Study On The Preparation And Tribological Performance Of Functionalized Graphene Oxide Composite Coatings

The implementation of the "Made in China 2025" strategy has not only promoted the development of up-market equipment manufacturing industry in China,but also brought new challenges to lubricating materials which are the blood of modern industry.As a micro-nano graphene-based material,graphene oxide(GO)has unique nano-layered structure and high specific surface area,which makes it easy to be adsorbed at the friction interface and reduce the friction coefficient and wear rate.Because of excellent lubricating performance,GO has wide application prospects in the fields of aerospace,defense,military industry and machinery manufacturing.It becomes a research hotspot of nano-lubricating materials.The researches of GO-based coatings have also attracted much attention.According to the model of Lerf-Klinowski,a large amount of hydroxyl groups and epoxy groups are randomly distributed on the base surface of the GO sheet,and the edge of the GO sheet contains oxygen-containing functional groups such as carbonyl and carboxyl groups.Therefore,GO can be combined with the base materials through a variety of modes of action such as ?-? interaction,hydrogen bonding,electrostatic interaction,nucleophilic substitution,esterification,and amidation.Due to the difference in the molecular structure of functionalized GO and the different surface properties of the base materials,the microstructure and order of GO coatings will also be different,which will affect its lubrication performance.In response to this problem,this paper used 2D Raman surface analysis technology to systematically study the influence of different structures of functionalized GO and different siloxane-modified glass substrate materials on the microstructure and lubrication properties of GO-based composite coatings.A series of preliminary research results were achieved.(1)The influence of different oxidation degree of GO on the tribological properties of GO-based coatings was researched.Firstly,the preparation process of GO-based coatings was optimized.The model compounds were two different oxidation degree of GO,the coupling agent was 3-aminopropyltrimethoxysilane(APTMS).2D Raman surface Analytical technology was used to systematically examine the influence of APTMS concentration,immersion time in GO solution,GO solution concentration,reaction temperature,etc.on the uniformity and compactness of the prepared GO-based coatings,the optimal preparation process of GO coatings was determined: APTMS concentration was 20 %,immersion time was 12 hours,GO solution concentration was 0.05 mg/m L,reaction temperature was 100 ?.Atomic force microscopy analysis showed that when the substrate surface had different properties(hydroxyl surface without APTMS and amino surface with APTMS),the arrangement of GO on the surface was also different.It was shown that GO had obvious wrinkles and arranged vertically on the amino surface.This phenomenon did not exist on the hydroxyl surface.Then,the tribological performance study found that GO-based coatings had good anti-wear properties.The introduction of APTMS can further enhance the tribological properties of GO-based coatings,which can reduce the wear rate by nearly 15 %.In addition,the higher the oxidation degree of GO,the better the tribological properties of GO coatings.(2)The influence of siloxanes with different structures on the tribological properties of GO-based coatings was researched.The bonding degree and coverage of siloxanes were different due to different structures and substrate materials,which will affect the structure and performance of GO-based coatings.Firstly,under the optimal process conditions,GO-based coatings(APDMS-GO coatings)were prepared with the transition layer of 3-(Dimethoxymethylsilyl)propylamine.Secondly,the tribological performance of the APDMS-GO coatings and the APTMS-GO coatings was compared.It was found that both composite coatings can reduce the friction coefficient and wear rate of the base material.Among them,the anti-friction effect of APTMS-GO coatings was better,while the anti-friction performance of the APDMS-GO coatings was also worthy to be recognized.(3)The influence of functional GO with different structures on the tribological performance of GO-based coatings was researched.Firstly,GO was functionalized at the base and edge by using n-octylamine,which were named as based-functionalized GO(b-GO)and edge-functionalized GO(e-GO),and the transition layer was APTMS.Under the optimal process conditions,APTMS-b-GO and APTMS-e-GO coatings were prepared.Secondly,the tribological performance study found that the functionalized GO coatings had good tribological performance.APTMS-b-GO coatings had the best anti-wear effect among them,and the wear rate was reduced by nearly 21 %.