Abstract
Thermal analysis methods have been used in many reports to determine the activation energy for hydride decomposition (dehydrogenation). In our preceding work, we showed that the dehydrogenation rate of Mg-5Ni samples obeyed the first-order law, and the Kissinger equation could thus be used to determine the activation energy. In the present work, we obtained the activation energy for dehydrogenation by applying data from a volumetric method to the Kissinger equation. The quantity of hydrogen released from hydrogenated Mg-5Ni samples and the temperature of the reactor were measured as a function of time at different heating rates (Φ) in a Sieverts-type volumetric apparatus. The values of dH(d)/dt, the dehydrogenation rate, were calculated as time elapsed and the temperature (T(m)) with the highest dH(d)/dt was obtained. The values of dH(d)/dT, the rate of increase in released hydrogen quantity (H(d)) to temperature (T) increase, were calculated according to time, and the temperature (T(m)) with the highest dH(d)/dT was also obtained. In addition, the values of dT/dt, the rate of increase in temperature to time (t) increase, were calculated according to time, and the temperature (T(m)) with the highest dH(d)/dt was obtained. Φ and T(m) were then applied to the Kissinger equation to determine the activation energy for dehydrogenation of Mg-5Ni samples.