Microstructure and hydrogen sorption properties of Mg–Ni/MmM5 multi-layer film by magnetron sputtering

To improve the hydrogenation properties of Mg–Ni-base alloys, Mg–Ni/MmM5 multi-layer film was fabricated by magnetron sputtering. The microstructure and hydrogenation properties of as-deposited film were characterized by X-ray diffraction, scanning electron microscopy and pressure-composition isotherm measurement. It was shown that the Mg–Ni layer is composed of preferred orientational nanocrystalline Mg2Ni and fine-crystalline Mg, while the MmM5 layer is in amorphous structure. PCI curve of Mg–Ni/MmM5 multi-layer film at 523 K is composed of two plateaus, which correspond to the hydriding and dehydriding reactions of Mg and Mg2Ni, respectively; A maximum hydrogen absorption content of 5.0 mass% is obtained at 523 K. The hydrogenation properties of Mg–Ni/MmM5 multi-layer film are greatly improved than that of the corresponding Mg–Ni alloy target, which is attributed to the nanocrystalline structure of the Mg–Ni layer and catalytic role of the amorphous MmM5 layer. However, the hydrogenation properties of Mg–Ni/MmM5 multi-layer film are deteriorated after several cycles.