HYDROGENATION OF INTERMETALLIC COMPOUND CeCo₃ WITH HYDROGEN AND AMMONIA

Interaction of the intermetallic compound CeCo3 with hydrogen (pressure of 25 atm) and ammonia (pressure of 6– 8 atm) is investigated at temperatures of 20–450 ºC: the composition of products is established, formation conditions of the hydride and nitride phases are determined. Dependence of a direction of intermetallide reaction with the ammonia, passing in presence of NH₄Cl (10 wt. % from quantity of intermetallic compound) as activator, from temperature is shown. Formation of hydride phase CeCo₃H₄ is established at hydrogenation of the intermetallide CeCo₃ with both hydrogen and ammonia at heating to 100 ºC. The treatment of an initial alloy with ammonia at temperatures to 250 ºC also ends by formation of tetrahydride CeCo₃H₄. Ammonia use as hydrogenating agent in such conditions leads to dispergation of an initial alloy that it is confirmed by increase in a specific surface area of a product with 5.7 to 18.4 m²/g at hydrogenation temperature of 100 and 250 ºC accordingly. At that calculated average size of particles makes ~1 and ~0.3 micron accordingly. The value of a specific surface area of the product received after carrying out of 5 cycles sorption-desorption at use of hydrogen made only 0.3 m²/g, that testifies to clear advantages of ammonia application for dispergation. In the conditions of the further temperature treatment (300–350 ºC) ammonia causes amorphization of an alloy. It is established, that at intermetallide heating in ammonia atmosphere in temperature area of 400–450 ºC the mixture of products (CeH_x, CeN, Ce₂Co₁₇H_x, Co) is formed according to data of the X-ray analysis. The availability of intermetallide use as working substance in the metal hydride accumulator of hydrogen working at temperatures up to 150 ºC is considered. The hydrogen accumulator based on CeCo3 will have the good operating characteristics: relatively low temperature of hydrogen desorption, acceptable hydrogen capacity, easy to charge and relatively low cost.

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