Synthesis and rheological investigation of a magnetic fluid using olivary silica-coated iron particles as a precursor

A new type of magnetic fluid was prepared by dispersing monodispersed iron–silica (Fe–SiO2) composite particles in polyethylene glycol (PEG) 400. The composite particles Fe–SiO2 were synthesized by hydrogen reduction from α-Fe2O3–SiO2 spheres. Their microstructures were observed by a high-resolution transmission electron microscope (HRTEM) and the magnetism was characterized with a superconducting quantum interference device (SQUID) magnetometer. Both steady-state and dynamic rheological properties of the magnetic fluid under different magnetic fields were studied by using a rheometer. Experimental results show that this magnetic fluid has a relatively high magnetoviscous effect at low shear rates. The yield stress of this material shows an increasing trend with a magnetic flux density. Also, viscoealstic properties of such materials are different from conventional ones.