Hydrogen desorption kinetics in intermetallic compounds C2, C51 and C52 with Laves phase structure

Desorption kinetics for the commercial hydride forming alloys C2, C51 and C52 with Laves phase structure were studied. Isothermal measurements in a close volumetric system were carried out in temperature range of −20–20°C. The normalized pressure dependence method (NPDM) was applied to interpret the experimental data and to compare with each other. The NPDM approach and its possibility were discussed. The kinetics was found to be very fast for the studied hydrides. Assuming first order for desorption processes the kinetic parameters were shown to correspond of the following: k=0.67, 0.43 and 1.08 s−1 at 20°C for C2, C51 and C52, respectively. Activation energy values in the above-mentioned temperature range were derived to be Ea=33, 40 and 30 kJ/mol for C2, C51 and C52, respectively. The hydrides thermodynamic equilibrium parameters ΔH and ΔS as well as maximum and minimum plateau Peqʹs were also derived. The specific thermal cooling power output Wsp was measured experimentally for C52. One has valued about 1.5 kW per 1 kg hydralloy for 2 min. These results were compared with those for commercial alloys HY STOR 205 and HY STOR 209.