Study of rheological properties of nanofluids based on ethylene glycol and graphene oxide

ABSTRACT

Graphene oxide (GO) is a carbon nanomaterial that has unique properties, including excellent thermal conductivity, which can be explored in nanocomposites, as well as in nanofluids. Ethylene glycol (ETG) is a heat transfer fluid that can have its thermal properties enhanced by the addition of GO. However, the GO dispersion capacity and suspension rheology can influence the characteristics of nanofluids, such as flow, stability and heat transfer. The rheological study of ETG/GO nanofluids is important for understanding the colloidal stability of these suspensions and the potential for application as heat transfer fluids. In this work, GO synthesized by modified Hummers method was used to prepare ETG/GO nanofluids for rheological studies. Instrumental techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and thermogravimetry (TGA), confirmed the GO synthesis with approximately 4 layers of graphene nanosheets and 38% of functionalization with oxygenated groups. The hydrophilic surface of GO nanosheets allowed good compatibility with ETG. The flow curve profiles of the ETG/GO nanofluid suspensions were investigated and classified as: non-Newtonian and pseudoplastic by the Ostwald-de Waele model. The insertion of GO to the ETG, increased the viscosity and storage module (G’) in 21% and 8%, respectively. The improved properties show potential of using GO nanofluids for applications in thermal systems.

Keywords
Rheology; Graphene oxide; Ethylene glycol; Nanofluids