Hydrogenation behavior of high-energy ball milled amorphous Mg ₂Ni catalyzed by multi-walled carbon nanotubes

Amorphous Mg₂Ni alloy was successfully synthesized by means of mechanical alloying. Then, the multi-walled carbon nanotubes (MWCNTs) were added by high-energy ball milling to catalyze the amorphous alloy. The X-ray diffraction (XRD) spectroscopy reveal that the as-cast Mg₂Ni alloy has presented a completely amorphous state under specific conditions of high-energy ball milling process. Different process parameters of ball-to-powder ratio (10:1, 20:1, 40:1) and milling time have been attempted for the preparation of amorphous Mg₂Ni alloy. The results show that the milling time and ball-to-powder weight ratio have significantly influence on the amorphization process of crystalline Mg₂Ni alloy. Before and after the milling, phase compositions and microstructures of the prepared materials were characterized by XRD, scanning electron microscope (SEM), electron energy dispersion spectrum (EDS) and transition electron microscope (TEM) approaches. The morphology of composite Mg₂Ni/MWCNTs was investigated, the TEM images show that the MWCNTs imbed on the surface of the particles after milling for 1 h, and the MWCNTs with and without tubular structure have been observed. The hydrogen storage properties of amorphous Mg₂Ni alloys were improved by the catalytic effect of MWCNTs. The catalytic effect and mechanism of MWCNTs on the hydrogen storage properties of amorphous Mg₂Ni alloy are discussed and investigated.