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YMgGa
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
2007 (English)In: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, Vol. 63, no 12, i195-i195 p.Article in journal (Refereed) Published
Abstract [en]

The crystal structure of YMgGa, yttrium magnesium gallide, is isotypic with LaMgGa and crystallizes in the hexagonal ZrNiAl type structure. It consists of a three-dimensional network of Mg and Ga atoms, in which Y atoms fill channels. There are two crystallographically independent Ga sites. One Ga atom (Ga1) has three Mg atoms as near neighbours and six Y atoms at a slightly longer distance, giving rise to a [3 + 6] coordination. Another Ga atom (Ga2) is also nine-coordinate but has six near Mg neighbours and three Y at a somewhat longer distance in a [6 + 3] coordination. The Mg atom is tetrahedrally coordinated by four Ga atoms and has two additional Mg neighbours at a slightly longer distance. The site symmetries for Y, Ga1, Ga2 and Mg are m2m, , 2m and m2m, respectively. The crystal used was an inversion twin.

Place, publisher, year, edition, pages
2007. Vol. 63, no 12, i195-i195 p.
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-12075DOI: 10.1107/S160053680705413XISI: 000251282300004OAI: oai:DiVA.org:uu-12075DiVA: diva2:39844
Available from: 2007-11-22 Created: 2007-11-22 Last updated: 2010-02-26Bibliographically 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, MartinGustafsson, TorbjörnAndersson, Yvonne

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