In Situ Preparation And Properties Of Multilayer Graphene Hydrogen Barrier Coating On Pipeline Steel

Hydrogen transportation is an important part of hydrogen energy utilization,and natural gas transportation mixed with hydrogen is a feasible large-scale energy transportation mode.However,the transportation of hydrogen will inevitably lead to the problem of hydrogen embrittlement.Graphene is considered to inhibit hydrogen permeation and diffusion effectively,but the preparation of graphene hydrogen barrier coating has obvious limitations.In order to realize the preparation and application of graphene hydrogen barrier coating on the surface of pipeline steel,the in-situ growth of multilayer graphene(MLG)was realized by C ion implantation on Ni and annealing.The effects of ion implantation and annealing parameters on the growth of multilayer graphene were studied.The structure and hydrogen resistance of multilayer graphene were studied.The growth mechanism and hydrogen resistance mechanism were discussed.At the same time,considering the influence of annealing on pipeline steel structure performance,the feasibility of coating preparation process was comprehensively evaluated and optimized.Such is the main content:(1)In situ preparation of multilayer graphene coating on X70 pipeline steel surface.The polycrystalline nickel catalytic layer with(111)crystal plane can be obtained by using alkaline sodium pyrophosphate bath system,and it has enough thickness and good bonding strength after annealing.Raman analysis showed that the graphene layers were disordered and multilayer.SEM analysis showed that the distribution of graphene layers was not uniform and the graphene layers were coated with the shape.TEM confirmed the layered structure of multilayer graphene.XRD,XPS and FT-IR results showed that the sp~2 hybrid structure of graphene was obtained with a little of oxygen-containing functional groups.Different process parameters affect the growth process of graphene by adjusting the nickel grain size and C segregation.(2)The effect of annealing on the inherent structural properties of X70 pipeline steel was studied.When the multi-layer graphene coating is prepared below the critical temperature of phase transformation(710?),the original structure of pipeline steel maintains and the hardness little changes,and the change of grain size weakens the strengthening effect of grain boundary,resulting in the decrease of strength and plasticity of pipeline steel after annealing,but it still meets the strength and toughness requirements of safe service.When the critical temperature is exceeded,the pipeline steel will undergo phase transformation,and the structural properties will decrease obviously,which could not meet the service requirements.Therefore,the preparation temperature of multilayer graphene hydrogen barrier coating should not be higher than 710?.(3)The hydrogen resistance of multilayer graphene coating was studied.X70 pipeline steel is brittle fracture after hydrogen charging,while the fracture of multilayer graphene sample is still dimple characteristic of plastic fracture.The multilayer graphene coating can significantly reduce the hydrogen permeability,improve the hydrogen embrittlement resistance sensitivity,and has excellent hydrogen resistance performance,which can effectively prolong the service life of pipeline steel.The number of graphene layers and the size of graphene grains jointly determine the hydrogen barrier properties of the coating.High efficiency hydrogen barrier can be achieved by extending the diffusion path,reducing the penetration area,enhancing the hydrogen adsorption capacity and inhibiting the surface hydrogen evolution reaction.