Electrochemical hydrogen storage performances of the nanocrystalline and amorphous (Mg24Ni10Cu2)100–xNdx (x=0–20) alloys applied to Ni-MH battery

Melt spinning technology was used to prepare the Mg2Ni-type (Mg24Ni10Cu2)100–xNdx (x=0, 5, 10, 15, 20) alloys in order to obtain a nanocrystalline and amorphous structure. The effects of Nd content and spinning rate on the structures and electrochemical hydrogen storage performances of the alloys were investigated. The structure characterizations of X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) linked with energy dispersive spectroscopy (EDS) revealed that the as-spun Nd-free alloy displayed an entire nanocrystalline structure, whereas the as-spun Nd-added alloys held a nanocrystalline and amorphous structure and the degree of amorphization visibly increased with the rising of Nd content and spinning rate, suggesting that the addition of Nd facilitated the glass forming of the Mg2Ni-type alloy. The electrochemical measurements indicated that the addition of Nd and melt spinning improved the electrochemical hydrogen storage performances of the alloys significantly. The discharge capacities of the as-cast and spun alloys exhibited maximum values when Nd content was x=10, which were 86.4, 200.5, 266.3, 402.5 and 452.8 mAh/g corresponding to the spinning rate of 0 (As-cast was defined as the spinning rate of 0 m/s), 10, 20, 30 and 40 m/s, respectively. The cycle stability (S20, the capacity maintain rate at 20th cycle) of the as-cast alloy always rose with the increasing of Nd content, and those of the as-spun alloys exhibited the maximum values for Nd content x=10, which were 77.9%, 83.4% 89.2% and 89.7%, corresponding to the spinning rate of 10, 20, 30 and 40 m/s, respectively.