Superior thermal conductivity of polymer nanocomposites by using graphene and boron nitride as fillers

• We study the defect dependence of the Raman spectrum of graphene sheet.
• We enhance thermal conductivity significantly in polymer nanocomposites.
• The thermal conductivities in polymer nanocomposites are in 6.2–9–9.5 W/mK.
• Polymer nanocomposites exhibit thermal conductivities as high as ∼21.6 W/mK.
• The polymer nanocomposite can lower the LED surface temperature by 21.1 °C.

We report a significant enhancement of thermal conductivity in polymer nanocomposites with graphene and boron nitride as fillers. Strong variations in the Raman spectra for different single-layer graphene flakes are related to the measured thermal conductivity in polymer nanocomposites. In the absence of doping, variations in the Raman parameters are most common, suggesting the presence of excess charges in the samples. Graphene has a Raman D-peak that indicates structural disorder is present, causing the large variations in Raman G peaks. Using this type of graphene and boron nitride for preparing the polymer nanocomposites, the thermal conductivities of the polymer nanocomposites are measured to be in the range of 6.2–9.5 W/mK. The absence of Raman D peaks suggests that structural defects are infinitesimal and the graphene is pristine. Polymer nanocomposites filled with graphene without a D-peak exhibit thermal conductivities as high as ∼21.6 W/mK. As a thermal management material, thermal imaging shows that the polymer nanocomposite can effectively lower the surface mounted LED temperature by 21.1 °C. The existence of Raman D peaks can be used to distinguish two different types of graphenes, establishing the primary prerequisite for achieving a higher thermal conductivity.