Graphene–Multilayer Graphene Nanocomposites as Highly Efficient Thermal Interface Materials

Abstract

We found that the optimized mixture of graphene and multilayer graphene, produced by the high-yield inexpensive liquid-phase-exfoliation technique, can lead to an extremely strong enhancement of the cross-plane thermal conductivity K of the composite. The “laser flash” measurements revealed a record-high enhancement of K by 2300% in the graphene-based polymer at the filler loading fraction f = 10 vol %. It was determined that the relatively high concentration of the single-layer and bilayer graphene flakes (∼10–15%) present simultaneously with the thicker multilayers of large lateral size (∼1 μm) were essential for the observed unusual K enhancement. The thermal conductivity of the commercial thermal grease was increased from an initial value of ∼5.8 W/mK to K = 14 W/mK at the small loading f = 2%, which preserved all mechanical properties of the hybrid. Our modeling results suggest that graphene–multilayer graphene nanocomposite used as the thermal interface material outperforms those with carbon nanotubes or metal nanoparticles owing to graphene’s aspect ratio and lower Kapitza resistance at the graphene–matrix interface.