Phase transformations of Mg2NiH4 at high-pressure thermal treatment

Rönnebro, Ewa; Fukai, Yuh; Yamamoto, Souichi; Sakai, Tetsuo

doi:10.1016/j.jallcom.2004.03.136

Cited by 11 publications

(9 citation statements)

References 16 publications

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“…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.…”

Section: Discussionsupporting

confidence: 68%

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

Lelis

Milčius

Wirth

et al. 2010

Journal of Alloys and Compounds

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Section: Discussionsupporting

confidence: 68%

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

Lelis

Milčius

Wirth

et al. 2010

Journal of Alloys and Compounds

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“…Previous studies on bulk Mg 2 NiH 4 (LT) have established that the compression under 1.3 to 2.0 GPa induces the transformation from LT structure into the pseudo-cubic HT form at room temperature. 30,31 This similarity suggests a nanosized / nanoconfined effect in the Mg 2 NiH 4 hydride. At nanoscale, thermodynamic description must take into account the interfacial energy or surface energy that contributes as an induced additional pressure increasingly important with decreasing the particle size.…”

Section: Discussion a Synthetic Reactionsmentioning

confidence: 80%

Tunable synthesis of (Mg–Ni)-based hydrides nanoconfined in templated carbon studied by in situ synchrotron diffraction

et al. 2013

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The formation of ultra-small Mg-based particles nanoconfined into the mesopores of a carbon template was studied by in situ synchrotron diffraction. Either Mg 2 Ni or Mg 2 NiH 4 nanoparticles can be directly formed starting from separate Ni and MgH 2 species by tuning the H 2 pressure. Both ultra-small Mg 2 Ni and Mg 2 NiH 4 nanoparticles (~4 nm) are extremely stable against coalescence during hydrogen sorption cycling and prolonged exposure to high temperature as compared to Mg and MgH 2 nanoparticles that show severe coalescence under same experimental conditions. The structural transition reported in bulk Mg 2 NiH 4 from high temperature cubic to low temperature monoclinic structure is no longer observed for the nanoconfined particles. Hydrogen absorption/desorption in nanosized Mg 2 Ni is reversible and desorption kinetics from Mg 2 NiH 4 proceeds very quickly (~5 min) even at 483 K. On the contrary, the thermodynamics properties are not altered by nanoconfinement. This study opens new routes for successful nanoconfinement of stoichiometric hydrides into the pores of carbon hosts along with a better understanding of nanochemistry.

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“…However, Mg-rich compositions in Mg-Ni have not been explored well using high pressure. On the other hand, Mg 2 Ni can hydrogenate to Mg 2 NiH 4 , as mentioned above [1], and some novel hydrides such as Mg 2 Ni 3 H 3.4 [14,15], MgNi 1.02 H 2.2 [16] and Mg 2 NiH 4 [17] were synthesized under GPa pressure. However, it is known that MgNi 2 does not form hydrides under conventional hydrogenation conditions.…”

Section: Introductionmentioning

confidence: 99%