Kinetics study on the nonlinear modified varying-size model of LaNi5 during hydrogenation/dehydrogenation

Due to the large kinetics model deviation caused by the actual expansion/shrinkage of LaNi5 particle during H-2 absorption/desorption process, the nonlinear modified varying-size model (M-VSM) was proposed based on varying-size model (VSM) to calibrate the kinetics equations precisely. The related hydriding and dehydriding kinetics experiments were conducted under various temperatures and pressures, and the model equations of LaNi5 were achieved based on M-VSM. Both experimental and simulation results confirmed the rate controlling step was internal diffusion. Moreover, the model accuracy of M-VSM was investigated and compared with other conventional models, and the results indicated that M-VSM owned the highest model precision than any other models including shrinking-core model, Johnson-MehlAvrami model and Jander diffusion model. Furthermore, the simplified hydriding/dehydriding equations were also derived, whose correlation coefficient R-2 could reach 0.98 and 0.99, respectively. Hence the M-VSM has favorable accuracy and convenience which will show its great potential application in the future. (C) 2019 Elsevier Ltd. All rights reserved.