Nanostructure fabrication in oil media for enhanced thermophysical properties

Recently, researchers have focused on molten-salt-based nanofluids, relying on their unique ability to form special fractal-like nanostructures due to the interaction between molten salt ionic molecules and the nanoparticles. These nanostructures are thought to be causing the observed heat capacity enhancement. Thus far, this phenomenon was believed to be exclusive to molten salt nanofluids. In this study, the nanostructure observed in molten-salt-based nanofluids is mimicked, and similar fractal-like nanostructures were formed in-situ in polyalphaolefin (PAO) oil as the base fluid by dispersing alumina (Al2O3) nanoparticles (1% wt. concentration) in the PAO and adding hydroxyl-ended polymer (PPG) (1% wt. concentration) as surfactants to form “artificial” nanostructures by ionically bonding to the nanoparticle's surface. The effect of these artificial nanostructures was studied to confirm that they affect the base fluid similar to the nanostructures formed in molten salt nanofluids. Results showed an increase of 4.86% in heat capacity, and a 42% increase in viscosity was measured at high shear rates, as well as a noticeable non-Newtonian rheological behavior at low shear rates. These results show that the nanostructure has formed and that the thermophysical and rheological properties of the oil have been affected as expected.