Ultrafine composite particles consisting of hexagonal (Cr, M)2N, bcc Fe(Cr), fcc Co(Cr) or fcc Ni(Cr) phases were found to form by the reaction between nitrogen plasma and molten Al-Cr-M (M=Fe, Co or Ni) liquid. The shapes of the AIN and (Cr, M)2N phases change with increasing M content into a cone for the AIN and a sphere for the (Cr, M)2N. The change from (Cr, M)2N to M(Cr) and the decrease in the formation amount of AIN with increasing M content and decreasing Cr content are due to the decrease in the alloy vapor and ultrafine liquid droplets. The composite AIN and M(Cr) particles are also thought to form through the vapor-liquid-solid (VLS) growth mechanisms in which alloy vapors containing Al, Cr, M and nitrogen are preferentially condensed in the remaining liquid M(Cr) region in a coexistent state with AIN solid phase.
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