A high performance magnetic fluid based on carbon modified magnetite (Fe3O4) nanospheres

Abstract This work reported a carbon layer modified magnetite (Fe3O4) nanospheres (Fe3O4@C) which could be applied in preparing high performance magnetic fluid. The porous Fe3O4@C nanospheres were prepared by calcinating the Fe3O4@Polydopamine (Fe3O4@PDA) precursor in N2 atmosphere. The shear stress of Fe3O4@C-based magnetic fluid was as high as 24.9 Pa at saturated magnetic field, which was about 3.8 times larger than pristine Fe3O4-based magnetic fluid (6.6 Pa). Furthermore, the particle level dynamic simulation was employed to analyze the microstructure evolution and shear stress of Fe3O4@C-based magnetic fluid under applying an external magnetic field. The chain-like model well explained the magnetorheological (MR) mechanism and the simulation results matched perfectly with the experimental data. Since the crystallinity of Fe3O4 was improved during the pyrolysis, Fe3O4@C nanospheres possessed a higher saturation magnetization. The stronger magnetic dipolar forces and chain-chain interactions resulted in a much steadier Fe3O4@C chain-like structure. As a result, it was found that the superior MR performance and high stability of the Fe3O4@C-based magnetic fluid were originated from the core-shell and porous structures of Fe3O4@C. This work proposed a valuable magnetic particle model to prepare high performance magnetic fluid and further understand the origination of MR effects.