Investigation On Hydrogen Storage Properties And Mechanism Of Mechanical Alloying CeMg₁₂Alloy

At present, magnesium base hydrogen storage alloys, including La₂Mg₁₇, Mg-Ni,RE-Mg₁₂（RE=La, Ce, Pr, Nd） were considered to be one of the most promising materialsfor hydrogen storage, because of their low cost, highest hydrogen capacity and abundantnatural resources. The emphasis of research was focused on reducing the alloy price,improving their electrochemical cycle stability and hydrogenation/dehydrogenation kineticperformance. Mechanical alloying （MA） is a new-type method to produce hydrogenstorage alloys and these alloys possess a great quantity of nanocrystalline, microcrystal andamorphous structure, which can effectively enhance the cycle stability of alloy. In thiswork, magnesium base CeMg₁₂series hydrogen storage alloys were prepared by MA. Inthe process of experiment, the change tendency of alloy hydrogen storage properties wasinvestigated by adjusting ball-milling, the content of Ni powder and TiF₃.Prolonging the ball-milling time can enhance the glass forming ability in theCeMg₁₂+100%Ni+0%TiF₃alloy, increase crystal defects （such as dislocations and grainboundaries） and strengthen the anticorrosion and antioxidition ability of milling alloy,which improve the electrochemical discharge and hydrogenation kinetic property.Optimum milling time will ameliorate dramatically electrochemical kinetic property ofmilled alloy. However, the increasing milling time reduces dehydrogenation kineticperformance.In milling process, the addition of TiF₃significantly enhance amorphous formationability of CeMg₁₂+100%Ni+Y%TiF₃（Y=0,3,5） alloy, improving the electrochemicaldischarge ability, cycle stability and hydrogenation kinetic property. Moderate TiF₃canenhance electrochemical kinetic property. Nevertheless, the addition of TiF₃will changethe thermostability of milled alloy hydride, which makes dehydrogenation kineticperformance of alloy deteriorate.The increase of Ni powder content is conducive to the glass phase formation ofCeMg₁₂+Y%Ni+0%TiF₃（Y=50,100,150） alloy. In the meantime, Ni powder has strongelectrochemical catalysis activation. The two factors work together to ameliorateelectrochemical properties and hydrogenation kinetic property of alloy. The addition of Nipowder changes the composition and heat stability of alloy hydride, which reduce thedehydrogenation kinetic property of milling alloy.Electrochemical discharge PCT（Pressure-Concentration-Tempreture） curves explainsthe differences of milled alloy electrochemical discharge property in the sight ofthermodynamics.