Decaying behaviors of V-40(TiCr)(51)Fe8Mn hydrogen storage alloys with different particle sizes

摘要

The decaying behaviors of V-40(TiCr)(51)Fe8Mn hydrogen storage alloys with different particle sizes from -60 to -500 meshes were investigated systematically in this work. XRD results indicated that particle sizes of the alloys affect little on the phase transformation from Body-centered Cubic (BCC) to Body-centered Tetragonal (BCT) before and after hydrogenation and dehydrogenation, respectively. The hydrogen desorption capacities of the alloys decrease with increasing the number of hydrogen absorption-desorption cycles, but their decaying rates can be obviously restrained as starting particle sizes change from -60 down to -400 meshes. Data fitting showed that the variation of the hydrogen desorption capacity has a similar exponential rule to cycle numbers as that of the micro-strain in the alloys. Possible reasons of the capacity decay are discussed. However, a superfine alloy with -500 meshes showed much larger decaying rate, which was possibly attributed to the poisoning of foreign gases. Generally speaking, the smaller the particle size, the less the micro-strain in the lattice. Namely, the alloy powders with finer sizes have less micro-stress and correspondingly better cycling stability (within -400 meshes in this work). (C) 2015 Published by Elsevier B.V.