Stability and thermophysical properties of water-based nanofluids containing triethanolamine-treated graphene nanoplatelets with different specific surface areas

Abstract

Abstract A novel synthesis procedure is presented for preparing triethanolamine-treated graphene nanoplatelets (TEA-GNPs) with different specific areas (SSAs). Using ultrasonication, the covalently functionalized TEA-GNPs with different weight concentrations and SSAs were dispersed in distilled water to prepare TEA-GNPs nanofluids. A simple direct coupling of GNPs with TEA molecules is implemented to synthesize stable water-based nanofluids. The effectiveness of the functionalization procedure was validated by the characterization and morphology tests, i.e., FTIR, Raman spectroscopy, EDS, and TEM. Thermal conductivity, dispersion stability, and rheological properties were investigated. Using UV–vis spectrometer, a highest dispersion stability of 0.876-relative concentration was reached after 100 days from preparation. Water-based TEA-GNPs nanofluids showed quite Newtonian behavior with an increase in the measured values of viscosity as weight concentration increases and temperature decreases. As the classical models of viscosity underestimated the experimental viscosity data for the TEA-GNPs nanofluids, a correlation was proposed and showed good agreement. Thermal conductivity values increased as the weight concentration, SSA, and temperature increased. Nanofluid containing TEA-GNPs with SSA of 750 m2/g and 0.1-wt% showed the highest increase in thermal conductivity, i.e., from 0.673 to 0.752 W/m K as the temperature increased from 20 to 40 °C. The novel type of nanofluids that were prepared in this study revealed notable potential for use as advanced working fluids in various heat transfer applications.