Investigation On Structural Characterization And Tribological Properties Of Nano Onion-Like Fullerenes

In recent years, the application of nanoparticles in the area of lubrication has attracted increasing attention to people at home and abroad and using nanoparticles as lubricant additives has become a hot part of the study. Carbon nano-materials have been widely used in the field of lubrication because they can restore their lubrication in the process of friction, such as carbon nanotubes (CNTs), C₆₀, carbon fibers. As a member of the family of fullerene, nano onion-like fullerenes (NOLFs) have potential values in restoration of its lubrication because of their special cage-like structure and the isotropy.In this paper, individual NOLFs and Fe nanoparticles encapsulating nano onion-like fullerenes (nano-Fe@OLFs) were synthesized by DC arc-discharge in water and chemical vapor deposition (CVD). NOLFs were functionalized by refluxing with stearic acid (SA). Their morphology and structure were characterized by high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD) and others. The tribological propertis of NOLFs as lubricant additives were investigated by using a four-ball type tribometer, and the typical worn surfaces in four-ball test were analyzed by field emission scanning electron microscope (FESEM). The conclusion is as follows:Firstly, individual NOLFs were synthesized by DC arc-discharge in water. The yield and productivity of NOLFs rose obviously with the increasing of current density in the range of 20 -50A. When the current above 50A, the higher current forced the accelerated consumption of anode. Graphite fragment was generated, so the yield and productive rate of NOLFs were falling.Secondly, NOLFs were coated with a modified layer of SA. The dispersion capability and stability of SA coated NOLFs as lubricant additive were effectively improved.Thirdly, NOLFs as a lubricant additive can improve the lubricating effect of base oil effectively by greatly improving carrying capacity and anti-wear properties, but the concentration inverse their carrying capacity and anti-wear properties; lubricant additives can greatly shorten the wear-in time of the base oil. CNTs and NOLFs has an anti-wear properties, however, the latter is superior in the anti-wear properties.According to nanoparticles anti-wear additives role mechanism, we speculate on NOLFs can play role of bearing load "ball bearing", so it can increase anti-wear ability effectively.