Synthesis And Electromagnetic Properties Of Chiral Polyaniline/Li_0.35Zn_0.3Fe_2.35O₄ Composites

Microwave absorption materials have been widely used in the fields of telecommunication apparatus,military stealth technology,electromagnetic interference?EMI?shielding and radiation protection.Ideal microwave absorbing materials are required to possess high absorption efficiency,wide absorption frequency range,tiny thickness and light weight.However,there is no such kind of materials could meet all the fore-mentioned requirements.The combination of different materials has become an effective approach to improve the properties of microwave absorption materials.Chiral polyaniline?PANI?/ferrites composites have been investigated in recent years because of their low density,superior electromagnetic parameters control,electromagnetic loss ability,wide microwave absorption band and high absorption intensity.In this work,chiral PANI was synthesised by interfacial polymerization using D-camphorsulfonic?D-CSA?as doping acid.The effect of the concentration of D-CSA on micromorphology,chiral property,electrical conductivity and microwave absorption performance were investigated.The results showed that the chiral degree of PANI was enhanced with the increase of the concentration of D-CSA.When the concentration of D-CSA was 0.6 mol/L,the average length and diameter of chiral PANI were 700 nm and 100 nm,respectively.In addition,the maximum electrical conductivity was 1.21 S/cm.The reflection loss?RL?of chiral PANI could reach-15.5 dB at 16.5 GHz with 1.4 mm thickness,and the corresponding bandwidth?RL <-10 dB?was 3.8 GHz?14.2¹8 GHz?.Based on the silane?APTS?-modified Li_0.35Zn_0.3Fe_2.35O₄?LZFO?ferrite,the chiral PANI/APTS/LZFO composites with different aniline-to-ferrite weight ratios?m_A/m_F?were synthesized through interfacial polymerization.The impact of m_A/m_F on the micromorphology,chemical structure,thermal stability and microwave absorption properties of chiral PANI/APTS/LZFO were studied systematically.The results showed that PANI fibers were grafted on the surface of LZFO and there existed some chemical interactions between chiral PANI and LZFO.The thermal stability of chiral PANI/APTS/LZFO was improved compared with chiral PANI.The microwave absorption properties of chiral PANI/APTS/LZFO were superior to chiral PANI and LZFO.When mA/mF was 1:1 and thickness was 2.5 mm,the widest bandwidth was achieved.The bandwidth?RL <-10 dB?was 5.8 GHz?4.5¹0.3 GHz?and the corresponding minimun RL was-41.5 dB.When mA/mF was 1:4 and with 2.5 mm thickness,the minimum RL was-57.5 dB and the bandwidth of RL <-10 dB was 3.8 GHz?8.5¹2.3 GHz?.The superior microwave absorption properties of chiral PANI/APTS/LZFO composites were ascribed to the improved impedance matching,enhanced interfacial polarizations,Debye relaxation,magnetic resonance and the cross polarization of microwave in chiral PANI.These novel composites with good microwave absorbing performance can be selected as a new candidate for microwave absorption.