Studying On Preparation And Properties Of Copper Nanoparticles/MWNTs Composite As Lubricating Oil Additives

Nano-particles lie in the junction of the cluster and the macroscopic objects.It has the specific capacities in the structural, optical,electronic, magnetic and chemical properties with small size effect, surface effect, quantum size effect and macroscopic quantum tunnel effect. Numerous studies show that the extreme pressure of lubricating oil with the nano-particles additives can be improved. Preparation and stable dispersion of nano-particles in lubricating oil is the key of nano-particles as the lubricant additives.In the article, properties,preparation and application of copper nano-particles and carbon nanotube used in the research were described, and the recently development of nano-particles as the lubricant additives was summarized.In order to prepare the nanocopper particles,thermal decomposion of Cu(HCOO)2 in the basic-lubricating oil(150SN) under specified condition of temperature was applied by using self-made Cu(HCOO)2 as a raw material. Influence of the concentration of Cu2+,time of ball milling, temperature of thermal decomposion and the speed of the stir on the diameter of nanocopper particles were studied.XRD and TEM were used to characterize the size and structure of the nanocopper particles.Experimental results show that the nanocopper particles are with spherical geometry, their surfaces are not oxidized, and the particle sizes is about 42nm in average,when the concentration of Cu2+ is 0.33mol/L, time of ball milling is 12h, temperature of thermal decomposion is 200℃and the speed of the stir is 30rad/min. Though copper nano-particles had been dispersed evenly in the lubricating basic oil,the dispersed stability of the copper nano-particles in the lubricating basic oil was not good by the 1-2h standing observation. In order to solve the dispersion stability of the copper nano-particles in the lubricating oil, preparation and properties of MWNTs/copper nano-particles composite as the lubricant additive were studied.Firstly, MWNTs have been chemically purified and oxidized using a mixture of concentrated H2SO4/HNO3 mixture (volume ratio:3:1),and MWNTs were modified by the esterification. The result of TEM shows that the purity of MWNTs had been improved markedly by the treatment of the concentrated H2SO4/HNO3 mixture.The result of FT-IR shows that MWNTs were introduced with carboxyl groups which presented at the side wall defect sites and the open ends of oxidized MWNTs by the treatment of the concentrated H2SO4/HNO3 mixture,and MWNTs modified alkane were prepared by the esterification. Secondly, by the test of XRD and SEM, and the result of standing observation, the dispersed stability of MWNTs/copper nano-particles composite in the lubricating oil was better than the copper nano-particles'Two kinds of lubricant additives were added to the methyl silicone oil.The tribological property of the oil was evaluated using four-ball extreme pressure tester. The result of the test shows that the PB of methyl silicone oil with the copper nanoparticles was improved by 98N, and the PB of methyl silicone oil with MWNTs/copper nanoparticles composites was improved by 294N.