College of Mechanical and Electrical Engineering , Beijing University of Chemical Technology , Beijing 100029 , China.
State Key Laboratory of Tribology , Tsinghua University , Beijing 100084 , China.
ACS Appl Mater Interfaces. 2019 Oct 9;11(40):36931-36938. doi: 10.1021/acsami.9b08993. Epub 2019 Aug 9.
Nanoparticles and two-dimensional (2D) nanosheets are well-investigated as lubricant additives, which can significantly reduce frictional energy consumption. However, the tribological properties of the additives will deteriorate because of the occurrence of aggregation in the lubricant and the difficulty in entering the frictional contact area. In the present work, the new sandwichlike nanostructure of MnO nanoparticles and graphene nanosheets (MnO@G) has been developed by an in situ green synthesis method; i.e., the impurities of Mn ions in crude graphite oxide as the precursor are directly transferred into MnO precipitate between the graphene sheets. The graphene has a lamellar structure without folds and wrinkles, and the MnO nanoparticles are not only uniformly anchored on the graphene surfaces but also intercalated in the layers of the graphene nanosheets. The MnO@G exhibits excellent tribological properties and high stability because of a synergistic lubrication effect between the graphene nanosheets and the MnO nanoparticles. Even at an ultralow concentration (0.075 wt %) and a high temperature of 125 °C, the friction coefficient and the wear depth have been reduced by 75% and 97% compared with base oil, respectively. The synthesis method and the MnO@G nanocomposite have significant potential in various tribological applications for saving energy.
纳米颗粒和二维（2D）纳米片作为润滑剂添加剂得到了广泛的研究，它们可以显著降低摩擦能耗。然而，由于添加剂在润滑剂中发生聚集以及难以进入摩擦接触区，其摩擦学性能会恶化。在本工作中，通过原位绿色合成方法开发了 MnO 纳米颗粒和石墨烯纳米片的新型夹层纳米结构（MnO@G）；即，作为前体的粗石墨氧化物中 Mn 离子的杂质被直接转化为石墨烯片层之间的 MnO 沉淀物。石墨烯具有无褶皱的层状结构，MnO 纳米颗粒不仅均匀地锚定在石墨烯表面上，而且还插层于石墨烯纳米片的层间。由于石墨烯纳米片和 MnO 纳米颗粒之间的协同润滑作用，MnO@G 表现出优异的摩擦学性能和高稳定性。即使在超低浓度（0.075wt%）和 125°C 的高温下，与基础油相比，摩擦系数和磨损深度分别降低了 75%和 97%。该合成方法和 MnO@G 纳米复合材料在节约能源的各种摩擦学应用中具有重要的应用潜力。
