Preparation And Electromagnetic Absorbing Properties Of Graphene-based Magnetic Composites

Currently, graphene-based magnetic composites are the hot research topic in the field of electromagnetic wave absorption. They can meet all of requirements, such as thin thickness, light weight, wide absorbing frequency and strong absorption. This paper reported three kinds of graphene-based magnetic composites, and explored electromagnetic absorbing properties of these graphene-based magnetic composites.1. Ni/RGO composites were synthesized through a facile and effective one-pot solvothermal method. Plenty of urchinlike Ni nanoparticles are deposited on the RGO nanosheets. Co-Ni/RGO composites were prepared under the same experimental condition. The magnetic hysteresis measurement reveals the ferromagnetic behavior of the Ni/RGO-1 composites at room temperature. The maximum reflection loss of Ni/RGO-1 composite is up to -32.1 dB at 13.8 GHz and the absorption bandwidth with the reflection loss less than-10 dB is 4.5 GHz (10.9-15.4 GHz) with the thickness of 2 mm. The Co-Ni/RGO composites exhibit excellent electromagnetic absorption properties. Moreover, for Co-Ni/RGO composites, the microwave absorption properties can be tuned easily by varying the Co/Ni ratio and thickness of the samples.2. A novel sandwich-like PPy/Fe3O4/RGO and PANI/Fe3O4/RGO composites were synthesized through a modified two-step method. Plenty of Fe3O4 nanoparticles are deposited on the RGO nanosheets. Conducting polymer(PPy or PANI) is coated on the two sides of Fe3O4/RGO composites. The magnetic hysteresis measurement reveals the superparamagnetic character of PPy/Fe3O4/RGO and PANI/Fe3O4/RGO composites at room temperature. These composites exhibit excellent electromagnetic absorption properties, such as wide frequency band and strong absorption, espeacially absorption at low frequency. The remarkable electromagnetic absorbing properties of PPy/Fe3O4/RGO and PANI/Fe3O4/RGO composites can be attributed to the multiple absorbing mechanisms.3. The ternary composites of Ag@Fe3O4/RGO were synthesized by a facile one-pot solvothermal route. Interestingly, plenty of Ag/Fe3O4 core/shell particles are well-distributed on the surface of RGO nanosheets. The magnetic hysteresis measurement reveals the superparamagnetic character of Ag@Fe3O4/RGO composites at room temperature. The introduction of Ag nanoparticles has lowered the e of the Fe3O4/composites, and improved the equality of ε andf μ, which helps to improve the level of impedance matching. Because of their synergetic effect, interficial polarization, dielectric loss and magnetic loss, these composites exhibit excellent electromagnetic absorbing properties. Moreover, for Ag@Fe3O4/RGO composites, the electromagnetic absorbing properties can be tuned easily by varying the Ag/Fe3O4 ratio and thickness of the samples.