Decaying behaviors of V40(TiCr)51Fe8Mn hydrogen storage alloys with different particle sizes

Abstract The decaying behaviors of V 40 (TiCr) 51 Fe 8 Mn 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).