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The isothermal sections of the Nd–Mg–Co phase diagram at 300 and 500 °C have been constructed on the basis of X-ray diffraction (XRD), Wavelength Dispersive Spectrometry (WDS) and Electron Probe Micro Analyzer (EPMA) analysis. The existence of two ternary compounds Nd 4 Mg 3 Co 2 (own structure type) and Nd 4 MgCo (Gd 4 RhIn type) was confirmed. The latter has homogeneity range defined as Nd 4- x Mg 1+ x Co with 0 ≤ x ≤ 0.2 at 300 °С and 0 ≤ x ≤ 0.3 at 500 °С. Four new ternary compounds were identified in this work: Nd 23- x Mg 4+ x Co 7 (Pr 23 Mg 4 Ir 7 type; −1.5 ≤ x ≤ 0.1 at 300 °С and −0.6 ≤ x ≤ 0.3 at 500 °С); NdMg 2 Co 9 (YIn 2 Ni 9 type), ∼Nd 77 Mg 14 Co 9 (cubic) and ∼Nd 56 Mg 6 Co 38 (unknown crystal structure). Two binary compounds, NdCo 2 and NdCo 3 , were found to dissolve significant amount of Mg with the formation of substitutional solid solutions Nd 1- x Mg x Co 2 (MgCu 2 type; x ≤ 0.1 at 300 °С and x ≤ 0.15 at 500 °C) and Nd 1- x Mg x Co 3 (PuNi 3 type; x ≤ 0.33 at 300 °С and x ≤ 0.5 at 500 °C), respectively. The Nd 4 Mg 3 Co 2 , Nd 4- x Mg 1+ x Co, Nd 23- x Mg 4+ x Co 7 and Nd 1- x Mg x Co 2 compounds irreversibly absorb hydrogen at room temperature and pressure 1–10 bar to form crystalline or amorphous hydrides with hydrogen content 1.6–2.1 wt. %. Hydrogen thermal desorption from these hydrides in vacuum results in their disproportionation with formation of binary NdH 2 hydride. The Nd 1- x Mg x Co 3 (0 ≤ x ≤ 0.5) alloys reversibly absorb up to 1.3 wt. % of hydrogen. NdMg 2 Co 9 compound has small hydrogenation capacity, absorbing only 0.5 wt. % at room temperature and hydrogen pressure 185 bar.

A number of ternary Mg–Ti–Ni alloys have been synthesized by high energy ball milling, followed by annealing heat treatment. On the basis of X-ray phase analysis of these alloys an isothermal section of the Mg–Ti–Ni phase diagram at 500 °C has been constructed. One ternary intermetallic compound with Mg 3 TiNi 2 stoichiometry that adopts an ordered Ti 2 Ni-type structure has been identified. Binary cubic TiNi compound dissolves considerable amount of Mg to form a ternary phase Mg x Ti 1−2/3 x Ni 1−1/3 x crystallizing in the CsCl-type structure and existing over the range of compositions 0 x ≤ 0.5. Other binary phases do not show appreciable solubility of the third component. The hydrogenation behavior of Mg 3 TiNi 2 compound and Mg 0.5 Ti 0.67 Ni 0.83 solid solution phase has been studied.

New ternary Mg–Mn–Ni alloys synthesised by high energy ball milling have been studied as hydrogen storage materials. A new Mg 3 MnNi 2 ternary intermetallic compound of the Ti 2 Ni type has been identified, its structure was studied by neutron diffraction. It has been shown that in the Mg–Mn–Ni system this intermetallic coexists with Mg, forming two-phase Mg–Mg 3 MnNi 2 alloys. The Mg 3 MnNi 2 compound reversibly absorbs about 1 wt.% of hydrogen already at room temperature and forms interstitial type Mg 3 MnNi 2 H ∼3 hydride. Substantially higher hydrogenation capacity has been observed in Mg–Mg 3 MnNi 2 alloys with high Mg content, e.g. 5.4 wt.% for the Mg 88 Mn 4 Ni 8 alloy at 250–350 °C. Hydrogen absorption–desorption kinetics of these alloys are drastically improved compared to undoped magnesium due to catalytic effect of the Mg 3 MnNi 2 phase.