Study On Graphene-based Transparent Electromagnetic Shielding Film

Electromagnetic interference(EMI)from radio frequency radiation is becoming a rising problem with the rapid development of current electronic technology and wireless communication technologies.To solve this severe problem,electromagnetic shielding technique based on the electromagnetic shielding materials,e.g.,metal materials,has been proposed as an efficient way for preventing the electromagnetic interference.However,most traditional electromagnetic shielding materials are non-transparent,solid and large-weight.It is difficult to meet the needs of future wireless communication systems with traditional electromagnetic shielding materials since the flexibility and transparency of the materials should be considered.Therefore,it is necessary to find a lightweight,flexible,transparent material to replace the traditional electromagnetic shielding material.Graphene nanosheets(GNS),a two-dimensional nanomaterial,have excellent properties such as conductivity,light transmission,and absorbing properties,which have caused widespread concern among scientists in the field of electromagnetic shielding.In this paper,to maximize the EMI shielding effectiveness(SE)is used to combine metal nanowires and graphene.A graphene-based transparent EMI shielding film is prepared by two-step spin coating method,and its properties are studied in Ku and K bands,respectively.The research work and results of the thesis are as follows:Firstly,the parameters affecting the EMI SE and light transmission of the film are investigated analytically.Then the trade-off between the EMI SE and transparency is carefully considered by utilizing the structural characteristics of both graphene and metal nanowires.Secondly,preparing methods of the GNS/AgNWs film is presented in this thesis.The liquid phase stripping method is employed to prepare the GNS with adjustable conductivity.The uniformly dispersed AgNWs is then prepared with the aid of the improved polyol method.As a result,the GNS/AgNWs film is achieved by using the two-step spin coating method.The light transmittance of the three films at 400-800 nm and the EMI SE at the Ku band and the K band were analyzed experimentally.Owing to the high transparency,good conductivity,and homogeneous distribution of both GNS and AgNWs,the obtained GNS/AgNWs film exhibits superb EMI SE and light transmittance,yielding a significantly high EMI SE up to 26 dB in both Ku-band and K-band and light transmittance higher than 78.4%.Finally,the stability of the film was tested and analyzed.The resistive stability results of the prepared GNS/AgNWs film showed that the resistance of the film was almost unchanged after bending.Moreover,the film could be restored to the original shape after bending,which also proved that the structural show good stability.Most importantly,the EMI SE of composite films and AgNWs films are also measured before and after bending.It is shown that after bending the AgNWs film the results were reduced while the GNS/AgNWs film still show same EMI SE performance in the Ku/K band.In addition,our results also shown that the EMI SE of the AgNWs film decreased while the GNS/AgNWs film remained unchanged after stewing for one month.It is confirmed that the GNS/AgNWs film have excellent chemical stability.The proposed two-step spin coating method in this thesis is proven to be a simple and operability way for preparing the graphene-based transparent EMI shielding film.The GNS/AgNWs film prepared by this method has excellent EMI SE and structural stability and also show great potential in the application of flexible,lightweight and transparent EMI shielding devices and smart electronic products.