IMPROVING TRIBOLOGICAL PROPERTIES OF ATOMICALLY THIN GRAPHENE WITH 1D/2D HYBRID-STRUCTURE

Abstract

Two-dimensional materials, such as single and multi-layer h-BN, MoS2 and graphene, with atomic thickness and exceptional material characteristics, such as high mechanical and low friction properties making them excellent for nanoscale applications such as protective and solid lubricant coating layers. However, it was found that the coating layer might be damaged under excessive contact pressure. Therefore, fundamental understanding of tribological properties of 2D materials is crucial for further implementation of these 2D materials as protective coating layer. In this work, a hybrid-structure of 2D and 1D materials was proposed for investigation of tribological properties. In particular, hybrid-structure of atomically thin graphene coated on CNT matrix was prepared for investigation of friction and wear properties and compare with those of graphene on SiO2 substrate. It was found that graphene on top of CNT matrix exhibited lower friction properties compare to that of graphene on SiO2 substrate. This may be due to in-plane strain which associated with partially support of CNT matrix and interaction with AFM tip during contact. In addition, low adhesion properties of graphene on CNT matrix also contribute to low friction properties of specimen. It was found that wear resistance of atomically thin graphene was enhanced with presence of CNT matrix under reciprocating scratch test. CNT matrix act as nano spring may help to reduce contact pressure so that minimize the damage of coating film. Furthermore, CNT matrix also helps to avoid the formation of pucker and hillock which may contributed by its low adhesion properties and mobility during scratch test. These characteristics assist graphene layer on CNT matrix avoid the failure primary failure mechanism of graphene and other 2D materials which associated with puckering effect. Overall, the results of this work show positive effects of CNT matrix on tribological properties of atomically thin graphene in 1D/2D hybrid-structure. The findings were expected to provide a fundamental understanding about tribological properties of 2D and 1D/2D hybrid-structure materials so that be helpful on design of these materials at protective coating layer.