Dispersion And Tribology Properties Of Carbon Base Nanoparticles In Lubricating Oil

Using lubricating additives has become one of important ways to improve lubrication performance and increase the use life and reliability of mechanical parts in order to improve the lubricity of lubricants.Carbon based nanoparticles have excellent mechanical properties,and thus have good prospects for application.However,due to the large specific surface area and high specific surface energy,nanoparticles are easy to agglomerate and difficult to form stable lubricating system with uniform dispersion,which restricts seriously their performance and production applications.In the present thesis,two kinds of carbon nanoparticles with different structure were used as lubricating additives,and dispersed and modified through different treatment processes,so as to achieve stable dispersion of particles in lubricating oil.On this basis,it was investigated their tribological properties containing carbon base nanoparticles with different contents under different loads.The characteristics of the particles were analyzed by means of Zeta potential,FIRT,XRD and Raman etc.The surfaces of the friction pair after rubbing process were analyzed by scanning electron microscope(SEM)and its energy spectrometer,3D laser scanner and Raman.It was also studied the friction and wear mechanisms of carbon base nanoparticles in the lubricating oils.It was studied firstly the dispersing process of nanodiamond in lubricating oil.The results showed that the size of nanodiamond was obviously reduced by strong acid treatment and high temperature treatment.The results of infrared spectrum analysis showed that the oxygen functional groups increased obviously on the modified nanodiamond surface.Static and centrifugal methods showed that nanodiamond had excellent dispersion stability in 32~#hydraulic lubricating oil.The dispersion mechanism was attributed to the decrease of particle size and the space steric effect on the surface groups.Graphene oxide has better dispersing precondition than graphene.Thus,the graphene oxide prepared by improved Hummers method was dispersed by two different processes.The results showed that the graphene oxide could be stably dispersed in diesel engine oil with help of oil amine,dispersing agent and detergent effect.However,the pre-treatment of high speed centrifugation for graphene oxide could obtain a clear and stable lubricating system of diesel engine oil containing graphene oxide.The tribological properties of the dispersed and stable 32~#hydraulic lubricating oil containing nanodiamond were studied with nanodiamond content and different loads.The results showed that the average friction coefficient and the wear spot diameter decreased firstly and then increased with the increase of nanodiamond under high load.However,the average friction coefficient and the wear scar diameter decreased and then stabilized with the increase of nanodiamond under low load.The maximum non-seizure load(P_B)of the tested lubricating oil was not changed under the low content of nanodiamond,and P_B of the tested lubricating oil was increased under high content of nanodiamond.The tribological properties of the dispersed and stable diesel engine oil containing graphene oxide were studied with the content of graphene oxide and different loads.The results showed that the graphene oxide had adverse antiwear effect on diesel engine oil and had little effect on antifriction performance under high load.The antiwear and antifriction performance of diesel engine oil could be improved obviously under low load.The friction reduction and wear resistance mechanisms were attributed to that graphene oxides formed a good lubricating film during rubbing under low load,which reduced the friction and wear effectively.