Irradiation Effects And Mechanism Research On Carbon Nanotube Array Adhesive Materials And Graphene Transparent Conductive Films

With lightweight,high-strength,and excellent properties,carbon nanomaterials are one of the best candidates for future aerospace materials and have become the focus of research in the aerospace field.In this thesis,we focus on the carbon nanotube array adhesion material and the graphene transparent conductive thin film.According to the actual functions of the two,combined with the space irradiation environment,we use ion irradiation experiments and molecular dynamics simulation to study the effects of ion irradiation on the overall structure and properties of graphene and diamond-like carbon.The main research contents and results are as follows:（1）Using molecular dynamics method,a graphene–single-walled carbon nanotube–graphene sand-wich structure model was constructed,and the steps of carbon nanotubes actually generating adhesive force were shown from a microscopic perspective.The adhesion force was simulated and calculated.The factors affecting the adhesion force of single-walled carbon nanotubes were explored from four aspects:the degree of deformation of single-walled carbon nanotubes,ambient temperature,vacancy defect size and defect types.The results show that the necessary condition for effective adhesion of single-walled carbon nanotubes is that the degree of deformation exceeds 70%.After the degree of deformation exceeds this threshold,the adhesion of single-walled carbon nanotubes increases with the degree of deformation.At the same time,its adhesion is greatly affected by ambient temperature,reaching a maximum at 300 K.As the size of vacancy defects increases,the adhesion of single-walled carbon nanotubes decreases linearly.（2）Multi-walled carbon nanotube arrays were prepared by chemical vapor deposition.Based on this,He²⁺irradiation experiments were further conducted.The adhesion and mechanical properties of the multi-walled carbon nanotube arrays were tested.The Raman spectroscopy test results show that the morphological irradiation fluence threshold of the multi-walled carbon nanotube array is 1×10¹⁶cm^-2,below which the multi-walled carbon nanotubes arrays can still maintain a relatively complete morphological structure.With the increase of He²⁺radiation fluence,the structure of multi-walled carbon nanotubes will develop from slight damage to the overall structure bending,deforming and collapsing,and produces a considerable amount of amorphous carbon.At the same time,the adhesion of the multi-walled carbon nanotube array obtained by the force curve test of atomic force microscope will also decrease almost linearly.The results of the nanoindentation test show that the multi-walled carbon nanotube array is a viscoelastic material.（3）The molecular dynamics method was used to construct a composition model of diamond substrate and multi-layer graphene.Subsequently,the diamond-like carbon film was actually prepared on the surface of the graphene transparent conductive film by using the simulation conclusions and optimized parameters.The sp³carbon atoms tend to accumulate in the middle part of the diamond-like carbon,because the middle part can provide appropriate stress,which causes the sp²bond to turn into sp³bond.The diamond-like carbon film produced by 70 e V incident ion has the highest sp³fraction and mass density.Considering all kinds of situations,when the incident carbon ion energy is 70 e V,the diamond-like carbon film with the best quality can be generated,and at the same time,it can maintain good adhesion ability with the graphene interface.Later experiment proves the feasibility of actually depositing diamond-like carbon films on the graphene surface.At the same time,it was also found that with the increase of the deposition time,the diamond-like carbon film will gradually connect from small particles to large pieces,and the number of sp²bond carbon atoms in it will continue to increase.（4）Using the simulation models and experimental samples obtained previously,low-energy ion irradiation experiments and swift heavy ion irradiation simulations were carried out.The relationship between the internal defect evolution and macroscopic properties of graphene and diamond-like carbon films was explored after ion irradiation with different energies.Low-energy He²⁺irradiation can cause serious damage to graphene without a protective layer,resulting in a significant decrease in electrical conductivity.Low-energy He²⁺irradiation would leave cracks in graphene and cause structural transformation in diamond-like carbon.Meanwhile,it will not only increases the instantaneous modulus of diamond-like carbon films,but also increases the hardness of diamond-like carbon films.Although a diamond-like carbon film with a higher sp³fraction can be used as a better protective layer of to protect graphene from mechanical and external forces,it will cause more serious damage to graphene during swift heavy ion irradiation.The research work in this thesis provides important theoretical support and experiments results for the study of the radiation effects and mechanism of carbon nanotube arrays,graphene transparent conductive films and protective diamond-like carbon layer under the space ion irradiation environment.This research work is of great significance to accelerate the practical application of carbon nanotube arrays and graphene transparent conductive films in the future space environment.