Hydriding kinetics of the composites 85 wt.% Mg-15 wt.% Mg2Ni1-xCox obtained by ball milling

The absorption-desorption properties of the nanocomposites 85 wt.% Mg-15 wt.% Mg 2 Ni 1-x Co x (x = 0.1, 0.2 and 0.3) prepared by ball milling in inert atmosphere have been studied. The hydriding proceeded at T = 573, 473, 423, 373 K and P = 1 MPa, while dehydriding was studied at T = 573 K and P = 0.15 MPa. A significant improvement of the hydriding kinetics of magnesium for all composites was established. The hydrogen absorption rate being 1.36 wt.% H 2 /min, 1.33 wt.% H 2 /min and 1.04 wt.% H 2 /min, for samples with x = 0.1, 0.2 and 0.3, respectively. The values of the absorption capacity (5.5-6.6 wt.% H 2 ) at T = 573 K and P = 1 MPa remained high upon lowering of the hydriding temperature. It was established that the composite 85 wt.% Mg-15 wt.% Mg 2 Ni 0.8 Co 0.2 preserved its absorption capacity even after 70 absorption-desorption cycles at T = 573 K and P = 1 MPa. The promising absorption-desorption characteristics of the investigated nanocomposites were explained by the catalytic action of the intermetallics Mg 2 Ni 1-x Co x , the presence of superparamagnetic Ni and Co particles on the sample surface and the effect of mechanical alloying.