Preparation And Electromagnetic Absorption/Shielding Properties Of Metal-Carbon And Metal-Polymer Composites

Microwave absorption/shielding materials are mainly used to eliminate the interference of external electromagnetic waves on electronic components,and have important applications in the fields of electronic communication,aerospace and military stealth.At present,a variety of microwave absorption/shielding materials,such as ceramic materials,magnetic metals and their oxides,carbon materials and conductive polymers,have been proposed.However,the single material has a single electromagnetic loss mode and limited absorption/shielding ability.Therefore,the preparation of composite absorbing materials with magnetic and dielectric losses in one is the key to solve the problem,and is also one of the research hotspots in this field.Metal-carbon composites show good electromagnetic wave absorption characteristics.But this kind of material belongs to rigid material,its electromagnetic property is difficult to realize dynamic control.For complex electromagnetic environment,it is of great significance to develop a dynamically adjustable electromagnetic absorption/shielding film.On the basis of understanding the microwave absorption mechanism of metal-carbon composites,this paper uses stretchable polymers(heat-shrinkable elastomers)to replace carbon materials,and uses stretching to regulate the electrical transmission characteristics of materials to develop electromagnetic shielding films with stretchable properties.The main research contents are as follows:1.The paper fiber and ferric chloride solution were used to prepare iron nanoparticles/carbon fiber composites through spraying,composite and reduction processes,and the electromagnetic absorption properties of the composites were explored.The effects of metal loading rate and thermal annealing temperature on the microstructure of the materials were investigated.The magnetic conductivity and dielectric constant of the material in the microwave band(2?18GHz)were studied.The influence of the microstructure on the impedance matching of the material was determined,and the experimental parameters with the best impedance matching were obtained.The microwave reflectivity of the material is calculated based on the transmission line theory.In the test range of 2?18GHz,the effective absorption bandwidth of the composite material reached5.5GHz,and the maximum loss value reached 40.1dB.This kind of low cost and scalable composite absorbing material has a certain application prospect in the field of military stealth..2.The reciprocating tensile ultrathin nano-porous Au/Au alloy/thermoplastic polyurethane composite film was designed and prepared by using dealloying method and spin coating method,and the influence of the film porosity on its electrical properties,mechanical properties and electromagnetic shielding characteristics was explored.The composite shows good electromagnetic shielding performance,and the shielding efficiency of the 150nm thin film at 18GHz is up to 24dB.At the same time,the electrical conductivity and electromagnetic shielding properties of the film can be reversibly adjusted by stretching.The film provides an effective solution for complex electromagnetic interference environments and wireless strain sensing applications.In conclusion,electromagnetic absorption based on the design of high performance materials and adjustable type electromagnetic shielding film as a starting point,respectively using cheap metal iron and high electrical conductivity,gold and silver nanoparticles is prepared/carbon fiber composite materials,porous gold and silver alloy/thermoplastic polyurethane composite membrane,were the two materials of different areas of the excellent shielding/absorption performance.The effects of preparation conditions on the microstructure of the material and its electromagnetic shielding/absorption performance were explored.The physical mechanism of the interaction between the material and the electromagnetic wave was analyzed.The influencing factors of the material structure and the basis for parameter optimization were obtained,which provided technical and theoretical reference for the development of efficient electromagnetic absorbing/shielding materials.