An analysis method diffusion controlled hydrogen desorption kinetic's of the hydrides of the LaNi_5 based alloys (LaNi_5, LaNi_(4.5)Al_(0.5), LaNi_(4.5)Mn_(0.5) and LaNi_(4.5)Co_(0.5))

摘要

The H_2 desorption rates of the hydrides of the H storage alloys(LaNi_5, LaNi_(4.5)Al_(0.5), LaNi_(4.5)Mn_(0.5) and LaNi_(2.5)Co_(0.5)) a were measured as a function of the H concentration by a volumetric method in the of temperatures from 298 K to 348 K and of H_2 pressures between 0.01M Pa and 0.6M Pa. The measured data exhibited that the desorption rates are controlled by the diffusion of H in the hydrides of the alloys. The obtained diffusion coefficient ranged from 3 X 10~(-10) cm~2s~(-1) to 5 X 10~(-9)cm~2s~(-1) for the alloy hydrides at these temperatures. The activation energy for H diffusion tended to increase with increasing H concentration in the hydrides of the alloys. However, the activation energy was found to he decreased by partial substitutions of Ni in LaNi_5 with Al, Mn and Co.