Facile synthesis and magnetorheological properties of superparamagnetic CoFe2O4/GO nanocomposites.

In this study, cobalt ferrite/graphene oxide (CoFe 2 O 4 /GO) nanocomposites were synthesized successfully by a facile sonochemical method. The microstructure and physical properties of CoFe 2 O 4 /GO nanocomposites were investigated in detail by TEM, XRD and SQUID. It was found that GO nanosheets were fully exfoliated and decorated homogeneously with CoFe 2 O 4 nanoparticles having diameters of 8∼15 nm. The field-dependent magnetization curve indicated superparamagnetic behavior of as-prepared CoFe 2 O 4 /GO with saturation magnetization ( M s ) of 34.9 emu/g at room temperature. The ferrofluid was prepared by the obtained CoFe 2 O 4 /GO with 25 wt% particles and its magnetorheological (MR) properties were tested using a Physica MCR301 rheometer fitted with a magneto-rheological module. The CoFe 2 O 4 /GO-based ferrofluid exhibited typical MR effect with increasing viscosity, shear stress and yield stress depending on the applied magnetic field strength. [ABSTRACT FROM AUTHOR]