Throughout human history, any society’s capacity to fabricate and refine new materials to satisfy its demands has resulted in advances to its performance and worldwide standing. Life in the twenty-first century cannot be predicated on tiny groupings of materials; rather, it must be predicated on huge families of novel elements dubbed “advanced materials”. While there are several approaches and strategies for fabricating advanced materials, mechanical milling (MM) and mechanochemistry have garnered much interest and consideration as novel ways for synthesizing a diverse range of new materials that cannot be synthesized by conventional means. Equilibrium, nonequilibrium, and nanocomposite materials can be easily obtained by MM. This review article has been addressed in part to present a brief history of ball milling’s application in the manufacture of a diverse variety of complex and innovative materials during the last 50 years. Furthermore, the mechanism of the MM process will be discussed, as well as the factors affecting the milling process. Typical examples of some systems developed at the Nanotechnology and Applications Program of the Kuwait Institute for Scientific Research during the last five years will be presented in this articles. Nanodiamonds, nanocrystalline hard materials (e.g., WC), metal-matrix and ceramic matrix nanocomposites, and nanocrystalline titanium nitride will be presented and discussed. The authors hope that the article will benefit readers and act as a primer for engineers and researchers beginning on material production projects using mechanical milling.

Magnesium hydride (MgH₂) holds immense promises as a cost-effective hydrogen storage material that shows excellent storage capacity suitable for fuel cell applications. Due to its slow hydrogen charging/discharging kinetics and high apparent activation energy of decomposition, MgH₂ is usually doped with one or more catalytic agents to improve its storage capacity. So often, milling the metal hydride with proper amounts of catalyst leads to heterogeneous distribution of the catalytic agent(s) in MgH₂ matrix. The present work proposes a cost-effective process for doping Mg powders with Zr₂Ni particles upon ball milling the powders with Zr₂Ni-balls milling media under pressurized hydrogen. Fine Zr₂Ni particles were gradually eroded from the balls and homogeneously embedded into the milled powders upon increasing the ball milling time. As a result, these fine hard intermetallic particles acted as micro-milling media and leading to the reduction the Mg/MgH₂ powders. Meanwhile, Zr₂Ni eroded particles possessed excellent heterogeneous catalytic effect for improving the hydrogenation/dehydrogenation kinetics of MgH₂. This is implied by the short time required to absorb (425 s)/desorb (700 s) 6.2 wt% H₂ at 200 °C and 225 °C, respectively. The as-milled MgH₂ with Zr₂Ni balls possessed excellent cyclability, indexed by achieving continuous 646 cycles in 985.5 h (~1.5 cycle per hour) without serious degradation.

Due to its affordable price, abundance, high storage capacity, low recycling coast, and easy processing, Mg metal is considered as a promising hydrogen storage material. However, the poor de/rehydrogenation kinetics and strong stability of MgH₂ must be improved before proposing this material for applications. Doping MgH₂ powders with one or more catalytic agents is one common approach leading to obvious improving on the behavior of MgH₂. The present study was undertaken to investigate the effect of doping MgH₂ with 7 wt% of amorphous(a)-LaNi₃ nanopowders on hydrogenation/dehydrogenation behavior of the metal hydride powders. The results have shown that rod milling MgH₂ with a-LaNi₃ abrasive nanopowders led to disintegrate microscale-MgH₂ powders to nanolevel. The final nanocomposite product obtained after 50 h–100 h of rod milling revealed superior hydrogenation kinetics, indexed by short time (8 min) required to absorb 6 wt% of H₂ at 200 °C/10 bar. At 225 °C/200 mbar, nanocomposite powders revealed outstanding dehydrogenation kinetics, characterized by very short time (2 min) needed to release 6 wt% of H₂. This new tailored solid-hydrogen storage system experienced long cycle-life-time (2000 h) at 225 °C without obeying to sever degradation on its kinetics and/or storage capacity.

