Nanotribological Properties And Wear Studies Of Graphene

In this paper, I used highly oriented pyrolytic graphite (HOPG) as raw materials with liquid-phase exfoliation, after sonication and centrifugation in ethanol, few layer graphene films were placed on newly cleaved mica surface. At the same time, its topography, friction of the samples and tip-sample adhesion were measured by atomic force microscope (AFM) in the vacuum. I found that the frictional force decreased as the number of layers increased. When more than-4mono-layer graphene (-4MLG), the friction coefficient of the graphene films were almost the same and friction forces also changed little. What’s more, tip-sample adhesion forces were almost indistinguishable for all thickness and the substrate. Further, I changed the scan angle and scan speed to observe the change of frictional force on the same few layer graphene film and also found indistinguishable. However, I unexpectedly found that the surface of few layer graphene damaged at the process of its nanotribology research in the vacuum. Wear phenomena of few layer graphene films of different thickness were very different, and～2mono-layer graphene (～2MLG) exhibited better wear resistance than～4ML graphene (～4MLG). And I observed no change by changing the scan angle. Therefore, I concluded that the substrate effect, fold effect and tip-sample adhesion force were not the main reason of the nanotribological properties, but its own nanotribological properties. Wear phenomena has a close relationship with the substrate effect.