Nanostructured rapidly solidified LaMg_(11)Ni alloy:Microstructure, crystal structure and hydrogenation properties

摘要

In our earlier publication (Poletaev et al.,) Alloys Compd., 509S (2011) S633) we reported a drastic variation of the structural and hydrogenation properties of LaMg_(-12) intermetallic alloy caused by Rapid Solidification (RS). In present work we have probed the effect of nickel during the chemical modification of LaMg_(12), in combination with RS, on the structure, microstructure and hydrogen absorption-desorption properties of the alloys. RS was performed at three solidification rates, 300-2000 rpm. Ni was found to form a solid solution replacing both La and Mg to yield La_(1.7)Mg_(16.7)Ni_(0.6) intermetallic. With increasing RS cooling rates, the very fine, almost amorphous microstructures were formed. The LaMg_(11)Ni alloy solidified at the highest cooling rate exhibited the fastest hydrogenation kinetics, reaching maximum hydrogenation capacity of 5.02 wt. % H. Studies of the hydrogenated RS ribbons showed the formation of the nano-scale embryos of MgH_2, growing to form polyhedral grains of magnesium dihydride.