Phase Composition and Microstructure of Mg–Ni Eutectic Alloy with Graphene-Like Material for Hydrogen Adsorption

Powder composites of hydrogenated eutectic Mg–Ni alloy with 10 wt % graphene-like material (GLM) were prepared mechanochemically at a hydrogen pressure of 30 atm. The effect that adding GLM, along with 10 cycles of desorption at 350°C and 1 atm and sorption at 300°C and 10 atm of hydrogen, has on the phase composition and microstructure of the composites is studied. It is shown that composites obtained mechanochemically (hbm composites) and subjected to cycles of hydrogen desorption–adsorption (dh composites) contain crystalline phases: α-MgH2 with rutile-type structure, Mg2NiH4 hydride with a disordered cubic structure (pseudo-ht-Mg2NiH4), and a solid solution of hydrogen Mg2NiH≤0.3. It is found that in hbm composites with GLM additives, the content of the pseudo-ht-Mg2Ni phase is higher than in composites without carbon additives. The Mg2Ni(H) and Mg(H) particles have a common boundary in composites, and cycling does not affect these features of the microstructure. The presence of GLM preserves the small particle sizes of both phases during cycling.