Microwave adsorption of core–shell structure polyaniline/SrFe₁₂O₁₉ composites

Abstract

Polyaniline/strontium hexaferrites (PANI/SrFe₁₂O₁₉) composites were synthesized by the oxidative chemical polymerization of aniline in the presence of APS. X-ray powder diffraction of ferrites indicated that the structure of core materials is hexagonal with lattice constants around 5.886–5.885 Å. The structural in the character of the sol–gel was investigated with Fourier transform infrared spectrometer analysis. SEM and TEM photographs show that the particle size of core material is around 50–200 nm. After coating with polyaniline, the particle size of the core–shell of PANI/SrFe₁₂O₁₉ has grown up to 100~300 nm. In the magnetization for the PANI/SrFe₁₂O₁₉ composites, it was found that the saturation magnetization (M _s) and coercivity (H _c) decreased after polyaniline coating. The composite under applied magnetic field exhibited the hysteretic loops of the ferromagnetic behavior, such as high saturation magnetization (M _s = 18.9 emu/g) and coercivity (H _c = 3850.0 Oe). The conductivity of the core–shell materials increased with increasing amounts of polyaniline as the temperature increased from 0 to 50 °C, the conductivity increased by about 13%. The polymerization mechanism for the core–shell composites was also investigated. The composite specimens of core–shell PANI/SrFe₁₂O₁₉ and thermal plastic resin (TPR) had band-width microwave absorption due to reflection losses from −27.3 to −37.4 dB at frequencies between 10.5 and 11.8 GHz as observed by High-frequency network analyzer.