Preparation And Microwave Absorbing Properties Of Magnetic Nanoparticles/Polyaniline Composites

Based on the designability of the structure of polyaniline and doping with proton acid,in this paper,several composites with different morphologies and microwave absorption properties were prepared via mechanical blending method and in-situ polymerization process.The microstructure,phase composition and absorbing properties were characterized by using of transmission electron microscopy?TEM?,scanning electron microscopy?SEM?,X-ray diffraction?XRD?,Fourier transform infrared spectroscopy?FT-IR?and vector network analyzer?VNA?.The main contents in details show as follows:?1?The hollow structured Fe Pt/PANI and Fe₃O₄/PANI microspheres with different sizes were prepared with the hard template method and mechanical blending method.The effects of different shell thickness on absorbing properties of as-preparedcomposites were studiedby adjusting the mass ratio of aniline/polystyrene.The results show that Fe Pt/PANI and Fe₃O₄/PANI microspheres are regular and uniform with the average sizes of 1?m and 2?m,and the minimum reflection loss peaks appeared with the matching thickness of 1.5 mm and 2 mm,and the bandwidths of the RL<-10 d B reach 7.8 GHz?9.2-18 GHz?and 5.1 GHz?11.71-16.81GHz?respectively.This indicates that the Fe Pt/PANI and Fe₃O₄/PANI composite materials absorb strongly the X band?8-12 GHz?and Ku band?12-18 GHz?microwave.When the aniline/PS ratio are 1:1.5,1:3,and 1:6 for Fe₃O₄/PANI composites,corresponding to the shell thicknesses of 100 nm,60 nm,and 50 nm,and the minimum reflection loss?RLmin?are-14.06 d B,-22.34 d B and-24.3 d B respectively.This means that the composition of the magnetic nanoparticles and the shell thickness of the microspheres affect significantly the microwave absorption properties of the as-prepared composites.?2?EG/PANI composites were synthesized by in-situ polymerization method,and EG/PANI/Fe₃O₄ composites were obtained by loading Fe₃O₄ nanoparticles onto the surface of EG/PANI composites.The microwave absorption properties EG/PANI/Fe₃O₄ composites were investigated by adjusting doping amount of HCl into polyaniline.The results show that the EG/PANI/Fe₃O₄ composites maintain the porous structure of expanded graphite.Theirvalue of RLmin reaches-37 d B at 8.64 GHz in the condition of 0.05 M doping concentration and 2 mm matching thickness.It is also found that double absorption peaks appeared when the matching thicknesses are greater than 3 mm,and the distance between two peaks decreased with the increase of the thickness.As the increase of doping concentration,the minimum reflection loss peak movestoward low frequency,and the matching thickness thickens gradually.In addition,the main loss mechanismsof EG/PANI/Fe₃O₄ composite may be attributed to dielectric relaxation polarization,eddy current loss and interference cancellation.