Kinetics of Hydrogen Absorption in Hydrogen Storage Alloy

Hydrogenation kinetics of MLNi_3.8(Co,Mn,Al)_1.2 and MLNi_3.7(Co,Mn,Al)_1.2Cu_0.1 alloy in α + β phase at the temperature range of 30~70 ℃ has been studied. The kinetic mechanism of hydrogen absorption is not affected by initial hydrogen pressure. Temperature does not influence the rate of hydrogen absorption obviously. In the prior and later period of hydrogen absorption the rate-controlling step is chemical reaction and hydrogen diffusion in the hydride phase respectively for MLNi_3.8(Co,Mn,Al)_1.2 alloy. Adding Cu, the rate-controlling step changes from chemical reaction to the nucleation and growth of β phase in the prior period and the process of hydrogen absorption still controlled by diffusion in the later period.