On the synthesis, characterization and hydrogenation behaviour of Mg-based composite materials Mg-x wt.% CFMmNi5 prepared through mechanical alloying

The present study deals with the investigations on the synthesis, structural/microstructural characteristics and hydrogenation/dehydrogenation behaviour of Mg-bearing composite materials Mg- x wt.% CFMmNi 5 prepared through mechanical alloying. The composite materials Mg- x wt.% CFMmNi 5 have been successfully synthesized through ball-milling (mechanical alloying) by employing a high energy attritor mill. The mechanical alloying has been carried out in hexane medium by varying the milling parameters say, speed (revolutions per minute) and milling duration. The as-milled composite materials have been activated at 400±10°C under a hydrogen pressure of ∼35–40 kg cm −2 . These composite materials exhibit high hydrogen storage capacity and fast absorption/desorption kinetics in comparison to the thermally melted counterparts. It has been found that the highest storage capacity material (∼5.4 wt.% at 350°C) corresponds to Mg-30 wt.% CFMmNi 5 . The composite material also exhibits fast desorption kinetics (about 90 cm 3 min −1 ), which is at least two times faster than conventionally prepared (RF melting) alloys. The highest hydrogen storage capacity and fast kinetics were obtained for the mechanically alloyed samples with the optimized milling conditions, i.e. speed ∼400 rev min −1 and time duration of 5 h. The hydriding rate and the improved hydrogen storage capacity of these composite materials have been found to be strongly correlated with structural and microstructural characteristics as brought out through XRD and SEM techniques. The uniform particle size distribution and interfacial grain boundaries explored from the SEM investigations paves the way for better hydrogen storage capacity and fast absorption and desorption kinetics.