The effect of tungsten addition on the magnetic properties and microstructure of SmFeN–α-Fe nanocomposites
Waldemar Kaszuwara , Marcin Leonowicz , J.A Kozubowski
AbstractThe effect of tungsten addition, in the range of 0–17 at.\%, on the magnetic properties and microstructure of SmFeN–α-Fe permanent magnet nanocomposites is presented. The magnets were prepared by mechanical alloying of elementary powders of Sm, Fe and W, followed by annealing and nitriding. The addition of tungsten leads to initial increase and further decrease of the coercivity with a maximum value of 250 kA/m for 7 at.\% W. The remanence, however, continuously decreases from 1.2 T for 0\% W down to 0.7 T for 17 at.\% W. The maximum value of (BH)max, (120 J/m3), was obtained for 2 at.\% W. The measurements of Curie temperature vs. W content showed a constant and decreasing values for α-Fe and the Sm2Fe17 phase, respectively. This behaviour can be explained by the dissolution of some W atoms in the Sm2Fe17 phase. X-ray diffraction analysis indicated, beside the α-Fe and Sm2Fe17 phases, the existence of pure W in the microstructure. Addition of W leads to reduction of the α-Fe crystallite size (20 nm for 0\% W, 18 nm for 7\% W and 8 nm for 17\% W). The high resolution electron microscopy investigations show randomly distributed small (below 20 nm) crystallites of tungsten. Thus for a small amount of W the remanence is still substantially enhanced. The increase of the coercivity, for W contents up to about 7 at.\%, can possibly be attributed to increased magnetic anisotropy of the Sm2(Fe,W)17N3 phase.
|Journal series||Materials Letters, ISSN 0167-577X|
|Keywords in English||magnetic properties, Microstructure, SmFeN–αFe, Tungsten|
|ASJC Classification||; ; ;|
|Publication indicators||= 5; = 9; = 11.0; : 2000 = 0.75; : 2006 = 1.353 (2) - 2007=1.822 (5)|
|Citation count*||11 (2015-04-25)|
* presented citation count is obtained through Internet information analysis and it is close to the number calculated by the Publish or Perish system.