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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 is a 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 subjected to mechanical activation. Analysis of the obtained thermodynamic and structural data allows us to consider the mechanically activated LaNi 4.8 Al 0.2 as the most appropriate for low-pressure and low-temperature application in the hydrogen separation composite membranes. La 0.7 Ce 0.3 Ni 4.5 Cu 0.5 and LaNi 5 with maximum activation treatment of 3 min are more promising for use at elevated pressures. • Effect of short mechanical activation on AB 5 -type alloys was studied. • Unit cell remains unaffected after MA. • Absorption capacity, isotherm plateau length and lattice volume expansion decrease. • The most appropriate compositions for metal-polymer membranes are suggested. [ABSTRACT FROM AUTHOR]

The first cycles of hydrogen absorption-desorption in LaNi5-H2 and LaNi4.5Cu0.5-H2 systems were studied using Tian-Calvet differential heat-conduction microcalorimetry, volumetric measurements, and powder X-ray diffraction. The diffraction profiles were analyzed, and the microstructure characteristics of the LaNi5 and LaNi4.5Cu0.5 systems at different stages of activation were determined. The pressure-composition isotherms were plotted, and the enthalpies of phase transitions α→β and β→α were calculated. The effect of substitution on the change in the thermodynamic parameters and microstructure characteristics of the hydride-forming intermetallic compounds during activation was shown. [ABSTRACT FROM AUTHOR]