Graphene–Graphene Interactions: Friction, Superlubricity, and Exfoliation

Abstract

Graphite's lubricating properties due to the "weak" interactions between individual layers have long been known. However, these interactions are not weak enough to allow graphite to readily exfoliate into graphene on a large scale. Separating graphite layers down to a single sheet is an intense area of research as scientists attempt to utilize graphene's superlative properties. The exfoliation and processing of layered materials is governed by the friction between layers. Friction on the macroscale can be intuitively understood, but there is little understanding of the mechanisms involved in nanolayered materials. Using molecular dynamics and a new forcefield, graphene's unusual behavior in a superlubric state is examined, and the energy dissipated between two such surfaces sliding past each other is shown. The dependence of friction on temperature and surface roughness is described, and agreement with experiment is reported. The accuracy of the simulated behavior enables the processes that drive exfoliation of graphite into individual graphene sheets to be described. Taking into account the friction between layers, a peeling mechanism of exfoliation is predicted to be of lower energy cost than shearing.

A novel route to the synthesis of an Fe3O4/h-BN 2D nanocomposite as a lubricant additive

“…Their adjacent layers bonded by weak van der Waals force, can slide easily against each other, which further reduces friction and wear. 3, [5][6][7] Recently, considerable efforts have been made to fabricate 2D nanocomposite lubricant additives, such as Cu/graphene, Fe 2 O 3 /graphene and Al 2 O 3 /nanotube, etc. [8][9][10][11] The 2D nanocomposites show better dispersion and lubrication properties than pure 2D nanomaterials, because the nanocomposites are able to disperse uniformly in lubricants and can form a synergetic protective tribolm on the rubbing surfaces.…”

Chirality-dependent motion transmission between aligned carbon nanotubes

“…with a potential well depth of = 2.4 meV, an equilibrium distance of σ = 0.34 nm and a cutoff radius of 1.2 nm [31]. The LJ potential has been reported to underestimate the surface energy corrugation [18,32]. We therefore compared the results obtained by using the LJ force field with those based on the more sophisticated Kolmogorov-Crespi (KC) force field, which has been reported to give an improved description to the overlap of π-orbitals between two graphene layers at a high load [32].…”

Flourishing Self‐Healing Surface Materials: Recent Progresses and Challenges

“…Due to surface associated CN bond breaking, the phenomena of crosslinking removal and N 2 desorption upon scratching occurred at interface as illustrated in Figure 4c, which made carbon nitride films as self‐healing material. In the area of the disrupting CN bonding, the structure swelled and reached graphitic‐like properties, which leads the layers to increasingly act as a solid lubricant at the nanoscale, thus reducing surface friction and wear damages.…”