Frictional Properties Of Graphene on Silica Surfaces With Nanoscale Roughness

Controlling friction and adhesion is critical in the operation of machines and devices and dramatically impacts their longevity and energy efficiency. While boundary lubricant additives are often employed in oils, advanced technologies such as microelectromechanical systems devices (MEMS) are not amenable to such hydrodynamic lubrication. A key challenge in developing lubrication schemes for such systems is how to reduce wear at the rough surfaces of such devices, where nanoscaled asperity-asperity contacts dominate the interfacial contacts. Recently, nanoscale carbon lubricants, such as graphene, have sparked significant interest as protective surface coatings for devices. Here we have investigated the frictional properties of graphene on silicon dioxide nanoparticle films (with surface roughness of 10 nm rms), which mimic the nanoscaled asperities found on realistic surfaces. Atomic Force Microscopy (AFM) studies revealed that graphene partially conforms to these rough surfaces and as the number of layers increase, conformity decreases due to stiffening of the thicker layers. Friction nominally decreases as a function of layer thickness, but was also found to depend on contact area of the tip and interfacial shear strain of the graphene associated with its adhesion to the substrate.

Frictional Properties Of Graphene on Silica Surfaces With Nanoscale Roughness Academic Article