Surfactant assisted exfoliation of high purity graphene in aqueous solution as a nanofluid using kitchen blender: Influence on dispersion, thermal conductivity and rheological properties

Abstract

In this work, graphene is exfoliated from graphite flakes in distilled water solution containing Tween 80 as surfactant and by using the mechanical exfoliation method through a kitchen blender. The blending time is an important parameter for the size reduction and concentration of graphene exfoliation in a nanofluid. Graphene obtained using a kitchen blender is of high purity having no basal plane defects, as depicted from Raman spectroscopic investigation. The viscosity of graphene nanofluid increases with blending time up to 7 h and thereafter the viscosity decreases. All graphene nanofluid samples prepared using different blending time shows shear thinning behavior by fitting the power law of non-linear viscoelastic measurement data. The linear viscoelastic region measured was in the strain range of 0.01–0.8%. Further, the frequency sweep measurement using a rheometer has indicated the gel-like behavior of graphene nanofluid in a certain frequency range and depends on the concentration of graphene. The use of two-dimensional nanosheets-based nanofluid has attracted the attention of researchers for improving pool boiling properties. Herein, the pool boiling of graphene nanofluid at 7 h of blending shows the 77.4% enhancement in critical heat flux (CHF). This work has established mechanical exfoliation as a process to synthesize the graphene nanofluid and can be used for heat transfer applications.