The Tribological Properties Research Of Alumina/Silica Composite Nanoparticles As Lubricant Additives

In recent years, the rapidly development of economy in our country, especially the vigorous development of transportation that demand for lubricant oil and lubricant oil additives continue to rise. However, the shortage of oil resource leads to the conflict between the demand and supply. This must bring new opportunities and challenges for the development of our country's oil market. The traditional lubricant additives cannot content the need of modern industrial development, as people environmental protection consciousness strengthening. The problems which how improve the anti-friction and anti-wear performance of lubricant oil, reducing wear and friction, reducing energy consumption, prolong the service life of the machine parts, reducing the harm to the environment, now, are the urgent problems to solve for scientific research personnel and users.Nano additives bring new hope as the development of nanotribology. For nearly a decade, the reports about nanoparticles as lubritant oil additives common occurance, a large number of researches proved: lubricant oil with nanoparticles not only has obvious anti-friction anti-wear performance but also environment friendly. This is the traditional lubricant oil cannot match. Nanoparticles as lubricant additives are widely attented by people.Al₂O₃/SiO₂ composite nanoparticles are the main research object in this paper, and its tribological properties as lubritant oil is the point we researched. In order to intensive study the friction mechanism, the aluminium isopropoxide (AIP) and tetraethoxysilane (TEOS) as raw materials prepared Al₂O₃/SiO₂ composite nanoparticles by hydrothermal method. The Al₂O₃/SiO₂ composite nanoparticles were modified with silane coupling agent, titanate coupling agent, aluminium zirconium coupling agent by surface grafted modification and in-situ modification. Finally, we researched the tribological properties of Al₂O₃/SiO₂ composite nanoparticles were studied by friction test. The main research contents of this paper as follows: (1) The preparation of Al₂O₃/SiO₂ composite nanoparticles: Using a variety of raw materials and methods prepared the Al₂O₃/SiO₂ composite nanoparticles, with the standards of morphology and size, the better raw materials and methods were choesd preliminary. The Influence factors of preparation were studied by orthogonal test. They are the molar ratio of Al₂O₃/SiO₂ composite nanoparticles, the dosage of dispersant, the kinds of alkali, preparation temperature. The optimal scheme is: Al₂O₃/SiO₂ composite nanoparticles molar ratio is 1:4, dispersant dosage is 2wt%, alkali is ammonia, preparation temperature is 220℃. The Al₂O₃/SiO₂ composite nanoparticles were charactered by SEM, TEM, IR, laser particle size analysis. Results show that the size of Al₂O₃/SiO₂ composite nanoparticles we prepared is small than 100 nm, the shape is sphere, amorphous states.(2) The modification of Al₂O₃/SiO₂ composite nanoparticles: The Al₂O₃/SiO₂ composite nanoparticles were modified with silane coupling agent, titanate coupling agent, aluminium zirconium coupling agent by surface grafted modification and in-situ modification. The optimal schemes of the two modification methods are: Al₂O₃/SiO₂ composite nanoparticles molar ratio is 1:4, titanate coupling agent and the dosage is 3wt%, pH is 7 in surface grafted modification; Al₂O₃/SiO₂ composite nanoparticles molar ratio is 1:4, silane coupling agent and the dosage is 3wt%, modification temperature is 220℃in in-situ modification. The Al₂O₃/SiO₂ composite nanoparticles were charactered by SEM, Zeta potential test, IR. It shows that the modified Al₂O₃/SiO₂ composite nanoparticles are spherical, size is small than 100 nm, amorphous states.(3) Tribological properties research of Al₂O₃/SiO₂ composite nanoparticles: The tribological properties of Al₂O₃/SiO₂ composite nanoparticles were analyzed by four-ball test and thrust-ring test. The test indexs are friction coefficient, wear scar diameter, abrasion loss, friction surface morphology. At the same time, the tribological properties of Al₂O₃/SiO₂ composite nanoparticles were compared with Al₂O₃ nanoparticles and SiO₂ nanoparticles. It showed that the tribological properties of lubritant oil with Al₂O₃/SiO₂ composite nanoparticles obvious improved than lubritant oil; both four-ball test and thrust-ring test are proved that the optimal additive concentration of Al₂O₃/SiO₂ composite nanoparticles is 0.5wt%, and the friction coefficient and wear scar diameter are smallest under this additive concentration, the scratches of friction surface are smoother and narrower; the anti-friction and anti-wear properties of Al₂O₃/SiO₂ composite nanoparticles are better than Al₂O₃ nanoparticles and SiO₂ nanoparticles; the anti-wear properties of Al₂O₃ nanoparticles is better than SiO₂ nanoparticles, the anti-friction properties of SiO₂ nanoparticles is better than Al₂O₃ nanoparticles; Al₂O₃/SiO₂ composite nanoparticles were diverted to the friction surface, and occurred physical chemistry function with the friction surface, formed a layer of dynamic self-repairing film on the friction surface, effectively protect the friction surface.