Zhang Ping-yu

Friction Reducing Anti-wear and Self-repairing Properties of Nano-Cu Additive in Lubricating Oil

Cu nanoparticles coated with dialkyl dithiophosphate (Cu-DDP) are synthesized in-situ by redox method.The size and structure of the nanoparticles are characterized by using transmission electronic microscopy (TEM) and electronic diffraction (ED) analysis.The anti-wear and friction-reducing and self-repairing behaviors of Cu-DDP as additive in base lubricating oil are investigated on both four-ball machine and MRH-3 stock-on-ring testing machine.Scanning electronic microscopy (SEM),X-ray photoelectron spectroscopy (XPS) and electronic balance (EB) are used to study the grinding crack topography,elemental composition and chemical valence,and the quality change of the self-repairing Cu film on the stock respectively.The test results show that at a load of 300 N a 4% additive amount of Cu nanoparticles exhibits the best self-repairing performance.The stock mass increases by 0.5 mg after 4-hour testing,and the wear scar diameter and friction coefficient are obviously decreased.The Cu nanoparticles is deposited on the frictional surface to form deposited film during the friction process,which could get synergetic effect with the friction chemical reaction film coated on the surface.As a result,the excellent anti-wear and self-repairing performances are obtained.

Investigation of tribological properties of composite C60-LB films

Composite C60-LB films were fabricated by the Langmuir-Blodgett (LB) technique, their micro-structures, micro-and macro-tribological properties were investigated using atomic force microscope/friction force microscope (AFM/FFM). The results showed that in the confined C60-LB films there were two kinds of structures for the special C60 assembly: grain diameters of one kind were in the range of 150–230 nm; the other was smaller than 20 nm. Micro-tribological studies showed that topographical images of tiny C60 aggregates (<20 nm) were consistent with their frictional ones very well, namely, low friction occurred on tiny C60 aggregates compared with fatty chains LB monolayer, and ‘Micro-rolling effect’ was apparent; but for big large ones frictional forces were relatively high and ‘ratchet mechanism’ was seen apparently. Macro-tribological data proved large C60 aggregates had wear resistance and load-carrying capacities and anti-wear lives for composite C60-LB films were prolonged greatly with dispersibility of C60 improved and its grain diameter reduced. Tiny C60 aggregates were mainly the lubricating agents. Friction coefficients of composite C60-LB films gradually reduced with loads increasing having the same friction coefficient-load relations with boundary lubrication films.