Tribological Properties And Mechanism Of Nitrogen-containing Borate Esters In Ionic Liquids Aqueous Solutions

With the global energy crisis and the increasing greenhouse effect,the water-based lubricants using in the field of lubrication are increasingly showing their superior characteristics,which are widely concerned by researchers.However,the inherent poor film-forming performance and low extreme pressure performance of water-based lubrication make it widely restricted in practical engineering applications,and the general approach is to add surfactants in water to improve its lubrication characteristics.As a new type of lubricating material,ionic liquid has shown its strong performance,while non-ionic surfactants have good synergistic effect with different kinds of water-based lubricants.In this paper,two kinds of water-based additives,boric acid with nitrogen（BN）and dihydroxyethyl lauric acid(B_OEAL),were selected and prepared.The lubricating fluid with different mass fractions was prepared and a series of tribological tests were carried out.（1）The B_OEAL was designed and synthesized.The structure of the product was analyzed by FTIR.The product was confirmed to be pure B_OEAL.（2）In the MRA-10 four ball friction tester,the friction and wear experiments of single solvent and compound solvent with different concentration gradients,different rotating speeds and loads were carried out.The experimental results show that the antifriction ability of pure water can be reduced to about 0.08 when B_OEAL ionic liquid is added into deionized water,and the antifriction ability of aqueous solution can be further reduced to 0.07 when nitrogen-containing BN is added into the mixture.At the same time,the excellent synergistic effect of the two lubricants can significantly shorten the running in process of the friction pair and greatly improve the stability of the friction coefficient.（3）The film-forming,wettability and viscosity temperature characteristics of water-based lubricants were studied by using NGY-6 film thickness gauge,contact angle meter and rotary rheometer.The experimental results are as follows:1)compared with pure water,the two lubricants can form stable lubricating film under the sliding speed of 700mm/S;2)the contact angle of ionic liquid solution on steel friction pair is significantly smaller than that of pure water;3)viscosity test performance for good mechanical properties of Newtonian fluid.（4）The mesoscopic simulation of dissipative ions in molecular dynamics was used to analyze the interaction and dispersion of water molecules and surfactant molecules in B_OEAL and B_OEAL-BN lubricating fluids,and the anti-wear mechanism was further analyzed.Experimental and simulation results show that B_OEAL ionic liquid can be used as extreme pressure additive in water-based lubrication,non-ionic surfactant BN promotes the formation of B_OEAL micelles to a certain extent,and the synergistic effect of the two can play a better lubrication effect.