Study On The Preparation And Properties Of Continuous Carbon Nanotube Films Composites

Carbon nanotubes(CNTs),one of the typical one-dimensional nanomaterials,have become the hot spot of the development of basic research and application due to their unique hollow structure,high length to diameter ratio and excellent chemical stability,mechanical,electrical and optical performance.In the nanoscale,an individual CNT super mechanical properties where the tensile strength is up to 100 GPa,Young’s modulus is more than 1 TPa,elongation at break is 30%,and the energy absorbing is 1 to 2 orders of magnitude than traditional high performance fiber.Meanwhile,CNTs have shown to be ballistic conductors at room temperature,and their current-carrying capacity is two orders of magnitude higher than that of Cu.The thermal conductivity of CNT is as high as 3500 W/mK,which is comparable to that of diamond.How to make fully use of these excellent mechanical,electrical and thermal properties of CNTs in their macrosacle assemblies is the key issue for the application of CNTs.In recent years,the structure and properties of CNT macrosacle assemblies has obtained wide research attention and substantial breakthroughs have already been made.CNT macrosacle assemblies have been recognized as the key materials for the future.The main achievement of this thesis is as follows.Firstly,thin CNT films were prepared by either array spinning method or floating catalyst method.According to the microscopic structure of CNT films,where CNTs in the array-based films has excellent orientation,while CNTs in the films made by floating catalyst method are randomly distributed,several approaches such as multi-layer winding,hot pressing,drawing and solvent shrinkage are developed to strengthen the mechanical property of the initial CNT thin film.The tensile strength of these two kinds of CNT films can be as high as 1500 MPa and345 MPa,respectively,which paves the way for the preparation and performance study of CNT composite films.In order to further improve the mechanical properties of CNT thin films,second component materials such as graphene,high polymer,and metal,were introduced into the CNT films made by array spinning way.According to CNT’s structural characteristics,different ways of composition were carried out.The focus of the research is the enhancement function of the second component materials’ introduction on the mechanical and electrical properties of composite thin films.Through the microstructure analyses and testing of mechanical and electrical properties,the mechanism of enhancement function was understood.And the optimum process parameter was obtained by adjusting the mass fraction and preparation conditions of the second component materials,which would be helpful for developing high performance and multifunction materials based on CNT films.The CNT/ UHMWPE composite materials were developed by stacking the CNT films made by floating catalyst method layer by layer,compositing with UD UHMWPE sheets,as well as laminated structure design.Through ballistic performance testing,the effect of the laminated structure of CNTs and UHMWPE UD on the bullet resistant velocity and trajectory depression was studied.The mechanism of energy absorption was analyzed by micro scanning electron microscope,transmission electron microscopy combined with damage mode of material ballistic structure.The focus of the investigation is to reveal the relationship between the ballistic V50 value and the laminating method of CNT thin films,intercalation position,as well as bullet type,which provided basic data support and theoretical basis to realize the application of CNT thin films in the bullet proof field.In order to make fully use of CNT films’ features of light and fast response to prompt energy,large size CNT thin films prepared by floating catalyst method were laminated with traditional high polymer protective materials(e.g.UHMWPE,Kevlar),the effect of composite process,laminated structure design,the number of plies of CNT thin films on puncture force and efficiency were studied,and the effect of puncture velocity,residual velocity and energy absorption was analyzed.The intrinsic mechanism of the introduction of CNT thin films to improve the stab resistance of traditional high polymer protective materials was investigated in deep.This provides a foundation for the preparation and application of CNT film based stab resistant materials which having features of lightweight and high efficiency of energy absorption and soft.Finally,based on the study of static and dynamic mechanical properties of the CNT thin films prepared by array spinning method and floating catalyst method,the superior thermal conductivity of CNT thin films was further developed.Using the CNT thin films prepared by array spinning way as the substrate,the enhancement function of graphene on the interface of carbon nanotube was studied.Upon high temperature carbonization treatment,covalent interaction between CNTs and graphene were formed and the thermal conductivity of the film can be as high as 2200 W/mK.The influence of graphene’s concentration,mass fraction,carbonization temperature on the thermal conductivity and flexibility of the composite thin films was analyzed.Through scanning electron microscopy,transmission electron microscopy,XPS and other characterization methods,the effect of graphene on increasing the phonon transmission channel and reducing the slip between CNTs was investigated.The results provide theoretical basis and support for the development of the next generation thermal interface materials.