Investigation on the synthesis, characterization and hydrogenation behaviour of new Mg-based composite materials Mg-x wt.% MmNi_(4.6)Fe_(0.4) prepared through mechanical alloying

摘要

Alloys with general formula Mg-x wt.%MmNi_(4.6) Fe_(0.4) have been successfully synthesized throughball milling employing a high energy attritor mill. The ball millinghas been done in hexane medium; various time durations andspeeds (rev. /min) have been employed. The hydrogenation anddehydrogenation behaviour of these new composite materials havebeen extensively investigated. The as-prepared (ball milled:mechanically alloyed) composite materials have been activated at400+-10 deg C under a hydrogen pressure of 40 kg cm~(-2). Thesecomposite materials have been found to possess one of the highestknown storage capacities. It has been found that the highest storagecapacity material ~5.0 wt.% at 350 deg C) corresponds to Mg-30wt. % MmNi_(4.6)Fe_(0.4). The said alloy exhibits fastabsorptiondesorption kinetics (about 80 cm~3 mm~(-1). It is alsoestablished that the optimum mechanically alloyed samples forhydrogen storage were obtained with milling at 400 rev. /minspeed and time duration of 5 h. The hydriding rate and theimproved hydrogen storage capacity of these composite materialshave been found to be strongly correlated with the structural andmicrostructural characteristics as brought out through XRD andSEM techniques. For example, the ball milled samples havingoptimum hydrogenation characteristics exhibited highly uniformparticle size distribution.