Synthesis and characterization of Nd2Fe14B-25 vol % Fe nanocomposite magnets

Synthesis of nanocomposite two-phase permanent magnet materials by mechanical milling requires optimization of the volume fractions of the two phases, milling time, heat treatment temperature, and time. In the present study, optimization of milling time, heat treatment temperature, and time have bee...

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Bibliographic Details
Published in:Journal of applied physics 1998-01, Vol.83 (2), p.921-929
Main Authors: Raviprasad, K., Funakoshi, M., Umemoto, M.
Format: Article
Language:English
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Summary:Synthesis of nanocomposite two-phase permanent magnet materials by mechanical milling requires optimization of the volume fractions of the two phases, milling time, heat treatment temperature, and time. In the present study, optimization of milling time, heat treatment temperature, and time have been carried out by fixing, respectively, the volume fractions of hard and soft phases at 75 and 25. Prior to the synthesis of nanocomposite magnets, the effect of milling on the magnetic properties of the hard phase was studied. The results on milling of hard phase have shown the lower and upper limits of milling time to be 108 and 144 ks, respectively. Milling for 144 ks and heat treatment at 823 K for 1.8 ks was found to result in nanocomposite magnets with the best properties. The microstructural characterization has shown clearly that when the heat treatment temperature is higher, grain growth takes place and consequently the magnetic properties of the nanocomposites deteriorate. Compositional analysis using transmission electron microscopy has shown grains richer in Fe and Nd. The rationalization of magnetic properties shows that to improve the energy product, coercivity needs to be improved. Alloying addition of Cr and Cu was found to improve coercivity and consequently the energy product. Finally, it was shown that by using finer Fe particles one can reduce the time required for milling and avoid many adverse effects resulting from long time milling.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.366779