石墨烯的纳米摩擦与磨损性质

采用乙醇溶剂剥离的方法制备石墨烯. 通过对溶剂温度、超声时间、超声功率和溶剂离心速度及时间的控制, 从高定向热解石墨(HOPG)制备得到少层石墨烯. 用原子力显微镜(AFM)研究了云母基底上不同层数石墨烯在真空中的纳米摩擦过程, 发现从约4 个原子单层(4 ML)起, 摩擦系数基本不再变化, 但摩擦力仍随着厚度的增加而显著减小, 7 ML之后, 其摩擦系数基本接近于零. 在磨损实验中, 少层石墨烯表面存在刮坏的现象,且不同厚度的石墨烯的磨损现象明显不同, 其中2 ML石墨烯相比4 ML石墨烯表现出较好的耐磨损性能, 且不具有摩擦方向依赖性. 测试了真空下少层石墨烯和云母表面的粘附力, 发现不同层厚的石墨烯相差不大, 因此认为基底效应并不是磨损性质差异的主要原因. 相对于单层石墨烯, 少层石墨烯在抗磨损涂层等领域有着很大的潜在应用价值.

Nanotribological and Wear Properties of Graphene

We prepared few-layer graphene samples by liquid-phase exfoliation in ethanol. By controlling the solvent temperature, sonication time and power, and centrifugation speed and time, we fabricated several-layer graphene from highly oriented pyrolytic graphite (HOPG). The obtained supernatant was added dropwise onto freshly cleaved mica surfaces. Nanotribological study of the samples under high vacuum by atomic force microscope (AFM) showed that frictional force decreased as the number of monolayers (ML) of graphene increased, and their frictional coefficient remained constant when the sample was thicker than about 4 ML. When the coverage reached 7 ML, the frictional coefficient was close to zero. In wear experiments, 2-ML graphene exhibited better wear resistance than the 4-ML sample and had no dependence on directional friction. We also measured the adhesion force of samples containing different numbers of layers of graphene and the mica surface, and found that substrate adhesion is not the main reason for the wear resistance properties of 2-ML graphene. Compared with single-layer graphene, the low friction coefficient of few-layer graphene makes it promising for application in areas such as data storage devices, nanoelectromechanical systems, and anti-wear coatings.