Hydrogen induced amorphization of LaMgNi4 phase in metal hydride alloys

Abstract

Available online xxxKeywords: Hydrogen absorbing alloys Hydrogen induced amorphization Metal hydride electrode Transmission electron microscope Re-crystallization a b s t r a c t Hydrogen induced amorphization (HIA) of the LaMgNi 4 phase at 30 C was found in three LaMgNi 4 /LaNi 5 two-phase metal hydride (MH)-forming alloys. The amorphizationhappened at the first dehydrogenation cycle from a fully hydrided alloy, and the process is reversible after annealing at 250 C for 1 h. The hydrogen storage capacity of the LaMgNi 4 phase in an amorphous state is higher than in its crystalline form. A scanning electron microscope study did not observe any significant changes in the shape of grains as a consequence of HIA and re-crystallization. A transmission electron microscope study confirmed the amorphous structure of the LaMgNi 4 phase after HIA. These findings suggest a new way to improve the performance of MH alloys when used in electrochemical applications.

The Effect of Y Content on Structural and Sorption Properties of A2B7-Type Phase in the La–Y–Ni–Al–Mn System

“…Previous studies have shown that by performing multiple substitutions of both the A element, and the B elements, the stability of the structure during cycling and storage capacities are affected [12][13][14][15]. It has been found that by substituting Mg for La in rareearth (RE) superlattice based A 2 B 7 -type metal hydrides, it is possible to achieve a higher storage capacity (compared to commercial AB 5 -type alloys), a lower self-discharge if used in batteries and improved cycle stability by preventing the occurrence of hydrogen-induced amorphization (HIA), when compared to pure La 2 Ni 7 [12,[16][17][18][19][20][21][22].…”