Effect of the calcium halides, CaCl2 and CaBr2, on hydrogen desorption in the Li-Mg-N-H system

Calcium-halide-doped lithium amide-magnesium hydride samples were prepared both by hand-grinding and ball-milling 2LiNH(2)-MgH2-xCaX(2) (x = 0, 0.1, and 0.15; X = Cl or Br). The addition of calcium halides reduced the hydrogen desorption temperature in all samples. The ball-milled undoped sample (2LiNH(2)-MgH2) began to desorb hydrogen at around 125 degrees C and peaked at 170 degrees C. Hydrogen desorption from the 0.15 mol CaCl2-containing sample began ca 30 degrees C lower than that of the undoped sample and peaked at 150 degrees C. Both the onset and peak temperatures of the CaBr2 sample (x = 0.15) were reduced by 15 degrees C compared to the chloride. Kissinger's method was used to calculate the effective activation energy (Ea) for the systems: Ea for the 0.15 mol CaCl2-containing sample was found to be 91.8 kJ mol (1) and the value for the 0.15 mol CaBr2-containing sample was 78.8 kJ mol (1). (C) 2015 Published by Elsevier B.V.