Preparation And Tribological Properties Of Functionalized Graphene And Its Composites

Wear,corrosion and fracture are the mains reasons for the invalidation of the mechanical equipment unit,of which about 80% failure of mechanical units result from wear.As the main lubrication medium of various types of machinery and equipment,the traditional lubricant has many innegligible limitations in a tough environment.Researchers have focused on developing advanced lubricating additives,especially abrasion self-repairing additives which provide a way to save materials and energy consumption.The dispersion stability of additive materials greatly affects the properties of the lubricant.Therefore,it is a great practical significance to study the abrasion self-repairing additives that can be stably dispersed in lubricating oil.In this thesis,several functionalized graphene and its composites with silicates were synthesized,and their tribological properties and abrasion self-repairing performance were systematically investigated.The following is the main research content.Home-made graphene oxide(GO)and commercial graphene oxide(CGO)were functionalized with silane coupling agent to form functionalized graphene samples signed as FGO and FCGO,respectively.The tribological properties of commercial graphene(GE),GO,CGO,FGO and FCGO were studied.With comparision,the functionalized graphene samples have a better affinity to lubricating oil with stabilization in lubricating oil for 10 days,which greatly improve the lubricating property.FGO,FCGO at the optimized concentration of 0.6 mg/m L exhibit the most excellent lubricating properties.Compared with the bare oil sample,the friction coefficient(FC)of oil samples containing FGO and FCGO decreases by 37.3 and30.5 %,respectively.And the wear scar diameters(WSDs)decreases by 13.0 and11.3 %,respectively.For FGO oil sample,the hardness of the wear scar increases by10.0 % compared with the surface of the steel ball.Although the FGO has similar tribological properties to GE,it is found that FGO shows the more excellent repairing performance of the wear scar surface.To gain the greater additives of lubricating oils,four functional graphene(FG)/silicate composite materials were fabricated through chemically bonding by hydrothermal-reduction process with FGO and bentonite(BTT),attapulgite(ATTP),antigorite(AGT),kaolin(KLT)),which were named FG/BTT,FG/ATTP,FG/AGT and FG/KLT.The synergy of the two materials effectively enhances the dispersion stability of the composites in oil samples.It is found that FG/BTT shows an outstanding lubricant property at 0.6 mg/m L.Compared with the bare oil sample,its FC and WSD decrease by 50.9 % and 17.3 % respectively.While the FG/ATTP?FG/AGT and FG/KLT oil samples show the excellent lubricant property at the concentration of 0.4 mg/m L.The FC and WSD of the FG/AGT oil sample decrease by52.3 % and 14.3 % respectively compared with the bare oil sample.The hardness of the wear scar of FG/BTT,FG/ATTP,FG/AGT and FG/KLT samples are 22.4 %,13.0 %,14.7 % and 15.3 % higher than the surface of the steel ball.