Microwave absorption and magnetic properties of thin-film Fe3O4 @polypyrrole nanocomposites: The synthesis method effect

Abstract

In this study, a thin film of magnetic polymer nanocomposite for microwave absorption was prepared using a core-shell structure in an epoxy resin medium. The co-precipitation technique was used to synthesize the Fe3O4 NPs; and core-shell Fe3O4 @polypyrrole nanocomposites were made by two different synthesis methods through chemical oxidative polymerization with and without hydrochloric acid (HCl) and then, they were filmed by mixing the resulting powder with epoxy resin to explore their microwave absorption properties. The Fe3O4, Fe3O4 @PPy-A, and Fe3O4 @PPy-B nanostructures were characterised using Fourier transform infrared (FTIR), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), and thermogravimetric analysis (TGA) techniques, and the results confirmed synthesis of nanomaterial's pure structure. The transmission electron microscopy (TEM) and field-emission scanning electron microscopy (FESEM) techniques were used to determine morphology, magnetic properties of the nanocomposites were investigated by vibrating-sample magnetometer (VSM) at room temperature and electrical conductivity were calculated by four-point probe method. Finally, the microwave absorption properties of Fe3O4, Fe3O4 @PPy-A, and Fe3O4 @PPy-B nanocomposites were determined by epoxy resin serving as a host using a vector network analyser. According to the results of assessing microwave absorption, it was found that addition of HCl played a significant role. However, the maximum reflection loss of the Fe3O4 @PPy-A and Fe3O4 @PPy-B nanocomposites was equal to − 33.8 dB (˃99.9%) at 11.5 GHz and − 26.2 dB at 7.2 GHz, but demonstrating an effective bandwidth of 6.5 and 1 GHz, respectively. Compared to other previously reported studies, microwave properties of the core-shell Fe3O4 @PPy-A nanocomposite not only had better reflection loss performance but also it possessed wider effective absorption bandwidth < −20 dB for thinner thickness of 1.5 mm.