Effects of Environmental Moisture and Functional Groups on the Sliding Adhesive Behaviour of Graphene Steps
H Fu and FL Duan, TRIBOLOGY LETTERS, 69, 104 (2021).
We carried out molecular dynamics simulations to study the effects of environmental moisture and functional groups on the sliding adhesive behaviour of graphene steps at the atomic scale. Environmental water plays a dual role in separating interfaces and additional passivation during the sliding process. For a diamond tip, functionalization of graphene steps exhibits different chemical properties. Hydroxyl passivation graphene step can destroy interfacial water layers due to high chemical activity and participation in forming a filter, thereby significantly enhancing interfacial contact area and interfacial bond strength. By contrast, the graphene step passivated by hydrogen atoms has less influence on the interfacial water layers, and no apparent adhesion is observed. Besides, the presence of graphene step significantly weakens the wear resistance of graphene sheets. And different environmental conditions and functional groups weaken it to various degrees. Generally speaking, the abrasion resistance of graphene sheets in a water environment is better than that in a vacuum environment. Excluding the influence of environmental moisture, wear resistance of graphene step edges with hydrogen passivation is better than that with hydroxyl passivation. This work provides new and further insights into the process and mechanism of sliding adhesive behaviour of graphene steps.
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