Microstructure and hydrogen storage properties of Mg–Sn nanocomposite by mechanical milling

To improve the hydrogen storage properties, the composition and microstructure of Mg–Sn alloys were modified through fabricating Mg/Mg2Sn nanocomposite by mechanical alloying. The microstructures were characterized by X-ray diffraction and scanning electron microscopy. It is found that Mg2Sn instead of Mg(Sn) solid solution is preferably formed during milling process. Although Mg2Sn is not a hydriding phase, the in situ formed nanosized Mg2Sn facilitates hydrogen absorption/desorption of Mg by forming Mg/Mg2Sn nanocomposite. The mechanically milled Mg–5 at.% Sn nanocomposite exhibits slightly elevated plateau pressure and destabilized thermodynamics due to the introduction of large amount of interface energy in Mg/Mg2Sn nanocomposite.

Research highlights▶ Phase transformation of Mg–Sn system during ball milling was investigated. It was found that solubility extension of Sn in Mg by milling is not feasible due to the preferential formation of Mg2Sn. But the formation of Mg2Sn facilitates the grain refinement of Mg. ▶ The microstructure and hydrogen storage properties of Mg–Sn nanocomposite were studied in detail. It was firstly reported that the Mg2Sn/Mg nanocrystalline structure obviously enhances the hydrogen absorption and desorption of Mg, and that the hydrogen desorption enthalpy of the Mg/Mg2Sn nanocomposite is lower than that of conventional pure Mg.