Increases of coercivity of Sm2Fe17Nx(x is about 3.1) magnetic powder passivated by phosphoric acid

The magnetic powder Sm 2 Fe 17 N x has recently garnered considerable interest due to its competitive pricing. In this study, the preparation of Sm 2 Fe 17 N x magnetic powder by melt quenching and nitriding process was successfully completed. In order to obtain a higher coercivity, the particle size of the magnetic powder was reduced to a diameter of less than 2 μm through ball milling. It was observed that as the ball milling time was extended, the coercivity of the magnetic powder exhibited a decline that was premature in comparison to the expected results. Additionally, the presence of minute particles of magnetic powder may appear spontaneous combustion phenomenon. Accordingly, Sm 2 Fe 17 N x magnetic powder with high coercivity ( H cj  = 842.8 kA/m) was prepared by phosphoric acid passivation process. Through XRD patterns, it was found that the phosphoric acid passivation process markedly enhanced the antioxidant capacity of the magnetic powder. Through SEM images, it is found that the fine magnetic powder exhibits a sheet structure and has strong shape anisotropy. The research indicate that the phosphoric acid passivation process is effective in enhancing the stability of Sm 2 Fe 17 N x magnetic powder and inhibiting the oxidation reaction of magnetic powder during use. This has a beneficial impact on the service life of permanent magnet devices in industrial production.