Phase Structure And Hydrogen Storage Properties Of REMg_8.35Ni_2.18Al_0.21（RE=La,Ce,Pr,Nd） Alloys

A series of Rare earth–Mg–Transitional metal elements based multiphase hydrogenstorage alloys REMg_8.35Ni_2.18Al_0.21（RE=La, Ce, Pr, Nd） are prepared by inductivemelting. The phases structure and hydrogen storage property of these alloys with differentRare earth are investigated in this paper. In order to further improve the hydrogen storageproperties of CeMg_8.35Ni_2.18Al_0.21alloy，the CeMg_8.35Ni_2.18Al_0.21+10wt.%TiF₃are prepaidand its hydriding/dehydriding characteristics are investigated.XRD and SEM show that the alloys are composed of multiphase including Mg₂Ni,（La, Pr, Nd）Mg₂Ni,（La, Ce）2Mg17,（Ce, Pr, Nd）Mg₁₂and Ce₂Ni₇phases. In the hydridingprocess, these phases decompose into Mg₂NiH4, MgH₂and REHxphases including LaH₃,CeH_2.51, PrH₃and NdH₃phases. After the dehydriding process, Mg₂NiH4and MgH₂phases give out hydrogen and change into Mg₂Ni and Mg phases respectively. The CeH_2.51phase transform into CeH_2.29phase, but LaH₃, PrH₃and NdH₃phases do not change. TheLaMg_8.35Ni_2.18Al_0.21alloy has the highest reversible hydrogen storage capacity. ThePrMg_8.35Ni_2.18Al_0.21alloy shows the highest hydrogen absorption rate and its hydrideshows the highest dehydriding plateaus. The reversible hydrogen storage property ofRE–Mg–Ni alloy is improved by the substituting La for Ce, Pr and Nd among which theCeMg_8.35Ni_2.18Al_0.21alloy shows the best performance. The lowest onset hydrogendesorption temperature for CeMg_8.35Ni_2.18Al_0.21hydride is464K which is114.02K lowerthan that of the LaMg_8.35Ni_2.18Al_0.21hydride, say CeMg_8.35Ni_2.18Al_0.21have the besthydrogen desorption properties.The ball-milled CeMg_8.35Ni_2.18Al_0.21+10wt.%TiF₃exhibit higher hydriding anddehydriding plateaus than the simply ball-milled CeMg_8.35Ni_2.18Al_0.21alloy and the ratio ofthe hydrogen desorption to hydrogen absorption of the CeMg_8.35Ni_2.18Al_0.21+10wt.%TiF₃alloys can reach to100%. TiF₃can improve the hydrogen absorption rate and lower theinitial desorption temperature of the hydrides.