Atomic Oxygen Effect On Microstructure And Tribological Behaviors Of Graphene

The atomic oxygen effects on the microstructure and the tribological performance of graphenes were investigated using molecular dynamics simulation and experimental research.The atomic oxygen interaction with graphene and the resulted microstructure were numerically calculated using Lammps software.The atomic oxygen exposure of the graphene film samples was conducted on a on-ground atomic oxygen simulator.The microstructure,morphology,and chemical composition of the atomic oxygen exposed graphene samples were analyzed by means of Raman spectrum,SEM,and XPS,which were used to verify the results of numerical calculation.The tribological properties were measured,in order to reveal the effect of atomic oxygen on the tribological behavior of the atomic oxygen exposed graphenes.Simulation results show that,the atomic oxygen interaction with graphenes and the resulted microstructure are related to temperature.At 300 K,atomic oxygen has a certain chemical erosion effect on the graphenens,resulting in the local damage in microstructure,a small quantity of C loss,and a small number of bonds of C and O.At 800 K,atomic oxygen shows a distinct chemical erosion effect on the graphenens,leading to sever damage in microstructure,a large amount of separated C atoms,and formation of a lot of C and O bonds.The graphenes with defects show a more sever atomic oxygen erosion.The atomic oxygen exposure test and its results confirm the chemical erosion effect of atomic oxygen on graphenes.The Raman spectral results show that,there are a large amount of defects forming in the atomic oxygen exposed graphenes.With increasing atomic oxygen fluence,the microstructure damage of graphenes is enhanced and some amorphous carbons are formed.The XPS analyses show that,chemical bonds of C-O,O-C=O,and C-O-C,are generated in the atomic oxygen exposed graphenes structure.The tribological test results show that,the atomic oxygen exposure results in increase of friction coefficient of the graphenes film.The analyses on the worn surface reveal that,the atomic oxygen exposure enhances the level of delimination wear,leading to increase of the surface roughness and friction coefficient.