Observation of High-Speed Microscale Superlubricity in Graphite

Abstract

A sheared microscopic graphite mesa retracts spontaneously to minimize interfacial energy. Using an optical knife-edge technique, we report first measurements of the speeds of such self-retracting motion (SRM) from the mm/s range at room temperature to 25 m/s at 235°C [corrected]. This remarkably high speed is comparable with the upper theoretical limit found for sliding interfaces exhibiting structural superlubricity. We observe a strong temperature dependence of SRM speed which is consistent with a thermally activated mechanism of translational motion that involves successive pinning and depinning events at interfacial defects. The activation energy for depinning is estimated to be 0.1-1 eV.

Experimental advances in superlubricity

“…8(d)). These observations suggest that defects, such as edge defects, can affect superlubricity, while thermal activation can weaken this effect [23].…”

“…For the first time, we measured the speed of selfretracting motion (SRM) in graphite by using a home-made optical in-situ recording system with knife-edge technology [30,23], as shown in Figs. 8(a) and 8(b).…”

Stiffness-dependent interlayer friction of graphene

“…In some of such nanodevices, sliding between graphene layers is typically induced to enable the device functions [4][5][6]. Meanwhile, owing to its weak interlayer van der Waals (vdW) and strong intralayer covalent bonds interactions, multilayered graphene could be ideal solid lubricants [7,8].…”

Ballistic Diffusion in Polyaromatic Hydrocarbons on Graphite

“…10,11 The existence of quadrupole or higher order interactions may cause the super-diffusivity between graphene and graphite observed with atomic force microscopy (AFM). 10,12,13 Interactions of the same nature exist in poly-aromatic hydrocarbons (PAH) adsorbed on graphitic substrates, 14,15 which are characterized by a very low energy barrier for lateral diffusion 16 and can act as nano-sized lubricants. 2 Scattering techniques such as quasi-elastic helium atom scattering (QHAS) and quasielastic neutron scattering (QENS) are powerful tools to investigate very fast molecular dynamics (pico-second time scale and atomistic length scale).…”