Title :
Solid-state phase transformation in nanocrystalline R2Fe 17Cx compounds (R=Sm or Nd; x=0-1)
Author :
Mao, O. ; Altounian, Z. ; Ström-Olsen, J.O. ; Yang, Jun ; Chen, X.
Author_Institution :
Dept. of Phys., McGill Univ., Montreal, Que., Canada
fDate :
9/1/1996 12:00:00 AM
Abstract :
A. Solid-state phase transformation (SSPT) is observed in nanocrystalline Sm2Fe17Cx, x=0-1 (Th 2Zn17-type carbides) prepared by both ball milling and rapid solidification. Upon annealing at 800°C the Sm2Fe14C (Nd2Fe14B-type) phase is formed for x⩾10.3. For x between 0.3 and 1.0, the Sm2 Fe17Cy, (y~0.3) and Sm2Fe14 phases co-exist. The process of the SSPT to Sm2Fe14C is faster in finer-grain samples. The annealing time required for a complete transformation varies from 15 min for a sample with an average grain size of 40 nm to 28 h for a 200 nm grain size sample. These results suggest that the SSPT is made accessible by reducing the grain sizes. Studies on Nd2Fe17C1.0 show that certain Nd2 Fe14C powders synthesized through SSPT contain highly anisotropic particles, suggesting a promising technique to produce anisotropic Nd2Fe14B-type permanent magnets
Keywords :
annealing; ferromagnetic materials; grain size; iron alloys; magnetic anisotropy; magnetic particles; neodymium alloys; permanent magnets; powder technology; rapid solidification; samarium alloys; solid-state phase transformations; 15 min to 28 h; 200 nm; 40 nm; 800 C; Nd2Fe17C; Nd2Fe17Cx; Sm2Fe17C; Sm2Fe17Cx; annealing; ball milling; grain size; highly anisotropic particles; nanocrystalline; permanent magnets; phases co-existence; rapid solidification; solid-state phase transformation; Anisotropic magnetoresistance; Annealing; Ball milling; Grain size; Iron; Neodymium; Permanent magnets; Powders; Solid state circuits; Zinc;
Journal_Title :
Magnetics, IEEE Transactions on
