Solid-state conversion of magnesium waste to advanced hydrogen-storage nanopowder particles

Recycling of metallic solid-waste (SW) components has recently become one of the most attractive topics for scientific research and applications on a global scale. A considerable number of applications are proposed for utilizing metallic SW products in different applications. Utilization of SW magnesium (Mg) metal for tailoring high-hydrogen storage capacity nanoparticles has never been reported as yet. The present study demonstrates the ability to produce pure Mg ingots through a melting and casting approach from Mg-machining chips. The ingots were used as a feedstock material to produce high-quality Mg-ribbons, using a melting/casting and spinning approaches. The ribbons were then subjected to severe plastic deformation through the cold rolling technique. The as-cold roll Mg strips were then snipped into small shots before charging them into reactive ball milling. The milling process was undertaken under high-pressure of pure hydrogen gas (H₂), where titanium balls were used as milling media. The final product obtained after 100 h of milling showcased excellent nanocrystalline structure and revealed high hydro/dehydrogenation kinetics at moderate temperature (275°C). The present study shows that primer cold rolling of Mg-strips before reactive ball milling is a necessary step to prepare ultrafine magnesium hydride (MgH₂) nanopowders with advanced absorption/desorption kinetics behavior. These ultrafine powders with their nanocrystalline structure are believed to play an important role in effective gas diffusion process. Moreover, the fine titanium particles came from the ball-powder-ball collisions and introduced to the Mg matrix have not only acted as micro-scaled milling media, but they played a vital catalyzation role for the process.