Reversible hydriding of LaNi5-xAlx-Pd composites in the presence of carbon monoxide

Carbon monoxide is one of the most dangerous impurities in gas mixtures involved in the hydriding of intermetallic compounds, and up to the present rime the concentration limit 0.03 vol.% CO has nor been surmounted The objective of the present work was to investigate the possibility of reversibly hydriding 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 at 300 MPa. The intermetallics were preliminarily dispersed by hydriding and mechanical grinding. The concentration of palladium black in the powder mixtures 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 carbon 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 raised the stoichiometric concentration above 0.5 stabilized the absorption properties 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 increased the stability of hydrogen absorption by the intermetallic. It is noted that the effect of palladium was more positive than that of aluminum.