Research On The Structure-activity Relationship Of Micro/Nano Metal Conductive Network

In the past decade,electronic technology and communication technology are thriving and well-developed and the popularization of a next generation of light and thin,highly integrated,high-performance electronic equipment has greatly facilitated people's lives.But it also gave rise to increasingly serious electromagnetic radiation pollution problems on human beings and other electronic equipment.High-performance electromagnetic(EMI)shielding materials are one of the most effective means to solve the electromagnetic radiation pollution.In the current study on EMI shielding materials and EMI shielding mechanism,the EMI shielding performance of shielding materials is largely determined by the intrinsic properties of shielding materials such as electrical conductivity,magnetic permeability and other physical parameters.However,with the development of nanomaterials and nanotechnology,EMI shielding materials with complex boundary shapes and nonuniform structures with different scales have been successfully prepared.Some of those materials show a low intrinsic electrical conductivity or magnetic permeability,but have relatively high EMI shielding performance.The influence of material structure on electromagnetic waves and the shielding mechanism are becoming hot topics in the study of EMI shielding materials.In this paper,micro-nano metals are used as highly conductive fillers and flexible and stretchable polymers are used as the matrix to construct highly efficient conductive networks.This paper is consist of the following three parts:(1)Reduced graphene oxide(RGO)coated polystyrene(PS)microspheres(PS@RGO)and silver nanowires(Ag NWs)are used as binary conductive fillers and they are mixed to be a suspension in absolute alcohol.Three-dimensional conductive networks are constructed by dry PS@RGO/Ag NWs composites on half-cured PDMS film and another PDMS layer is cured on the top of PS@RGO/Ag NWs/PDMS layers to prepare a sandwiched PDMS/PS@RGO/Ag NWs/PDMS composite film(SPS@RGO/Ag NWs),which is flexible,stretchable,highly conductive and high EMI shielding effectiveness.By changing the weight ratio of conductive PS@RGO microspheres and Ag NWs,the electrical conductivity of S-PS@RGO/Ag NWs is controllable and high-performance flexible EMI shielding composite film was obtained by the facile preparation method.The influence of electrical conductivity on the EMI shielding performance of the composite film was studied.(2)Ag/TPU conductive silver paste is prepared by mixing silver flakes(Ag)and thermoplastic polyurethane(TPU)/DMF solution,and the patterned EMI shielding materials with desired pattern structures of square,serpentine and circular are precisely printed.The structure-performance relationship between the geometric structure and size of different network patterns and their shielding effectiveness are further studied.(3)The 3D printing method successfully constructs patterns structures with the accurate and controllable pattern shape and size,which provides a solid foundation for building three-dimensional models in simulation software.COMSOL simulation analysis and numerical calculation of different patterns structures(geometric structure)is carried out by finite element method.The numerical calculation results and the structure-performance is collaboratively analyzed to study the structure-performance relationship to figure out the shielding mechanism.The influence mechanism of factors such as geometry and size on its electromagnetic shielding performance is deeply investigated.The simulation results show,stronger current is observed on the edge of the pore of the pattern structure,smaller the Pore Area is,stronger current is observed,and larger the eddy current is generated,and higher the EMI SE of pattern structure is.Besides,the electrical conductivity and Pore Area mainly determine the EMI SE of patter structure but the line width shows less influence on the EMI SE.