Deuterium thermal desorption from Ni-rich deuterated Mg thin films

A mechanically switchable metal–insulator transition in Mg2NiH4 discovers a strain sensitive, nanoscale modulated resistivity connected to a stacking fault

“…This was supported by observing that red cubic "single crystals" consisting of multiple twins with cubic symmetry, grown at temperatures above 510 K, relaxed back to the monoclinic phase when crushed into a fine powder. A similar cubic phase has also been reported by groups who worked with different forms of ball milled Mg 2 NiH 4 powders [22], ultra high pressure treated powders (up to 5.6 GPa) and thin film materials [23][24][25][26][27]. It needs to be understood why the conventional monoclinic low temperature phases under certain conditions are not formed.…”

Hydrogenography of Mg Ni1−H gradient thin films: Interplay between the thermodynamics and kinetics of hydrogenation

“…Ouyang et al [54] recently calculated that, if Mg and Mg 2 Ni grains are assumed to be spheres with an average diameters of 40 and 20 nm, the enthalpy of the eutectic metallic alloy, and hence the hydrogenation reaction, will be destabilized by 5 kJ (mol H 2 ) À1 by the extra interfacial energy. This mixing effect, also observed by thermal desorption spectroscopy [55], probably explains most of the increase in enthalpy observed as one approaches the eutectic composition.…”

Catalysis and evolution on cycling of nano-structured magnesium multilayer thin films

“…Similarly, figure 2 shows diffraction patterns taken for the three thin film samples in their hydrogenated state after 60 cycles of hydrogenation and dehydrogenation. It is clearly visible that the samples have all undergone similar changes in their microstructure, evident by the emergence of β-magnesium hydride and Mg 6 Pd phases in all three samples. In the two catalysed samples there is also evidence of crystalline phases of BCC chromium (Mg/Cr) and BCC vanadium (Mg/V) and all three samples exhibit traces of unreacted magnesium as well as magnesium oxide.…”

“…Many attempts have been made to reduce the temperatures required to reversibly store hydrogen in magnesium-based materials including the addition of transition metals and their oxides to form catalysed structures resulting in faster kinetics at lower temperatures including a range of systems using thin film techniques to incorporate these catalysts into the magnesium-based material. Examples include systems of Mg-Pd [1,2] Mg-Ti [3,4] and Mg-Ni [5,6]. Previous work [7] has shown improved kinetics for a magnesium-based multilayer system catalysed by a nickel-rich transition metal mix.…”