Formation reaction of Mg2FeH6: effect of hydrogen absorption/desorption kinetics

Materials Research

Alexandre Augusto Cesario Asselli²  Walter José Botta¹  Jacques Huot² 

[1] ,Université du Québec à Trois-Rivières Institut de Recherche sur l'Hydrogène Québec,Canada

关键词: metal hydrides;    high-energy ball milling;    kinetics;   

DOI  :  10.1590/S1516-14392013005000122

来源: SciELO

【 摘 要 】

In this paper we address some aspects of the kinetics of hydrogen absorption and desorption of Mg2FeH6 nanocomposite powder. The Mg2FeH6 material was prepared from a 2Mg-Fe composition by reactive milling under H2 pressure at room temperature. After mechano-chemical processing, the material was mainly constituted of Mg2FeH6 having a hydrogen gravimetric capacity corresponding to 94% of the theoretical capacity. The kinetics of hydrogen absorption at constant temperature and the transformation of phases during this process were studied. The kinetics of hydrogen absorption presented a two-step behaviour. First, β-MgH2 was formed with faster kinetics than Mg2FeH6 under constant temperature and H2 pressure. Then, β-MgH2 reacted with α-Fe forming Mg2FeH6 in a much slower reaction. Unexpectedly, reaction of hydrogen desorption showed an one-step kinetics, even if Mg2FeH6 and β-MgH2 phases were previously present in the powder.

【 授权许可】

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