Giant electrorheological effect in Fe2O3 nanofluids under low dc electric fields

In this paper, we report the electrorheological (ER) properties of low concentration Fe2O3 nanofluids prepared in ethylene glycol (EG). Spherical Fe2O3 nanoparticles (NPs) were obtained by emulsion method in powder form. The obtained NPs were stabilized in time by acetylacetone in EG. The prepared Fe2O3 NPs were characterized using X-ray diffraction and transmission electron microscopy. Fe2O3 nanofluids were tested for ER behavior at low dc electric fields. Giant ER (GER) effect was observed in Fe2O3 nanofluid of higher concentration at electric field of 10 V/mm. The current passing through suspensions and electrohydrodynamic (EHD) convection was reflected in ring like structure formation of Fe2O3 NPs. Relation between suspension viscosity and Mason number revealed that the analysis has to be revised for GER fluids. (C) 2010 American Institute of Physics. [doi:10.1063/1.3462445]