Highly Improved Gaseous Hydrogen Storage Characteristics of the Nanocrystalline and Amorphous Nd-Cu-added Mg2Ni-type Alloys by Melt Spinning

The nanocrystalline and amorphous Mg-Nd-Ni-Cu quaternary alloys with a composition of (Mg24Ni10Cu2)100−xNdx (x = 0-20) were prepared by melt spinning. The X-ray diffraction and transmission electron microscopy inspections reveal that, by varying the spinning rate and the Nd content, different microstructures could be obtained by melt spinning. Particularly, the as-spun Nd-free alloy holds an entire nanocrystalline structure but the as-spun Nd-added alloy has a nanocrystalline and amorphous structure, which implies that the addition of Nd facilitates the glass forming in the Mg2Ni-type alloy. Also, the degree of the amorphization in the as-spun Nd-added alloys clearly increases with increasing the spinning rate and the Nd content. The H-storage capacity and the hydrogenation kinetics of amorphous, partially and completely nanocrystalline alloys were investigated and it was found that they are dependent on the microstructure and the phase composition of the alloys. Specially, enhancing the spinning rate from 0 (the as-cast was defined as the spinning rate of 0 m/s) to 40 m/s makes the hydrogen absorption saturation ratio (R5a) (a ratio of the hydrogen absorption quantity in 5 min to the saturated hydrogen absorption capacity) increase from 35.2% to 90.3% and the hydrogen desorption ratio (R10d) (a ratio of the hydrogen desorption quantity in 10 min to the saturated hydrogen absorption capacity) rise from 12.7% to 44.9% for the (x = 5) alloy. And the growing of the Nd content from 0 to 20 gives rise to the R5a and R10d values rising from 85.7% to 94.5% and from 36.7% to 54.8% for the as-spun (30 m/s) alloys, respectively.