Substitution effect of Hf on hydrogen storage capacity and cycling durability of Ti_(23)V_(40)Mn_(37) metal hydride alloys

摘要

In order to improve the hydrogen storage capacity and cycle durability, hafnium (Hf) is used to partial substitute for Ti in Ti23V40Mn37 alloy. Microstructure, hydrogen storage properties and their relationship have been investigated systematically. The results show that Ti23-xHfxV40Mn37 (x = 0, 2 and 4) alloys are consisted of BCC and C14 Laves phases. With increasing of Hf content, the ratio of C14 Laves phase increases. The hydrogen desorption capacity of Hf substituted alloys is improved significantly, and it reaches the value of 1.88 wt% at 293 K when the composition is Ti19Hf4V40Mn37. Effective hydrogen storage capacities decrease to 89.1% and 93.3% of their initial values after 20 cycles for 2 and 4 at.% Hf substituted alloys, respectively. The alloy with 4 at.% Hf substitution has the better cycle durability, which is caused by more V element solid solution in BCC phase. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.