Study Of Preparation And Tribological Properies Of Two-Dimensional Graphene Multiple Nanoadditives

Due to the excellent self-dispersion stability and outstanding tribological properties,graphene multiple nanocomposite as lubricant additives with two-dimensional structure can reduce the friction and wear of mechanical parts and extend the service time of the equipments.In order to boarden the application of graphene nanocomposites as lubricant additives in industry,the preparatrion and tribological properties of two novel graphene multiple nanocomposites were further analyzed and discussed in this paper.Two novel graphene multiple nanocomposites:iron manganese oxide/graphene（Mn-Fe-O/G）and oleic acid modified calcium carbonate/graphene（Ca CO₃-OA/G）were successfully synthesized via a simple and effective method.The micromorphology and chemical structure were analyzed.The results indicated that multiple nanoparticles with different shapes（sphere and prism）were uniformly anchored on the graphene sheet with regular lamellar structure;moreover,functional groups of oleic acid were connected on Ca CO₃-OA/G,which confirmed the surface modification of oleic acid.The two-dimensional structure is the basis of excellent tribological properties.The tribological properties of graphene multiple nanocomposites,graphene,nanoparticles and graphene binary nanocomposites were compared under the same friction conditions in the paper.The results showed that graphene multiple nanocomposites exhibited the best tribological properties.The influence of working conditions such as load,sliding velocity,temperature and so on was analyzed.It was found that the two graphene multiple nanocomposites had more obvious friction and wear enhanced properties under extreme conditions such as heavy load and high temperature,the antifriction and antiwear properties could be improved by more than 20%and60%respectively in detail.The affect of additive concentration and base oil types on the tribological properties was also discussed.The research indicated that appropriate concentration（0.5wt.%～1.0wt.%）had best antifriction and antiwear properties;in addition,graphene multiple nanocomposites had more obvious friction and wear enhance properties in base oil with higher polarity.Finally,the lubrication mechanisms of graphene multiple nanocomposites were investigated,which revealed the synergistic antifriction and antiwear mechanisms which consisted of the formation of tribofilm and slide-roll effect.CFD simulation of the fluid film on the wear interface was adopted and the influence of nanolubricant additives on the properties of fluid film was studied.The results revealed that the velocity difference in fluid film helped the nanoparticle enter the friction interface and promoted the film formation;the addition of nanoparticles increased the viscosity and film thickness,reduced the shear rate on the wear interface,improved the direct contact status of rough peaks and enhanced the lubricating and wear-reduction properties.The wear analysis model under fluid lubricating conditions was also established,and the friction and wear characteristics lubricated by various nanofluid were analyzed.Combined with the experimental results,it was indicated that the analysis model could predict the wear volume correctly,and had the potential of the judgement of wear failure of mechanical equipments.The developed two graphene multiple nanocomposites as lubricant additives exhibit outstanding tribological properties under extreme coditions such as heavy load and high temperature and have synergistic antifriction and antiwear effect consisted of the formation of tribofilm with high interface adsorption as well as stability and slide-roll effect.The research in this paper provides theoretical basis and technical support for industrial development and engineering application of graphene nanocomposite.