The Effect of van der Waals Forces on the Exfoliation of Graphene Sheets from Graphite by Frictional Motion

Abstract

For the application of graphene in engineering, cost-effective and mass production methods are essential. A simple way to obtain graphene sheets is through the use of frictional forces by rubbing bulk graphite on a surface. In this friction-induced fabrication, however, controlling the number of exfoliated graphene sheets presents difficult challenges. Obtaining a quantitative understanding of the relationship between frictional force and graphene exfoliation is important for mass production over a larger area. In our study, we investigated the effect of the van der Waals forces on graphene exfoliation using molecular dynamics simulations. For these simulations, nano-sized graphite was compressed and slid on a SiO2 coated Cu substrate at different thicknesses of the SiO2 layer. The study showed that the critical compressive strain for exfoliation decreases as the coating thickness decreases, achieving multiple layers of exfoliation. The results suggest that van der Waals forces play an important role in the friction-induced exfoliation mechanism, controlling the number of exfoliated layers. In addition, varying the thickness of the coating layers on substrates can be a useful approach for controlling the frictional force in an engineering mass production application.