Synthesis and analysis of the properties of ferro-fluids

We report the rheological properties of ferro-fluid (FF) containing iron oxide nano-particles. At first, a FF was synthesized by using chemical co-precipitaton[1]. The microstructure study using SEM revealed that the FF contained nano-particles with the mean particle size of 35nm. The XRD study revealed that we have well crystallized structures of magnetite; they appeared to be approximately single crystalline structures. The rheological results proved that the FF has non Newtonian behavior, it is a shear thinning fluid in all magnetic fields, Moreover, the magnetic field increases the viscosity in a definite shear rate due to the nano-particles agglomerations and formation of chain-like clusters. It was concluded that the FF underwent the separation phase condensation at magnetic fields higher than about 100 kA/m. In this case that the instrument reveals negative viscosity in the low shear rates, a phenomenon reported in some articles previously in the case of oscillating magnetic field, but In our case the magnetic field is constant but the ferro-fluid is under rotation.