High coercive Sm-Fe-Co-N powder prepared by applying the HDDR process

The Hydrogen Disproportionation Desorption Recrystallisation process (HDDR) is still used to achieve high coercive fine powders of Nd2Fe14B. Here we s tudy the solid-gas reactions (hydrogenation and nitrogenation) on Sm-2(Fe1- xCox)(17) alloys. In order to insure stoichiometry of the Sm2M17 alloys alo ng the thermal treatments, some iron has been substituted by cobalt (x = 0. 3, 0.5). Fine particles were achieved by using a planetary miller, and siev ed up to a size less than 10 mu m. Solid-gas reactions (Sm-2(Fe1-xCox)(17)/ H-2, N-2) were analysed by using a thermomagnetic balance, the sample react ing under the flowing gas. Clear relationships between the particle sizes a nd the kinetics of reactions were found. The HDDR process was optimised for recrystallisation rate, plateau temperature and duration. High coercive Sm -2(Fe1-xCox)(17)N-y powders with H-cj up to 18 kOe were achieved. (C) 1999 International Association for Hydrogen Energy. Published by Elsevier Scienc e Ltd. All rights reserved.