Abstract:The carbonyl iron (CIP)/NiLa_0.02Fe_1.98O₄ double layer composite absorber was designed based on the electromagnetic transmission line theory and impedance matching principle, and the microwave absorbing coating with high performance was prepared based on epoxy resin. XRD and SEM were used to characterize the structure of the powder and coating. The coaxial method was used to mensurate the electromagnetic parameters of CIP and NiLa_0.02Fe_1.98O₄. The reflectances of the surface layer and the bottom layer under the conditions of different thickness and different orders were calculated by using MATLAB software. The results show that, taking NiLa_0.02Fe_1.98O₄ as a surface layer and CIP as the bottom layer can greatly expand the coating absorption bandwidth and decrease the reflectance peak. While NiLa_0.02Fe_1.98O₄ for surface layer, CIP for the bottom layer, with a thickness of 1.5mm and 0.6 mm, respectively, the absorbing effect of the coating is the best, the reflectance peak is -38.2 dB, and the bandwidth, which is less than -10 dB, is 13.4 GHz. The absorbents overall dispersion in the coating prepared meets the requirement, there are no obvious defects that exist. By comparison of the experimental and theoretical values, the accuracy of the optimal results is verified, thus, the requirements of microwave coatings strong absorption with a lesser thickness and the wideband are met.

Key words: absorbing materials; impedance matching; double layer; electromagnetic property