Phase structure and hydrogen absorption property of LaMg 2Cu

Abstract

LaMg 2Cu alloy was prepared by inductive melting and then was annealed at 723 K for 10 h in 0.1 MPa argon atmospheres. X-ray diffraction (XRD) and scanning electron microscopy (SEM) showed that the alloy consisted of LaMg 2Cu 2 phase, LaMg 3 phase and a few of unknown phases. The annealing treatment improved the equilibrium pressure and hydrogen absorption capacity of LaMg 2Cu alloy. The hydrogen absorption capacity of the as-cast and annealed alloys at 473 K were 2.86 and 3.33 wt.%, and the equilibrium pressure were 1 and 3 MPa, respectively. The enthalpy and entropy of LaMg 2Cu–H hydriding reaction were determined. LaMg 2Cu alloy could absorb hydrogen with rapid hydriding kinetics, the hydrogen absorption rate of LaMg 2Cu increased from 423 K to 498 K and the uptake time for hydrogen content to reach 90% of the maximum storage capacity for annealed alloy was less than 550 s at 498 K. The experimental curves of hydrogen absorption kinetics could be fitted with good accuracy by Jander equation. It suggested that the hydriding of LaMg 2Cu alloy was a three-dimensional diffusion-controlled process. And the activation energy and pre-exponential factor of LaMg 2Cu alloy were also calculated.