Study On The Tribologial Performance Of Carbon Microspheres And TiO₂ As Lubricant Additives

With the gradual maturity of solid lubrication theory and the successful application of solid lubricants,the research which concerning with the application nanoparticles as lubricant additives in base lubricant oil has become an important direction in the development of lubrication.Among them,carbon nanomaterials and titanium dioxide have attracted more and more attention due to their own special structure and properties.In this paper,we studied micro-carbon spheres and nano-titanium dioxide particles,prepared by green hydrothermal synthesis and sol-gel method,respectively.Their surface morphology,composition and crystal phase were examined.The tribological properties of the lubricants micro-carbon spheres and nano-titanium dioxide in the three basic lubricants were investigated.The lubrication mechanism was discussed by means of Raman and energy spectrum.The experiment has achieved some results as follows:(1)The micro-carbon spheres with a perfect spherical structure and a size of about 300nm was prepared by hydrothermal method by using glucose as the precursor compound.The their main constituent elements and the functional groups contained on the surface of the micro-carbon spheres studied by conducted by using the eds spectrometer and infrared spectrometer analysis.They were added to vegetable oil,synthetic oil and mineral oil,and the effects of different loads and rotational speeds on the lubricating properties were studied.It was found that the microcarbon spheres exhibited good lubricating properties under low load.(2)The micro-carbon spheres were surface-modified by quaternization reaction.According to the surface morphology and infrared spectrum analysis,the modified micro-carbon spheres were coated with a layer of polymer to reduce the agglomeration effect.The experiment was carried out by adding it to synthetic oil,and it was found that the better anti-wear performance of the micro-carbon ball was improved as compared with the unmodified micro-carbon ball.(3)Lubrication mechanism of micro-carbon spheres as lubricating additives was investigated by using Raman spectroscopy.It is shown that the micro-carbon spheres enter the lubrication contact zone during the sliding process.Some of micro-carbon spheres are rearranged under the action of compressive stress and thermal stress,forming a layer of lubricating film.The undestroyed micro-carbon sphere may fill the inside of the rough peak or acts as the rolling ball to reduce the friction and wear.(4)The titanium dioxide nanoparticles were prepared by sol-gel method.There is the transformation for titanium dioxide from amorphous to anatase,then to rutile phase after calcination at different temperatures.The experiments are carried out by adding them into the fully formulated engine oil.It is found that the lubrication performance of titanium dioxide is gradually lowered as the heat treatment temperature is increasing.The addition of titanium dioxide after treated at 300~oC shows best friction-reducing and wear protection performance.This is mainly due to the fact that the formation of crystal of titanium dioxide changes at higher calcination temperature,which gradually increases the hardness of the nanoparticles.Thus the abrasive wear phenomenon becomes more and more serious.