Preparation And Electromagnetic Wave-absorbing Properties Of Hollow Polyaniline-based Multi-Composites

Electromagnetic wave (EM) absorbing material is one of functional materials which can absorb and attenuate the electromagnetic wave energy, then transform them into thermal or other energy. In recent years, more and more researchers were focus on strengthening absorption efficiency, widening absorption band, reducing coated thickness and obtaining the cheap EM absorbing materials. The composites combining dielectric loss and magnetic loss are arouse wide concern on their different properties and they were superior to single components. In this paper, we prepared a series of hollow polyaniline-based composites, and the microwave absorption mechanism were explored, we can draw the following conclusions:Firstly, the polyaniline (PANI)/Fe3O4/carbon black (CB) microspheres with hollow-structure were successfully synthesized through the method of interfacial polymerization and Pickering emulsion polymerization. The crystal structure, morphology, electromagnetic properties, and microwave absorbing properties of these materials were characterized by X-ray diffractometer (XRD), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and the four-probe meter, vector network analysis (VNA) respectively. We investigated the effect of additive amount of CB or Fe3O4 on microwave absorbing properties. When a certain amount of Fe3O4 was added, the hollow-structured microspheres’minimum reflection loss (RL) shifted to low frequency with the increase of coating layer thickness. Two peaks occurred as the coating layer thickness increased to 5.0 mm, which respectively located in C band (4-8 GHz) and Ku band (12～18 GHz). When the mass ratio of Fe3O4 and CB was 125:1, the minimum reflection loss is up to-52.6 dB at 17.3 GHz with the coating layer thickness of 5.0 mm, which exhibited excellent electromagnetic wave absorbing properties, and the absorption bandwidth with reflection loss values below-10 dB is in the range of 16 to 18 GHz. It was believed that PANI/Fe3O4/CB could be a potential electromagnetic wave absorbing material by regulating the ratio of carbon black with Fe3O4.Next, Polyaniline nanotubes were prepared with succinic acid as dopant. PANI/NixFe1-xFe2O4 composites were successfully prepared by coprecipitation method with PANI nanotubes as template. Finally hydrochloric acid (HC1) was used to redope the composites with different concentration. The crystal structure, morphology, electromagnetic properties, and microwave absorbing properties of these materials were characterized by X-ray diffractometer (XRD), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and the vector network analysis (VNA) respectively.We analysized the concentration of HC1 influence on microwave absorbing properties. The absorbing data analysis showed that, when the concentration of HC1 was 1.0 mol/L, the minimum reflection loss reached-17.6 dB at 6.7 GHz with the coating layer thickness of 5.0 mm, which exhibited excellent electromagnetic wave absorbing properties, and the absorption bandwidth with reflection loss values below-10 dB was in the range of 5.4 to 8.7 GHz. The EM absorption mechanism of composites were the destructive interference of the reflection wave from the interface and the EM loss.It indicated that the EM absorbing performance of PANI/NixFe1-xFe2O4 composites could be obviously improved by HC1 doped.