Attempts to improve Mg2Ni hydrogen storage by aluminium addition

Toyoto Sato, Helen Blomqvist, Dag Noréus

Research output: Contribution to journalConference articlepeer-review

32 Citations (Scopus)

Abstract

In an attempt to destabilize Mg2NiH4, the starting alloy, Mg2Ni, was doped with aluminium by ball milling before hydrogenation. The structure of Mg2NiH4 is based on an electron-rich d10 [NiH4]-complex stabilized by a Mg ion framework and from theoretical calculations it had been suggested that a further destabilization of the hydride could be obtained by substituting some Mg for Al. After hydrogenation, the structure, color and phase transition temperature of Mg2NiH4 was found to be affected by Al addition. The conventional monoclinic low-temperature (LT) structure of Mg2NiH4 was not observed by X-ray diffraction for Mg2-xAlxNiH4, which instead could be indexed with a cubic unit cell, a=6.519 Å, that is very close to the dynamically disordered, cubic, high-temperature (HT) phase of Mg2NiH4 (a=6.490 Å). In contrast, the Al-doped Mg2NiH4 is stable at room temperature. Furthermore, the typical orange color of Mg2NiH4 was not observed and differential scanning calorimetric measurements (DSC) of the Al-containing hydride showed a 10 °C decrease in phase transition temperature. This is interpreted as a transition from a statically disordered pseudo-HT structure to the dynamically disordered HT phase. However, the monoclinic structure of the LT phase of Mg2NiH4 could again be observed at room temperature after 10 hydriding/dehydriding cycles, indicating that the Al-doping of Mg2NiH4 is counteracted by cycling and only has a temporary influence on the properties.

Original languageEnglish
Pages (from-to)494-496
Number of pages3
JournalJournal of Alloys and Compounds
Volume356-357
DOIs
Publication statusPublished - 2003 Aug 11
Externally publishedYes
EventProceedings of the Eight International Symposium on Metal Hyd (MH 2002) - Annecy, France
Duration: 2002 Sep 22002 Sep 6

Keywords

  • Calorimetry
  • Hydrogen storage materials
  • Mechanical alloying
  • X-ray diffraction

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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