| With the the rapid development of the information society, the electromagnetic radiation which is mainly produced by all kinds of electronic machinery becomes more and more serious. Management and protection of electromagnetic radiation has aroused a great attention of international community, and the electromagnetic wave absorption material will become the focus of research and industry soon. The electromagnetic wave absorption coating with the advantages of Small occupancy area and flexible application become an important research direction of electromagnetic radiation protection materials. Especially in military stealth application, it has an important practical significance of the research.At present, the traditional magnetic absorbing coating mainly contains ferrite, the carbonyl iron and so on. But the disadvantages of high density, narrow absorption band and poor adhesion problems cannot meet the actual application demand. The preparation of the "wide, light, thin, strong" absorbing coating is urgent.This thesis aims at preparing radar absorbing coating with high performance with taking advantages of dielectric material whose electromagnetic parameters can be adjusted to overcome the shortcomings of the magnetic material according to theoretical design. In the experiment conductive carbon black, carbon fiber act as absorbing agent, epoxy resin as base material for absorbing material preparation. Through a series of research on the monolayer, multilayer samples, good absorption, light absorption coating is innovatively achieved.First, the length and amount of fiber, the amount of carbon black are analyzed to study the change of absorbing property according to monolayer coating. The results show that when the length of fiber is2mm, the amount is0.3%, the absorbing effect is better. In certain concentration range, the change rule of dielectric constant is obvious. With the increasing of the length and amount, the absorbing effects become better at first but worse finally and the peak position move to low frequency. The study of carbon black is similar to carbon fiber. Monolayer coatings have the problem that the absorbing frequency band is narrow and the peak value is small.The study of multilayer composite structure indicates that when the upper strata are carbon fiber, that is, carbon fiber is resistance matching layer, the absorbing frequency band is narrow. However, when the upper strata are carbon black, that is, carbon black is resistance matching layer, the absorbing frequency band is good. When the amount of carbon black in the first layer is16%and the thickness is1.5mm, and the amount of carbon fiber in the second layer is0.3%and the thickness is1.5mm, the absorbing effect is good. The absorbing amount is below-10dB in the frequency band of8.7-18GHz. According to the double-deck design, three-layer composite structure is designed. When the amount of carbon black in the first layer is16%and the thickness is1.5mm, the amount of carbon fiber in the second layer is0.3%and the thickness is0.5mm, and the amount of carbon fiber in the second layer is0.5%and the thickness is lmm, the resistance matching effect is ideal. The design can realize the goal that the absorbing amount is below-lOdB in the frequency band of8-18GHz.For the further study, multilayer film structure was designed based on that. The theoretical simulation indicted that three-membrane structure is better. While the resistance of epoxy/resistive film composite three membrane absorber based on carbon black-filler are about300,500,1000?/?and the total thickness is4mm,the absorber showed better absorbing properties(within8-18GHz band reflectivity are below-lOdB, The maximum peak is-18.5dB). Carbon fiber instead of resistance film was studied in this article. The study shows that in4.8-18GHz absorption band, the amount of absorption is below-8dB. In5-7.8GHz and in13-18GHz band, absorption are below-lOdBw, and the maximum amount is-12.2dB/5.8GHz. The results show that this kind of samples has a very wave absorbing effect... |
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