| With the rapid development of information technology,the ever-changing electronic equipment has greatly improved the efficiency of social production,making people's daily life more and more convenient,and at the same time,it has also brought a lot of electromagnetic pollution.In the military field,stealth technology is effective to improve the survival.Therefore,the research of high-performance electromagnetic wave absorbing materials is extremely important in life or military field.Carbon materials have the advantages of high conductivity,light weight,low density,strong corrosion resistance,easy processing,and large specific surface area.They are excellent carriers for preparation of microwave absorption materials.Compared with traditional carbon materials,biomass carbon materials have the characteristics of rich sources,low cost,and green and pollution-free preparation process.Biomass carbon material has a natural pore structure,and after carbonization,it can get more kind of pore structure and higher specific surface area,which is beneficial to improve the microwave absorbing performance.In this paper,Fe@Fe3C/C nanocomposites were prepared by impregnating ferric nitrate solution and carbonizing using fir as the carbon source.Secondly,a partially ordered fir-based carbon material was prepared by crushing and sieving.Finally,with the help of the concept of metamaterials,fir-based carbon materials with ordered microstructures are designed as the coating materials to study the absorbing properties of infinite plates and periodic cross array structures through electromagnetic simulation.The main research contents are as follows:(1)In this paper,the Fe@Fe3C/C nanocomposite material was prepared by impregnating ferric nitrate solution and carbonizing using fir as the carbon source.The core-shell structure produced a large number of interfaces,which enhanced the interface polarization,improved the dielectric constant,permeability and the loss ability of the material.The electromagnetic parameters of the material were tested by a vector network analyzer.It was found that the Fe-1 sample has the most excellent absorption performance by calculation.When the thickness is 1.54 mm,the maximum reflection loss is-59.2 dB,and the effective absorption bandwidth is 4.1 GHz(12.9-17 GHz).(2)Secondly,we prepared fir-based carbon materials with ordered microstructures by crushing and sieving.Compared with control group,the ordered microstructures produced more interfaces and enhanced the interface polarization and the dielectric constant of the material.At the same time,the existence of this kind of microstructure is also effective to enhance the material's loss of electromagnetic waves.The study found that S-1 and S-2 samples have the most excellent absorbing properties.When the thickness of sample S-1 is 2.3 mm,its effective absorption bandwidth is 6.0 GHz(11.5-17.5 GHz),and when the thickness of sample S-2 is 1.87 mm,its effective absorption bandwidth is 5.7 GHz(12.3-18 GHz).(3)Finally,the enhancement effect of the millimeter scale ordered structure on the absorbing performance of the material was investigated by electromagnetic simulation.Taking the performance of fir samples with ordered microstructure as the primary parameter of the physical model,the influence of millimeter structure ordering on electromagnetic absorption effect was explored by modeling the infinite plate and cross array structure.Compared with the infinite plate structure(second-order disorder),the cross-array structure(second-order order)has a better absorption effect.And the absorption effect becomes stronger with the increase of the number of layers of the cross-array structure,which is mainly due to the generation of capacitance and inductance resonance,as well as the cascade effect between the upper and lower layers.The three-layer cross array structure has strong absorption for the electromagnetic waves of different incident angles and greater applicability. |
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