Direct synthesis of BaAlH5 and Ba2AlH7 from BaH2 and Al system and their hydriding/dehydriding characteristics

Xiangfeng Liu, Kohta Asano, Etsuo Akiba

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

BaAlH5 and Ba2AlH7 were successfully synthesized through reactive ball milling commercially available BaH2 and Al powders for the first time. The effects of the mole ratios of BaH2/Al on the phase formation and structural properties were investigated by means of X-ray diffractions and a subsequent Rietveld refinement. For different BaH2/Al mole ratios (0.5, 1.0 and 2.0) the main phases were BaAlH5, Ba2AlH7 and BaH2, respectively. Ba2AlH7 can also be prepared by ball milling BaH2/Al (1:1) under Ar and a subsequent hydrogenation. The phase transition and hydriding/dehydriding characteristics of the ball milled BaH2/Al (1:1) system under Ar were investigated using in-situ differential scanning calorimeter (DSC) under H2 atmosphere and pressure-composition isotherms (PCI). The mechano-chemistry induced phase transformation of the BaH2/Al (1:1) mixture to a BaH2/BaAl4 (3:1) mixture during ball milling under Ar was first observed. The hydrogenation enthalpy of BaH2/BaAl4 (3:1) to form Ba2AlH7 was determined to be -20.0 kJ mol-1 from a van't Hoff plot. The phase transitions during ball milling under Ar and PCT measurements were proposed as follows:28 Ba H2 + 28 Al underover({long rightwards arrow}, Ar, Ball milling) 21 Ba H2 + 7 BaA l4 underover(⇌, - H2, + H2) 12 B a2 Al H7 + 4 BaA l4.

Original languageEnglish
Pages (from-to)744-748
Number of pages5
JournalJournal of Alloys and Compounds
Volume477
Issue number1-2
DOIs
Publication statusPublished - May 27 2009

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Ball milling
Phase transitions
Hydrogenation
Rietveld refinement
Calorimeters
Powders
Isotherms
Structural properties
Enthalpy
Scanning
X ray diffraction
Chemical analysis

All Science Journal Classification (ASJC) codes

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

Cite this

Direct synthesis of BaAlH5 and Ba2AlH7 from BaH2 and Al system and their hydriding/dehydriding characteristics. / Liu, Xiangfeng; Asano, Kohta; Akiba, Etsuo.

In: Journal of Alloys and Compounds, Vol. 477, No. 1-2, 27.05.2009, p. 744-748.

Research output: Contribution to journalArticle

Liu, Xiangfeng ; Asano, Kohta ; Akiba, Etsuo. / Direct synthesis of BaAlH5 and Ba2AlH7 from BaH2 and Al system and their hydriding/dehydriding characteristics. In: Journal of Alloys and Compounds. 2009 ; Vol. 477, No. 1-2. pp. 744-748.
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