The Preparation And Hydrogen Storage Properties Of Nano Mg-ni-based Hydrogen Storage Materials

Based on the research status of the magnesium-based hydrogen storage materials, the Mg-Ni system was chosen to be experimental material. The following four works have been carried out: (1) the nanostructural hydrogen storage materials Mg₂Ni-x wt%Pd(x=0,l,3,10) and Mg-30 wt%LaNi_4.7Al_0.3-3 wt%Pd were prepared by mechanical alloying.(2)the effects of Pd content on the phase formation and hydrogen storage properties of Mg-Ni based hydrogen storage alloys were investigated.(3)the phase structures and the properties of Mg-30 wt%LaNi_4.7Al_0.3-3 wt%Pd-hydrogen system were also investigated.(4)the hydrogen sorption properties of nanocrystalline Mg₂Ni-l wt%Pd were studied in detail, and the results were compared with those of conventional polycrystalline Mg2Ni in order to clarify the effect of nano-crystallized on the hydrogen sorption properties of Mg₂Ni.(5)the properties of nanocrystalline Mg₂Ni-l wt%Pd-deuterium system in thermodynamics and kinetics and the anti-poisoned properties were reported up to now. The results show that:Mg₂Ni-x wt%Pd (x=0, 1, 3, 10) could absorb hydrogen at 473K without activation. Among these materials, Mg₂Ni-l wt%Pd had the fastest hydriding/dehydriding rate and the most reversible storage capacity (3.01 wt%). The plateau pressure of hydrogen absorption increased with the increasing Pd content, but the plateau pressure of hydrogen desorption firstly increased and then decreased. XRD analysis indicated that Mg₂Ni-x wt%Pd (x=0, 1, 3) transformed to a lot of Mg₂NiH₄ while the hydrides of Mg₂Ni-10 wt%Pd were composed of MgH₂ and a small quantity of Mg₂NiH₄.Mg-30 wt%LaNi_4.7Al_0.3-3 wt%Pd composite material had the hydrogen storage capacity of 3.42 wt%. Under the initial hydrogen pressure of 1.17MPa, the hydriding rate and capacity increased with the increasing temperature. The composite material can absorb hydrogen more quickly. That is due to the formation of multi-phase nanocrystalline materials. Acting as a "short path" for hydrogen diffusing, LaNi_4.7Al_0.3, Pd and Mg₂Ni catalyzed Mg in hydrogen absorption and desorption process.XRD and AFM showed that the particle sizes of Mg₂Ni-1 wt%Pd alloy was about 10nm -50nm. Nanocrystalline Mg₂Ni-1 wt%Pd showed better performances of activation and hydrogen absorption kinetics at lower temperatures than conventional crystalline Mg₂Ni.The sample can easily absorb hydrogen at 423K and 473K under the initial hydrogen pressure of 1.17MPa without activation, and the hydrogen absorption rate and the capacity increased with the temperature increasing. But the hydriding rate and the storage capacity decreased with the cycle's number increasing at the beginning, and then didn't decrease when decreasing to some...