氧化石墨烯对锂基润滑脂摩擦学性能的影响

The Influence of Graphene Oxide on the Tribological Properties of Lithium-based Grease

目的研究氧化石墨烯(GO)作为添加剂对润滑脂摩擦性能的影响。方法将鳞片石墨利用经典的Hummers氧化法氧化得到GO,并表征了GO,再分别以不同的质量分数(0.1%、0.3%、0.5%、1.0%、1.5%)与润滑脂复配。同时增加了空白润滑脂与石墨粉复配的润滑脂作为对比。利用Optimol SRV型摩擦磨损试验机评价其摩擦学性能。利用非接触三维表面轮廓仪、扫描电子显微镜(SEM)观察磨斑表面和深度。通过特征X射线能谱仪(EDS)和X射线光电子能谱仪(XPS),对磨斑表面的元素化学状态分布进行分析。结果与空白锂基润滑脂相比,添加了石墨粉的锂基润滑脂在经过钢/钢摩擦副的摩擦后,其摩擦因数均有降低,但随着试验的进行,其摩擦因数均逐渐提高,摩擦副表面出现了润滑失效的现象,而添加GO的锂基润滑脂其摩擦因数迅速降低至0.13左右,降低了35%,且在试验时间内没有出现润滑失效的现象。SEM及三维轮廓图显示,在添加GO的润滑脂润滑后,其钢块磨斑最低,磨痕最浅;EDS显示其润滑后的磨痕有较多的氧元素,说明具有含氧官能团的GO能够牢固地吸附在基体表面,形成润滑层。XPS证实了分别添加有石墨和GO的润滑脂在摩擦试验过程中均与基体发生了摩擦化学反应,由铁的氧化物形成了一层润滑薄膜。结论GO作为润滑脂添加剂可以有效降低摩擦因数,减少磨损量,延长润滑时间,提高润滑性能。

The effect of graphene oxide(GO)as an additive on the friction properties of greases was studied.The flake graphite was oxidized by the classic Hummers oxidation method to obtain GO,and GO was characterized,and then mixed with grease in different proportions(0.1wt%,0.3wt%,0.5wt%,1.0wt%,1.5wt%),meanwhile,and we also added the blank grease and the grease compounded with graphite powder as a comparison.The tribological performance was measured by Optimol SRV friction and wear tester,and the 3D profiler and scanning electron microscope(SEM)were used to observe the surface and depth of the worn surface.The chemical state distribution of the elements on the worn surface was analyzed by X-ray energy spectrometer(EDS)and X-rayphotoelectron spectra(XPS).The results indicate that compared with the blank lithium grease,the friction coefficient of the graphite powder-added lithium grease reduced after the friction of the steel/steel friction pair,but as the experiment progressed,the friction coefficient gradually increased,and a wear-out on the surface of the friction pair occurred.While the friction coefficient of the lithium-based grease added with GO was rapidly reduced to about 0.13,which is reduced by 35%,and there was no wear-out on the surface of the friction pair during the experiment time.The SEM and 3D profiler shows the lowest and shallowest wear scar after lubrication with GO grease.At the same time,the EDS shows that the wear scar has more oxygen elements,indicating that GO with oxygen-containing functional groups can be firmly adsorbed on the substrate surface to form a lubricating layer.The XPS confirms that the grease added with graphite and GO has a tribo-chemical reaction with the matrix during the friction test,forming a lubricating film formed by iron oxide.GO as a grease additive can effectively reduce the friction coefficient and the amount of wear,as well as extend the lubrication time and improve the lubricating performance.