Microstructure Design And Wave Absorbing Properties Of Porous Carbon Matrix Composites

Rational design of the structure and components of the material is important to optimize the performance of the material.Due to the popularity of electronic communication equipment,electromagnetic interference is becoming more and more serious and the preparation of high-performance electromagnetic wave absorption materials has become critical.However,traditional electromagnetic wave absorbing materials often have problems such as high density,thick thickness,narrow band width and low absorption strength.Consequently,the design and preparation of new high-performance“thin,light,wide and strong”wave absorbing materials has become a significant research direction.Porous carbon materials are ideal material for the preparation of high-performance electromagnetic wave absorbers due to the characteristic of light weight,low density,high electrical conductivity and dielectric tunability.Therefore,it is of great significance to improve the impedance matching characteristics of porous carbon absorbers,enhance the attenuation ability of porous carbon materials to electromagnetic wave energy and achieve efficient wave absorption performance.In this thesis,the influence of the structural components of porous carbon materials on their electromagnetic wave absorption performance is investigated by improving their impedance matching properties and enhancing their attenuation of electromagnetic wave energy through structural and component design of porous carbon materials.The main findings of the study are as follows.(1)Structural design of porous carbon materials:fish skin was used as the carbon precursor,and three-dimensional porous carbon materials were successfully synthesized through KOH activation and subsequent carbonization process.The structure of the porous carbon material was designed by adjusting the carbonization temperature during the carbonization process to optimize the impedance matching characteristics of the porous carbon material.The results show that the porous carbon material obtained by carbonization at 650 ^oC has excellent impedance matching properties,with an extreme value of reflection loss of-52.6 d B at a thickness of 2.6 mm,and a maximum effective absorption bandwidth of 8.6 GHz at a matching thickness of 3.0 mm,covering the frequency band of 9.4-18 GHz.The excellent electromagnetic wave absorption performance is mainly due to the porous carbon's own conductivity loss,dipole polarization loss,interfacial polarization loss and multiple reflection scattering phenomena.(2)Component design of porous carbon materials:magnetic/porous carbon composites are prepared by combining magnetic nanomaterials with porous carbon materials.The addition of magnetic nanomaterials makes up for the lack of magnetic loss in porous carbon materials on the one hand,and increases a large number of heterogeneous interfaces on the other hand,causing the accumulation of electrons and facilitating the enhancement of interfacial polarization loss.Specifically,Fe₃O₄/C composites were prepared by combining magnetic Fe₃O₄ nanospheres with porous carbon materials.The addition of magnetic loss significantly improves the matching thickness of the material,and the results show that the matching thickness corresponding to the maximum reflection loss of the material is reduced to 1.9 mm,which is effectively improved.The Ni Co/Co NiO₂@C composite prepared by compositing multi-component Ni Co alloy/Co NiO₂ nanoflowers with porous carbon material.Compared with the pure porous carbon material,the composite shows the enhanced electromagnetic wave absorption.The reflection loss of-89.3 d B was achieved for the composite material prepared by combining core-shell structured Co@Co₃O₄ nanoparticles with porous carbon material.The Fe₃N@C composite material was prepared by using nitrogen-containing groups of amino acids in fish skin as the nitrogen source,and due to the excellent magnetic loss capability of Fe₃N,the composite material showed excellent electromagnetic wave absorption performance,with the minimum reflection loss reached-77.6 d B at a matched thickness of 2.2 mm,while the maximum effective absorption bandwidth reached 7.76 GHz at a matched thickness of 2.7mm.Therefore,the composite of magnetic nanomaterials with porous carbon materials is an effective means to enhance the electromagnetic wave absorption performance of porous carbon materials.This thesis takes porous carbon materials as the main research subject,and explores the law that the structural components of porous carbon materials affect their electromagnetic wave absorption performance through the reasonable structural component design,and achieves the purpose of effectively improving the electromagnetic wave absorption performance of porous carbon materials.This study provides a scientific basis and design method for the preparation of high-performance broadband high-efficiency porous carbon electromagnetic wave absorbing materials,and provides a basic theory and basis for exploring the design innovation of“thin,light,wide and strong”new nano-electromagnetic wave absorbing materials.This study will provide an important basis for the preparation and design and control of new high-performance porous carbon-based composites,and provide an important reference for the effective management of electromagnetic radiation and electromagnetic pollution.