Direct synthesis of BaAlH(5) and Ba(2)AlH(7) from BaH(2) and Al system and their hydriding/dehydriding characteristics

作者：Liu Xiangfeng; Asano Kohta; Akiba Etsuo^*

来源：Journal of Alloys and Compounds, 2009, 477(1-2): 744-748.

DOI：10.1016/j.jallcom.2008.10.103

• Hydrogen storage materials
• Alkaline earth metals (AE)-based alanates
• Pressure-composition isotherms (PCI)
• Phase transformation

BaAlH(5) and Ba(2)AlH(7) were successfully synthesized through reactive ball milling commercially available BaH(2) and Al powders for the first time. The effects of the mole ratios of BaH(2)/Al on the phase formation and structural properties were investigated by means of X-ray diffractions and a subsequent Rietveld refinement. For different BaH(2)/Al mole ratios (0.5, 1.0 and 2.0) the main phases were BaAlH(5), Ba(2)AlH(7) and BaH(2), respectively. Ba(2)AlH(7) can also be prepared by ball milling BaH(2)/Al (1:1) under At and a subsequent hydrogenation. The phase transition and hydriding/dehydriding characteristics of the ball milled BaH(2)/Al (1:1) system under At were investigated using in-situ differential scanning calorimeter (DSC) under H(2) atmosphere and pressure-composition isotherms (PCI). The mechano-chemistry induced phase transformation of the BaH(2)/Al (1:1) mixture to a BaH(2)/BaAl(4) (3:1) mixture during ball milling under At was first observed. The hydrogenation enthalpy of BaH(2)/BaAl(4) (3:1) to form Ba(2)AlH(7) was determined to be -20.0 kJ mol(-1) from a van';t Hoff plot. The phase transitions during ball milling under At and PCT measu

• 出版日期2009-5-27