Improving the dynamics of a Nd–Mg–Ni-based alloy by combining Ni element and mechanical milling

To improve the reversible kinetics and electrochemical performance of a Nd–Mg–Ni-based alloy, NdMg₁₁Ni + x wt% Ni (x = 100 or 200) samples were prepared through combining the addition of Ni element and ball-milling technology. Meanwhile, the effects of the addition of Ni element and the duration of milling on the NdMg₁₁Ni samples were researched. The results indicate that the addition of Ni element has a beneficial effect on the dynamics of the samples. Meanwhile, the milling duration also has a beneficial effect on the high-rate discharging capabilities, the gaseous hydrogenation rate, and the dehydrogenation dynamics. When the ball-milling time is increased from 5 h to 60 h, the value of R^d₂₀ (the ratio of the dehydrogenation capabilities within 20 min to the saturated hydrogenation capabilities) is raised from 62.20% to 71.59% for the x = 200 sample, and from 58.03% to 64.81% for the x = 100 sample; this is believed to be due to a decline in the activation energy resulting from an increase in the Ni content and ball-milling time. In addition, the E_a value of NdMg₁₁Ni + 200 wt% Ni with a ball-milling time of 60 h is 55.7 kJ mol⁻¹.

Both ball grinding and increasing the nickel content can effectively reduce the dehydrogenation activation energy of a RE–Mg-based alloy.