Research On Antiwear And Reduce Friction Properties Of Nano-ZrO₂ Additive In Lubricating Oil

Adding additives into oil to reduce friction and wear and even to mend the worn surface has been widely applied in lubrication engineering for quite a long time. Although up to now, there are four generations of additives which have been created or invented, the research and development of more effective additives have never been ceased since all kinds of additives mentioned above are still not perfect, especially their effect of the wear repairing is far from satisfactory. Professionals in lubrication research field have been looking for the new materials to meet the requirement of repairing function to the lubricant additives all the time.In the past few years, the emergence of nano-materials has provided a new choice for the development of lubricant additive. With the aid of nano-materials, a lot of novel work has been done with enormous encouraging achievements obtained because the tribological properties have been enhanced obviously. As for the mechanism of anti-wear and friction reduction, the following explanation has been predicted by most of professionals that the nano-particles act as spacer between the two friction surface, and some ever proposed that the nano-particles were rolling like a ball in the grinding area which leads to the reduction of friction coefficient, but now more and more people believe that nano-particles deposit on the friction surface and compensate the loss of mass, the so-called mending effect. However, systematic work for investigating the mechanism of the mending effect of nano-particles has rarely performed.In order to make further research of anti-wear and friction reduction mechanism, the author adopted chemical precipitation method to make ZrO2 nano-particles. Silicon Coupling Agent is mixed to study the surface modification and tribological performances of ZrO2 nano-particles as lubricating oil additives were studied in friction and wear test machine. The main conclusions are reached as followed.1. ZrO2 nano-particles was made from precursor ZrOCl2·8H2O through the method of chemical precipitation. The parameters for achieving the optimum technological conditions in making ZrO2 nano-particles were obtained by carefully observing the precursor concentration, amount of solvent precipitants, the temperature on each stages and the behavior of reactors. Sphere in shape, the manufactured nanometer zirconia powder particle are even in size with 10nm under the TEM and SEM, and they have a narrow distribution of particle size with excellent dispersant adequacy. Analysis of powder through XRD demonstrates that ZrO2 appear in amorphous structure.2. These surface-modified nano-particles consist of inorganic nano-cores with organic capped-layer chemically absorbed on the surface of the nano-cores. Owing to the hydrophobic property of hydrocarbon chain in the organic modification layer, these surface-modified nano-particles have a good dispersity in organic solvents exhibit a rather uniform size distribution.3. The friction reducing and anti-wear behavior of the ZrO2 used as additive in lubricant oil were analyzed on wear tester. As additive, it can increase the anti-wear and friction reducing ability of base oil. The base oil doped with 0.25wt% nano-ZrO2 particles showed the best tribological properties among the tested oil samples. SEM and EDS are used to analyze the inorganic repaired layer formed on the friction surface. Based on the test result, it is found that the additive creates certain deposited film on the friction surface. Elements of the additive are added into the surface. The additive has obvious anti-wear effect for the steel/steel friction pair.