Reaction Synthesis Of Mg-based Polyphase Hydrogen Storage Materials

Hydrogen energy is one of the most clean and richest resources in natural resources, and the development and application of hydrogen storage materials play a significant role in environmental protection and energy development. In all hydrogen storage materials, Magnesium-based hydrogen storage materials are one of the most promise and popular materials, which has been highly focused more and more people, due to its advantages of magnesium alloy, such as high discharge capacity,light weight,low cost and abundant natural resources and so on.The feasibility and reaction process of different materials(Mg-Al-Ni powder and Mg-Li alloy)were discussed and investigated by thermodynamic calculation in this paper. The effects of material proportioning, mill time, mill energy density were also investigated by XRD analysis and TG-DSC technique, and analyzed the essence mechanism.The preparation of two material systems Mg-Al-Ni powder and Mg-Li alloy, through the reactive ball milling processing at 0.40 MPa hydrogen atmosphere, obtains a series of Mg-based polyphase hydrogen storage materials with different constitute. Analyze the hydrogenation resultants with X-ray and TG-DSC technique, the following results were obtained.â‘ the experiment result of Mg-Ni-Al powder shows that, along with the increase of milling time the grain size decrease dramatically. Nanosize MgH₂ and Mg(AlH₄)₂ phases could be directly synthesized after ball-milling technology at work30/stop30 by 8h.The synthesis mechanisms of reaction was that: first Mg reacts with H2 to produce MgH₂, then MgH₂ reacts with Al and H2 to produce Mg(AlH₄)₂, meanwhile the accessory reaction also product Al3Ni; The decompose mechanisms of the Mg-based polyphase hydrogen storage materials which prepared before was that: first, Mg(AlH₄)₂ decomposed to MgH₂, after that MgH₂ decomposed to Mg, finally, Mg reacts with Al to produce Mg17Al12.â‘¡the experiment result of Mg-Li alloy shows that Mg(AlH₄)₂, LiAlH4 and MgH₂ phases could be directly synthesized after milling 16h, LA91 milling composite can disabsorb 6.2% hydrogen and LA141 milling composite can disabsorb 10.6% hydrogen. The synthesis mechanisms of reaction was that: firstly Mg reacts with H2 to produce MgH₂, subsequently MgH₂ reacts with Al and H2 to produce Mg(AlH₄)₂; At the same time, Li hydrogenise to LiH and LiAl react with H2 to produce LiAlH4. The decompose mechanisms of the Mg-based polyphase hydrogen storage materials which prepared before was that: firstly,Mg(AlH₄)₂ decomposed to MgH₂, then LiAlH4 decomposed to Li3AlH6 and LiH, finally, MgH₂ and LiH were decomposed.