Research On Preparation And Electromagnetic Characters Of Graphene/Polyaniline Absorber

To study the microwave dielectric property of graphene and polyaniline,in this paper,the HCl doped polyaniline and graphene/polyaniline composites were prepared by chemical method and in situ polymerization,respectively.The mircrostructure and morphology of specimen are characterized by Fourier transform infrared spectra(FT-IR),X-ray diffraction spectroscopy(XRD),Raman spectroscopy(Raman),Scanning electron microscopy(SEM),Transmission electron microscope(TEM),and other analytical methods.The electromagnetic parameters of products were analyzed by Vector Network Analyzer.Moreover,we established the adsorption model of graphene/polyaniline and used the first-principle calculation to study interfacial interaction,binding energy,electron density of states,and hence to explain the mechanism of the change of dielectric properties of composites at microscopic scale.The analysis results indicate that doped polyaniline prepared by chemical oxidation has certain crystallinity and the microscopic morphology distributes as nanofibers.The test results of electromagnetic parameters show that doped polyaniline exhibits good dielectric properties,and the electromagnetic waves absorption mechanism is mainly electric loss.However,low magnetic loss resulting in poor impedance matching,so that the simple dielectric dissipation material of polyaniline is poor in absorbing performance.The maximum absorption of the synthetic polyaniline in the frequence range of 2~18 GHz frequency is only-11.5dB,which is not a very ideal absorbing material.Graphene/polyaniline composites were prepared by in situ oxidation polymerization,and PANI nanoparticles were intertwined and inlaid with graphene surfaces.The testing of electromagnetic parameters of composites indicates that graphene/polyaniline belongs to dielectric loss material,and shows special dielectric response characteristics.Compared with pure polyaniline,both the complex permittivity and the dielectric loss angle tangent increases,which is related to the dipole relaxation polarization effect.The first principle calculations confirms the hybridization phenomena between graphene and polyaniline,and the hybridization between the orbits enhances the dipole polarization and electron polarization intensity.The monolayer reductive oxidation graphene was prepared by chemical reductive oxidation using hydrazine hydrate,then immediately combined with polyaniline to prepare RGO/PANI composites with special structure.The polyaniline nanofiber arranged vertically aligned on RGO nanosheets.The results show that the dielectric properties of composites are closely related to the concentration of aniline,too low or too high concentraions can not form the special structure of PANI directional cladding on RGO.The optimum dielectric loss performance can only be obtained when the optimum synthetic conditions(0.07mol/L)are met.The first principle calculations confirmed the interaction and charge transfer between graphene and polyaniline.The redistribution of the charge leads to the enhancement of the polarization.Compared with pure polyaniline,the absorbing properties of RGO/PANI composites were improved remarkably.In the four samples prepared,when the aniline concentration is 0.07mol/L,the microwave absorbing properties is the most excellent.The maximum reflection loss reaches-43 dB at 12.4 GHz with a thickness of 4 mm.