Superlubricity through graphene multilayers between Ni(111) surfaces

TL;DR

This study demonstrates that inserting multiple graphene layers between Ni(111) surfaces significantly reduces adhesion and friction, enabling superlubricity through electronic coupling and suppression of non-equilibrium phonons.

Contribution

First-principles calculations reveal the superlubricant effect of multilayer graphene between Ni(111) surfaces, highlighting the role of electronic interactions and layer number in friction reduction.

Findings

Adhesion and friction decrease with more graphene layers.

Transition from stick-slip to continuous sliding observed.

Superlubricity achieved with multilayer graphene between Ni(111).

Abstract

A single graphene layer placed between two parallel Ni(111) surfaces screens the strong attractive force and results in a significant reduction of adhesion and sliding friction. When two graphene layers are inserted, each graphene is attached to one of the metal surfaces with a significant binding and reduces the adhesion further. In the sliding motion of these surfaces the transition from stick-slip to continuous sliding is attained, whereby non-equilibrium phonon generation through sudden processes is suppressed. The adhesion and corrugation strength continues to decrease upon insertion of the third graphene layer and eventually saturates at a constant value with increasing number of graphene layers. In the absence of Ni surfaces, the corrugation strength of multilayered graphene is relatively higher and practically independent of the number of layers. Present first-principles calculations reveal the superlubricant feature of graphene layers placed between pseudomorphic Ni(111) surfaces, which is achieved through the coupling of Ni-3d and graphene-$\pi$ orbitals. The effect of graphene layers inserted between a pair of parallel Cu(111) and Al(111) surfaces are also discussed. The treatment of sliding friction under the constant loading force, by taking into account the deformations corresponding to any relative positions of sliding slabs, is the unique feature of our study.