Research On Synthesis Of Graphene Composites And Their Electromagnetic Shielding Performance

With the development of science and technology, electromagnetic pollution widelyexists in the environment. Absorbing electromagnetic wave is one of the effective ways ofprevention and control of electromagnetic pollution. So the demand for absorbing materialsincreases. Strong absorption, wide band, light, thin thickness of absorbing material is thedevelopment direction of the future absorbing material.Due to its high dielectric loss and low density graphene is an effective electromagneticwave absorption material. However, high permittivity and low permeability of the highquality graphene lead to the low impedance matching characteristics and then affect itsabsorbing performance. Therefore, this paper prepared the reduced graphite oxide RGO bychemical reduced graphite oxide. Compared with high quality graphene, RGO with lowerpermeability has better impedance matching characteristics. High-quality grapheneabsorbing performance is weak. With the thickness and defects increase the absorbingproperties slightly increase. The maximum reflection loss of KNG-180was only-0.85dB.RGO absorbing performance was much better than the high-quality graphene. Thereflection losses at7.4GHz peak reached-6.88dB.Prepared RGO/nitrile rubber(NBR) composites by mixing RGO and NBR in xylenesolvent, curing to elastomer at room temperature. Due to the great dispersibility, grapheneabsorbing material with NBR matrix helps improve the absorbing properties. RGO in NBRmatrix uniformly dispersed in the NBR matrix with layered and porous structure. Thereflection loss is quite high with mass radio of RGO10%. In2mm thickness, in thefrequency range of14.6GHz~18GHz the reflection loss is below-10dB, and theminimum reflection loss reaches-38.70dB at16.2GHz. RGO/NBR composite combineslightweight, high electromagnetic wave absorption properties of RGO with high flexibility,machinability and heat resistant performance of NBR. RGO/NBR composite can bemade into structural absorbing material with broad prospects for development.Spherical carbonyl iron powder has absorbing properties in2~18GHz, but has thereflection loss at-10dB or less only at a very narrow bandwidth in16~18GHz. RGO/carbonyl iron powder composite material was prepared and the microwave absorbingperformance was studied by the method of simple wet-chemical method. Compared withthe previous reports of microwave absorbing material, wave absorption performance ofRGO/carbonyl iron powder composite absorbing material was superior. The ratio of qualitywas3:20between graphite oxide and carbonyl iron powder. It can produce strong and wideabsorption peaks with center around9.4GHz and the peak is-52.18dB under thickness of3mm. In the range of7.8~11.6GHz, the reflection loss is less than-10dB, and less than-10dB in the range of8.8～10.0GHz. The composites with both magnetic loss anddielectric loss, is conducive to realize impedance matching and absorption band broadening,and can reduce the density of the composite.