| In this thesis, the research and development on Mg-based hydrogen storage alloys (HSAs) have been reviewed. REMguNi (RE=La, Ce) and CeMg12 alloys were modified by mechanical grinding in tetrahydrofuran (THF). The influences of mechanical grinding (MG) modification on the structure, morphology, surface state and hydriding properties of these two series of Mg-based hydrogen storage alloys have been investigated and the related mechanisms have been discussed.XRD analysis results indicated that the diffraction peaks were all weakened and broadened with increased milling time. SEM observation results showed that the particle sizes of the alloys reduced and the sharpness of the alloy particles decreased with increasing milling time.From AES depth profiles analysis, no significant change of RE concentration and no enrichment of alloying elements were formed. XPS analysis results indicated that the surface oxides were changed into hydroxides after modification. It was believed that the improvement of the activation and hydriding properties of the modified alloys was mainly caused by the change of the structure of the surface. The surface activity of hydrogen storage alloys was improved by the charge transfer between the surface element of alloys and the carbon atoms of THF during mechanical milling.The activation properties and hydriding behaviors are remarkably improved after MG modification in THF. Under the conditions of 448K and 3.2MPa, no activation process is needed for LaMgnNi, CeMgnNi and CeMgi2, which were milled in THF for 20h, and the hydrogen absorption amounts reached 3.5wt%, 4.3wt% and 5.3wt% separately. Even at room temperature the three modified alloys can absorb hydrogen to 2.0wt%, 1.5wt% and 0.98wt%. The desorption rates are also improved significantly by the MG modification in THF. For the CeMgi2 alloys modified in THF for 20h, 5.0wt% of hydrogen was released at look within 30min at 600K, which was more than 90 percent of the absorbed hydrogen. |
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