Preparation Of The Metal Nanoparticles/Graphene As Lubricatingadditives

To design multifunctional nanocomposite lubricating additives improving the performance and bearing capacity of marine lubricating oil,the Cu/graphene composite powders,Fe/graphene composite powders and W/graphene composite powders were prepared by plasma assisted ball milling.The morphology and structure of composite powders were characterized by SEM,TEM,XRD,Raman and FT-IR spectrometer.The dispersibility and tribological property of composite powders in base oil were tested.(1)The prepared mechanism of graphene was studied.It was found that after milled for 10h,graphene with three layers was prepared and the I_D/I_G value of graphene was 0.493 when W with the highest Moh's hardness was used as the milling medium;graphene with six layers was prepared and the I_D/I_G value of graphene was 0.292 when Fe with the middle Moh's hardness was used as the milling medium;graphene with six layers was prepared and the I_D/I_G value of graphene was the minimum with only 0.193 when Cu with the lowest Moh's hardness was used as the milling medium.The heating effect of plasma,the impacting and shearing actions of milling ball coordinating with the scraping and inserting effects of metal powders could effectively promote the expanded graphite stripped into graphene,and the metal with higher Moh's hardness as the milling medium scratched and stripped the expanded graphite more significantly.(2)The morphological evolution of different metals was studied.It was found that after milled for 10h,Cu with the lowest melting point were all transformed into spheres,and Fe with the middle melting point were in both spherical and irregular shapes on the graphene,but W with the highest melting point were still in irregular shape.(3)The degree of grain refinement of different metals was studied.It was found that after ball milled for 10h,the grain size of Cu,Fe and W was 22.1nm,40.2nm and 31.5nm,respectively.Cu was more prone to obtain deformation and thermal explosion in ball milling,this was because the plasticity of Cu was the best and the melting point of Cu was the smallest than that of Fe and W.For Fe and W with the same metallic crystal structure,W was easier to obtain grain refinement than Fe due to its higher melting point.(4)The dispersion and tribological property of metal nanoparticles/graphene additives in lubricating oil were studied.It was found that the metal/graphene additives prepared by milling for a longer time had better dispersion in lubricating oil.It was also found that the Cu/graphene additives prepared by milling for 10h had the best anti-friction performance,while the W/graphene additives had the worst anti-friction performance.It demonstrated that the anti-friction and anti-wear properties of metal/graphene additives were tightly related with the hardness and shape of metal nanoparticles,the metal nanoparticles with smaller hardness and the additives with more spherical particles showed better anti-friction performance.