▎ 摘　　要

Purpose: In the current study, the preparation of water-based graphene nanoplatelets (GNP) nanofluids has been in-depth studied with various characterization techniques including zeta potential measurements, surface tension measurements, rheological analysis along with thermal conductivity measurements. It was aimed to investigate the effect of specific surface area and concentration of nanoparticles on thermophysical and rheological properties of aqueous GNP nanofluids. Theory and Methods: The two-step method was carried out for the nanofluid preparation. The GNP concentrations of the nanofluids were prepared at 0.5, 1.0, and 2.0 wt% in 50 mL distilled water. The probe type direct ultrasonication device (UP400S, Hielscher Ultrasonics GmbH, Teltow, Germany) was adjusted to 0.5 cycles and 50% amplitude. The ultrasonication was performed in 100 mL wide neck borosilicate glass bottles. Results: It has been observed that the zeta potential increases with the increase in the specific surface area of nanoplatelets. While shear thinning behavior was observed at high concentration nanofluids in the low shear rate region with the increase in nanoparticle concentration, shear thickening was observed with the increase in the shear rate. The increase in thermal conductivity was measured with the 3 omega method, and the thermal conductivity increment decreased with increasing GNP specific surface area. As for the surface tension measurements, a decrease in surface tension values compared to distilled water was observed due to the hydrophobic nature of GNP. Conclusion: The results show that GNP nanofluids are promising, with increased thermal conductivity values and favorable rheological behavior. However, it is necessary to continue rapidly in nanofluid research for better nanofluidic stability and popularization of use in practical applications.