Tribological Performance Of Cerium Oxide And Copper Nanoparticles As Lubricating Additives

The nanotechnology already plays an important role in many scientific fields, for example in physics, chemistry, materials science, biology, medicine, engineering, computer simulation and so on.Nanoparticles appeared in the literature around 1980s in connection with powder particles having physical dimensions of less than 100nm in diameter. In comparison, the diameter of a human hair is about 20,000 nm wide and a smoke particle is about 1,000 nm in diameter. Effects controlling the properties of nanostructured materials include size effects, surface effect, quantum effect, quantum tunneling effect and so on. The nanotechnology used in lubricating oil additives have received considerable attention in recent years, since their physical, chemical and tribological properties are quite different from those of the bulk materials.Nanotechnology-based extreme-pressure and anti-wear additives were found to have high chemical and physical stability, even under extreme conditions. These properties translate to longer equipment operation, increase efficiency, extend maintenance intervals and alleviate friction, which reduces noise, heat and vibration. Environmental benefits include reduced energy consumption and decreased air pollution. The lower cost of maintenance, extended equipment life, improved machine performance and reduced downtime provide significant economic benefitsAdditives for lubricating oils were used first during the 1920s, and their use has improved lubricating oils tremendously. Additives, in improving the performance characteristics of lubricating oils, have been used significantly in the development of industrial machinery, modern car engines, automatics transmission, railroad and marine diesel engines as well as many other types of equipment. Today, practically all types of lubricating oils contain at least one additive and some oils contain additives of several different types. The amount of used additives can reached to 20% or more of lubricating oils. The entire lubricating oil industry is becoming more and more dependent on additive suppliers to supply technology and additives to meet oil specification requirements. The development of the lubricant additive industry started with automotive manufacture and the need for specialized lubricants. The largest market of additives is in the transportation field, such as trains, cars, trucks, locomotive and ships.There are several different types of lubricating additives. The traditional oil-soluble anti-wear and friction-reducing additives always produce the environment pollution and disadvantages in severe conditions. Nowadays, it is the application of nanoparticles in lubrication that provides a new way.In recent years, researches on nanocrystalline materials are gaining popularity in scientific and industrial fields. Large-scale nanotechnology programs, institutes, and research networks have been initiated recently on a wide range of topics in American, Europe, Japan, China, and other countries. Intense investigations have been stimulated by several envisaged application areas for this new class of materials. However, relatively limited attention has been paid to their tribological properties, especially as additives in lubricating oils because of their poor dispersion capacity. The reason is that nanoparticles have low stability and tend to agglomerate or make aggregates because of their strong cohesiveness and high specific surface areas. It is usually not easy to disperse them. Therefore, it is important to study lubricating oil additives of nanoparticles. In recent years, the research institute, universities, the experts have carried out this research work, and obtained certain results. Some investigations have been undertaken, and the results implied that the nanometer-sized particles would be potential additives of lubricating oils in the near future. Much more work is still required to establish how the lubricating oils will be affected by the various changes of nanoparticles and oils.In this paper, the author studies the tribological performance of cerium oxides and copper nanoparticles as lubricating additives.The paper includes 5 chapters. Chapter 1 introduces about nanoparticles characteristics, development of lubrication oil and its additives, mechanism of nanoparticle lubricating additives and international research work in present condition. Chapter 2 is selection and characterization of CeO₂ and Cu naoparticles. Chapter 3 is dispersion and surface modification of CeO₂ and Cu nanoparticles mixtures in lubricating oil. Chapter 4 is studies of tribological performance of CeO₂ and Cu nanoparticles as lubricating additives. Chapter 5 is conclusion and future work.In this paper, the author reported the tribological performance of cerium oxides and copper nanoparticles as lubricating additives. The main conclusions are followed.1. The crystal structure and average sizes of nanoparticles of CeO₂ and Cu have been tested by aD/max-rB X-ray diffractometer. And the shapes and average sizes of nanoparticles of CeO₂ and Cu have been measured through TEM. The results indicated that both nanoparticles of CeO₂and Cu appeared as spherical powders, and their diameters are 10.4nm and 60nm, respectively.2. On the basis of HLB values, suitable surfactants such as Tween-20, Tween-60, and Span-20and Polyether are selected. The results show that they make nanoparticles having very good dispersion and stability in the lubricating oils. It is the "capsules" of nanoparticles in lubricating oils that give a new way to get good dispersion and stability.3. The tribological performance of base oil and lubricating oil with nanoparticles which were measured using a four-ball tribotester according to the GB/T 12583—1998 The results showed that CeO₂ and Cu nanoparticles additive can improve the tribological performance of the lubricating oils and nanoparticles can be used as anti-wear and extreme-pressure additives with excellent performances. The optimum concentration and proportion of nanoparticles is Wt_CeO2% WtCu% =1:1 and the optimum total content is about 0.6%.In the optimum concentration, naoparticles appears to work much better.In lower and higher concentration, naoparticles can not have long durability.4. CeO₂ and Cu nanoparticles in the frictional surfaces could have "minute ball bearing" effect. Under more heavy load and higher temperature conditions, the minute ball-bearing effects of nanoparticles existed between the rubbing faces and form a sliding system. It makes the friction surface more flatness, so it can reduce the friction factor and the wear rate.There are many lubricating oil with nanoparticles additives worldwide to reduce friction and decrease wear significantly, especially under extreme conditions such as at higher loads and temperature. But much more work is still required. This research is preliminary.The suggestion for future research works are following:1. Study and understand the change reasons in properties of the lubricating oils as a result ofincorporation of the nanoparticles.2. The selection of surfactants for surface modification of naoparticles is considered in order to geta good dispersion and stability of nanoparticles in lubricating oils.3. In order to have a wide use for industrial applications, the experimental test results should befurther transited to industrial application.The present study is part of "Research on Nanometer material's application in lubricating technology" (05FZ31), key project of Shanghai Educational Committee. More researches are expectably to be further developed.