Nano Cerium Oxide And Silicon Dioxide Composite Particles As The Tribological Properties Of Lubricating Oil Additives And Mechanistic Studies

The tradition lubricants are occupying dominant position in the market, but their application limitation can't be neglected on high bearing ability, high temperature and environment amity. Nano-particles have many special characters such as high relative surface, the superficial atomicity, surface energy and tensile force of surface, which increase sharp along as particle size drop. Nano-particles have predominant performances which are different from conventional materials because they possesse the light-sized effect, the surface effect, the quantum size effect and the macroscopic quantum tunnel effect and so on. So nano-particles possess the heat, the magnetism, the light, chemistry catalysis characteristic and superficial stability. These characters are different from conventional particles. With the development of preparing, characterization and surface modification of nano-particles, their application research on lubrication domain get improved. The characterization, tribological performance and mechanism of anti-wear and friction reduction of nano-particles of cerium dioxide and silicon dioxide are studied in this paper. The main conclusions are reached as followed:1. The crystal structure and average sizes of nano-particles of cerium dioxide and silicon dioxide have been tested by a D/max-rB X-ray diffractometer. And the shapes and average sizes of nano-particles of cerium dioxide and silicon dioxide have been measured through TEM. The results indicated that both nano-particles of cerium dioxide and silicon dioxide appeared as spherical particles, and their diameters are about 10.4nm and 20nm, respectively.2. On the basis of HLB values suitable surfactants such as Tween-20, Tween-60 and Span-20 were selected. The nano-particles of cerium dioxide may restrain accumulation of other nano-particles in lubricants. The results show that they can make nano-particles have very good dispersiveness and stability in the lubricating oils.3. Tribological performances of nano-particles of cerium dioxide and silicon dioxide as lubricating oil additives were studied in friction and wear test machine of MRS-1J. The results indicated that dispersion and stability of nano-particles are key factor to use them as lubricating oil additives. Only with evenly-distributed cluster can the function of anti-wear and friction reduction be achieved. 4. The optimal proportion of nano-particles of cerium dioxide and silicon dioxide: Wt_CeO2:Wt_SiO2=1:1, and the total content Wt_(CeO2+SiO2) is about 0.6%.5. The tribological mechanism of nano-particles of cerium dioxide and silicon dioxide was studied through Scanning Electron Microscope(SEM). The mechanism of anti-wear and friction reduction has been discussed and individual opinions are proposed.1) The average diameters of nano-particles of cerium dioxide and silicon dioxide are 10.4nm and 20nm, respectively. At the beginning, nano-particles in lubricant oils work as "tiny polish" to cut bulges of friction surfaces. Then the nano-particles work as "tiny ball bearing" between friction surfaces after friction surfaces become more smooth and some nano-particles can fill in and repair worn surfaces.2) Only with appropriate proportion, can nano-particles of cerium dioxide and silicon dioxide concertedly function as properties of anti-wear and friction reduction. In our research, the best proportion and concentration of cerium dioxide and silicon dioxide is Wt_CeO2:Wt_SiO2 =1:1 and Wt_(CeO2+SiO2)=0.6%, respectively. The nano-particles of cerium dioxide can effectively restrain accumulation of nano-particles of silicon dioxide in lubricant oils on the condition of this proportion and concentration. And nano- particles of cerium dioxide and silicon dioxide may disperse in lubricant oils evenly and stably so they may become oil film of nano-particles between friction surfaces. They can partition friction surfaces. At the beginning, nano-particles of cerium dioxide and silicon dioxide in lubricant oils between friction surfaces may work as "tiny polish", and then nano-paritcles may work as "tiny ball bearing" and "fill-in and repair worn surface".This paper is a part of "Study on key technology of industry application of nanoparticles lub-oils additives" (05FZ31) of the science and technology project of Shanghai Education Committee. More research are expected to be further developed.