SYNTHESIS, CHARACTERIZATION AND INITIAL HYDROGEN SORPTION PROPERTIES OF A LmNi5-Ni MIXTURE OBTAINED BY LOW ENERGY MECHANICAL ALLOYING

B.A. TALAGAÑIS; M.R. ESQUIVEL; G. MEYER

CIUDAD DE SAN NICOLAS-BUENOS AIRES-ARGENTINA

Congreso; JORNADAS SAM/CONAMET 2007; 2007

ASOCIACION ARGENTINA DE MATERIALES

In this work, the A site of different AB5 intermetallics is replaced by Ce rich mischmetal, (Mm) (52,1 wt% Ce, 25,5 wt% La, 16,9 wt% Nd, 5,5 wt% Nd), La and La enriched mischmetal (Lm) (18,6 wt% Ce,  67,2 wt% La, 4,89 wt% Pr, 7,74wt% Nd). LmNi5 intermetallic was synthesized by low energy mechanical alloying of MmNi5 and LaNi5. The structure parameters of hexagonal MmNi5 and LmNi5 were obtained from Rietveld refinements of x ray diffraction (XRD) patterns of as milled and heated samples. LmNi5 and MmNi5 cell parameter values obtained are a = 4,975 Å and c = 3,976, and  a = 4,922 Å and c = 3,987 Å, respectively. Particle morphology of milled LmNi5 was obtained from scanning electron microscopy (SEM) images. The sorption properties of LmNi5 were studied by a volumetric technique.  As milled LmNi5 samples show excellent kinetics properties. No activation stage is needed since hydriding-dehydriding behavior is the same at first and tenth cycle. Hydriding and dehydriding curves were obtained at room temperature, 50 ºC and 90 ºC. Ninety percent of experimental sample absorption value is reached in 115s in absorption and 189s in desorption at room temperature.