Effects of annealing treatment on the microstructure and electrochemical properties of low-Co hydrogen storage alloys containing Cu and Fe |
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| Authors: | Suxia Yang Zhiping Liu Shumin Han Wei Zhang Jianzheng Song |
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| Affiliation: | (1) State Key Laboratory of Metastable Materials Science and Technology, Qinhuangdao, 066004, P.R. China;(2) Department of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao, 066004, P.R. China;(3) Department of Material Science and Engineering, Yanshan University, Qinhuangdao, 066004, P.R. China; |
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| Abstract: | The effects of annealing treatment on the microstructure and electrochemical properties of low-Co LaNi3.55Mn0.35Co0.20Al0.20Cu0.75Fe0.10 hydrogen storage alloys were investigated. X-ray diffraction (XRD) analysis indicated that annealing treatment remarkably reduced the lattice strain and defects, and increased the unit-cell volume. The optical microscope analysis showed that the as-cast alloy had a crass dendrite microstructure with noticeable composition segregation, which gradually disappeared with increasing annealing temperature, and the microstructure changed to an equiaxed structure after annealing the alloy at 1233 K. The electrochemical tests indicated that the annealed alloys demonstrated much better cycling stability compared with the as-cast one. The capacity retention at the 100th cycle increased from 90.0% (as-cast) to 94.7% (1273 K). The annealing treatment also improved the discharge capacity. However, the high rate dischargeability (HRD) value of the annealed alloy slightly dropped, which was believed to be ascribed to the decreased exchange current density and the hydrogen diffusion coefficient in alloy bulk. |
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| Keywords: | hydrogen storage alloys annealing phase structure microstructure electrochemical properties |
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