Preparation And Electromagnetic Microwave Absorption Properties Of Carbon-based Porous Materials

In this paper,a porous structure is introduced into a carbon-based material,and the prepared carbon-based porous material is used in the field of microwave absorption.The purpose of this design is to ensure that the porous structure can reduce the density of the material itself and improve the impedance matching of the material itself,while at the same time causing multiple scattering of electromagnetic waves entering the material,in order to obtain an excellent microwave absorption material suitable for a plurality of practical fields.Three different carbon-based porous materials including three-dimensional ordered hollow carbon materials,porous boron nitride/nanocarbon composites and three-dimensional ordered carbonbased（Fe/C）porous materials of native wood template were prepared.The materials obtained are all excellent microwave absorption materials with light weight,thin thickness,wide absorption band and strong absorption characteristics.A three-dimensional ordered hollow carbon（3DOHC）with a honeycomb-like structure was designed and synthesized by SiO₂ particle hard template method.The carbon wall has a rich pore size and the thickness is only tens of nanometers,and its crystal structure is amorphous amorphous carbon.The structure adjustment can be effectively achieved by adjusting the pore size of the SiO₂ particle used for the template.The porous structure after the template removal can also e ffectively reduce the density of the 3DOHC material,and the material has a high specific surface area.At the same time,the obtained 3DOHC material has a certain dielectric property and excellent impedance matching,and the regular hollow structure of the material itself can also improve multiple reflection.The 3DOHC material obtained by the test has been confirmed to have excellent microwave absorption properties,and only a small addition amount（5 wt.%）is required in the preparation of the absorber.The synthesis of porous boron nitride/carbon nanomaterial composites（including BN@CNTs（Carbon Nanotubes）and BN/MG（Multilayer Graphene））mainly includes two processes of synthesis and heat treatment of precursors.The morphology of the synthesized precursor directly determines the morphology of the final product.The final product consists of a layer of amorphous BN microrods and carbon nanotubes coated on the surface of the microrods or multilayer graphene distributed between the rods and the rods.Composite materials have high specific surface area and low density characteristics,and the density and specific surface area of the composite can be adjusted by adjusting the amount of porous BN in the final product.The microwave absorption properties of the composites were tested and the results show that the excellent impedance matching and the multiple reflections present make the composite an excellent lightweight microwave absorption material.In addition,the decomposition process of different precurso rs was studied in detail.The results show that the decomposition process of pure porous BN and composite s precursors is nearly identical,which proves the feasibility of controllable adjustment of the composite morphology.At the same time,it provides a new idea for the composite design of the porous BN and other materials.A regular ordered three-dimensional ordered carbon-based（Fe/C）porous material with a few micrometers thick carbon walls connected and separated by a channel with a side length of several tens of micrometers was designed and synthesized using the native wood template method.The obtained three-dimensional ordered carbon-based（Fe/C）porous material possesses certain dielectric properties and excellent impedance matching,and also causes a magnetic loss mechanism due to the introduction of Fe,and a regular ordered channel structure can also cause Multiple reflections.Therefore,the material has been tested to have excellent microwave absorption properties.The reason why the microwave absorption performance is improved is that the introduction of Fe proves to be effective in the magnetic loss mechanism,and at the same time promotes the level of graphitization of the carbon wall.