Investigations of synthesis and characterization of MmNi4.3Al0.3Mn0.4 and MmNi4.0Al0.3Mn0.4Si0.3, hydrogen storage materials through thermal and spin melting processes

The present study deals with investigations on the synthesis and characterization of negative electrode material for high energy density Ni-MH battery. The hydrogen storage material (MH) has been synthesized through thermal and spin melting techniques. A comparative study of materials synthesized by these two techniques with emphasis on the characteristics relevant to battery electrode applications has been carried out. In the present study, the modified composition of AB(5)-type corresponds to the spin as well as thermal melted versions of MmNi(4.3)Al(0.3)Mn(0.4) and MmNi(4.0)Al(0.3)Mn(0.4)Si(0.3). Structural characterization has revealed that, whereas for the spin melted MmNi(4.3)Al(0.3)Mn(0.4) the dominant growth is perpendicular to the c-axis, it is parallel to the c-axis for MmNi(4.0)Al(0.3)Mn(0.4)Si(0.3). The hydrogenation behaviour of these materials has been monitored through P-C-T and kinetic curves. Attempts have been made to establish a correlation between the structure and hydrogenation behaviour. The spin melted material (MmNi(4.3)Al(0.3)Mn(0.4)) exhibits reduced pulverization and hence is expected to have increased cycle life. This version of the material also exhibits higher storage capacity, faster kinetics and faster activation as compared to the conventionally prepared bulk form. The bulk version of the alloy with silicon has been found to undergo easy activation (2nd cycle) as compared to the bulk version of the alloy without silicon (6th cycle). The spin melted version of the material with silicon leads to smaller (finer) particle size material compared to the alloy form without silicon. (C) 1997 International Association for Hydrogen Energy.