STABILIZATION OF HIGH DISSOCIATION PRESSURE HYDRIDES OF FORMULA LA1-XCEXNI5 (X=0-0.3) WITH CARBON-MONOXIDE

We have previously demonstrated the efficiency of CO and SO2 surface t reatments for the stabilization of the LaNi5 hydride. The as-treated h ydrides were stable in air at room temperature. Here, CO surface treat ment is applied to higher dissociation pressure systems, La1-xCexNi5 ( x = 0, 0.1, 0.2 and 0.3) compounds. Stabilization of the hydrides is s tudied at two temperatures, 273 and 298 K. We found that the hydrogen retention time for CO-treated La1-xCexNi5 hydrides is dramatically imp roved compared with that of untreated hydrides. Nevertheless, for both temperatures, the hydrogen retention time in treated hydrides is foun d to decrease with increasing cerium content. The results are explaine d on the basis of P-C-T measurements carried out at room temperature. As expected, the hydrogen absorption and desorption pressures and the hysteresis increase with cerium content. The dehydrogenation kinetics of CO-treated hydrides is related to the cerium content of the alloys. (C) 1998 Elsevier Science S.A.