| The use of low-sulfur fuel in marine engines can lead to increased wear on key components such as piston-cylinder liners.Adding suitable nano-lubricating additives to the lubricating oil can effectively improve the performance and bearing capacity of the lubricating oil,which provides a feasible method for reducing the friction and wear of moving parts of marine engines.In this paper,two sets of graphene/potassium borate lubricant additives were prepared using expanded graphite and potassium borate as raw materials,oleic acid as surface modifier,and plasma-assisted ball milling technology under different discharge current parameters.XRD,Raman,FT-IR and other testing methods were used to analyze the microstructure and surface characteristics of the prepared graphene/potassium borate lubricant additives,and the dispersing and tribological properties of the graphene/potassium borate lubricant additives in lubricant oil were tested.The main research contents of this papaer are as follows:1)Study the formation mechanism of graphene and the loading of nano-potassium borate on graphene.Under the condition of 2A discharge current,the number of graphene layers obtained by plasma assisted ball milling for 20 h is 8 and the nano-potassium borate particles are evenly distributed on the graphene.This is mainly because under the thermal effect of the plasma,the interlayer distance of the expanded graphite becomes larger,which promotes the peeling of graphene from the graphite sheet,and the micro-area heating effect of the high current discharge plasma will also melt and heat the potassium borate particles.Explosive splash,then quickly condensed and distributed on the graphene sheet,and part of the potassium borate particles are wrapped by graphene.2)Analyze the effect of the discharge current of plasma assisted ball milling on the preparation of graphene/potassium borate.When the discharge current is reduced to 1.5A,plasma assisted ball milling can obtain 9 layers of graphene for 10 h,and potassium borate particles are about 10 nm.This is because potassium borate is used as a dielectric material.The thermal effect of 1.5A discharge current plasma on potassium borate is lower than 2A current.The potassium borate particles are not easy to melt and agglomerate,which makes the continuous embedding and scraping of graphite in the ball mill Played a major role in accelerating the exfoliation to form graphene.3)Test the dispersibility and tribological properties of graphene/potassium borate additives in lubricating oil.The test results show that with the extension of plasma assisted ball milling time,the better the dispersibility of graphene/potassium borate additives in lubricating oil.At 2A discharge current,the graphene/potassium borate additive prepared by ball milling for 20 h had the best tribological properties,but the graphene/potassium borate additive ball milled for 10 h at 1.5A discharge current showed the same performance as the graphene/boric acid ball milled at 15 A for 2h Potassium additives have similar friction properties,that is,they can produce graphene/potassium borate composite materials with comparable performance faster at 1.5A current,thereby reducing ball milling time.4)Explore the tribological mechanism of graphene/potassium borate composite oil.For composite oils,graphene/potassium borate lubricating oil additives easily enter between the frictional contact surfaces.Due to the large surface area of graphene,graphene-loaded potassium borate is adsorbed and deposited on the surface of the friction pair and wear marks on the worn surface Gully is filled and repaired to reduce the surface roughness of the friction pair.Under the synergistic effect of both potassium borate and graphene,graphene/potassium borate deposits on the friction surface to form a protective layer,and exerts a good anti-friction and anti-wear effect. |
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