NM08.03.01 : Characterization of Thermophysical Properties of Graphene Oxide and Reduced Graphene Oxide Nanofluids

5:00 PM–7:00 PM Apr 3, 2018 (America - Denver)

PCC North, 300 Level, Exhibit Hall C-E

Monikangkana Talukdar1 Iman Sengupta1 Surjya Pal1 Sudipto Chakraborty1

1, Indian Institute of Technology Kharagpur, Kharagpur, , India

Since the Scotch Tape Method has been discovered in the early 21st century, Graphene has attracted a gob of attention due to its novel electrical, mechanical and thermal properties. It can be produced by various methods such as chemical and thermal reduction of graphene oxide (GO), epitaxial growth by chemical vapor deposition, oxidation by microwave assisted heating and via micro-mechanical cleavage of graphite. Apart from the layered structure, GO nanosheets profusely contain hydroxyl, epoxide, carbonyl and carboxyl groups which make it hydrophilic in nature and leads to the formation of a stable colloidal suspension. In this study, Graphene oxide (GO) has been synthesized by Improved Hummers method or Tour’s method with some modifications and it is converted to reduced graphene oxide (rGO) via thermal treatment. The current work focuses on the characterization of the colloidal suspension of GO and rGO which includes measurement of thermal conductivity, surface tension and detailed study on the rheological properties. Here, authors have measured the thermo-physical properties of GO and rGO at different concentrations ranging from 50-200 ppm (30oC). It has been observed that maximum thermal conductivity for both the nanofluids viz. GO and rGO are found to be at 50 ppm and 100 ppm, respectively. Higher thermal conductivity and lower surface tension of the nanofluid are considered beneficial for any heat transfer application as higher thermal conductivity results in more efficient heat transfer in shorter time and lower surface tension helps in improving the coolant spreadability over the hot surface. Authors have further inquired about the surfactant aided (Cetyl trimethylammonium bromide (CTAB), Sodium Dodecyl Sulfate (SDS) and Tween 20) thermo-physical properties of the nanofluids at the optimized concentration. Surfactant addition leads to reduction in surface tension for both GO and rGO which enhances the wettability of the nanofluid and also contributes in making the suspension stable.The maximum reduction in surface tension for both nanoparticle (rGO) and surfactant aided nanoparticle (SDS + rGO)suspension was found out to be 14.11% and 56.14%, respectively. Similarly, for GO it is 2.55% and (GO+SDS) it is 58.58 %. Maximum enhancement in thermal conductivity of rGO is observed at 100 ppm which is 28.87% higher than that of the base fluid while almost three times increment (88.70%) is reported with addition of SDS. However, the trend is quite different for GO as there is slight increment in thermal conductivity (3.3%) with respect to base fluid and is merely insignificant with addition of SDS(0.4%). In terms of the rheological property, both GO and rGO nanofluids follow shear thinning non-newtonian behavior and are viscoelastic in nature.