How the fluorographene replaced graphene as nanoadditive for improving tribological performances of GTL-8 based lubricant oil

Fluorographene,a new alternative to graphene,it not only inherits the 2-dimensional(2D)layered structure and outstanding mechanical properties,but also possesses controllable C-F bonds.It is meaningful to reveal the evolution processes of the tribological behaviors from graphene to fluorographene.In this work,fluorinated reduced graphene oxide nanosheets(F-rGO)with different degree of fluorination were prepared using direct gas-fluorination and they were added into gas to liquid-8(GTL-8)base oil as lubricant additive to improve the tribological performance.According to the results,the coefficient of friction(COF)reduced by 21%,notably,the wear rate reduced by 87%with the addition of highly fluorinated reduced graphene oxide(HF-rGO)compared with rGO.It was confirmed that more covalent C-F bonds which improved the chemical stability of HF-rGO resisted the detachment of fluorine so the HF-rGO nanosheets showed less damage,as demonstrated via X-ray photoelectron spectroscopy(XPS),Raman spectra,and transmission electron microscopy(TEM).Meanwhile,the ionic liquid(IL)adsorbed on HF-rGO successfully improved the dispersibility of F-rGO in GTL-8 base oil.The investigation of tribofilm by TEM and focused ion beam(FIB)illustrated that IL displayed a synergy to participate in the tribochemical reaction and increased the thickness of tribofilm during the friction process.

Tuning F-doped degree of rGO:Restraining corrosion-promotion activity of EP/rGO nanocomposite coating

Given that graphene features high electrical conductivity,it is a kind of material with corrosion-promotion activity.This study aimed to inhibit the corrosion-promotion activity of graphene in coatings.Here,we report an exciting application of epoxy matrix(EP)/F-doped reduced graphene oxide(rGO)coatings for the long-term corrosion protection of steel.The synthesized F-doped rGO(FG)did not reduce the utilization of rGO by a wide margin and possessed distinctive electrically insulating nature.The electrical conductivity of rGO was approximately 1500 S/m,whereas those of FG-1,FG-2 and FG-3 were 1.17,5.217×10^−2 and 3.643×10^-11 S/m,respectively.FG and rGO were then dispersed into epoxy coatings.The chemical structures of rGO and FG were investigated by transmission electron microscopy(TEM),scanning probe microscopy(SPM),X-ray photoelectron spectroscopy(XPS),Fourier-transform infrared spectroscopy(FTIR),and X-ray diffraction(XRD).EP/FG coatings exhibited outstanding corrosion protection in comparison with blank EP and EP/rGO coatings mainly because the corrosion-promotion effect of rGO was eliminated.The anticorrosion ability of EP/FG coatingswasimproved with increased F-doped degree of FG.In addition,electrochemical impendance spectroscopy(EIS)results indicated that the Rc values of EP/FG-2 and EP/FG-3 were four orders of magnitude higher than those of EP/rGO in diluent NaCl solution(3.5 wt.%)after immersion for 90 days.