Preparation Of Oil-Soluble Zinc Oxide And Cerium Oxide Nanoparticles And Investigation Of Their Multifunctional Properties As Lubricant Additives

Oxide can greatly improve the tribological properties of lubricating oil,hence it is very meaningful to research and develop oxide in the field of lubrication.However,the oxide nanoparticles are easily prone to agglomerate.The application of oxide nanoparticles in the field of tribology is still hindered by their poor dispersibility associated with high surface energy and activity leading to agglomeration in lubricant base oils.In order to solve the problems,oil-soluble zinc oxide and cerium oxide nanoparticles were prepared in this paper.Besides,we characterized the tribological properties of zinc oxide and cerium oxide nanoparticles as lubricant additives on three kinds of base oils?diisooctyl sebacate DIOS,poly-?-olefin PAO and liquid paraffin LP?and explored the tribological mechanism of nanoparticles in the base oils for reducing friction,anti-wear properties.The antioxidant of zinc oxide and cerium oxide nanoparticles was investigated.In addition,we prepared oleylamine modified cerium oxide nanoparticles by directly decomposing in liquid paraffin?LP?base oil and explored the tribological properties in LP base oil.?1?Preparation of zinc oxide nanoparticles and evaluation of their multifunctional properties as lubricant additiveOleic acid?OA?modified zinc oxide nanoparticles with an average size of 4.0 nm were prepared via a facile in situ one-step route.The as-prepared zinc oxide nanoparticles were characterized by x-ray diffraction,transmission electron microscopy,and fourier transform infrared spectroscopy.The light-absorbing performance and thermal stability of the as-prepared zinc oxide nanoparticles were evaluated by ultraviolet-visible light spectrophotometry and thermogravimetric analysis,and their tribological behaviours as the lubricant additive in diisooctyl sebacate?DIOS?,poly-alpha olefin?PAO?and liquid paraffin?LP?base oils were evaluated with a four-ball machine.The surface morphology of the wear scar was observed with a scanning electron microscope and a three-dimensional optical profiler,and the element composition of the wear scar was determined by energy dispersive spectrometry.The antioxidation of zinc oxide nanoparticles was determined by ultraviolet-visible light spectrophotometry.It was found that the surface-capping of zinc oxide nanoparticles by OA helps to greatly increase their dispersibility and thermal stability.In the meantime,OA-modified zinc oxide nanoparticles can effectively improve the antiwear and friction-reducing abilities as well as the load-carrying capacity of the three base oils,which is due to the formation of a tribofilm in association with the tribo-sintering and/or adsorption of the additives on the rubbed steel surfaces.Furthermore,the friction-reducing and antiwear performances of the as-prepared zinc oxide nanoparticles as lubricating oil additives seem to be closely related to the polarity of the base oils.Namely,the OA-modified zinc oxide additive exhibits better tribological behaviour in apolar PAO than in polar DIOS.The zinc oxide nanoparticles showed untable tribology properties due to the different of oil soluble in LP base oils.The zinc oxide nanoparticles showed antioxidant properties?2?Preparation of cerium oxide nanoparticles and evaluation of their multifunctional properties as lubricant additiveOleylamine modified cerium oxide nanoparticles were synthesized by directly decomposing in liquid paraffin?LP?base oil.The phase composition,microstructure,size and chemical structure of the product was analyzed by XRD,TEM and FTIR.The tribological properties used as lubricant additive in LP were tested by four-ball friction tester.The chemical states of typical elements on the worn surfaces of the steel balls were analyzed by a scanning electron microscope and a three-dimensional optical profiler,the tribological mechanism of the additives was discussed.The results show that cerium oxide nanoparticles showed anti-friction and anti-wear performance in LP.The reason may be that the lubricant film was formed with the tribo-sintering and/or adsorption of the additives on the rubbed steel surfaces.Oleylamine?OM?modified cerium oxide?CeO₂?nanoparticles have been successfully synthesized by a one-pot pyrolysis method.The morphology,structure and chemical composition of the nanoparticles have been analyzed by means of X-ray power diffraction?XRD?,transmission electron microscopy?TEM?,and Fourier transform spectrometry?FT-IR?,the tribological properties of as-prepared nanoparticles used alone and with a certain proportion in DIOS,PAO and LP were evaluated with a four–ball machine.The chemical states of typical elements on the worn surfaces of the steel balls were analyzed by a scanning electron microscope,a three-dimensional optical profiler and x-ray photoelectron spectroscopy,the tribological action mechanism of the additives was discussed.The antioxidation of cerium oxide nanoparticles was determined by ultraviolet-visible light spectrophotometry.The results show that the cerium oxide nanoparticles have different tribological properties in different base oils.The cerium oxide nanoparticles showed different tribology properties in different oils due to the different ploar of the base oil.The cerium oxide nanoparticles showed untable tribology properties due to the poor dispersion in LP base oils.The cerium oxide nanoparticles showed antioxidant properties.