The Hydrolysis Properties Of Mg 3 Re Based Hydrides And The Effect Of Ni And Al Addition On Hydrolysis

The characteristics of MgH2 in hydrolysis are high hydrogen purity and environment friendly. However, the passivation of Mg(OH)2 hinders the further hydrolysis and leads to the low hydrogen generation yield. To overcome these shortcomings, in this thesis, it not only focuses its attention on the hydrolysis properties of Mg₃RE (RE=La, Ce, Pr, Nd and Mm) hydrides, but also the effect of Ni and Al addition on the hydrolysis, based on the reviewing of world wide development of hydrolysis. The Mg₃RE and the Mg₃RE-based alloys prepared by induction melting were hydrogenated fully, and then hydrolyzed at room temperature. the phase structure before/after ball-milling and hydrolysis reaction agent was investigated by using X-ray diffraction(XRD) and energy dispersive X-ray spectroscopy(EDX) in order to understand the reaction mechanism during the process of hydrogenation and hydrolysis. And meanwhile, the hydrolysis processes were also tested. Based on the data of hydrolysis, the hydrolysis kinetics was also analyzed.Based on the XRD analysis, Mg₃RE alloys are composed of the D03 structure. While the phases of Mg₃RENi_0.1 alloys are are composed of Mg₃RE with D03 structure phase and small amount of REMg2Ni and/or RE2Mg17. The products of Mg₃RE based alloys after hydrogenated are MgH2 and REH2³. Except that the products of Mg₃Nd hydrides (H-Mg₃Nd) after hydrolysis are Nd2H5 and Mg(OH)2, and Mg₃CeNi_0.1 hydrides (H-Mg₃CeNi_0.1) are Mg(OH)2 and CeO2, the products of other Mg₃RE hydrides alloys after hydrolysis are Mg(OH)2and RE(OH)2³.In the first 5 min, the hydrogenated Mg₃Mm had the quickest hydrolysis rate (131ml/(g.min)) and the hydrogenated Mg₃Nd reacted with water at the slowest hydrolysis rate (82ml/(g.min)). And the highest hydrogen yield is 1039 ml/g for the hydrogenated Mg₃Mm. The hydrolysis mechanism of H-Mg₃RE was also discussed in this thesis.After introducing the Ni element into Mg₃RE alloy, the hydrogen generation capacity for Mg₃RENi_0.1 hydrides (H-Mg₃LaNi_0.1, H-Mg₃CeNi_0.1, H-Mg₃PrNi_0.1, H-Mg₃NdNi_0.1 and H-Mg₃MmNi_0.1) were up to 9.05 wt%,9.71 wt%,8.52 wt%,7.49 wt% and 8.48 wt%. In the first 5 min, H-Mg₃MmNi_0.1 had the highest hydrolysis among all these alloys.When Al was introducd into Mg₃LaNi_0.1, it could be found that Mg₃LaNi_0.1Al_0.1 hydrides (H-Mg₃LaNi_0.1Al_0.1) had the quickest hydrogen generation rate, which is up to 120 ml/g?min. this is due to the addition of Ni and Al, the hydrolysis mechanism had been changed.