There are many hydrogen storage alloys, but the MmNi(5) family of alloy is of great importance as it has good properties for technological uses like hydrogen capacity, plateau pressure, repeatability and Ease of activation. In the present paper we describe the hydrogen absorption mechanism of two samples of MinNi(4.5)Al(0.5), having two different misch metal compositions. Sample-I with misch metal composition (Ln 20%, Cc 52%, Nd 15% and Pr 11%) and sample-2 with misch metal composition (Ln 9.17%, Cc 17.43%, Pr 1.86% Nd 5.34%). These two different samples have variation of composition of misch metals in MmNi(4.5)Al(0.5). The absorption decomposition cycles in these two samples have been studied in the re,temperature range from room temperature (30 degrees C) to 85 degrees C. H/M ratio of these samples was measured using volume displacement method. It was found that H/M M ratio for two samples have slight difference and it varies from .06 to 0.8 in sample-1, while for sample-2 from .08 to 1.0 showing it has batter composition of misch metal for hydrogen storage. The H/M for sample-I becomes 0.8 at 80 psi of the hydrogen pressure while sample-2 it attains a value of 1.0 at 30 psi. The time taken for activation of sample-2 was found to be small compared to sample-1 and the plateau in pressure in sample-2 was found to be lower than sample-1, Therefore sample-2 has better hydrogen absorption-desorption properties and hence it is better for technological uses of hydrogen energy.
