| As an important functional rare earth materials, CeO2 is widely used in industry. Graphene and polyaniline possess excellent dielectric loss properties, and the microwave absorption properties of composites can be improved by combining graphene(polyaniline) with CeO2, which could extend the microwave absorption application of CeO2 nanocomposites.In this work, graphene and polyaniline was introduced as supporter to fabricate the CeO2/reduced graphene oxide (CeO2/RGO) and CeO2/polyaniline (CeO2/PANI) nanocomposites, respectively. The micromorphology and structure of composites were characterized by FE-SEM, TEM, XRD, FT-IR, Raman spectra and XPS. The microwave absorption parameters of composites were measured by vector network analyzer, and the mechanisms of microwave absorption were also explored. In addition, in order to guide the processing and application of graphene oxide/conductive polymer nanocomposites, the rheological behavior of graphene oxide/polyaniline (GO/PANI) was investigated by rheometer. The main contents are as follows:1. Graphene oxide (GO) was synthesized by improved Hummers method, and CeO2/RGO were synthesized by one-step hydrothermal method using GO and Ce(NO3)3·6H2O as precursor, without using surfactant or reducing agent. The micromorphology, structure, dielectric and microwave absorption properties of composites were investigated. The results show that CeO2 nanoparticles are uniformly dispersed on the RGO sheets with charge transfer between CeO2 and RGO. Compared with pristine RGO or pure CeO2 nanoparticles, the reported nanocomposites achieved both wider and stronger wave absorption in the frequency range of 2-18 GHz. An optimal reflection loss of -32 dB(99.9% of electromagnetic wave absorption) is found at 17 GHz with a coating layer thickness of 1.5 mm. The product with a coating layer thickness of only 2.0 mm shows a bandwidth of 4.3 GHz, corresponding to reflection bss at -10 dB (90% of electromagnetic wave absorption).2. CeO2 nanorods were prepared by hydrothermal method using Ce(NO3)3·6H2O as precursor, and CeO2/PANI was synthesized by an in situ polymerization using aniline as raw material, HCl as dopant and APS as initiator. The micromorphobgy, structure, dielectric and the effects of CeO2 content on microwave absorption properties of composites were investigated. The results show that CeO2 nanorods are coated by PANI to form a well-defined hierarchical structure, and CeO2 is well incorporated into the PANI matrix. CeO2/PANI exhibits excellent microwave absorption properties at 2-18 GHz. Especially, with increasing CeO2 content to 30 wt.%, an optimal reflection loss of -40 dB (99.99% of electromagnetic wave absorption) is found at 8.8 GHz, and the frequency bandwidth corresponding to 90% of electromagnetic wave absorption is crossing the X band. However, when the CeO2 content exceeds a certain value, a weak reflection loss is observed due to the decreased dielectric loss affected by the insulation of CeO2.3. GO/PANI was synthesized by an in situ polymerization in the presence of GO using aniline as raw material, HCl as dopant and APS as initiator. The micromorphology, structure and steady state rheology behavior of composites were investigated. The results show that the GO sheets are homogeneously coated with PANI to form flake-like structure, and strong interactions exist between GO and PANI, which induces the highly oriented structure of PANI chains. The zero shear viscosity of GO/PANI dispersions is significant higher than that of PANI dispersions, and GO/PANI dispersions showed characteristic Newtonian-pseudoplastic transition with increasing the nanocomposites concentration. A Newtonian-pseudoplastic transition with power law relation between zero shear viscosity and concentration was observed above the critical concentration. In addition, the nonlinear rheological behavior of GO/PANI dispersions exhibit significant temperature dependence. |
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