Hydrogen storage properties of Ti1xScxMnCr Laves phase alloys

The hydrogen storage properties of Ti1xScxMnCr (x=0.05, 0.10, 0.15, 0.22, 0.27 and 0.32) alloys are studied by pressure-composition isotherms at 060 degrees C and 1 kPa4MPa. The relevant crystal structures of the alloys and their hydrides are examined by the X-ray diffraction and electron microscopy. The alloys are basically C14 type Laves phase with slightly different lattice parameters owing to the difference in composition. Except for x=0.05 alloy, the bulk samples of these alloys can be easily activated under ambient conditions and attain the maximum hydrogen storage capacities during the initial hydrogenation. As Sc content increases, the hydrogen storage capacity of the alloy increases whereas the pressure of the absorption/desorption plateau decreases. No hydrogen-induced disproportionation is observed, and the hydrogen-induced defects and pulverization are not severe after hydriding/dehydriding cycles of these alloys. The Ti0.78Sc0.22MnCr alloy exhibits the best reversible hydrogen storage capacity of similar to 2wt% in between 1 and 4000 kPa at room temperature. Except for the x=0.32 alloy, the average thermodynamic values of |H| and |S| in the system increase approximately linearly with Sc content in the alloys. The thermogravimetry-differential scanning calorimetry (TG-DSC) on desorption of the hydride of Ti0.68Sc0.32MnCr indicates that the thorough release of hydrogen in the alloy can be achieved at 658K. Copyright (c) 2012 John Wiley & Sons, Ltd.