Study On The Preparation, Dispersal And Tribological Behaviors Of Different Morphology Nano-structured Copper And Nickel

In lubrication process, oil additives have been widely used in all kinds of lubricating oils, which are effective in improving wear, friction reduction, and other aspects of performance. In recent years, nano-materials provide a new choice for the lubricant additives, some researches show that tribological performances have been improved significantly by lubricant with nano-metal additives. As the morphology of nano-particles determined their properties, the wear and friction properties also have quite different from lubricating oils with different morphologies nano-materials. So the anti-wear and friction reducing mechanism for different morphology of nano-particles remains to be further studied.In this paper, we choose a simple and easy-to-industrial chemical reduction method for the synthesis route, which need a simple device and mild reaction conditions. Different particle size and morphology of the nano-metals Cu, Ni samples were prepared through assisted heating as hydrothermal, ultrasound, and microwave method, which were characterized by X-ray diffraction respectively (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). Subsequently, ultraviolet spectrophotometer was used to investigate the effect of different morphologies nanostructured Cu, Ni dispersed in ethanol. Then the different morphology of the nano-metals were added into SF15W/40 lubricating oil, which friction and wear properties were tested by UMT-II friction and wear testing machine and four-ball friction and wear testing machine. After that, the friction coefficient (μ) of nano-metal, extreme pressure value (P_b) and wear scar diameter (WSD) were analyzed. Finally, the effect of the friction changed with different temperature was investigated by M-2000 friction and wear testing machine, and the anti-wear and friction reducing mechanism of the nano-metals with different particle size and morphology was explored. The experimental results were shown as follow:1. With water-oil interface growth method combines with liquid chemical reduction method, modified by Tween-85, as-spherical nano-Cu was obtained by hydrothermal heating, spherical, polyhedral, and a large particle size distribution of nano Cu was synthesized by ultrasonic heating; regular spherical nano-Cu was fabricated by microwave heating.2. With water-oil interface growth method combines with liquid chemical reduction method, modified by Tween-85, spherical nano-Ni was prepared by hydrothermal heating, irregular spherical nano-Ni was fabricated by ultrasound heating, needle-like nano-Ni was synthesized by microwave heating.3. In the dispersion experiments, anionic surfactants oleic acid was used to modify the nano-copper, and nano-nickel, which were dispersed in anhydrous ethanol. The optimum dispersion technique about nano-copper is: 2wt.% oleic acid, 15min ultrasonic time. The optimum dispersion technique about nano-nickel is: 2wt.% oleic acid, 10min ultrasonic time.4. Lubricants standing settlement experiments showed that: the lubricating oil with 0.5wt.% addition of different morphology of nano-copper, or nano-nickel were prepared, regular morphology of nano-copper dispersed had the best dispersing effect, while the dispersion of spherical nano-copper or nano-nickel were the next, and the morphology of irregular nano-copper or needle-like nickel had the inferior effect.5. The oil samples were tested by the UMT-II friction and wear test machine. Tribological test results showed that: compared with pure oil, the friction coefficient of oil added regular morphology nano-copper decreased 45.16%, and the wear volume decreased 72.09%. Analysis showed that the regular morphology of the spherical nano-particles played the "ball bearing" role in the friction surface which led to the optimum improvement of the tribological performance, while the anomalistic morphology nano-particles had the inferior improvement with their adsorption, deposition on the friction surface.6. Extreme pressure, anti-wear performance of the spherical nano-copper, nano-nickel and their composite powders were tested by four-ball friction and wear testing machine. The results showed that: in heavy load condition, the composite powders had the excellent extreme pressure and anti-wear performance because these powders deposited on the friction surface and formed the copper-nickel alloy to play the anti-wear and friction reduction effect.7. The effect of the reduce friction with different temperature was investigated by M-2000 friction and wear testing machine, the results showed that: the lubricants had the best reduce friction effect at 40°C, however, with the temperature increasing continually, the effect of the reduce friction gradually decreased.