Effect of RE Content on Microstructure and Hydrogen Storage Properties of Mg-RE-based Alloys
In order to investigate the influence of RE(La and Ce)and Ni content on the microstructure and hydrogen storage performance of magnesium-based alloys,Mg90NixRE10-x(x=4,5,6)alloys are prepared using induction melting.The alloys are characterized and tested by XRD,SEM,EDS,and PCT.The results reveal that the alloy consists of phases of Mg,Mg2Ni,CeMg12,Ce2Mg17,LaMg12,and La2Mg17.After hydrogen absorption,MgH2,Mg2NiH4,CeH2.29,and LaH3.05 pha-ses are formed,while the phases after hydrogen desorption include Mg,Mg2 Ni,CeH2,and LaH2.The results of hydrogen ab-sorption and desorption kinetic test show that the optimal ratio of RE to Ni elements in the alloy is 1∶1,while the activation performance and hydrogen storage capacity are best.The maximum hydrogen absorption and desorption capacities are 5.21％and 5.19％(Mass fraction),respectively.The in situ formed REHx and Mg2Ni/Mg2NiH4 phase have synergistic catalyst effect on hydrogen transport in the alloy.The Mg90Ni5RE5 alloy exhibits the lowest activation energy during hydrogen desorp-tion reaction of 87.14 kJ/mol.Entropy change(ΔH)of the alloys,which are calculated by using the PCT data and the Van't Hoff equation,have no significant relationship with the RE content.
magnesium-based hydrogen storage alloyrare earthmicrostructurehydrogen absorption and desorption ki-neticsthermodynamics
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