Synthesizing And Characterization Of Graphene/Fe₃O₄Composite Powder And Their Microwave Absorbing Properties

Carbon nanomaterials have been attracting more and more attention fromscientific researchers for their special physical and chemical properties. As atraditional magnetic material, Fe₃O₄have been applied in electromagnetic microwaveabsorbing field. Combining carbon nanomaterials and Fe₃O₄make the compositespossess light weight, thin coating, wide absorption bandwidth and strong absorptioneffect. It is meaningful for developing novel microwave absorbing materials.In this article, we used decomposition and reduction method and solvothermalmethod to synthesize graphene coated with Fe₃O₄composite powder, investigated theinfluence of PEG, ethanediamine and pH on the synthesizing of composite powder,systematically, and discussed the effects of reaction temperature, reaction time and Fesource on the preparation of the composite powder synthesized by addingethanediamine. XRD, SEM, TEM, TGA and PPMA were employed to exploredmorphologies, structure and magnetism etc. The reflection loss was calculated withtheir electromagnetic parameters and the absorption mechanism was also discussed.The results show that the composite powder synthesized by decomposition andreduction method has monocrystalline Fe₃O₄nanoparticles and the maximumabsorption could reach-22.2dB at17.3GHz. The particle size of composite powdersynthesized by adding ethanediamine increased with increasing the amount ofethylenediamine, but the load capacity was lower and their maximum microwaveabsorbing frequency shifted from high frequency to low frequency. The absorbingbandwidth became much wider with the increasing amount of ethylenediamine andthe maximum reflection loss reached-29.23dB at16.64GHz. Prolonging the reactiontime, elevating the reaction temperature and increasing the Fe source have littleinfluence on the preparation of composite powder and their microwave absorbingperformance. The variation of morphologies and performance of the compositepowder synthesized by changing the pH value was similar with the composite powdersynthesized by adding ethylenediamine. But the maximum reflection loss onlyreached-16.03dB. In summary, the best microwave absorbing property was obtainedby adding12mmol ethylenediamine and reacting at200oC for10h. And in this condition, the size and the distribution of particles were very homogeneous. Althoughthe reflection loss was-16.94dB, its absorbing bandwidth reached5.27GHz.