NITROGENATION STUDY OF BULK SM-2(FE,CO)(17) COMPOUND - COMPARISON BETWEEN 2 PROCESSES

The nitriding of bulk Sm-2(Fe0.5Co0.5)(17) compound was carried out by two different processes: fluidized bed and gaseous nitrogenation. It was investigated by X-ray diffraction and Mossbauer spectrometry. The site occupancy of iron atoms in Sm-2(Fe0.5Co0.5)(17) was determined, s howing a full 6c site filling. The Mossbauer hyperfine parameters incr ease upon nitrogenation; an enhancement up to 50 kOe is noticed for th e hyperfine field. Due to modifications of the sample's surface condit ions, the time dependence of the nitrogen surface concentration differ ed according to the nitrogenation process, evidencing that the nitridi ng kinetics is controlled by an interfacial reaction for gaseous nitro genation, and by diffusion for the fluidized-bed process.