Design And Performance Of Gypsum Based Wave-absorbing Materials With 3D Periodic Structure

Excessive electromagnetic radiation will cause potential harm to people's health,as well as electromagnetic interference,information leakage and other negative effects.The application of absorbing building materials can effectively solve the problem of electromagnetic radiation pollution in building space.However,the existing design technology of electromagnetic wave absorbing building materials is difficult to meet the needs of wide-band application of materials in the complex electromagnetic environment of building space.Therefore,this paper breaks through the traditional design technology of absorbing building materials,selects nano carbon black as the electromagnetic modifier and gypsum as the matrix material,and designs three kinds of three-dimensional(3D)periodic structured absorbing materials based on the theory of3 D periodic structure.In this paper,the high frequency structure simulator(HFSS)is used to analyze the electromagnetic field and absorption rules of gypsum based materials with 3D periodic structure.It is found that compared with the traditional plate materials,the 3D periodic structure design can significantly improve the absorption performance and expand the absorption bandwidth.The 3D cubic periodic structure can expand the effective frequency band of reflectivity below-10 d B to 4.2-18 GHz,while the 3D cylindrical and hexagonal periodic structure can achieve the reflectivity of electromagnetic wave below-10 d B in the frequency band of 2-18 GHz.The geometrical parameters and material electromagnetic characteristics of 3D periodic structure are important factors that affect its absorbing efficiency and effective frequency band.The simulation results show that there is a certain matching relationship between the 3D periodic structure size and the incident wavelength.The increase of the side length or diameter of the structural unit results in the shift of the reflection absorption peak to the low frequency,which improves the absorption performance of the material in the low frequency range;the increase of the height of the structural unit results in the increase of the number of absorption peaks,and widens the overall absorption bandwidth.The electromagnetic modifier of carbon black mainly affects the absorbing effect by influencing the electromagnetic parameters of the material.If the carbon black content is too high or too low,the absorbing effect will be reduced to a certain extent,and there is the best content(2wt.%).The actual test results and simulation results show the same law.The dielectric loss of nano carbon black is the basis of electromagnetic wave absorption.The results of electric field analysis of gypsum based materials with 3D periodic structure show that the structure effect of materials plays an important role inelectromagnetic wave absorption: the interference of electromagnetic wave on the surface of materials is the main attenuation mechanism of electromagnetic wave in low frequency band,and the scattering,diffraction and multiple reflections of electromagnetic wave in the edge and gap of periodic structure unit are the main attenuation mechanism of electromagnetic wave in high frequency band.The results of this work provide a new idea for the research and design of broadband absorbing building materials,and have certain guiding significance.