Reactive Ball-milling Synthesis Of Mg-based Polyphase Hydrogen Storage Materials

Hydrogen storage and transportation are the key to the development of hydrogen energy technologies. In all hydrogen storage materials, Mg-based hydrogen storage materials is one of the most promising and popular materials, which has been highly focused by more and more people, due to its advantage of high storage capacity, low density, pollution free and a relatively low cost and so on. However, there's still a long way for Mg-based alloys to be used as an ideal carrier of hydrogen because of its bad thermodynamics and kinetics properties in hydrogen absorption and desorption.In this paper, Mg-based hydrogen storage materials have been made of Mg-Li-Al alloy by reaction ball milling in hydrogen atmosphere, attempting to achieve the synthesis and modification of hydrogen storage materials simultaneously. In this thesis, four groups of alloy series (Mg-Li-xAl (x=0, 1, 3), Mg-14Li-Al+Al and 1420, Mg-yLi-Al (y=9, 14), Mg-14Li-3Al+Transition metal oxides) were synthesized by reaction ball-milling. These alloys have been studied in detail by X-ray, TG-DSC, FT-IR, XPS and other modern analytical tools, including the phase evolution of materials, hydriding properties and the microstructure. The main results are as follows:①Mechanical ball-milling under hydrogen atmosphere could promoteβ-Li (bcc) translating toα-Mg (hcp), and also could increase the solubility of Li atom in Mg lattice, which is conducive to Li-Mg-H transition phase formation. The transition phase (Li-Mg-H) translated into Mg-Li-Al-H with the stable coordination structure by further reaction.②The contents of Li-Mg-H transition phase and Mg-Li-Al-H phase in the product increased with Al/Li ratio of the original materials, but the total amount of hydrogen release of product reduced. The total amount of hydrogen release of Mg-14Li-Al alloy could be up to 10.2wt% below 300℃. The synthesized hydrogen storage materials could decompose to release hydrogen in a temperature lower than 100℃. The decomposition temperature of MgH2 phase reduced with the Al/Li ratio decreasing, and in the Mg-14Li-3Al alloy, the decomposition temperature of MgH2 can be reduced about 150℃.③The content of ligand groups [AlH4]-1 in the final product increased with Al/Li ratio increasing in the raw materials. The infrared absorption peak of Al-H bond shifted to lower wave number duo to the existence of Li. ④Transition metal oxides could promote the structure of bccβ-Li translating to hcpα-Mg in an inert atmosphere, has a positive effect on the synthesis of Li-Al-Mg-H transition phase and its further reaction, in the same time promoted the Mg reacting with H2 and directly synthesized MgH2 at a low temperature.