Properties of bulk magnets prepared by hot pressing using Zn- coated Sm-Fe-N magnetic powder by electrodeposition

The adequate dispersion of Sm-Fe-N magnetic powders and Zn powders with limited content is the key to improving the comprehensive performance of Sm-Fe-N/Zn bonded magnets. In this paper, a uniform and low-oxygen-content Zn coating was electrodeposited on the surface of Sm-Fe-N magnetic powders in an ionic liquid by homemade magnetic stirring fluidized bed electrodeposition equipment. Subsequently, Sm-Fe-N/Zn composite magnets were obtained by hot pressing. It is shown that the Zn content adjustments can be effectively realized by electrochemical amounts of electricity, and with the increase of Zn content, the intrinsic coercivity Hcj and the compressive strength δs of the magnet increase. Compared to directly mixing commercial Zn powders and Sm-Fe-N powders, The hot-pressed magnet prepared by electrodeposited magnetic powders has higher coercivity and compressive strength even though the Zn content is lower. This is attributed to the improved dispersion uniformity of the Zn powders with the magnetic powders, as well as the reduced oxygen content of the powders. During hot pressing, the electrodeposited Zn particles melt at high temperatures and flow around the magnetic powder to form a "core-shell" structure. The properties of Sm-Fe-N bulk magnets obtained by hot pressing with magnetic powders containing 7.06 wt.% Zn coated are: (BH) max= 25.74 MGOe, HCj= 5.68 KOe, δs=174 MPa.