Preparation Of Waterproof Carbon Nanotube/Graphene Hybrid Film With Pority And Strong Electromagnetic Shielding

Electromagnetic interference（EMI）shielding is an isolation,which can isolate the electromagnetic fields between two spatial areas to reduce the harmful effects on communication systems,sensitive electronics and living organisms.According to electromagnetic theory,the main mechanism of EMI shielding is composed of reflect radiation from impedance mismatch and attenuate wave energy from dielectric loss or magnetic loss.Therefore,the shields with high electrical conductivity will demonstrate high EMI shielding effectiveness（SE）.Metals,carbon and polymer composites have been widely studied as EMI shielding materials for their electrical conductivity.However,it is difficult to further improve the EMI SE only considering their electrical conductivity and permeability.Therefore,it is still a big challenging to fabricate shielding materials with high EMI SE.Herein,we proposed a bubble structure to improve the EMI SE of the shield.In addition,the shield indicates an excellent waterproof and flexible property.（1）Based on the porous structure of Graphene,the CNTs/GO hybrid film was prepared by CVD method by introducing GO into CNTs.Further,the CNTs/GO hybrid film was reduced in two steps for constructing a porous and layered structure,which is suitable for multiple reflections in the interior of the shield.Then,the SiO₂/GO solution was sprayed on the surface of the hybrid film before the second reduction.And thereby the surface of the CNTs/GO hybrid film was changed to hydrophobic and formed waterproof property.（2）Due to the multilayer structure of graphene and the generated gases from the thermal reduction of GO,the oxygen-containing functional groups of GO in the CNTs/GO hybrid film would be partially eliminated at chemical reduction and low-temperature thermal reduction processes,and the bonding between them would be broken and formed gases.These gases will stretch the layer structure of the hybrid film.And it will increase the interlayer spacing of the graphene sheets.Then the interior of the hybrid film would be expanded and formed porous layered structure,which exists on the surface of the hybrid film as bubbles.The obtained hybrid film indicates flexible,and the morphology of the shield has negligible change even after multiple rubbing operations,which suggests their potential applications.（3）The static contact angle and rolling angle of the hybrid film were tested after surface of the SiO₂@CNTs/r GO was coated by small SiO₂particles.The results showed that the hydrophobic property of the SiO₂@CNTs/r GO was successfully constructed,the static contact angle could reach155°and the roll angle is smaller than 5°.The hydrophobic and self-cleaning experiments show that the hybrid film could be used in practical applications.The EMI SE of the SiO₂@CNTs/r GO hybrid film has been also tested by the waveguide method.The results indicate that the SE of the hybrid film was improved significantly.After the electrical conductivity measurement,rolling experiment,theoretical and experimental comparison,it can be concluded that the improvement of the SE is closely related to the porous layered structure formed by the internal expansion,and the electromagnetic waves were attenuated in the porous structure.More porous structure in interior,more waves can be multiple reflected,and it results the loss of the electromagnetic wave in the shield.