Study On Fluorescence Characteristics And Tribological Properties Of Metallic Carbon Dots

In this paper,copper and lanthanide carbon quantum dot nanoparticles were successfully prepared by hydrothermal synthesis.The tribological properties of two particles as additives for water-based lubrication were studied on UMT-2 friction and wear tester.By means of modern characterization methods,the surface morphologies of wear marks of the dual parts were analyzed to explore the relevant friction and wear mechanism.The wear-resistant protective film is formed on the surface of metal base,which overcomes the single lubrication performance of traditional carbon quantum dots,and makes the matrix material reduce wear to a certain extent,which has a good application prospect in the mechanical field.The average size of copper-based carbon point particles prepared is about 8.33 nm.The particles have strong fluorescence,showing light blue fluorescence under the irradiation of ultraviolet lamp.The surface of the particles contains a large number of hydrophilic groups such as hydroxyl(-OH)and carboxyl(-COOH),with good water solubility.When Cu-CQDs are used as lubricant,it is found that the particles can effectively improve the wear resistance of lubricating oil,and a dense layer of copper film is formed on the surface of steel plate.The steel plate soaked in the solution of Cu-CQDs can also form a dense film coating,and the thickness of copper film is different with different soaking time.The steel plate soaked in the solution of Cu-CQDs(0.5 wt %)for 1 h has the best film forming effect,and the coating thickness is about 174 ?m.The steel plate with copper film was used as the base material of the lower sample and the steel ball was used as the upper sample.The tribological behavior of Cu-CQDs was investigated using pure water and solutions containing Cu-CQDs with different concentrations as lubricating media.The results show that: Based on the existence of copper film,the solution of Cu-CQDs has excellent antiwear and antifriction properties,which is attributed to the fact that the copper film can effectively separate the interface of friction pair and prevent the direct contact between steel ball and steel plate,thus playing a good antiwear effect.Comparison of the two adding methods shows that: Using water as a lubricant,friction induced film easy to peel,but not completely,lead to the friction coefficient and wear rate increased,the copper film on the steel plate with copper base point carbon particles as a lubricant,anti-wear anti-friction effect is more apparent,its mechanism may be due to the Cu-CQDs in the process of friction and lubrication and self-healing function,The friction behavior can promote the continuous growth of copper film and isolate the direct contact of friction pair so as to play an antiwear and antifriction effect.In conclusion,Cu-CQDs can improve the antifriction effect,and the antiwear and antifriction effect of copper film in Cu-CQDs solution is more significant.At the end of the friction experiment,the mixed solution of particles and abrasive chips was collected,and the fluorescence of the solution decreased gradually with the increase of the load.The weak fluorescence may be due to the fact that the fluorescence quantum dots in the Cu-CQDs participate in the formation of the copper film,so the phenomenon of weak fluorescence occurs.The size of La-CQDs prepared is about 2.48 nm.The particle solution has light blue fluorescence under ultraviolet lamp irradiation,and the particle surface contains a large number of hydrophilic groups such as hydroxyl and carboxyl,which has good hydrophilicity and good dispersion in pure water.In this paper,the La-CQDs solution is directly added to the steel plate without treatment and the lanthanum carbon dot solution is used as lubricant on the La-CQDs coating.Friction experiments show that compared with pure water lubrication,La-CQDs can effectively improve the anti-wear and anti-friction properties of pure water.The comparison of the two adding methods shows that: It is better to use La-CQDs solution as lubricant on La-CQDs coating for antiwear and antifriction reduction.Its antiwear and antifriction reduction mechanism is mainly attributed to the deposition of La-CQDs in the friction process for self-repair,repairing the wear surface,and filling the wear gully to achieve antiwear and antifriction reduction effect.In short,adding a certain amount of La-CQDs into pure water can significantly improve the lubrication performance of pure water,play a good antiwear and antifriction effect.It was found that the fluorescence intensity of the solution was weak,and the higher the friction load,the lower the fluorescence intensity.This is attributed to the formation of the deposition coating of fluorescent carbon quantum dots in lanthanide carbon dot nanoparticles and the increase of abrasive particles in the mixture of abrasive particles,which may lead to the decrease of the fluorescence intensity of the solution.