Reversible hydriding of LaNi5-xAlx-Pd composites in the presence of carbonmonoxide

Carbon monoxide is one of the most dangerous impurities in gas mixtures inv olved in the hydriding of intermetallic compounds, and up to the present ri me the concentration limit 0.03 vol.% CO has nor been surmounted The object ive of the present work was to investigate the possibility of reversibly hy driding LaNi5-xAlx-Pd composites in gas mixtures containing up to 5 vol. % CO. The experimental specimens were mixtures of palladium black and LaNi5. LaNi4.7Al0.3, LaNi4.5Al0.3, LaNi4.2Al0.8 and LaNi4Al powders cold pressed a t 300 MPa. The intermetallics were preliminarily dispersed by hydriding and mechanical grinding. The concentration of palladium black in the powder mi xtures was varied from 0 to 1.5 mass%. Ir was shown that it is possible to reversibly hydride LaNi5-xAlx-Pd composites in mixtures of hydrogen and car bon monoxide containing up to 5 vol.% CO at the temperatures 423 and 473 K, Ir was established that alloying LaNi5 with aluminum in amounts which rais ed the stoichiometric concentration above 0.5 stabilized the absorption pro perties of LnNi(5-x)Al(x)-Pd in the presence of CO. The composition LaNi4Al was optimal. Palladium additions to LaNi5-xAlx-Pd composites also increase d the stability of hydrogen absorption by the intermetallic. It is noted th at the effect of palladium was more positive than that of aluminum.