Enhanced Microwave Absorption Properties of Absorbing Materials Induced by Complex Coupling Agents

The microstructure and electromagnetic parameters of carbonyl iron powder (CIP) modified by complex coupling agents were studied to analyze the characteristics of absorbing materials. The samples were detected by scanning electron microscope, X-ray diffraction (XRD), Raman scattering spectroscopy, and vibrating sample magnetometer. The electromagnetic parameter was measured by vector network analyzer. The result indicated that the typical flaky-shape was obtained for all samples after milling. In addition, a similar structure was confirmed by XRD and Raman. With the use of the complex coupling agents, the saturation magnetization (Ms) increased and the coercivity (Hc) did not change significantly. According to transmission line theory, the reflection loss (RL) and loss tangent of absorbing material were calculated. When the thickness was 2 mm, the RL peak reached to -15 dB near 2 GHz for CIP modified by ternary coupling agents; the effective absorption bandwidth was 1 GHz (1.6-2.6 GHz) when the RL <; -10 dB. And, the adding of complex coupling agents boosted the magnetic tangent loss of the composites significantly, particularly in the high frequency. Therefore, the proper doping of complex coupling agents can achieve good impedance matching and achieve the purpose of improving the absorbing properties of the absorbing materials. It would lay a good foundation for further engineering application.