The Preparation And Microwave Absorbing Property Of Co/Fe Composite Absorber Based On Polyaniline

With the advent of information age, microwave pollution and informationsecurity lead to much physical damage and economic loss, which makes thefabrication of high-qualified microwave absorber is increasingly becoming the focusof study. Because of the advantages and disadvantages in all pure absorbers,preparation of the composite becomes the researchers’ consensus to materialmicrowave absorbers, although large amount of absorbers have been reported. Due tothe controlled synthesis of electromagnetic parameters, PANI opens up new horizonfor microwave absorber. To improve the property of microwave absorption, greatattention of PANI absorbers has been paid to the composites with magnetic lossmaterials, because the PANI is a typical kind of dielectric loss materials. In this paper,PANI and Fe₃O₄are the main research objects to fabricate the high-performancecomposite microwave absorbers with core-shell structure, and then the magneticmetal particles are introduced to optimize the microwave absorption of compositematerials further. The deep investigation of electromagnetic parameters in compositeshows the effect to the characteristic impedance match.Via the solvothermal method and in situ polymerization, the Fe₃O₄@PANIabsorber with core-shell structure has been prepared, whose permittivity can beimproved to optimize the characteristic impedance match and enhance themicrowave absorption of composite materials, by adjusting the shell thickness ofPANI. Due to the cooperation of dielectric, interfacial and magnetic loss, PANI-Fe₃O₄microspheres perform considerable microwave absorbing property. The furthercalculation to the normalized impedance of composite exhibits the proper matchingimpedance plays an important role in reflection loss enhancement.The magnetic Cobalt is induced to adjust the parameters of Fe₃O₄, which mayrealize to further improve the property of PANI microwave absorbers, based on thepreparation of PANI-Fe₃O₄microspheres. The adjustment of Co²⁺reducing rate cancontrol the morphology and microstructure of elementary Cobalt substance in theseexperiments, formatting the shell on the surfaces of Fe₃O₄microspheres and thePANI-Co-Fe₃O₄composites. The deep study indicates that the imaginary parts ofpermittivity monotonously increase with frequency, differing from most microwaveabsorbers, which may improve the dielectric loss in high-frequency range, byadjusting the coating Cobalt to control the complex permittivity of compositematerials.PANI nanoparticles are synthesized via the method of reverse dropping aniline into APS. It is shown that PVP and the dropping rate of aniline contribute to themorphology directly, and the restriction of PVP also depends on the dropping rate ofaniline. Through the analysis of doped PANI synthesis, the possible mechanism isdeduced and proved by some characterization methods. The polymerization degreeand oxidation state can be controlled by the dropping rate of aniline monomers,which decrease the complex permittivity and increase the microwave absorption ofdoped PANI. Under proper synthesis condition, PANI nanoparticles reach thereflection loss of-40.5dB at5.8GHz, achieving a comparable property of compositematerials. The investigation of electromagnetic parameters indicates the outstandingmicrowave absorption of PANI nanoparticles should be attributed to the suitablecomplex permittivity, optimized impedance match and multiple dielectric relaxation,and the absorption band can be simply modulated by manipulating the thickness tosatisfy the applications in different frequency bands.