On the Al Content and Characterization of MmNi5-XAlx Synthesized by Mechanical Alloying

The development of new technologies applied to hydrogen thermal compression is oriented to the design of reversible hydride forming compounds that reach the desired pressure conditions by modifying the temperature. Particularly, the main efforts are focused on the research of multi substituted AB5 compounds.In this work, three mixtures of Mm/(5-xn)Ni/(xn)Al (Mm = Mischmetal = La0.25Ce0.52Nd0.17Pr0.06) with nominal composition xn = 0.5, 0.75 and 1 were milled by low energy reactive milling to synthesize the intermetallic of composition MmNi5-xAlx. Samples were annealed under Ar atmosphere at 600 ¼C for 24 h. The structure and microstructure were characterized by X-ray powder diffraction (XRD). The content x of Al in the AB5 structure was calculated by means of a geometrical model developed under the hypothesis of rigid spheres. The effect of annealing on the microstructure for each nominal composition was analyzed. Minor Mm-Ni phases formed were quantified. The results of this work are framed within a project including the synthesis and optimization of materials applied to the development of multi stage thermal compressors.