| In this paper, graphite oxide was prepared by modified Hummuers method, and M type barium ferrite (BaFe12O19) was synthesized by hydrothermal method. Barium ferrite/Reduced Graphene Oxide (BaM/RGO) binary complex material was prepared by ultrasonic added hydrothermal reduction, taking GO and BaFe12O19 as precursors. And then, BaM/RGO/PANI was synthesized through PANI coated on the BaM/RGO surface by in-situ polymerization. The morphology, structure and spectroscopy characteristics of the GO, BaM, BaM/RGO and BaM/RGO/PANI composite were characterized by Scanning electronic microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectra (FT-IR). The Vibrating sample magnetometer (VSM) and Vector network analyzer (VNA) were used to analyzed the microwave absorbing performance and magnetic parameters of BaM, BaM/RGO and BaM/RGO/PANI composite. The effects of different percentage of RGO and PANI on microwave absorbing performance of binary and ternary composites was further further researched.The results showed that graphite structure layer oxidized have various oxygen-containing functional groups such as hydroxyl group (C-OH), carboxy group (-COOH), and epoxy group (C-O-C), which gives strong ion-exchange of GO. With the increasing of the oxidation degree, the contents of C-O-C and -COOH increased gradually, while the content of C-OH increased first then decreased slightly. The cation exchange capacity of GO samples is also shown to increase first and then decrease. The content of C-OH is the main factors inflluence the cation exchange capacity of GO, the cation exchange capacity of GO samples increase with the increase of the content of C-OH. When the mass ratio of graphite to KMnO4 is 1:3, the maximum of the cation exchange capacity of GO is 4.50 mmol·g-1.During the processes of hydrothermal method to prepare BaFe12O19 (BaM), pure hexagonal barium ferrite powders was synthesized at 200℃ for 12 h when Ba/Fe ratio is 1:8, pH is 13 and OH/Cl ratio is 5. For the as synthesized sample, the saturation magnetization (Ms), remanent magnetization (Mr) and coercive force (Hc) are 35.52 emu/g,16.99 emu/g and 1.242 kOe respectively. Besides, the maximum reflection loss of the sample can reach-11.24 dB at 16.16 GHz with a thickness of 2.0 mm and the bandwidth corresponding to the reflection loss below -10 dB is 1.49 GHz. When the thickness of the sample is 2.0 mm, the absorption bandwidth can cover a frequency range of 15.9～18.0 GHz.During the processes to prepare BaM/RGO binary composite, GO transforms to RGO by exfoliation added with ultrasonic and hydrothermal reduction, and BaM particles are dispersed on the surface of RGO sheets or insertion between RGO sheets, thus formed multilayaer structure of tulle-like graphene coating BaM. The addition of RGO not only reduce the agglomerates of BaM, but also increase dielectric loss of the composite material, which is improves microwave-absorbing properties. On the another hand, the layered structure, the functional groups and the remaining lattice defects of RGO contribute multiple reflection to increase the absorption. However, the impedance matching is destroyed when the content of RGO is excessive. By contrast, when the content of RGO is 3%, BaM/RGO has the best performance of microwave absorption. The maximum reflection loss can reach -21.4 dB at 13.8 GHz with a thickness of 1.8 mm, and the bandwidth is 4.55 GHz (<-10 dB). Its wave absorbing performance is obviously better than that of single barium ferrite.The BaM/RGO/PANI ternary composites is prepared by the wrapping of BaM/RGO with a network polyaniline (PANI), which was prepared through the in situ chemical oxidation polymerization of aniline. The prepared multifunctional nanocomposites showed an outstanding and improved microwave absorption property, compared to the pristine BaM/RGO and BaM. The addition of PANI not only improves the bandwidth and absorbing strength, but also reduces the absorbing thickness. When 6%PANI is added, the BaM/RGO/PANI ternary composites show the best wave absorbing performance. The maximum reflection loss of BaM/RGO/PANI ternary composites can reach to -44.92 dB at 13.42 GHz, and the bandwidth exceeding-10dB can reach to 5.0 GHz. Under such a condition, the absorbing thickness is only 1.8 mm. |
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