NEW MECHANICAL GRINDING PROCESS FOR ANISOTROPIC SM2FE17NX POWDER WITHA NANOCRYSTALLINE STRUCTURE

A new mechanical grinding (MG) process in NH3 and subsequent nitriding in N-2 without a crystallization treatment was developed for synthesi zing Sm2Fe17Nx powders. This process features a shorter MG time compar ed to conventional MG to prevent amorpharization of the alloy structur e and to avoid hydrogen in the ground powders which promotes a diffusi on of nitrogen atoms into their particles. The Sm2Fe17Nx powder with x =3.2 prepared by grinding for 10 h and subsequent nitriding at 723 K f or 6 h showed magnetic anisotropy and its magnetic properties were I-r =1.00 T, H-i(c)=0.61 MA m(-1), and (BH)(max)=129 kJ m(-3) (16.1 MGOe). (C) 1997 American Institute of Physics.