Atomic Scale Simulation on the Anti-Pressure and Friction Reduction Mechanisms of MoS₂ Monolayer.

Yang Liu,Yuhong Liu,Tianbao Ma,Jianbin Luo

doi:10.3390/ma11050683

Abstract

MoS2 nanosheets can be used as solid lubricants or additives of lubricating oils to reduce friction and resist wear. However, the atomic scale mechanism still needs to be illustrated. Herein, molecular simulations on the indentation and scratching process of MoS2 monolayer supported by Pt(111) surface were conducted to study the anti-pressure and friction reduction mechanisms of the MoS2 monolayer. Three deformation stages of Pt-supported MoS2 monolayer were found during the indentation process: elastic deformation, plastic deformation and finally, complete rupture. The MoS2 monolayer showed an excellent friction reduction effect at the first two stages, as a result of enhanced load bearing capacity and reduced deformation degree of the substrate. Unlike graphene, rupture of the Pt-supported MoS2 monolayer was related primarily to out-of-plane compression of the monolayer. These results provide a new insight into the relationship between the mechanical properties and lubrication properties of 2D materials.

Highlights

IntroductionWhen used as lubricant additives or solid lubricants, graphene and few-layer MoS2 can improve the extreme pressure (highest load without seizure of the friction pairs) and reduce the friction of rubbing surfaces [16,17]
When used as lubricant additives or solid lubricants, graphene and few-layer MoS2 can improve the extreme pressure and reduce the friction of rubbing surfaces [16,17]
It can be speculated that the achievement of the strain out-of-plane compression is the main reason for the rupture of the MoS2 monolayer supported by Pt substrate, both in-plane stretch and out-of-plane compression can bear load during the indentation process

Summary

Introduction

When used as lubricant additives or solid lubricants, graphene and few-layer MoS2 can improve the extreme pressure (highest load without seizure of the friction pairs) and reduce the friction of rubbing surfaces [16,17]. These excellent lubricating properties, including the anti-pressure effect and friction reduction effect, are usually attributed to the better mechanical properties of 2D materials than metal friction pairs [18]. As the friction reduction effect of the monolayer rests on its ability to share extra load when covering the substrate [20], the scratch process was carried out at different indentation depths

Simulation Details

Indentation Process

Structural Deformation

Scratch Process

Conclusions