Due to its availability and high storage capacity, Mg is an ideal material in hydrogen storage applications. In practice, doping Mg/MgH₂ with catalyst(s) is necessary in enhancing the de/rehydrogenation kinetics and minimizing both of decomposition temperature and its related apparent activation energy. The present study proposed a new heterogeneous catalytic agent that consisted of intermetallic compound (ZrNi₅)/metal oxide (Nb₂O₅) binary system for using with different concentrations (5−30 wt%) to improve MgH₂. Doping MgH₂ powders with low concentration (5, 7, 10 wt%) of this new catalytic system led to superior absorption/desorption kinetics, being indexed by the short time that is required to absorb/desorb 4.2−5.6 wt% H₂ within 200 s to 300 s. Increasing the doping dose to 15–30 wt% led to better kinetic effect but a significant decrease in the hydrogen storage capacity was seen. The dependent of apparent activation energy and decomposition temperature of MgH₂ on the concentration of ZrNi₅/Nb₂O₅ has been investigated. They tended to be linearly decreased with increasing the catalyst concentrations. The results elucidated the crucial role of catalytic additives on the disintegration of MgH₂ into ultrafine powders (196 nm to 364 nm diameter). The formation of such nanoparticles enhance the hydrogen diffusion and shorten the time that is required for the hydrogenation/dehydrogenation process. Moreover, this refractory catalytic system acted as a grain growth inhibitor, in which Mg/MgH₂ powders maintained their submicron level during the cycle-life-test that was extended to 100 h at 200 °C.

The global interest in MgH₂ is due to the natural availability of Mg and its capacity to retain hydrogen at a concentration of up to 7.60 wt.%. Despite its appealing characteristics and ease of production on an industrial scale at ambient temperature using the reactive ball milling (RBM) technique, MgH₂ is a highly stable chemical with sluggish hydrogenation and dehydrogenation rates below 300 °C. Among the different methods used to improve the hydrogenation/dehydrogenation kinetic behavior of MgH₂, mechanical treatment and/or catalysis are regarded to be the most effective methods. The purpose of this research was to explore the effectiveness of several cold rolling (CR) stages on the hydrogenation properties of recycled magnesium rods, as well as the effect of the resulting RBM on the final product. For this process, the as-received waste Mg-rods were firstly cold-rolled 200 times and then remilled under H₂ atmosphere for 100 h. The as-RBM powders were then cold-rolled for 100 passes and then ball-milled with 10 and 15 wt.% Nb₂O₅ powders for 50 h. The results showed that when the materials were subjected to different types of defects (dislocations, stacking faults, and twining) generated by CR and RBM, their gas absorption/desorption kinetics were improved. This was indexed by their ability to achieve a long cycle lifetime at lower temperatures when compared with the as-received materials. The powders were further improved in terms of kinetics and decomposition temperature upon RBM with Nb₂O₅ for 50 h. The nanocomposite MgH₂/10 wt.% and 15 wt.% Nb₂O₅ exhibit good hydrogen storage capabilities at a comparatively low temperature (225 °C) with a long cycle life that extended from 110 h to 170 h, without serious degradation in storage capacity and kinetics.

Hydrogen has been receiving great attention as an energy carrier for potential green energy applications. Hydrogen storage is one of the most crucial factors controlling the hydrogen economy and its future applications. Amongst the several options of hydrogen storage, light metal hydrides, particularly nanocrystalline magnesium hydride (MgH₂), possess attractive properties, making them desired hydrogen storage materials. The present study aimed to improve the hydrogen storage properties of MgH₂ upon doping with different concentrations of zirconium carbide (ZrC) nanopowders. Both MgH₂ and ZrC were prepared using reactive ball milling and high-energy ball milling techniques, respectively. The as-prepared MgH₂ powder was doped with ZrC (2, 5, and 7 wt%) and then high-energy-ball-milled for 25 h. During the ball milling process, ZrC powders acted as micro-milling media to reduce the MgH₂ particle size to a minimal value that could not be obtained without ZrC. The as-milled nanocomposite MgH₂/ZrC powders consisted of fine particles (~0.25 μm) with a nanosized grain structure of less than 7 nm. Besides, the ZrC agent led to the lowering of the decomposition temperature of MgH₂ to 287 °C and the reduction in its apparent activation energy of desorption to 69 kJ/mol. Moreover, the hydrogenation/dehydrogenation kinetics of the nanocomposite MgH₂/ZrC system revealed a significant improvement, as indicated by the low temperature and short time required to achieve successful uptake and release processes. This system possessed a high capability to tackle a long continuous cycle lifetime (1400 h) at low temperatures (225 °C) without showing serious degradation in its storage capacity.