The Studies Of The Hydrogen Storage Properties Of Mg-based Alloys After Modification By Mechanical Grinding With/without Tetrahydrofuran (THF)

In this thesis, previous research work on Mg-based hydrogen storage alloys have been comprehensively reviewed. On this basis, the following works have been carried out Firstly, LaiMgitNi alloy was selected for hydrogen storage properties determination and the effects of mechanical grinding on the phase structures, surface characteristics and hydrogenation properties of l^MgieNi alloy were studied. Partial substitution of La by Y and Ni by Co were also investigated. Secondly, for the purpose of improving the kinetic properties of hydriding/dehydriding, I^MgieNi and Mg2Ni alloys were modified by mechanical grinding in tetrahydrofuran (THF), and the phase structures, surface characteristics and hydriding/dehydriding properties of modified alloys have been investigated.The experimental results show that rare-earth magnesium alloys have high hydrogen absorption capacities and rather good hydriding properties and are promising for hydrogen storage. Mechanical grinding improves the dehydriding properties of La2Mg]6Ni, but deteriorates the activation properties and has no influence on the hydrogen absorption capacity. It may be due to intrinsic stress accumulation and inexistence of apparent reduction of the particle size during mechanical grinding.Partial substitution of Ni by Co for La2Mgi6Ni alloy does not change the phase structure, while the hydrogenation properties improve to some extent. The effects of partial substitution of La by Y for LaiMgieNi alloy were also studied, and no positive effects were found.Modification by mechanical grinding in tetrahydrofuran (THF) improves remarked the activation properties of La2Mg]6Ni and MgjNi alloys. Such alloys show high activities for hydriding even at relatively low temperature (for La2Mgi6Ni, that is room temperature; for Mg2Ni, that is about 323K). For modified I^MgieNi alloys, XRD analysis indicates that these alloys have been amorphized to a great extent The same phenomenon, while to a rather little extent, was also observed in the case of Mg2Ni alloy. It is believed that charge transfer occurs to some extent on the surface of modified alloys and thus results in the formation of electron donor-acceptor (EDA) complexes, which provide active sites for hydrogen sorption and further diffusion to the underlying intermetallic phase.