Application of a new kinetic model for the hydriding kinetics of LaNi5−xAlx (0 ≤ x ≤ 1.0) alloys

The hydriding kinetic mechanism of LaNi5−xAlx (0 ≤ x ≤ 1.0) is clarified using Chou model, involving the influence of temperature, pressure and Al content. The results indicate that the rate-controlling step of the hydriding reaction in LaNi5 and LaNi4.7Al0.3 is diffusion, but in LaNi4Al, it is surface penetration at the temperature range of 30–80 °C. Moreover, the hydriding reaction rates increase with increasing temperature for the three alloys. Based on the results calculated using the Chou model, the rate-controlling steps for LaNi5 and LaNi4.7Al0.3 correspond to surface penetration and diffusion under different pressures ranging from 0.47 to 1.0 MPa, and the hydrogenation rate increases with an increase in pressure. A suitable addition of Al can obviously improve the hydrogen absorption reaction rate. For LaNi5−xAlx (x = 0, 0.15, 0.5 and 1.0) under a hydrogen pressure of 1.00 MPa at 30 °C, the hydrogen absorption reaction rate is as follows: LaNi5 < LaNi4Al < LaNi4.5Al0.5 < LaNi4.85Al0.15.

Research highlightsIn this paper, Chou model was successfully used to analyze the hydriding kinetic mechanisms of LaNi5−xAlx (0 ≤ x ≤ 1.0). The experimental results can be well described by Chou model as far as the influence of temperature, pressure and different Al content is concerned. The results show that suitable addition of Al can obviously improve the hydrogen absorption rate of LaNi5 alloys. The study is very useful for the future work of hydriding kinetics of LaNi5−xAlx system alloys.