Magnetorheological properties of Fe-Co nanoparticles with high saturation magnetization and low coercivity

Fe-Co alloys exhibit an excellent saturation magnetization, which makes them become a potential candidate for the high property magnetic particles in magnetorheological fluids (MRFs). How to decrease their coercivity and residual magnetization without sacrificing the saturation magnetization is a crucial problem to be solved. In this study, Fe-Co nanoparticles were prepared by DC arc discharge and further disposed through low temperature annealing in Ar atmosphere. The successful synthesis of Fe-Co nanoparticles was proved by x-ray diffraction and EDS. The vibrating sample magnetometer results revealed that the prepared Fe-Co nanoparticles had a saturation magnetization of 208 emu g(-1), while the coercivity and remanent magnetization were 58 Oe and 5.8 emu g(-1), respectively. The MR properties of Fe-Co nanoparticles based MRFs (FeCoNP-MRFs) with 10% particles by volume fraction were systematically investigated. The FeCoNP-MRFs showed up to 4.61 kPa dynamic shear stress at 436 kA m(-1) magnetic field and an excellent reversibility. The MR properties of FeCoNP-MRFs were fitted well by Bingham and power law model, and described by Seo-Seo and Casson fluid model. Meanwhile, the sedimentation ratio of FeCoNP-MRFs was still 87.3% after 72 h, indicating an excellent sedimentation stability.

Automated summary

Fe-Co nanoparticles were successfully synthesized by DC arc discharge and low temperature annealing in Ar atmosphere, with a saturation magnetization of 208 emu g(-1), coercivity of 58 Oe, and remanent magnetization of 5.8 emu g(-1). FeCoNP-MRFs exhibited a dynamic shear stress of 4.61 kPa at a magnetic field of 436 kA m(-1), excellent reversibility, and a sedimentation ratio of 87.3% after 72 hours, indicating good sedimentation stability.