Research On The Preparation Of Graphene Composite With Silicate And Its Tribological Properties

Lubrication plays a vital role in reducing energy consumption and saving costs in industrial production.The common lubrication measure is to add lubricating medium to the parts which are prone to wear.Lubricating oil is a main lubricating medium.However,with the increase in production demand,traditional lubricating oil is not only difficult to meet the lubrication requirements when the machine works in a relatively harsh working environment,but also has a certain limit in its lubricating effect even in normal working conditions.Therefore,lubricant additives are often added to the lubricating oil to improve its performance.In this thesis,several different composite materials of graphene and natural silicate mineral powder were prepared by simple synthetic methods,and they were added as additives to oil to explore their lubricating properties and principles.The main research contents are as follows:Three composite materials of modified graphene oxide（MGO）with different layered silicate minerals（muscovite（Mu）,talc（HS）and chlorite（CLT））,were prepared by a simple hydrothermal method and using silane coupling agent as surface modifier.The composites are MGMu,MGHS and MGCLT,respectively.Through the dispersion stability experiment,it can be seen that three composites prepared can be dispersed in the oil relatively stably.Then they were used as additives to prepare different oil samples and tribological tests were carried out on a four-ball friction and wear tester.The test results showed that the three materials prepared can effectively improve the lubrication performance of the base oil,and their average friction coefficient is decreased by 64.4%,63.2%and 41.4%,respectively,when compared with that of the base oil.The lubricating properties of MGMu and MGHS are even better.At the same time,the average wear scar diameters were reduced by 20.0%,22.6%and18.9%,respectively,compared with the base oil.Through the concentration gradient experiment,it’s displayed that when the concentration of MGMu and Mu CLT is0.4mg/m L,the lubricating performance is the best,and the best performance concentration of MGHS is 0.3mg/m L.In order to explore the lubrication mechanism,SEM,EDS,microhardness and XPS tests were further carried out on the wear scar.The analysis results of SEM and EDS show that the three materials prepared above have a repairing effect on wear scars,and the effect of MGMu is the most apperant.In the friction process,a high hardness repaired layer with C,O,Si,Fe and other elements is formed with the surface of the friction pair.Compared with the wear surface of the base oil,after adding MGMu,MGHS and MGCLT,the microhardness increase of 16.1%,28.3%and 38.9%,respectively,which indicates that some reaction between the additive component and the friction pair has occurred.Finally,by analyzing the results of XPS,and combining mineralogical principles,the reaction mechanism of the three composite materials in the friction process was discussed.It shows that the three composite materials will react with elements in the friction pair and produce Si O₂,Si C,metal carbonates and metal oxides during the friction process.,MGMu and MGCLT will produce new metal silicates due to their special structure and mineralogy properties.