Preparation Of Dispersible Copper、Copper Composite Nanoparticles And Investigation Of Their Tirbology Behavior

Attempting to establish a feasible and practicable route for preparing copper nanoparticles withdesired lubricity, in the present research we systematically study the surface-modification techniques ofcopper nanoparticles in-depth and characterize their structure. Besides, the tribological properties ofas-prepared surface-capped Cu nanoparticles as environmentally friendly lubricant additives have also beenevaluated. The main contents and research results of this thesis are as follows:（1） Preparation and characterization of oil-soluble copper nanoparticles co-modified by oleic acidand oleylamineCu nanoparticles co-modified by oleic acid and oleylamine were prepared by chemical reduction andtwo phase extraction method with copper nitrate as the precursor and sodium borohydride as the reductant.The morphology, structure and thermal properties of as-prepared Cu nanoparticles were investigated bymeans of transmission electron microscopy （TEM）, X-ray powder diffraction （XRD）, Fourier transforminfrared spectrometry （FT-IR）, and thermogravimetric analysis （TG）. The tribological behavior ofas-prepared Cu nanoparticles as an additive in liquid paraffin was evaluated with a four-ball friction andwear tester. The morphology and elemental composition of worn steel surfaces were analyzed using ascanning electron microscope equipped with an energy dispersive spectrometer （EDS）. The tribochemicalreaction mechanism was analyzed using an X-ray photoelectron spectroscope （XPS）. It has been found thatas-prepared copper nanoparticles have a small and uniform size and can be well dispersed in organicsolvents such as petroleumether, chloroform, benzene, liquid paraffin, and poly-alpha olefin （PAO）.Besides, Cu nanoparticles as lubricating additive in liquid paraffin show good antiwear properties at lowand moderate loads.（2） Preparation and characterization of oil-soluble Cu@Fe₃O₄composite nanoparticles co-modifiedby oleic acid and oleylamineTransparent Cu sol was prepared in aqueous solution in the presence of cupper sulfate as the precursor,ammonia as the complexing agent, and hydrazine hydrate as the reducing agent. As-obtained Cunanoparticles were then coated with FeCl2and FeCl3generating Cu@Fe₃O₄nanoparticles. Cu@Fe₃O₄nanoparticles were finally surface-capped with oleic acid and oleylamine, generating oleic acid/oleylamineco-modified oil-soluble Cu@Fe₃O₄composite nanoparticles. The morphology and structure of as-prepared Cu@Fe₃O₄composite nanoparticles co-modified by oleic acid/oleylamine were investigated by means ofTEM, XRD, and FT-IR. The tribological behavior of as-prepared Cu@Fe₃O₄composite nanoparticles asadditive in PAO was evaluated with a four-ball friction and wear tester. It has been found that as-preparedCu@Fe₃O₄composite nanoparticles co-modified by oleic acid/oleylamine have a small and uniform sizeand can be well dispersed in organic solvents such as petroleum ether, chloroform, benzene, liquid paraffin,and PAO. Besides, as a lubricant additive in PAO, Cu@Fe₃O₄composite nanoparticle co-modified by oleicacid/oleylamine shows good antiwear ability.（3） Preparation and characterization of water-soluble copper nanoparticles modified by clayWater-soluble Cu nanoparticles were prepared by chemical reduction with hydrazine hydrate in thepresence of clay as a surface-modifying agent. The morphology and structure of as-prepared Cunanoparticles were investigated by means of TEM and XRD. A meter for measurement of coefficient ofthermal conductivity was performed to determine the thermal conductive behavior of as-prepared Cunanoparticles as water-based lubricant additive. The tribological properties of as-prepared Cu nanoparticleswere evaluated using an Optimol SRV-IV oscillating friction and wear tester in ambient condition.Moreover, the tribochemical reaction mechanism was analyzed by means of XPS. It has been found thatas-prepared water-soluble copper nanoparticles have a small and uniform size and can be well dispersed inaqueous solution. Besides, Cu nanoparticles as water-based lubricant additives show good antiwear andfriction-reducing properties.（4） Preparation and characterization of water-soluble Cu-Ag composite nanoparticles modified byclayWater-soluble Cu-Ag composite nanoparticles were prepared via chemical reduction of copper nitrateand silver nitrate by hydrazine hydrate in the presence of clay as the surface-modifying agent. Themorphology and structure of as-prepared Cu-Ag nanoparticles were investigated by means of TEM andXRD. The thermal conductive behavior of as-prepared Cu nanoparticles as water-based lubricant additivewas examined based on measurement of coefficient of thermal conductivity. The tribological properties ofas-prepared Cu-Ag nanoparticles were evaluated using an Optimol SRV-IV oscillating friction and weartester in ambient condition. It has been found that as-prepared water-soluble Cu-Ag nanoparticlessurface-capped by clay have a small and uniform size and can be well dispersed in aqueous solution. Besides, as-prepared Cu-Ag nanoparticles as water-based lubricant additive show good antiwear andfriction-reducing abilities.