Vertically and compactly rolled-up reduced graphene oxide film/epoxy composites: a two-stage reduction method for graphene-based thermal interfacial materials

Graphene-based thermal conductive composites have come into notice in recent years. A considerable number of works have been devoted to increasing their thermal conductivity by increasing the graphene loading. However, it is not practical for the fabrication process when the graphene content is too high. In this work, a novel fabrication method of graphene-based composites is proposed, by which a thermal-reduced vertically aligned reduced graphene oxide (TR-VArGO)/epoxy composite was obtained. This method mainly involves a two-step reduction of graphene oxide and a hand-rolling process of reduced graphene oxide film. The thermal conductivity of the TR-VArGO/epoxy composite is up to 2.645 W m(-1) K-1, i.e. an enhancement of as high as 887% compared to pure epoxy. By contrast, a randomly distributed TR-rGO sheets/epoxy composite with the same rGO loading has a thermal conductivity of only 1.270 W m(-1) K-1. This difference is attributed to the vertical alignment of TR-VArGO films, which provides a rapid and effective heat-transfer path. This mechanism of high thermal conductivity is further confirmed by theoretical prediction and finite element calculation. The results obtained indicate that the vertically aligned reduced graphene oxide/epoxy composite may become a good candidate for thermal interfacial materials.