Comparison of dehydriding kinetics between pure LaNi5 and its substituted systems

The kinetic mechanisms of dehydriding reaction in La0.8M0.2Ni5 and LaNi4.5T0.5 were comparatively investigated by the Chou model and the first order model, and the former was superior to the latter from the comparison of theoretical calculated results and experimental data. According to the characteristic time (t(c)) in the Chou model, substituting La (t(c) = 71.36 s) with Ce (t(c) = 35.64 s), Nd (t(c) = 30.82 s) and Pr (t(c) = 28.86 s) increased the dehydriding reaction rate, but partial substitution of Ni (t(c) = 71.36 s) with Co (t(c) = 102.29 s), Fe (t(c) = 116.70 s) and Cu (t(c) = 120.62 s) decreased the hydrogen desorption reaction rate. The Chou model was also used to discuss the effect of different amount of Ni substituted with Fe and Co. The dehydriding reaction rates of La(Ni1-xFex) 5 increased with x leveling from 0 to 0.20 but decreased with x increasing from 0.20 to 0.30, while that of LaNi5-yCoy decreased with increasing the amount of Co from 0 to 3.00. In addition, the Chou model was successfully applied to predicting the kinetic properties of LaNi4.8Sn0.2 at 40 degrees C and 60 degrees C, which exhibited an excellent agreement with the experimental data. (C) 2011 Elsevier B.V. All rights reserved.