Study On The Preparation And Lubrication Properties Of Deep Eutectic Solvents

Conventional lubricants mostly contain harmful elements such as phosphorus,sulfur,chlorine,etc,their widespread use is limited,and it is difficult to meet increasingly demanding working conditions,so the preparation of new and more effective green lubricants has been put on the agenda.Ionic Liquids(ILs)are a class of well-stabilized,non-flammable,highly polar liquids that are not volatile.They exhibit excellent lubricity in the lubrication field,but there are cumbersome synthetic processes,unclear toxicity,and price.The disadvantages of high cost and low yield are not conducive to industrial large-scale production.Therefore,the synthesis of low-cost,low-toxicity and biodegradable eutectic Solvents(DES)has become the focus of research.In this paper,the preparation of L-carnitine series DES instead of traditional ILs is expected to become a new generation of green,high-performance lubricants,and explore its application prospects.By analyzing the performance studies of DES and lubricating oil,graphene and DES compound lubricants,the results are as follows:(1)Four kinds of DES(L-carnitine-gallic acid,salicylic acid,malic acid,citric acid)with different anions and cations were prepared by synthesis.Infrared spectroscopy scanning and thermal stability tests were carried out.It was found that the synthesized DES contained the main elements of the synthetic raw materials,and the solvent was successfully synthesized.The four DES have good thermal stability.At 600?,the quality remains.And the remaining amount is ranked as gallic acid>salicylic acid>malic acid>citric acid,indicating that it is suitable for use in a high temperature environment.(2)With the help of the reciprocating friction method,the Si3N4 ball is used as a grinding ball to explore the lubricating friction effect on the metal substrates of 316,copper,aluminum and titanium alloy when the different DES is used as the lubricant.The comprehensive friction coefficient,The data analysis of wear scar morphology,SEM,XPS and wear scar volume shows that the lubricating effect of malic acid and citric acid is outstanding.The main lubrication mechanism is that DES forms an effective physical adsorption protective film and tribochemical reaction film during the friction process.A more complex lubricating coating of iron-containing compounds is formed,which together enhances the lubricating performance,and the lubricating effect on the Cu and 316 substrates is particularly prominent.(3)20%,50%malic acid and gallic acid were respectively used as additives for gear lubricating oil to prepare a composite lubricant,and the lubricating property was tested on the 316 substrate.lt is found that when the gallic acid is used as an additive,the friction coefficient of the matrix,the depth of the wear scar,the wear volume and the like are superior to the pure lubricating oil,especially the lubricating oil+20%gallic acid is especially prominent.Proven use of DES as a base oil additive is promising.(4)DES as a base oil,0.1%,0.3%graphene as an additive of malic acid and citric acid,respectively,to produce four composite lubricants,and test lubrication,friction and wear properties.The results show that DES can be adsorbed on the surface of the wear scar while lubricating,and a protective film is formed to reduce the friction coefficient and reduce the wear volume.This study shows that DES is a green lubricant,and DES is simple to prepare,biodegradable,relatively low in cost,and advantageous for industrial production,which will greatly improve lubricant performance.