Improving hydrogen storage thermodynamics and kinetics of Ce-Mg-Ni-based alloy by mechanical milling with TiF3

Abstract

Mg-based hydrides are too stable and the kinetics of hydrogen absorption and desorption is not satisfactory. An efficient way to improve these shortcomings is to employ reactive ball milling to synthesize the nanocomposite materials of Mg and additives. In this experiment, TiF3 was selected as an additive, and the mechanical milling method was employed to prepare the experimental alloys. The alloys used in this experiment were the as-cast Ce5Mg85Ni10, as-milled Ce5Mg85Ni10 and Ce5Mg85Ni10 + 3 wt.% TiF3. The phase transformation, structural evolution, isothermal and non-isothermal hydrogenation and dehydrogenation performances of the alloys were inspected by XRD, SEM, TEM, Sievert apparatus, DSC and TGA. It revealed that nanocrystalline appeared in the as-milled samples. Compared with the as-cast alloy, ball milling made the particle dimension and grain size decrease dramatically and the defect density increase significantly. The addition of TiF3 made the surface of ball milling alloy particles markedly coarser and more irregular. Ball milling and adding TiF3 distinctly improved the activation and kinetics of the alloys. Moreover, ball milling along with TiF3 can decrease the onset dehydrogenation temperature of Mg-based hydrides and slightly ameliorate their thermodynamics.