(479a) Graphene Sheets-Oil Nanocomposites: Equilibrium and Transport Properties From Molecular Simulation

Graphene sheets (GSs), one-atom-thick layers of carbon atoms, are receiving enormous scientific attention because of extraordinary electronic and mechanical properties. These intrinsic properties will lead to innovative nano-composite materials that could be used to produce novel transistors and thermally-conductive polymeric materials. Such materials could be obtained by dispersing thermally conductive nanoparticles within polymers.

We conducted molecular dynamics simulations of functionalized graphene sheets dispersed in liquid organic linear alkanes (oils) at room conditions. We observed that as the GS volume fraction in GS-oil dispersion increases, the system manifests different morphologies. At low GS volume fraction, the GSs appear uniformly dispersed throughout the matrix. At high GS volume fraction, the GS yield a system with no positional order, but with long range orientational order. This is reminiscent of a lyotropic phase transition from a disordered to a nematic phase which was characterized using the order parameter approach. The phase boundaries are likely to depend on the GS size and functionalization. Nematic phases may yield to anisotropic heat transfer properties.

We conducted non-equilibrium molecular dynamics simulations for GSs dispersed in octane to characterize heat-transfer properties of the GSs. It was found that the resistance to heat transfer offered by the interface between the GSs and the oil, called the Kapitza Resistance (RT), is less than that found for carbon nanotubes dispersions.