Structural evolution and hydrogen sorption properties of an AB5 obtained by mechanical alloying of an AB5-AB5´mixture

M. RODRIGUEZ; M.R. ESQUIVEL; G. MEYER

Reyhavik, Iceland

Conferencia; MH2008-International Symposium on Metal-Hydrogen Systems; 2008

Hannes Jónsson-Svein Ólafsson-University of Iceland

Commercial La(NiAl)5 was activated by less than 5 hydriding/dehydriding cycles and La0.25Ce0.52Nd0.17Pr0.06Ni5 was sinthesized by low energy mechanical alloying of a La0.25Ce0.52Nd0.17Pr0.06 + 5Ni mixture [1]. Both structures were annealed 24 h at 600 ºC and mixed mechanically. The powders mixture was mechanically alloyed in a low energy mill under Ar atmosphere to obtain  a (LaCeNdPr)(Ni,Al)5 intermetallic according to the following scheme: La(NiAl)5     +    La0.25Ce0.52Nd0.17Pr0.06Ni5               =                           (LaCeNdPr)(Ni,Al)5 The temporal evolution of the mixture during milling was followed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The formation of the new AB5 structure was detected at times as short as 15 h   These are mild conditions of synthesis since these integrated milling time values were only observed in high energy mills. Thermal behavior was studied by differential scanning calorimetry (DSC). Unlike samples obtained in these type of mills, no crystallization peaks were observed for synthesized (LaCeNdPr)(Ni,Al)5 samples when heated from room temperature to 570 ºC.  These unique structural properties of the material were correlated to the hydrogen sorption properties obtained by volumetric methods. References : 1.  M.R. Esquivel, G. Meyer, J. Alloys Compd., 446-447, (2007) , 212-217.