Preparation And Microwave Absorption Properties Of Conductive Polyaniline/Barium Ferrite Composite Materials

The serious increase of electromagnetic radiation and the development of stealth technology promoted the research of radar absorbing materials. Conductive polyaniline (PANI) has been considered as one of the most potential microwave absorbing materials because of its low density, absorption frequency bandwidth and the controlable dielectric constant. The M-type hexagonal barium ferrite (BaFe12O19, BF) with high Curie temperature, magnetic anisotropy, magnetization and good chemical stability can be used as a microwave absorber. Conductive polyaniline/barium ferrite nanoparticles as absorbing materials, with a combination of dielectric loss and magnetic loss, may have broad application prospects.Conductive polyaniline (PANI) doped by hydrochloric acid was synthesized by oxidative polymerization. PANI prepared with different molar ratios of (NH4)2S2O4, (APS) and aniline (An) was studied by SEM, IR, UV-Vis spectra and four-probe electrical conductivity. The results indicated that PANI showed coralloid fibrillar morphologies; The major doping dot of PANI was imine nitrogen atom, and after doping the absorption peaks had red shifts because of induction effect and conjugative effect. The yield of PANI increased and the conductivity value of PANI increased first and decreased later with the increase in the concentration of APS. When APS∶An(mol)=1.0, a maximum conductivity of 0.25 S·cm^-1 was obtained. Analysis of electromagnetic parameters showed the main loss mechanism of conductive PANI was dielectric loss. When APS∶An(mol)=0.4 0.6 , PANI had good microwave absorption properties, with the maximum absorption rate of 15.8 dB, and the absorption rate was greater than 10 dB within the frequency of 11.36-15.46 GHz.Flaky barium ferrite was synthesized by reverse microemulsion technique, and composite of PANI containing containing BF was synthesized using in situ polymerization method. The results showed that the composite material possessed coralloid fibrillar morphologies with fibers having an average diameter in the range of 20-50 nm. With the increase in the content of BF, the growth of the branches of the coralloid structure was restrained because large amount of aniline monomers were consumed during surface polymerization. There was no evident chemical interaction between PANI and ferrite nanoparticles, but the chain structure and crystallinity of PANI were damaged with the introduction of BF and the doping degree was reduced; The composite material was a kind of hard magnetic materials with alternative conductivities and magnetic properties. The composite material had strongest absorption capacity with the maximum absorption rate of 20.11 dB when WAn∶WBF = 2∶1, and the absorption rate was greater than 10 dB within the frequency of 12.87¹6.66 GHz.