The Study On Electromagnetic Shielding Performance Of Fe₃O₄ Nano-Particle Synergistically Enhanced Graphene /Waterbornepolyurethane Composite Films

Magnetic and conductive composite materials are the electromagnetic radiation protection materials, which have the characteristics of light, thin, absorption band width, the high efficiency, low cost and easy to use. This kind of material can be used in medical, military, aviation, electronics and other fields. Therefore, it has higher application value.In this paper, the magnetic and conductive composite materials with different contents are prepared by using Fe₃O₄ load on the graphene as electromagnetic shielding filler and water polyurethane （WPU） as matrix, and its properties have been studied.Firstly, the nano Fe₃O₄ are loaded on the surface of the graphene oxide （GO） by coprecipitation method and hydrothermal method respectively. And then get graphene@Fe₃O₄ composite particles by reducing. The graphene@Fe₃O₄ are characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy and scanning electron microscopy,then the properties of electrical properties and magnetic detection are tested. The results showed that: the composite particles have significantly lamellar structure and iron oxide particle loads evenly bycoprecipitation, while its organic solution has good dispersion stability. Therefore, we can get the better performance of composite particles by coprecipitation through the microstructure dispersion stability factor, resistivity, magnetic, and other experimental conditions. And optimal experimental scheme is:200ml 6mg/ml aqueous graphene oxide, adjusting pH>11, added reactants Fe2+/Fe3+ molar ratio of 1:1.7, the Fe₃O₄ loading amount of 1.2g, the hydrated 16ml of hydrazine reduction 5h, and it can obtain good performance of composite particles.Secondly, to prepared graphene@Fe₃O₄/waterborne polyurethane composite materials, with the composite particles and waterborne polyurethane blend by ultrasound. The distribution of GNs@Fe₃O₄ composite particles in the composite filmsby scanning electron microscopy, transmission electron microscopy. The mechanical properties, thermal stability, magnetic, electrical and electromagnetic shielding performance of composite materials are studied.The results showed that:the composite particles have excellent conductivity, and its saturation magnetic intensity can reach 20.15emu/g. In addition, the mechanical properties, thermal stability and electrical properties of the composite materials can be improved greatly when added an appropriate amount of composite particles. When the composite particles is 3%, the tensile strength of the composite material can reach 27.5 Mpa from the original 22.3 Mpa, and its conductivity can reach 0.7 S/m. Besides, saturation magnetization intensity can reach 4.03 emu/g. Finally, when the composite particles reached 5%, the electromagnetic shielding effectiveness of composite coatings can reach 36dB in 8.2-12.4GHz frequency range.