A NEW METHOD OF NITROGENATION OF M(2)FE(17) POWDER ALLOY VIA CHEMICAL-REACTION WITH SODIUM-AZIDE (NAN3) AS A NITROGEN-SOURCE (M=Y OR LN)

Nitrogenation of M(2)Fe(17) (M=Y or Ln) intermetallic ahoy has been su ccessfully performed by heating, at 573 < T/K < 723 in a closed contai ner, compact mixtures of the powder alloy with sodium azide (NaN3) as a solid nitrogen source. A detailed study of the reaction mechanism wa s investigated for a Y2Fe17 alloy. The NaN3 fine powder was found to b e very convenient as an oxygen-free nitrogen source. Its high efficien cy in the nitrogenation process seems to be related to its low decompo sition temperature, and tb-its capability of supplying,at the surface of the particles of the alloy; a very reactive sodium (T-melt = 370 K) that very rapidly cleans the surface of the alloy particles by reduci ng the oxides and hydroxides of the passivation layer. This mechanism improves considerably the diffusion rate of nitrogen through the surfa ce, so that the reaction can come to completion within a few hours at temperatures <673 K.