Preparation And Tribological Study Of Bi Nanoparticles And Its Composite Nanoparticles

With the development of nanotechnology, the theoretical study and application of nanomaterial in lubricant were accelerated, especially nanoparticles have showed excellent lubrication performance in slashing running conditions, some displayed renovation function and present friendly to environmental protection. The dissertation is aimed to research and develop lubricating oil additives with environment friendly, good anti-wear and extreme-pressure. The tribological properties of metal nanopartic-les and composite nanoparticles as lubricating oil additives were investigated, and their tribological mechanisms were also evaluated.Here, Bi nanoparticles and Bi/Cu composite nanoparticles were successfully prepared by the reverse microemulsions method with the use of OP-10as the surfactant,n-amyl alcohol as the cosurfactant, cyclohexane as the oil phase and water, which in the microemulsion I and II were salt solution and N2H4·H2O as a reducing agent. The morphology and structure of the resulting were characterized by using Transmission electronmicroscopy (TEM), X-raydiffraction (XRD), UV sperctrophot-ometry (UV-Vis), Thermogravimetry (TG) and Differential thermal analysis (DTA). Bi nanoparticles and Bi/Cu composite nanoparticles were modified with stearic acid. The results showed the way of stearic acid adsorbed the surface of nanoparticles was chemisorpion processes. Therefore, the surface property of modified product with good wetting and dispersity in liquid paraffin was changed from hydrophilicity to hydrophobicity.Friction and wear behaviors of Bi nanoparticles and Bi/Cu composite nanoparticles modified with stearic acid were evaluated with four-ball maehine to test their antifriction. Test results indicated that the both used as lubricant additives shows good friction-reducing and excellent antifriction. The optimal mass fraction of Bi nanopart-icles and Bi/Cu composite nanoparticles is0.05%, the wear scar diameter can be decreased by22.2%and31.9%respectively. When Bi nanoparticles as additive in paraffin oil was0.10wt%, PB reached a maximum510N. And when Bi/Cu composite nanoparticles was0.20wt%, PB reached570N. The morphologies, typical element distribution of the worn surfaces were characterized by SEM and EDS respectively. Anti-wear mechanism as follows:quasi-spherical Bi nanoparticles and Bi composite nanoparticles had functions of the small-scale bearing and the support pad in surface layer possessing, that made friction reducing and anti-wear properties improving. The rubbing acting come into being a hard films to enhance extreme-pressure capacity.