Nano-iron, Rare Earth Composite Particles As The Tribological Properties Of Lubricating Oil Additives Studied

With the development of science and technology, lubricating oils become one of the important departments of the economic development. Nowadays, more and more lubricating oils are required, and how to save energy and protect environment in using lubricating oils has become a topic that everybody concerns about. Therefore .science and technology workers from every country work hard and have done a lot of research work, they try to add different additives to lubricating oils and expect to realize an aim of improving the lubrication of the lubricating oil,and they really obtain many important laboratory achievements. But, they have not drawn a persuasive conclusion in the respects of dispersibility and stability of the lubricating oils. In this paper, nano iron and nano rare earths are selected as lubricating oil additives.The dispersibility, stability, tribological performance and mechanism of anti-wear and friction reduction of nano-particles iron and rare earths are studied in this paper, and following conclusions are obtained:1. The shapes and average sizes of nano-particles of iron and rare earths were measured through TEM. The results indicated that both nano-particles of iron and rare earths appear as spherical powders, and their diameters are 78nm and 11nm, respectively.2. On the basis of HLB values suitable surfactants such as Tween-60, Span-20, Span-80and Polyether are selected. The results have shown that above surfactants have good effect in the lubricating oil and attain an intended goal.3.The tribological performance of the nano iron and nano rare earth composite additives has been tested on the wear machine.The results show that the optimal proportion of nano-particles of iron and rare earths is: WtFe%: WtRe%=1:1 .and the totel content Wt(Fe+Re)=0.6%.4. The tribological mechanism of nano-particles of iron and rare earths is studied through Scanning Electron Microscope(SEM) and atomic force microscope(AFM).5. The mechanism of anti-wear and friction reduction of nano-particles of iron and rare earths was discussed and individual opinions of nano-particlesproposed.(1) The results have shown that the nano-particles have very good dispersiveness and the tribological performance of the nano lubricating oils improved. But.the nano iron and the nano rare earths must have a optimal proportion.(2) In the experiment, the function of the nano iron and the nano rare earths are not always the same.the diameter of the the nano iron is bigger, it mainly works as "tiny ball bearing".However, the diameter of the nano rare earths is relatively smaller, and they can fill in and repair worn surfaces in time.(3) In the process of friction some of the nano iron and nano rare earths are deposited onto metal surfaces.They can repair the worn surface and always keep the friction surface flattering.(4) In the process of friction, the nano-particles of iron and rare earths form a deposited film on the worn surface, It keeps friction surfaces from contacting directly and improve the ability of supporting loads, resulting in restraining adhesion wear and contacting fatigue on friction surfaces.(5) Only with appropriate proportion, can nano-particles of iron and rare earths give full play to properties of anti-wear and friction reduction. More iron nano-particles work similar to "tiny ball bearing", which can mostly support loads; on the contrary, more rare earths nano-particles mostly fill in and repair worn surfaces. These two nano-particles alone give neither full play nor co-operating play to properties of anti-wear and friction reduction . In our researchs, when the proportion of nano-particles of iron and rare earths is: WtFe%: WtRe%=1:1, and the total content is 0.6%,the compound bring into play good synergetic function.The present study is part of "Research on nanometer particle's tribology mechanism as lubricating oil additives" of Shanghai Scientific and Technological Committee and "Nanometer material's application in lubricating technology" of key project of Shanghai Educational Committee. More researchs are expected to be further developed.