Increasing studies have demonstrated excellent tribological properties of graphene as lubricant additive. Thus, extended explanations of the relationship between microstructure and tribological properties are needed. This paper reported the effects of thickness and particle size of graphene on its frictional performance, using a ball-on-plate tribotester under reciprocating condition. Graphene with few-layer (G2) or multi-layer (G10) structure was added to PAO4 as lubricant additive. The particle of G10 was further separated through centrifugation into two types, large size G10 (G10L) and small size G10 (G10S). G10S exhibits excellent reduction in friction (37%) and wear (47%) relative to the neat base oil, indicating the superior tribological properties of graphene with more layers and smaller particle size. Wear scar analysis shows that the surface lubricated with G10 is flatter and glossier than that of G2. It can be hypothesized that the interlaminar shear slip is more likely to occur in multi-layer graphene, leading to better friction reduction and wear resistance performance. Graphene with smaller particle size is not only less prone to structural defects and wrinkles, but also more easily adsorbed onto the sliding surface to form a lubricating film, providing enhanced wear and frictional performance. The present work suggests that the thickness and size may have direct influence on the tribological properties of graphene, providing theoretical and experimental guidance for the application of graphene as lubricant additive.

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中文翻译：

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厚度和粒径对石墨烯作为润滑油添加剂的摩擦学性能的影响

越来越多的研究表明，石墨烯作为润滑剂添加剂具有优异的摩擦学性能。因此，需要对微观结构与摩擦学性质之间的关系进行扩展的解释。本文报道了在往复运动条件下使用板载三botester石墨烯的厚度和粒径对其摩擦性能的影响。将具有少层（G2）或多层（G10）结构的石墨烯作为润滑剂添加剂添加到PAO4中。通过离心将G10的颗粒进一步分离成两种类型，大尺寸G10（G10L）和小尺寸G10（G10S）。相对于纯净的基础油，G10S表现出出色的摩擦减小（37％）和磨损（47％）的降低，表明石墨烯具有优异的摩擦学性能，具有更多的层和更小的粒径。磨损痕迹分析表明，G10润滑的表面比G2润滑的表面更光滑。可以假设在多层石墨烯中更可能发生层间剪切滑移，从而导致更好的摩擦降低和耐磨性能。粒径较小的石墨烯不仅不易出现结构缺陷和褶皱，而且更容易吸附到滑动表面上形成润滑膜，从而增强了磨损和摩擦性能。目前的工作表明，厚度和尺寸可能直接影响石墨烯的摩擦学性能，为石墨烯作为润滑剂添加剂的应用提供理论和实验指导。可以假设，层间剪切滑移更可能发生在多层石墨烯中，从而导致更好的摩擦降低和耐磨性能。粒径较小的石墨烯不仅不易出现结构缺陷和褶皱，而且更容易吸附到滑动表面上形成润滑膜，从而增强了磨损和摩擦性能。目前的工作表明，厚度和尺寸可能直接影响石墨烯的摩擦学性能，为石墨烯作为润滑剂添加剂的应用提供理论和实验指导。可以假设在多层石墨烯中更可能发生层间剪切滑移，从而导致更好的摩擦降低和耐磨性能。粒径较小的石墨烯不仅不易出现结构缺陷和褶皱，而且更容易吸附到滑动表面上形成润滑膜，从而增强了磨损和摩擦性能。目前的工作表明，厚度和尺寸可能直接影响石墨烯的摩擦学性能，为石墨烯作为润滑剂添加剂的应用提供理论和实验指导。而且还更容易吸附到滑动表面上以形成润滑膜，从而增强了磨损和摩擦性能。目前的工作表明，厚度和尺寸可能直接影响石墨烯的摩擦学性能，为石墨烯作为润滑剂添加剂的应用提供理论和实验指导。而且还更容易吸附到滑动表面上以形成润滑膜，从而增强了磨损和摩擦性能。目前的工作表明，厚度和尺寸可能直接影响石墨烯的摩擦学性能，为石墨烯作为润滑剂添加剂的应用提供理论和实验指导。

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