快淬Mg2Ni型合金的结构及贮氢动力学

用快淬技术制备Mg2-xLaxNi(x=0,0.2,0.4,0.6)贮氢合金,用XRD,SEM和HRTEM分析合金的微观组织结构;测试合金的气态及电化学贮氢动力学。结果表明:快淬二元Mg2Ni合金具有典型的纳米晶结构,而快淬La替代合金明显地具有非晶结构,La替代Mg提高Mg2Ni型合金的非晶形成能力。La替代Mg明显地改变Mg2Ni型合金的相组成,当x=0.4时,合金的主相改变为(La,Mg)Ni3+LaMg3。快淬及La替代明显影响合金的气态及电化学贮氢动力学,La替代使合金的吸氢动力学先降低后增加,但使合金的气态脱氢及电化学贮氢动力学先增加后降低。快淬对合金气态及电化学贮氢动力学的影响与合金的成分相关,对于La0.4合金,合金的气态吸氢动力学随淬速的增加先增加后减小,其放氢动力学随淬速的增加而增加。

Structure and hydrogen storage kinetics of as-spun Mg2Ni-type alloys

The Mg2-xLaxNi(x=0,0.2,0.4,0.6) alloys were fabricated by melt-spinning technology.The structures of the as-cast and spun alloys were characterized by XRD,SEM and HRTEM.The gaseous and electrochemical hydrogen storage kinetics of the alloys was tested.It is found that the as-spun binary Mg2Ni alloy displays a typical nanocrystalline structure,whereas the as-spun alloys substituted by La exhibit an evident amorphous structure,suggesting that the glass formation of the Mg2Ni-type alloy was facilitated by substituting Mg with La.The results show that substitution of La for Mg visibly changes the phase composition of the alloys.The major phase of the alloys changes to the(La,Mg)Ni3+LaMg3 phases by increasing La content to x=0.4.Both the melt spinning and the La substitution visibly ameliorate the gaseous and electrochemical hydrogen storage kinetics of the alloys.The substitution of La for Mg causes the hydrogen absorption kinetics of the alloy first to decrease and then to increase,but it leads to a contrary action on the hydrogen desorption kinetics and the high rate discharge ability of the alloy.The action of the melt spinning on the hydrogen storage kinetics of the alloy is associated with the chemical composition of the alloy.The hydrogen absorption kinetics of the La0.4 alloy first increases and then decreases with rising spinning rate,whereas its hydrogen desorption kinetics always grows with increasing spinning rate.