Hydrogen Storage Performances of Nanocrystalline and Amorphous NdMg₁₁Ni + x wt% Ni (x = 100, 200) Alloys Synthesized by Mechanical Milling

Abstract

Nanocrystalline and amorphous NdMg₁₂-type NdMg₁₁Ni + x wt% Ni (x = 100, 200) alloys were successfully prepared through ball milling (BM). The microstructures and electrochemical properties were systematically studied to get a more comprehensive understanding of the sample alloys. The maximum discharging capacity could be obtained at only two cycles, indicating that as-milled alloys have superior activation capability. The more the Ni content, the better the electrochemical properties of the as-milled samples. To be specific, the discharge capacities of x = 100 and x = 200 (BM 20 h) samples are 128.2 and 1030.6 mAh/g at 60 mAh/g current density, respectively, revealing that enhancement of Ni content could significantly improve the discharging capacities of the samples. Additionally, milling duration obviously influences the electrochemical properties of the samples. The discharging capacity always rises with milling duration prolonging for the x = 100 sample, but that of the (x = 200) sample shows a trend of first augment and then decrease. The cycling stability of the (x = 100) alloy clearly decreases with extending milling duration, whereas that of the (x = 200) alloy first declines and then augments under the same conditions. In addition, the high rate discharge (HRD) abilities of the sample display the maximal values as milling duration changes. The HRD (HRD = C₃₀₀/C₆₀ × 100%) values of the as-milled alloys (x = 100, 200) are 80.24% and 85.17%, respectively.