Kinetics and thermodynamics of near eutectic Mg-Mg2Ni composites produced by casting process

Nanocrystalline Mg2Ni for Hydrogen Storage

“…Despite the high hydrogen content of MgH 2 , the main limiting factors of such hydrides as hydrogen storage material are: (a) poor kinetics of hydrogenation and dehydrogenation reactions, (b) high desorption temperature (>350 °C), and (c) sensitivity to atmospheric oxygen [23] . The slow hydrogenation reaction is due to slow dissociation rate of hydrogen molecules on the Mg surface and the formation of thick oxides/hydroxides surface layers caused by the strong affinity of Mg to oxygen [24], [25]. In fact, metallic Mg does not react with hydrogen at all at low temperatures and reacts only very slowly at high temperatures.…”

“…Tremendous research efforts were devoted to tackling the reactions kinetic limitations of Mgbased alloys. It was reported that such slow kinetic behaviour can be alleviated by adopting different approaches such as i) nano-structuring or nanocrystallization of Mg, ii) introducing the catalyst into the Mg system, and iii) altering the stability of the hydride phases either mechanically, via using severe plastic deformation techniques, or thermodynamically [25].…”

“…Transition metals, such as Ni, Co and Fe, have been employed widely to enhance the sorption kinetics of magnesium-based alloys due to their catalytic effect on the hydrogen dissociation and diffusion, good hydrogen gravimetric density and excellent reversible hydrogen absorption properties [25]. Such metals were used to form the Mg-based ternary hydrides such as Mg 2 NiH 4 , Mg 2 CoH 5 , and Mg 2 FeH 6 .…”

Calorimetric Studies of Magnesium-Rich Mg-Pd Alloys

“…To overcome these difficulties, small amounts of additives are added to magnesium to create magnesium compounds, which, in relation to pure Mg, improves the unfavorable thermodynamics and sometimes the kinetics of the reaction [ 8 ]. Significant improvements were made in this field in order to modify the thermodynamics of Mg-based systems starting more than 50 years ago [ 9 , 10 ], but the research is in this area is continuing, including alloying with transition [ 11 , 12 , 13 , 14 , 15 , 16 , 17 ] catalysts [ 18 , 19 ], complex hydride additives [ 20 ], and even mechanical processing [ 21 , 22 , 23 ]. It has been indicated that the addition of noble metals, such as palladium or silver, can enhance the storage properties of magnesium [ 16 , 24 , 25 , 26 , 27 ].…”

Fabrication of Multiple-Phase Magnesium-Based Hydrides with Enhanced Hydrogen Storage Properties by Activating NiS@C and Mg Powder

“…Furthermore, the MgS phase existed and remained unchanged during the de/hydrogenation cycles, indicating the role of the catalyst in the system. Notably, the Ni phase was detected after hydrogenation, which theoretically would react with Mg to form the Mg 2 Ni phase according to the Mg−Ni binary phase diagram 43. It was suspected that during the hydrogenated process, some of the diffused Ni atoms integrated with Mg atoms to form the Mg 2 Ni phase, and the remaining scattered Ni atoms would not further react with Mg atoms due to the impediment of the newly generated MgS phase.…”