Structure and hydrogenation features of mechanically activated LaNi5-type alloys

The effect of short-term mechanical activation in a ball mill on the thermodynamics of interaction with hydrogen and the structure of intermetallic and hydride phases was studied for a series of AB(5) type alloys from the standpoint of their use as filler in metal-polymer membranes. It was found that the activation processing leads, as expected, to a decrease in the size of coherent scattering domains and an increase in the lattice strain, while the phase composition and unit cell parameters remain unaffected. Despite this, there isa significant change in the pressure-composition isotherms, a reduction of the total capacity ad the plateau region. XRD study of the hydride phases evidences smaller volume expansion of the intermetallic crystal lattice at hydrogen absorption for the alloys sub-jected to mechanical activation. Analysis of the obtained thermodynamic and structural data allows us to consider the mechanically activated LaNi4.8Al0.2 as the most appropriate for low-pressure and low-temperature application in the hydrogen separation composite membranes. La0.7Ce0.3Ni4.5Cu0.5 and LaNi5 with maximum activation treatment of 3 min are more promising for use at elevated pressures. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Short-term mechanical activation in a ball mill can significantly change the pressure-composition isotherms, lattice strain, and coherent scattering domain size of alloys, while reducing the volume expansion of certain alloy lattices. The study shows that mechanically activated alloys have different application potentials, allowing for the selection of appropriate materials based on various pressure and temperature requirements.