Nanofluids, suspensions of nanomaterials in a base fluid, have various superior properties compared with those of their base fluids. The distinguished features of nanofluids make them potentially useful in several applications such as in cooling of electronic equipment, vehicle engines, nuclear reactors, biomedical engineering, and energy efficiency enhancement. Among all the physical properties of nanofluids, the transport properties are the most important for many applications [1]. Highly stable graphene and graphene oxide (GO)-based nanofluids were prepared without using any surfactant. Electrical conductivity (EC), thermal conductivity (TC), and rheological properties of the nanofluids were measured at different mass fractions and various temperatures. The viscosities of ethylene glycol (EG), glycerol, and GO/EG and graphene/glycerol nanofluids as functions of shear rate and temperature were measured. The results showed that the viscosity of nanofluids decreased nonlinearly with increasing shear rate at low shear rates indicating the strong “shear-thinning” behavior. This shear thinning behavior becomes more pronounced at the higher GO or graphene concentrations due to the stronger sheet–sheet and multi-sheet interactions with the increase in concentrations. 401.49% enhancement in viscosity of glycerol was achieved by loading of 2% graphene nanosheets at shear rate 6.32 s-1 and 20 oC. GO/EG nanofluids exhibited a non-Newtonian shear thinning behavior followed by a shear-independent region. The EC of GO/distilled water increased linearly with increasing mass fraction of GO and it reached to about 232 μS/cm for a mass fraction of 0.0006 at 25 °C. 25,678 % enhancement, in EC of distilled water was observed by loading 0.0006 mass fraction of GO at 25 oC. Maximum of ca. 30 % enhancement in TC was achieved for GO/EG nanofluid with mass fraction of 0.07.

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