Nanostructured MgH2 obtained by cold rolling combined with short-time high-energy ball milling

Abstract

MgH 2 was processed by short time high-energy ball milling (BM) and cold rolling (CR). A new alternative processing route (CR + BM) using the combination of CR followed by short time BM step was also applied. The effects on the final morphology, crystalline structure and H-sorption properties were evaluated. The CR + BM processing (compared to BM and CR process) resulted in an inhomogeneous particle size distribution and the biggest crystallite size of MgH 2 , showing that there is a clear dependence between the size/shape of the particles which compose the starting material and the efficiency of crystallite size reduction during the BM process. On the other hand, we observed that a short BM step improved the kinetic properties of the cold rolled material. It shows that the particle size reduction of MgH 2 obtained by CR combined with the increase in specific surface area attained by short BM step could be key factors to allow the use of the CR + BM route.

Impact of severe plastic deformation on kinetics and thermodynamics of hydrogen storage in magnesium and its alloys

“…Intensive cold rolling was effectively used to refine the microstructure and disperse the particles of catalysts. Intensive rolling was used to process mixtures of MgH2-Fe as an alternative to reach the grain size reduction typically obtained by ball milling [79,80]. Cold rolling of commercial MgH2 was considered equivalent to ball milling in terms of microstructure refinement [81], as also observed for Mg-LaNi5 composites [82].…”

Mechanochemistry of Metal Hydrides: Recent Advances

“…The effects of CR on magnesium and its alloys have been extensively studied [157,200,201,202,203,204,205,206,207,208,209,210,211,212,213,214,215,216,217,218,219,220,221,222,223,224,225,226,227]. One reason is that magnesium has a high hydrogen storage capacity (7.6 wt%).…”

Hydrogen Storage in Mg and Mg-Based Alloys and Composites Processed by Severe Plastic Deformation

“…The results indicated that cold rolling could be equivalent to ball milling in terms of microstructural refinement, a result, which already had been observed by other research groups. 3) Extensive CR and cold forging (CF) of MgH 2 Fe mixtures 6,7) were also very effective in decreasing the crystallite sizes to the nanometric range and in assuring a relatively homogeneous distribution of Fe particles resulting in compacted flakes. Activation was slow in the as deformed flakes but improved significantly with additional short time milling, most likely due to the creation of cracks or new surfaces, in the flakes.…”