Studies On Growth And Anticorrosion Property Of Low Temperature CVD Graphene On Zirconium Alloy Substrate

Currently,zirconium alloy is the only fuel element cladding material used in nuclear power reactor piles in the world.However,the corrosion seriously affects the service life of zirconium alloys in nuclear reactor piles.Therefore,effective anticorrosion protection of the zirconium alloy is imminent.The main anticorrosion coatings on the surface of the zirconium alloy currently developed are high hardness,poor toughness,poor bonding with the substrate,and a certain thickness,which changes the size of the zirconium alloy and reduces the thermal conductivity of the zirconium alloy.Although it has a certain anticorrosive properties,after a long period of irradiation,the zirconium alloy cladding expands and creeps,causing the coating to crack and flake,and eventually fail.Therefore,it is an inevitable choice for seeking and developing of new types of anti-corrosion coatings for zirconium alloy cladding,which have high temperature resistance,good toughness,ultra-thin,dense structure,good anti-penetration performance,good binding force with the substrate,excellent mechanical properties,and does not affect the thermal conductivity and size of the substrate in the future.Graphene has excellent thermal and chemical stability,high sealing,hydrophobicity and good thermal conductivity,which meets all the requirements of the ideal coating of zirconium alloy cladding.Therefore,in this paper,the low temperature chemical vapor deposition(LTCVD)method is used to directly grow the graphene anti-corrosion coating on the surface of the zirconium alloy to achieve the purpose of improving the corrosion resistance of the zirconium alloy.At the same time,the microstructure of the coating/substrate interface is analyzed and characterized,and the formation mechanism of the graphene coating on the surface of the zirconium alloy is initially discussed which has an important theoretical role for the future application of graphene as a zirconium alloy anticorrosion coating.The main research contents are as follows:(1)Using polymethyl toluene acrylate(PMMA)as a solid precursor,a graphene film is prepared on a zirconium alloy substrate by LTCVD.Scanning electron microscope(SEM),high-resolution transmission electron microscope(HRTEM),optical microscope(OM)and Raman spectrometer(Raman)are used to analyze and characterize the morphology,structure and quality of graphene,and the effects of reaction temperature,precursor content and reaction time on the formation of graphene are studied.The ideal parameters for the preparation of graphene film with less defects and good continuity on the surface of zirconium alloy are 500°C reaction temperature,120 mg precursor content,and30 min reaction time.The interface between graphene and zirconium alloy at the nanoscale is studied by focused ion beam(FIB)and HRTEM.The result shows that the m-Zr O₂ on the surface of zirconium alloy catalyzes the formation and growth of graphene.(2)The corrosion resistance of the sample in 3.5 wt.%Na Cl solution is tested by electrochemical corrosion method,and the effect of graphene prepared at different temperatures and different precursor contents on the corrosion resistance of zirconium alloy is studied.The results show that the layer number,continuity,and quality of graphene directly affect the corrosion resistance of graphene.The high quality graphene with good continuity and more layers has the excellent corrosion resistance,but the discontinuous,high defects,low crystallinity graphene will accelerate the corrosion of the zirconium alloy.