Fe2O3/Fe3O4/PANI/MWCNT nanocomposite with the optimum amount and uniform orientation of Fe2O3/Fe3O4 NPs in polyaniline for high microwave absorbing performance

The purpose of this study was to develop a method that modifies the surface of carbon nanotubes with magnetic nanoparticles. The well-known conductive polyaniline polymer (PANI) was directly polymerized on the surface of the Fe2O3/Fe3O4 hybrid NPs and the Fe2O3/Fe3O4/PANI nanocomposite was obtained. Then, multi-walled carbon nanotubes (MWCNTs) were decorated with the specific weight ratio of Fe2O3/Fe3O4/PANI nanocomposites. The scanning electron microscopy of the final product (Fe2O3/Fe3O4/PANI/MWCNT nanocomposite) shows that the main area of CNT’s surface was decorated with individual or small clusters of Fe2O3/Fe3O4 NPs. Although, in some areas (probably at the extremities and on surface defects) can be seen large clusters of Fe2O3/Fe3O4 NPs. Transmission electron microscopy images demonstrate the uniform distribution of Fe2O3/Fe3O4 NPs, which are dispersed in the PANI background, overlapping the surface of the CNTs. The saturation magnetization of Fe2O3/Fe3O4/PANI/MWCNT nanocomposite as expected is 25% smaller than that of Fe2O3/Fe3O4/PANI nanocomposite, due to the presence of nonmagnetic MWCNT. However, Fe2O3/Fe3O4/PANI nanocomposite shows excellent absorption performance and effective bandwidth between 4 and 8 GHz. At the matching thickness of 3.2 mm, the loss of reflectance reaches its highest value, −88.8 dB at 10.6 GHz. The broadest effective bandwidth is larger than 8 GHz, between 9.7 and 18 GHz for 3 mm thick.