Anisotropic Sm-Fe-N particles prepared by surfactant-assisted grinding method

Anisotropic Sm-Fe-N submicron particles were synthesized by a surfactant-assisted ball milling in the heptane solvent. It was found that oleic acid (OA) additions are effective in decreasing particle size and avoiding inhomogeneous pulverization. The final product shows uniform and flake-like morphology with the particle size in the single-domain scale. Considering the high sensitivity of this ultra-fine powder to the oxygen and water, further milling in a mixture of the OA and silane coupling agent solution was carried out to fabricate powder with corrosion resistance. Corrosion tests for about one year confirmed that the as-coated powders show improved corrosion resistance as compared to the noncoated samples. Simultaneously, surfactant-assisted milling could produce well dispersed flake particles which would improve the particle alignment and formability of bonded magnets under a magnetic field. Mechanisms responsible for these effects induced by surfactant have been discussed in this paper. (C) 2014 Elsevier B.V. All rights reserved.