A new method of nitrogenation of M2Fe17 powder alloy via chemical reaction with sodium azide (NaN3) as a nitrogen source (M = Y or Ln)

Abstract

Nitrogenation of M₂Fe₁₇(M = Y or Ln) intermetallic alloy has been successfully performed by heating, at 573 < T/K < 723 in a closed container, compact mixtures of the powder alloy with sodium azide (NaN₃) as a solid nitrogen source. A detailed study of the reaction mechanism was investigated for a Y₂Fe₁₇ alloy. The NaN₃ fine powder was found to be very convenient as an oxygen-free nitrogen source. Its high efficiency in the nitrogenation process seems to be related to its low decomposition temperature, and to 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 reducing the oxides and hydroxides of the passivation layer. This mechanism improves considerably the diffusion rate of nitrogen through the surface, so that the reaction can come to completion within a few hours at temperatures < 673 K.