To enhance the lubricating and extreme pressure(EP) performance of base oils, two types of oil-soluble ionic liquids(ILs) with similar anion albeit dissimilar cations were synthesized. The physical properties of the prepared ILs were measured. The anticorrosion properties of ILs were assessed by conducting corrosion tests on steel discs and copper strips, which revealed the remarkable anticorrosion properties of the ILs in comparison with those of the commercial additive zinc dialkyldithiophosphate(ZDDP). The tribological properties of the two ILs as additives for poly-α-olefin-10(PAO10) with various mass concentrations were investigated. The tribological test results indicate that these ILs as additives are capable of reducing friction and wear of sliding contacts remarkably as well as enhance the EP performance of blank PAO10. Under similar test conditions, these IL additives exhibit higher lubricating and anti-wear(AW) performances than those of ZDDP based additive package in PAO10. Subsequently, X-ray photoelectron spectroscopy(XPS) and energy dispersive spectrometer(EDS) were conducted to study the lubricating mechanism of the two ILs. The results indicate that the formation of tribochemical film plays the most crucial role in enhancing the lubricating and AW behavior of the mixture lubricants.
Guowei HUANGQiangliang YUZhengfeng MAMeirong CAIFeng ZHOUWeimin LIU
We directly monitor the absolute separation profiles that function as film thickness between a single glass disk and the charged polyelectrolyte brushes decorated steel slider in water using a home-made slider-on-disk apparatus, which reflects the structural conformation variations and interactions of polymer brushes under externally applied pressure, in addition to probing the relative variation of friction forces under different applied loads and sliding velocities. We find that the polyelectrolyte brushes modified surfaces can sustain high pressure and have extremely low friction coefficients(around 0.006 at pressures of 0.13 MPa; 0.5-0.6 without brushes). The water-lubrication characteristics are correlated to the structural conformation changes of the polyelectrolyte brushes that are mainly governed by electrostatic interactions and the osmotic pressure of counterions inside the polymer chains, which can be used to support and distribute the normal pressure. The apparent thickness of the brush decreases with the increase of loading forces, an increase in the ionic strength causes the polymer chains collapse, and the friction forces increase. This fundamental research is of great importance to understand the mechanical and structural properties of polyelectrolyte brushes and their influences on the tribological behaviors, and helps to design friction/lubrication-controlled surface/interface by taking advantage of polyelectrolyte brushes.
Both the academic society and the industry are hunting for new energy forms for the future.However,the world should not forget the conventional technologies that contribute to the sustainable society by technical innovations.Among them,lubrication plays a significant role in energy saving and in low CO2emission by increasing the fuel efficiency and by prolonging the service life of machines.With the advance of novel synthetic approaches,and nanoscience and technologies,novel lubrication oils and additives and their formulations are being developed to reduce friction and wear,and novel surface treatment routes and surface coatings are invented and provide more efficient lubrication.These technologies create tremendous chances for machines to work more efficiently with low energy consumption.Here we review the recent progresses and challenges associated with some novel lubrication techniques that include novel surface treatment(such as texturing,high-performance nanocomposite coatings,adapting coating),tribology design(solid and liquid lubrication),energy-conserving engine oil and novel lubricants and formula(such as ionic liquids,low S,P content additives)which are to be adopted to enhance the fuel efficiency to achieve energy saving and low carbon emission.There is increased demand to replace fossil lubricants by degradable green lubricants.Specially designed coatings can reduce drag significantly during navigation of both airplanes and ships.All these aspects will be also reviewed in the paper.
