Preparation And Electromagnetic Wave Absorption Performance Of Composite Fiber Materials Based On Electrospinning Technology

The rapid development of wireless communication technology makes the human society closely related to its surrounding electromagnetic environment.The disordered and excessive electromagnetic radiation not only interferes with electronic devices,but also endangers human health and affects the natural environment on which human beings live.Ensuring an environment suitable for mankind while utilizing electromagnetic resources is an issue that is concerned worldwide.Besides,the complex electromagnetic environment of the modern battlefield also makes electromagnetic wave absorbing materials have an important strategic position in the military field.It is also one of the research focuses for countries to ensure the survivability of weapons and equipment in the face of various advanced probing systems with electromagnetic waves.On this basis,electromagnetic wave absorbing materials that can effectively absorb and attenuate electromagnetic waves have been widely concerned and developed.However,it is difficult for current materials to satisfy low thickness,low density,high absorption intensity,and wide absorption bandwidth at the same time.In addition,the lack of complicated environmental adaptability to high temperature,oxidation,corrosion and impact also limits its application.To overcome these shortcomings,a variety of one-dimensional nanocomposite fibers were synthesized based on electrospinning in this study.By combining the dielectric and magnetic components with the carbon fiber matrix,the obtained nanocomposite fibers have good impedance matching and rich electromagnetic wave loss paths.In this thesis,a series of nanocomposite fibers with one-dimensional large aspect ratio were synthesized by electrospinning technology.Besides,we characterized the phase composition and morphological structure,measured the electromagnetic parameters,calculated the electromagnetic wave absorption performance,and analyzed the absorption mechanism of the material.The specific research results are exhibited as follows,(1)To explore the electromagnetic wave absorption mechanism and acknowledge the electromagnetic wave absorption performance of magnetic/dielectric/carbon material ternary composite fibers,the Ni/MnO/C nanocomposite fibers were successfully prepared via the facile electrospinning and carbonization approach.The influences of the introduction of Ni and MnO components on the microstructure and electromagnetic parameters were investigated.The characterization results showed that the metallic Ni and MnO components which uniformly distributed in the carbon matrix can effectively prevent the agglomeration of carbon fibers during the carbonization process,and form composite fibers with a diameter of about 250 nm.The preferred N1M1 nanocomposite fibers with optimized composition ratio exhibited a minimum reflection loss of-52.3 dB at a frequency of 14.0 GHz and a thickness of 2.3 mm,and a maximum effective absorption bandwidth of 6.5 GHz at a thickness of 2.9 mm,exhibiting excellent electromagnetic wave absorption capability.The introduction of MnO could improve the impedance matching of nanocomposite fibers,and the introduction of metallic Ni enhanced the magnetic loss capability of the composites and reduces the matching thickness of the material.The effective synergistic effect between the various components enriched the loss path of electromagnetic waves while optimizing the impedance characteristics of the material,and finally improved the electromagnetic wave absorption performance of the material.(2)To increase the magnetic loss and improve the electromagnetic wave absorption performance of the material in the middle frequency bands.We replaced the metallic Ni with metallic Co,which has larger saturation magnetization,and successfully prepared Co/MnO/C nanocomposite fibers with the same approach.The influences of the proportion of Co and MnO components on the microstructure and electromagnetic parameters were efficiently investigated.Characterization results showed that the metallic Co and MnO nanoparticles are uniformly distributed in carbon fiber matrix with a diameter of about 300 nm.The preferred C1M1 nanocomposite fibers had a minimum reflection loss of-71.7 dB at a frequency of 14.1 GHz and a thickness of 2.3 mm,and a maximum effective absorption bandwidth of 6.3 GHz at a thickness of 2.6 mm,exhibiting a much more excellent electromagnetic wave absorption capability than that of other component ratios.The research results showed that the threedimensional conductive network formed by the overlap of one-dimensional fibers could effectively promote the movement of carriers.The uniformly loaded nanoparticles not only optimized the impedance matching of the material,but also increased the heterogeneous interface among the components,provided abundant sites for the multiple scattering of electromagnetic waves and increased the polarization loss capability of the material.The rational composition and unique structural endowed the Co/MnO/C nanocomposite fibers with excellent electromagnetic wave absorption performance.(3)To expand the applicable scenarios,we replaced the MnO component with the ZnO component and adjusted its distribution to successfully fabricate C/Co@ZnO nanocomposite fibers with a core-shell structure.The effects of the growth time of the outer ZnO shell on the surface morphology and electromagnetic parameters were investigated.Characterization results showed that the fiber diameter is about 700 nm,and the shell is composed of ZnO nanorods with lengths of 100-200 nm,which distributed radially along the fiber surface.In terms of electromagnetic wave absorption performance,all of the composite fibers with the growth time of 2-8 h exhibited a good electromagnetic wave absorption ability,indicating the feasibility and universality of the C/Co@ZnO ternary composite system.The preferred nanocomposite fibers among them had a minimum reflection loss of-73.2 dB at a frequency of 7.5 GHz and a thickness of 3.4 mm,and a maximum effective absorption bandwidth of 5.4 GHz at a thickness of 1.9 mm.The fine microstructure constructed on the fiber surface by introducing nano-ZnO components not only optimized the impedance matching,but also improved the potential in terms of high-temperature resistance and oxidation resistance of the material.This provides a reference and feasible scheme for the design of the fiber surface structure and the preparation of the multi-component one-dimensional electromagnetic wave absorbing material.