Construction And Tribological Properties Of Spherical Carbon-based Core-shell Structure Lubricant Additives

At present,the degree of functionalization,systemization and intelligence of mechanical products is constantly improving,and the friction and wear problems faced by the mechanical structure of advanced equipment are more prominent,which puts forward high efficiency and intelligent requirements for lubricating products.Carbon spheres（CS）,as a conventional lubricant additive,have problems such as poor self-healing property and single function,which are difficult to meet the current requirements.The core-shell structural materials have the advantages of adjustable structure and diverse functions,which are conducive to the realization of high efficiency and intelligence of lubricating additives.In this paper,three spherical carbon-based core-shell lubricant additives（C@MoS₂,C@Ag,C-NFs）were prepared,which provided reference for the development of new lubricant additives.（1）The C@MoS₂ core-shell structure lubricating additive has the advantage of synergistic lubrication:The anti-friction and anti-wear performance of C@MoS₂ core-shell material is better than that of single material or mechanical hybrid material,reflecting the advantage of synergistic lubrication.In addition,this core-shell type lubricant additive has adaptability to multiple working conditions,and can play a good lubricating effect under different surface roughness and different load ranges.During the friction process,C@MoS₂ core-shell particles forming a composite friction film with high load-bearing and easy shearing through three stages:shell fragmentation,shell-core separation and formation of a friction film,which can effectively reduce friction and wear.However,due to the inability to form a complete and dense tribo-film,the core-shell material cannot exhibit efficient and intelligent lubricating properties.（2）The C@Ag core-shell structure lubricating additive has efficient lubricating properties:The C@Ag core-shell material prepared by the redox method has excellent anti-friction and anti-wear properties when used as a lubricating additive.When the addition amount is 0.5 wt%,the wear volume is 88.0%lower than that of the base oil.The C@Ag core-shell particles can improve the adsorption capacity and integrity of the tribo-film through fusion bonding during the friction process,which is the main reason for its outstanding lubricating performance.Although the core-shell material has the advantage of efficient lubrication,it cannot achieve active regulation of the friction state.（3）The C-NFs core-shell structure lubricating additive has intelligent lubricating effect:The C-NFs have excellent anti-friction and anti-wear effect whether used as a lubricant alone or as a lubricating additive of PEG400,and can actively control the friction state through electrical stimulation,so as to realize intelligent lubrication.In the absence of electrical stimulation,the average friction coefficient of pure C-NFs can be reduced by 26.0%compared with PEG400;and when an external electric field of 1.5 V is applied to the friction pair,the friction coefficient of pure C-NFs can be further reduced by 16.3%in 3 s.and can be repeated many times.The regulation of the structure of the tribo-film by electrical stimulation is a key factor in realizing intelligent lubrication.