Structures and hydrogen storage properties of magnesium-based composites prepared by HCS+MM

Mg₉₅Ni₅-x%TiFe_0.8 Mn_0.2Zr_0.05 (x = 0, 10, 20, 30) (mass fraction) composites were prepared by hydriding combustion synthesis (HCS) and the products were mechanically milled (MM) to obtain Mg-based hydrogen-storage composites. By means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS) and pressure-composition-temperature (PCT) measurements, the phase structure, microstructure, particle composition and hydriding/dehydriding properties of the composites were studied. Results show that the Mg₉₅Ni₅-30%TiFe_0.8 Mn_0.2Zr_0.05 composite has the best comprehensive hydriding/dehydridingn properties. It requires only 50 s to absorb its saturated hydrogen capacity of 4.11 wt% at 373 K and desorbs 1.91 wt% and 4.3 wt% hydrogen within 1800 s at 493 K and 523 K, respectively. Moreover, the dehydriding onset temperature of the composite is 420 K, which is 20 K lower than that of Mg₉₅Ni₅. The improvement of hydriding/dehydriding properties are related greatly to the structures of the composites, and the addition of TiFe_0.8Mn_0.2Zr_0.05 can improve the dehydriding kinetics of the composites.