Tribological Properties Of Carbon-based Micro-nano Lubrication Additives

In recent years,more and more attention has been paid to environmental problems and ecological balance.A new type of green additive is urgently needed in industrial production to meet different lubrication media and conditions.With the rapid development of carbon nanomaterials,researchers are committed to developing a new type of green lubrication additive.Carbon microspheres,because of the special shape,can be used as micro-bearings to physically separate the contact interface and convert sliding friction into rolling friction,which shows good lubrication and anti-wear effect.Based on hydrothermal method and chemical reaction,multi-scale carbon microspheres,talc/carbon spheres composite powder and silver-loaded carbon microspheres are prepared as lubrication additives,and then dispersed in base oil after modified with oleic acid to obtain composite lubrication.In addition to characterizing the physical and chemical properties of the prepared powders,the effect of powder additives on the tribological properties of base oil is evaluated by a ball-on-disc tribometer.(1)The multi-scale carbon microspheres are prepared via cellulose by a simple one-step hydrothermal method.The carbon microspheres with wide size distribution of 300-1000 nm after modified with oleic acid are uniformly dispersed on the 85W-90 gear oil(base oil),which lubrication performances are evaluated by a ball-on-disc tribometer.The results show that the optimal tribological property is obtained when the concentration of carbon microspheres is 0.5 wt.%.Under 50 N,the friction coefficient lubricated with 0.5 C-oil is 0.10,which decreases by 28.6%compared with base oil.The wear rate of steel disc is only 2.63·10~-77 mm~3/(N·m),which is 32.4%lower than that of base oil.The superior performance of multi-scale carbon microspheres as oil-based lubrication additives is attributed to having the particles dispersed as individual particles and maintaining the physical and chemical stability in the friction process,which allows for gap-filling and ball-bearing to reduce friction.(2)Talc/carbon sphere composite powders are successfully prepared by one-step hydrothermal method.The tribological properties of talc/carbon spheres composite powder as lubrication additive are studied by a pin on disc tribometer.The friction test results show that the friction coefficient of 0.5 TC-oil decreases by 33.6%,35.3%and 23.8%compared with the base oil when the applied loads are 3 N,5 N and 8 N,respectively.The results of mechanism study show that talc/carbon spheres composite powder as lubrication additive combines the advantages of talc and carbon spheres,and has self-repairing performance and ball-bearing effect,which further improves the tribological properties of base oil.(3)Silver particles are successfully loaded on the surface of carbon microspheres by silver mirror reaction.The tribological properties of silver-loaded carbon microspheres as lubrication additives are studied by a pin on disc tribometer.The results show that silver-loaded carbon microspheres(0.10Ag@C)prepared at 0.10 mol/L concentration of silver nitrate solution possess the optimal tribological property.And the friction coefficient of 0.10Ag@C-oil is only 0.08,which decreases by 27.3%compared with the base oil when the load is 80 N.