A Comprehensive Review on Hydrogen Absorption Behaviour of Metal Alloys Prepared through Mechanical Alloying

Abstract

Hydride-forming alloys are currently considered reliable and suitable hydrogen storage materials because of their relatively high volumetric densities, and reversible H2 absorption/desorption kinetics, with high storage capacity. Nonetheless, their practical use is obstructed by several factors, including deterioration and slow hydrogen absorption/desorption kinetics resulting from the surface chemical action of gas impurities. Lately, common strategies, such as spark plasma sintering, mechanical alloying, melt spinning, surface modification and alloying with other elements have been exploited, in order to overcome kinetic barriers. Through these techniques, improvements in hydriding kinetics has been achieved, however, it is still far from that required in practical application. In this review, we provide a critical overview on the effect of mechanical alloying of various metal hydrides (MHs), ranging from binary hydrides (CaH2, MgH2, etc) to ternary hydrides (examples being Ti-Mn-N and Ca-La-Mg-based systems), that are used in solid-state hydrogen storage, while we also deliver comparative study on how the aforementioned alloy preparation techniques affect H2 absorption/desorption kinetics of different MHs. Comparisons have been made on the resultant material phases attained by mechanical alloying with those of melt spinning and spark plasma sintering techniques. The reaction mechanism, surface modification techniques and hydrogen storage properties of these various MHs were discussed in detail. We also discussed the remaining challenges and proposed some suggestions to the emerging research of MHs. Based on the findings obtained in this review, the combination of two or more compatible techniques, e.g., synthesis of metal alloy materials through mechanical alloying followed by surface modification (metal deposition, metal-metal co-deposition or fluorination), may provide better hydriding kinetics.

Ni0.6Zn0.4O Synthesised via a Solid-State Method for Promoting Hydrogen Sorption from MgH2

“…Ali et al [ 56 ] introduced CoTiO 3 to MgH 2 and showed that the particle size of the composite changed to a finer and smaller size. According to the research results of Somo et al [ 63 ], smaller particle sizes allow quick dissociation into the surface of materials. Besides that, the addition of Nb to MgH 2 creates a large number of hydrogen diffusion channels and speeds up hydrogen flow along the MgH 2 /Mg interfaces, continuing to improve the sorption kinetics of MgH 2 [ 64 ].…”

Designing an AB2-Type Alloy (TiZr-CrMnMo) for the Hybrid Hydrogen Storage Concept

“…The loss of hydrogen capacity of the material after the grinding process was ascribed to these amorphous-like structures, where hydrogen cannot be placed. Somo et al reported in a review about mechanical milling applied to metal alloys that as-milled alloys are more prone to oxide layer formation, hindering the fast hydrogen absorption, and in several cases, diminishing the capacity [74]. Hence, a non-energetic mixing procedure was chosen as the most feasible method for laboratory and larger scales.…”

Mechanical Alloying: Processing and Materials

“…A second article revises the hydrogen absorption behavior and the absorption/desorption kinetics of metal hydrides produced by mechanical alloying [8]. It is a critical overview on the effect of mechanical alloying in binary (CaH 2 , MgH 2 , etc.)…”