Electromagnetic And EW-Absorbing Properties Of Composites With Core-shell Structure

Due to the utmost application of electromagnetic wave absorbing materials (EMAM) in electromagnetic radiation pollution control, electromagnetic compatibility of Electronic products and military stealth, EMAM has been valued highly in international community, resulting in that it will be an important research hotspot in21st century.With the rapid development of science and technology, there are more requirements in good EMAM. To achieve the target:thin, wide band, light and high absorption, the abilities of new material designing and electromagnetic parameter adjusting has become focus of research. With special structure and design-ability, core-shell structure has performed excellent in many aspects including EMAM, attracting many researchers. With that as the core of this paper, preparations of core-shell structure, adjustment of electromagnetic parameters and absorption ability have been studied highly.Firstly, with the flaky FeSiAl micropowders as cores, FeSiAl/PANI composite was prepared by in-situ polymerization and then analyzed by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and Infared spectroscopy (IR). The aims of this study are to inspect the influence of factors such as reaction temperature, reaction time on the compactness, uniformity of the PANI shell and its electromagnetic property. The results show that FeSiAl/PANI composite with good coating quality and excellent electromagnetic absorbing performance can be made under the conditions as follows:0-10℃, nDBSA/AN=1.5:1, nAPS/AN=3:2, mFeSiAl/AN=2:1and8h. The results indicate that after coating PANI shell, the complex permittivity ε’and ε" increase while complex permeability μ’ and μ" decrease, causing the absorbing performance is improved. Based on the FeSiAl/PANI’s electromagnetic parameters measured and theoretical simulation of monolayer absorber at thickness4mm, it has been discovered that at6GHz the maximum absorption is reached,-37.7dB and the band width below-10dB is3.34GHz. With thickness increasing, there will be two absorption peaks, at low and high frequency respectively, and the peaks have the tendency of moving to low frequency.CIP/ZnO composite with core-shell structure was prepared by chemical precipitation method on the surface of Carbonyl iron particles. In process by controlling the component ratio between core and shell, it has been found that the more ZnO particles are coated on the CIP surface, the smaller electromagnetic parameters become. Therefore, the amount of ZnO could be adjusted elaborately to achieve optimal electromagnetic property of CIP/ZnO composite. The theoretical simulation results show that the minimum RL of CIP/ZnO composite is-10dB, better than former CIP particles. CIP/MnO2composites were prepared through oxidation-reduction method, finding that due to dielectric loss and interface polarization loss the complex permittivity ε’ and ε" of MnO2increases while μ’ has no much difference and μ" decrease a bit. By contrast absorption abilities of CIP、MnO2and CIP/MnO2, it’s found that CIP/MnO2’s absorption at4frequency increases, which is good for the development of low-frequency-absorption.In this paper, a series of electromagnetic functional materials with core-shell structure were prepared successfully. The overall studies show that the electromagnetic parameters of core-shell structure composites could be regulated effectively by adjusting composition and structure of core-shell materials, so as to optimize its EWA-property and lay the foundation for preparation of high performance EWAM.