Electromagnetic Shielding Performance Of 3D Printed Carbon Nanotube/chitosan Composites

Carbon nanotubes and their composites have a series of advantages,such as high conductivity,light weight,large surface area,environmental protection,good flexibility,low density,good chemical stability,excellent mechanical properties and so on.They are ideal materials for preparing light,thin and high electromagnetic shielding properties.However,in the study of carbon nanotubes composites,the easy agglomeration of carbon nanotubes composites will restrict the conductivity and electromagnetic shielding properties of carbon nanotube composites.In addition,in the preparation of carbon nanotubes polymer composites,the microstructure of the material can not be controlled,and the structural reproducibility is very poor.In view of the above problems,in this paper,a ball milling method is proposed to realize the uniform dispersion of carbon nanotubes in composite materials,and 3D printing technology with the characteristics of accurate microstructure control,strong reproducibility and no molding mold is used as the molding method.The porous reticulated carbon nanotubes /chitosan module is prepared by 3D printing.By studying the ball milling time and carbon nanotubes concentration in the preparation of printing ink,explored the relationship between them and electrical conductivity and electromagnetic shielding performance.The main research contents of this topic include the following aspects:(1)The conductive and electromagnetic shielding characteristics of the carbon nanotubes/chitosan component of the 3D printing porous network structure are explored by changing the ball-milling time in the ball-milling parameters to prepare the 3D printing ink,which is uniformly dispersed in the composite material.The results show that the increase of the ball milling time can effectively improve the electrical conductivity and the electromagnetic shielding performance of the carbon nanotubes/chitosan composite component.The best ball-milling time occurs at 8h,and in the frequency range of 8.2 GHz to 12.4 GHz,the electromagnetic shielding effectiveness value can reach 25.1 d B.(2)By preparing 3D printed carbon nanotubes/chitosan modules with different carbon nanotubes concentrations,the feasibility of selecting the concentration of carbon nanotubes in the early stage was verified,and the relationship between theconcentration and the electromagnetic shielding characteristics was further explored.The results show that the increase of carbon nanotubes concentration can effectively improve the conductivity and electromagnetic shielding effectiveness of the module,and when the concentration of carbon nanotubes is 50wt%,it reaches the state of conductive saturation.Further increasing the concentration of carbon nanotube does not obtain effective conductivity and electromagnetic shielding effectiveness.That is to say,it is verified that the carbon nanotubes has the best electromagnetic shielding effectiveness when the concentration of carbon nanotubes is 50wt%,and the maximum can reach 25.07 d B.(3)Through the measurement of absorption loss and reflection loss,it is found that the absorption loss is the main way of electromagnetic wave loss when carbon nanotubes is introduced.And with the increase of ball milling time and carbon nanotubes concentration,the ratio of absorption loss to absorption loss increases accordingly.In addition,through TGA test and thermal conductivity test,it is found that the introduction of carbon nanotubes is helpful to improve the thermal stability and thermal conductivity of the material.(4)In view of the square-hole grid structure of the 3D printing model in this paper,the minimum size of electromagnetic wave attenuation in the square-hole structure is calculated to be 3.23 mm by the waveguide effect and the cut-off frequency theory.After considering the waveguide effect,the influence of aperture and material conductivity on electromagnetic shielding performance is analyzed by matlab program.the results show that the theoretical results are in good agreement with the experimental results,and it is verified that the electrical conductivity of the material has a greater influence on its electromagnetic shielding performance than the change of the pore size for the non-magnetic material.