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

Xiangfeng Liu, Kohta Asano, Etsuo Akiba

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2 Citations (Scopus)


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
Issue number1-2
Publication statusPublished - May 27 2009
Externally publishedYes

All Science Journal Classification (ASJC) codes

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


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