| With the wide popularization and rapid development of network communication equipment,electromagnetic pollution is around us all the time,and the problem of electromagnetic radiation is becoming more and more important all over the world.Excessive microwave radiation and electromagnetic interference will not only have adverse effects on people’s health,but also affect the daily operation of precision instruments.At present,electromagnetic protection technology is one of the most direct and effective means of protection.It can block the propagation of electromagnetic waves through the attenuation and absorption of electromagnetic waves,and reduce the secondary damage of electromagnetic waves to the environment and human body.In this project,polyurethane and epoxy resin are used as adhesives,and copper powder and graphene are used as absorber coating materials.Coated and structural absorber fabrics with convenient method,good stability,wide effective absorption frequency band and excellent absorber efficiency are prepared,and their properties are studied.The main work is as follows:(1)Firstly,the cotton fabric is used as the substrate,and the metal micro-powder copper powder is doped in the adhesive polyurethane and coated on the cotton fabric by the coating process.Through the test of the performance of the coating fabric with different contents,it is found that within the test frequency range,the complex dielectric constant increases with the increase of the copper powder content in the coating,and the polarization is generated under the action of the external electromagnetic field.Increased dielectric loss to electromagnetic waves;When the copper powder content increases to 11%,the reflection loss at 9.0,10.5,12.8GHz is the lowest of-20.4,-28.3,-25.6d B,the effective absorption bandwidth is 0.2,1.3,1.1GHz,and the shielding efficiency is 16.59,21.10,25.92 d B.The experimental results provide a new feasible practical scheme for the preparation of simple coated wave absorbing materials.(2)Secondly,by combining different concentrations of copper powder with graphene,the optimal matching mode of copper powder/graphene composites with different contents was studied,and the wave absorption property of copper powder/graphene composites was discussed.It is found that in the range of 8～13GHz,when the coating contains 11% copper powder and 15% graphene,the minimum reflectance reaches-14.7d B and-19.1d B,and the corresponding effective absorption bandwidth is 2.53 GHz and 2.81 GHz.The minimum reflectance is-25.73 d B,the effective absorption bandwidth is 3.73 GHz,and the electromagnetic shielding efficiency is increased to 36.38 d B.The experimental scheme provides some practical guidance for the preparation of composite absorbing materials with good stability and absorbing efficiency.(3)Finally,the above coating materials were further optimized,and the wave absorbing coatings with different grid structures were designed and prepared.Through the study of different absorber contents and different size grid structures,the optimal matching method between the wave absorbing materials and the grid structure was constructed.The results show that with the decrease of the mesh structure size,the tensile properties of the composite absorber structure coating are gradually enhanced.In the range of the test frequency band,with the increase of the graphene content in the coating,the minimum reflectance of the composite absorber coating with 15% graphene mesh structure size of 2 mm×2 mm is-28.06 d B.The effective absorption bandwidth is 4.68 GHz,and the corresponding electromagnetic shielding efficiency is 30.25 d B.The composite method proposed in this experimental scheme can be used as a simple and effective method to provide certain theoretical support for the preparation of graphene-based structural absorber materials,and has certain guiding significance for promoting the research of composite materials combining coating type and structural type. |
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