AB3型合金的贮氢特性

AB3型合金的贮氢特性　　Storing hydrogen by solid-state material is a very attractive manner since it allows for safe storage.However,the gravimetric hydrogen density of this manner is too low for mobility and transport applications,many efforts have therefore been made to develop new materials with higher energy density and better kinetic behavior.For instance,in search for new metal hydrides,recent attention has been dedicated to the family of AB3-type intermetallics.In general,AB3-type intermetallics crystallize either in the PuNi3-type rhombohedral Ring neodymium magnet structure(R-3m space group) or in the hexagonal CeNi3-type structure(P63/mmc space group),but with the difference in the long-range stacking arrangement only.The PuNi3-type rhombohedral structure can be considered as alternating stacking of AB5 (CaCu5,Haucke phase) and AB2(MgZn2,Laves phase) subunits.Nevertheless,the experimental studies on AB3-type intermetallics reveal that the reversibility in hydrogen storage is rather poor.The underlying mechanism responsible for this is not yet well understood,but indispensable for further improvement in performance. Considering the structural feature,we assume that these may be related to the AB2 subunit in AB3-type crystal structure.
　　To prove this assumption,in this paper,the hydrogen storage behaviors of AB3-type intermatallics were systematically studied and compared with those of AB2-type ones. First,various AB3- and AB2-type intermatallics were designed and prepared by changing the element for the A-side from La,Ce to Y,while that for the B-side was fixed as Ni(called as ANi3 and ANi2 samples hereafter).These samples were then subjected to the hydrogen absorption/desorption cycling under hydrogen gas and the electrochemically hydrogen charging/discharging in alkaline solution,respectively. Finally,the relevance of hydrogen storage properties of ANi3 intermetallics to the ANi2 subunits http://www.chinamagnets.biz in their crystal structures was discussed,based on the experimental results. The main results achieved in this paper are given as below:The ANi3 and ANi2 samples with nominal compositions,LaNi3,CeNi3,YNi3, LaY2Ni9,CeY2Ni9,LaNi2,CeNi2 and YNi2,were prepared by induction melting.The phase components of each sample were checked by X-ray diffraction(XRD),and the diffraction patterns were further analyzed by the Rietveld refinement method to obtain the lattice and structural parameters of the main phases.The results showed that the as-prepared ANi3 samples crystallized in the PuNi3-type structure(R-3m space group), except CeNi3 in the CeNi3-type structure(P63/mmc space group).For the ternary intermetallics LaY2Ni9,most of the La atoms lay on site 3a and Y atoms on site 6c; while CeY2Ni9 had a randomly distribution of Ce and Y over the two sites.In the solid-H2 reaction,all the ANi3 samples underwent hydrogen-induced amorphization(HIA) to some extent,and the tendency of HIA could be described in the order YNi3/LaY2Ni9