Rich magnesium ternary compound so-called LaCuMg<sub>8</sub> derived from La<sub>2</sub>Mg<sub>17</sub>. Structure and hydrogenation behavior
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en
Article de revue
Ce document a été publié dans
Intermetallics. 2011, vol. 19, n° 3, p. 336-341
Elsevier
Résumé en anglais
The magnesium metal rich composition La<sub>10</sub>TM<sub>10</sub>Mg<sub>80</sub> (with TM = Ni and Cu) were synthesized from the elements in sealed tantalum tubes in an induction furnace. The results show differences ...Lire la suite >
The magnesium metal rich composition La<sub>10</sub>TM<sub>10</sub>Mg<sub>80</sub> (with TM = Ni and Cu) were synthesized from the elements in sealed tantalum tubes in an induction furnace. The results show differences depending on the transition metal used. The sample with Ni demixed into ternary and binary compounds with composition close to LaMgNi<sub>2,</sub> La<sub>2</sub>Mg<sub>17</sub> and Mg<sub>2</sub>Ni. Only the sample with copper forms a ternary compound. Crystal structure of this new compound was determined by X-ray diffraction on single crystals with an exact formulation La<sub>1.744(5)</sub>Cu<sub>1.53(5)</sub>Mg<sub>15.73(4)</sub>. It crystallizes with the La<sub>2</sub>Mg<sub>17</sub> structure type, space group P6<sub>3</sub>/mmc, <i>a</i> = 10.1254(2) Å and <i>c</i> = 10.0751(2) Å. The Mg atoms form hexagonal tubes along the <i>c</i>-axis filled by La and Mg. The Cu atoms are located in these tubes on or around the La and Mg positions, inducing disorder. This compound so-called LaCuMg<sub>8</sub> absorbs around 2 wt% of hydrogen at 603 K, 30 bar and reversibility is possible. Nevertheless, after the first hydrogenation, decomposition into MgH<sub>2</sub>, LaH<sub>3</sub> and MgCu<sub>2</sub> have been shown. The pathway of the reaction is described herein.< Réduire
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