Effect of ball milling methods on synthesis and desorption properties of nanocrystalline Mg_2FeH_6 hydrogen storage materials

A Uni-Ball-Mill 5 and an XQM-4 type planetary ball mill were adopted respectively in order to compare effects of milling methods on synthesis of Mg2FeH6 hydrogen storage materials.Hydrogen pressure loss,X-ray diffraction(XRD),scanning electron microscopy(SEM) and thermoanalysis were conducted to determine the structure and performance of the milled powders.The results show that the powder milled in XQM-4 type planetary ball mill for 150 h yields 70% of Mg2FeH6 phase and can release about 2.66% of hydrogen,desorp at 380 ℃ and 100 kPa,the powders have flake shapes and grain sizes below 7 nm.Whereas,the powders milled in Uni-Ball-Mill 5 with process P2 for 270 h have lower yield of Mg2FeH6 phase,only 39.1%,desorp 1.15% at 350 ℃ and 100 kPa,and show spherical shape.The difference may be attributed to the fact that the planetary ball mill has higher milling efficient than the Uni-Ball-Mill 5.