AN INVESTIGATION OF THE INTRINSIC DEGRADATION MECHANISM OF LANI5 BY THERMAL-DESORPTION TECHNIQUE

The intrinsic degradation behavior of LaNi5 was investigated by the changes of pressure-composition-temperature (P-C-T) curves of LaNi5-H2 system and the hydrogen desorption technique after the pressure induced hydrogen absorption-desorption cycling. Thermal desorption experiment of LaNi5 hydrides showed only one peak in the hydrogen evolution rate vs temperature plot for the activated samples but two peaks for the degraded samples. The low temperature peak of the degraded samples and a peak of the activated samples were related to the hydrogen evolved from the sites which hydrogen could absorb into and desorb from reversibly. The high temperature peak of the degraded samples seems to be associated with the hydrogen from the stable hydrides such as several series of La-Ni stoichiometric compound hydrides and LaH2.