Effect of Functionalization Process on Thermal Conductivity of Graphene Nanofluids

In this research, Graphene was synthesized by chemical vapor deposition (CVD) method in atmosphere pressure (14.7 psi). Different functionalization method was used for oxidizing of graphene such as acid and alkaline treatments. The Functionalized graphene (FG) was characterized by FTIR and Raman spectroscopy. Nanofluid with water and different concentration (0.05, 0.15 and 0.25 wt %) of FG were prepared. Thermal conductivity of nanofluids was measured by transient hot wire method. The acid functionalization introduces significant defects in graphene structure, degrading its unique properties such as superior carrier mobility, mechanical strength and chemical stability. In alkali functionalization method, the graphene is not effectively defected. Therefore, the transport properties of graphene maintained and this method showed enhancement in thermal conductivity more than acid fictionalization in same conditions. In optimum condition (0.25 wt % graphene of alkaline method in water), thermal conductivity ratio were increased (24.4% at 20°C and 33.9% at 60°C).