorption from YH2. ScAl1-xMgx is presented here for the first time as a hydrogen storage material. It absorbs hydrogen by forming ScH2 and Al(Mg) in a fully reversible reaction. It is shown that the hydrogen desorption temperature of ScH2 is reduced by more than 400 °C by alloying with aluminium and magnesium.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 56 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 666
Keyword
Metal-hydrogen compounds, hydrides, hydrogen storage, X-ray diffraction, neutron diffraction, thermal desorption spectroscopy
National Category
Chemical Sciences Inorganic Chemistry
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-107380 (URN)978-91-554-7585-7 (ISBN)
Public defence
2009-09-25, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2009-09-04 Created: 2009-08-10 Last updated: 2009-09-04Bibliographically approved

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Sahlberg, MartinAndersson, Yvonne

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