Dispersions of Graphene for use as Thermal and Functional Fluids

Abstract

Graphene's combination of properties makes it a material with great potential in a wide range of applications. High thermal conductivity and good tribological properties mean graphene has been proposed as an additive for both lubricants and thermal fluids; being used to form nanofluids with improved properties. However, the use of graphene in these applications requires the significant challenge of dispersing graphene in applied fluids to be overcome.

In this work graphene, and its functionalised derivatives were dispersed in both polar and non-polar fluids using a range of techniques, following which the properties of these fluids were analysed. Initially, the dispersibility of reduced graphene oxide (rGO) in water was investigated and a novel method of using N-methyl-2-pyrrolidone (NMP)to act as a dispersant for rGO in polar fluids was developed. Using this method dispersions of rGO in water were produced at over six times the concentration possible by standard dispersion.

Working in more applied fluids efforts were made to improve the dispersibility of graphene materials in applied polar fluids such as oils. Stable dispersions of graphene materials in commercial oils were produced through functionalisation of graphene, with a range of reagents, to improve its compatibility with non-polar solvents. These functionalised graphenes were then dispersed in commercial lubricants to form stable dispersions and the tribological properties of these dispersions were tested showing that it was possible for functionalised graphenes to improve the performance of commercial lubricants.

To assess the impact of graphene on the thermal properties of applied fluids dispersions of graphene materials were prepared in a commercial coolant. The thermal properties of this nanofluid were then determined and it was shown that the addition of graphene materials can improve the thermal properties of applied fluids.