Abstract
This study investigated the friction behavior of graphene in air and nitrogen atmosphere environments. The microstructural evolution caused by the variation of atmosphere environments and its effect on the friction coefficient of the graphene is explored. It is demonstrated that graphene can exhibit excellent lubricating properties both in air and nitrogen atmosphere environments. In air, a highly ordered layer-by-layer slip structure can be formed at the sliding interface. Oxygen and H2O molecules can make edge dangling bonds and defects passive. Thus the interaction between the nanosheets and the layers of nanosheets is weak and the friction coefficient is low (0.06–0.07). While the friction coefficient increases to 0.14–0.15 in a nitrogen atmosphere due to the interaction of defects generated in the sliding process, the nitrogen molecules with lone pair electrons can only make the nanosheets passive to a certain degree, thus the ordered slip structure is destroyed and friction is higher. This work reveals the influence of environmental molecules on the macroscale tribological performances of graphene and its effect on the microstructure at the sliding interface, which could shed light on the lubricating performance of graphene in environmental atmospheres and help us to understand the tribological behaviors of graphite at the macroscale.
Highlights
Reducing friction and wear losses has great value for the moving components of sliding conditions (Holmberg and Erdemir, 2017)
To investigate the microstructural evolution of the sliding contact interface caused by the variation of atmosphere and its effect on the friction coefficient of the graphene in the entire process, we further explored the microstructure in subsequent tests
Graphene shows excellent lubricating behaviors in air and nitrogen atmosphere environments, which are attributed to the formation of the uniformly transferred film and lubricating film
Summary
Reducing friction and wear losses has great value for the moving components of sliding conditions (Holmberg and Erdemir, 2017). It is indicated that the tribological behaviors of graphite are affected by atmospheric environments, and it exhibits low friction in the air atmosphere and high friction in vacuum or inert atmospheres (Savage, 1948; Savage and Schaefer, 1956). During the last few decades, most research and practical applications have been concerned with the tribological performance of graphite (Lancaster and Pritchard, 1981) and few studies have focussed on the intrinsic microstructure that determines the tribological properties of graphite. The structural change of three-dimensional (3D) graphite is difficult to observe. The system of practical applications is usually complicated. The exploration of the effect of the atmospheric environment on the intrinsic structure of the underlying origin of macroscale
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