New Mg–Mn–Ni alloys as efficient hydrogen storage materials

Phase equilibria in the Mg–Ti–Ni system at 500 °C and hydrogenation properties of selected alloys

“…The phase of Ref. [15] was found in the quaternary Mg 1.7 Ti 0.3 Ni 0.8 Mn 0.2 alloy (ball milled and sintered at 550 C) and reported lattice parameter a ¼ 11.6178(2) A [15] is intermediate between the lattice parameter of Mg 3 TiNi 2 (this work) and that of Mg 3 MnNi 2 a ¼ 11.5617(3) A [17]. Thus, the earlier reported compound [15] should be regarded as Mg 3 Ti 1Àx Mn x Ni 2 , rather than pure ternary Mg 3 TiNi 2 .…”

“…Rietveld refinements based on X-ray data have shown that both of these sites are vacant in Mg 3 TiNi 2 prepared in this study. Moreover, interstitial atoms have not been observed in a neutron powder diffraction study of the isostructural Mg 3 MnNi 2 compound [17]. Taken together, these data confirm that Mg 3 TiNi 2 forms as the ternary compound, without stabilization by oxygen or other light non-metallic interstitials.…”

“…Another ternary compound e Mg 3 MnNi 2 e reversibly absorbs about 1 wt.% of hydrogen at room temperature with formation of an interstitial hydride. This ternary compound also has catalytic effect on the hydrogenation of the elemental magnesium [17,21].…”

“…On the other hand, the introduction of a third component into Mg 2 Ni alloys generally results in the formation of corresponding ternary intermetallic compounds with the Ti 2 Ni-type structure, for example, Mg 3 AlNi 2 and Mg 3 TiNi 2 [15], Mg 3 GeNi 2 [16], and Mg 3 MnNi 2 [17]. Two compounds, namely Mg 3 AlNi 2 and Mg 3 TiNi 2 , were found to absorb hydrogen from gaseous phase or electrochemically [18e20], but neither the hydrogenation capacity nor the thermal stability of these hydrides was determined.…”

The kinetics of lightweight solid-state hydrogen storage materials: A review

“…When the temperature is below 300 C, these materials will desorb hydrogen in slow reactions [160,161]. The addition of catalysts/additives with transition-metal oxides [162,163] and metal halides was demonstrated to accelerate the hydrogen kinetics of these light metal-based materials.…”