The Preparation And Properties Of Functional Graphene Films

With the development of science and technology,a large number of electronic devices have emerged which would inevitably produce much electromagnetic wave with different frequency and wavelength.The electromagnetic wave not only affects the normal use of a variety of electronic devices,but also causes serious harm to people's physical and mental health.Therefore,how to develop advanced electromagnetic shielding materials has become an urgent topic.According to the research,graphene is now known to be the one of the best materials with high conductive performance and mechanical properties,which also has excellent thermal conductive,light weight and other advantages.So the graphene is the best choice for the preparation of electromagnetic shielding materials.Herein,the purpose of this research topic is preparing the electromagnetic shielding graphene films,and try to reduce the thickness and increas the tensile properties of the films while ensuring the electromagnetic shielding performance at the same time.The contents of this subject are as the following parts:1.Study on properties of PEI-rGO thin films.Firstly,natural graphite sheets were oxidized via Hummers method to introduce oxygen-containing functional groups on their surfaces to obtain graphene oxide(GO).Secondly,branched polyethyleneimine(PEI)was added to the GO to obtain PEI-GO thin films.The massive amine groups of PEI can not only occur amide reaction with the carbonyl groups of GO,but also nucleophilic substitution reaction with the epoxy groups.The experimental results show that the PET is grafted on the surfaces of GO by covalent bond and the interlayer spacing of GO films is increased.Thirdly,the PEI-GO thin films were reduced by high temperature to obtain PEI-rGO thin films.The experimental results suggest that,after high temperature reduction,the PEI-rGO films have excellent electrical conductivity which can reach 7.69 x 104 S·m-1.The electromagnetic shielding effectiveness of the PEI-rGO thin films is around 30 dB,and the reflection and absorption of electromagnetic wave can reach 99.9%.At the same time,the tensile strength of PEI-rGO films can achieve(18.0±0.75 MPa).2.Study on properties of PEI-rGO/PAN thin film.Firstly,we get PEI-rGO/PAN thin films,.After high temperature,the PEI-GO/PAN thin films were reduced to PEI-rGO/PAN thin films.The experimental results suggest that,after high temperature reduction,PEI-rGO/PAN films have excellent electrical conductivity which can reach 7.14×104 S·m-1,and the addition of PAN has almost no effect on the electrical conductivity of the films compared with the PEI-rGO thin films.But compared with pure rGO films(4.34×104 S·m-1),the electrical conductivity has been greatly improved.The electromagnetic shielding effectiveness of the PEI-rGO/PAN thin films is around 30dB,and the highest one can reach 34 dB.Similarly,the addition of PAN has almost no effect on the electromagnetic shielding effectiveness of the films compared with the PEI-rGO thin films.But compared with pure rGO films(22 dB),the electromagnetic shielding effectiveness has been greatly improved.At the same time,the tensile strength of PEI-rGO/PAN films can achieve(21.6±0.51 MPa),compared with the PEI-rGO thin films,the tensile strength has increased 22.2%,and compared with the pure rGO films(4.0±0.65 MPa),the tensile strength has increased 450%.3.The effect of pH value on the properties of GO films.Firstly,after comparing different obtained GO via different methods,we chose the better S-GO to do the next experiments.With the pure S-GO as the matrix,we can obtain GO films with excellent properties by adjusting the pH value of the GO hydrosol.The experimental results suggest that,when the pH value of GO hydrosol is about 8-9,the obtained films exhibit the best structure,closely packed and orderly.Specifically,the tensile property can achieve as high as 205.0-231.5 MPa.In order to maintain the excellent tensile property,we obtain the rGO-9 thin films by HI acid reduction,whose tensile property can achieve(310.0 ± 8.02 MPa),which has increased 37.7%compared with GO-9 thin films.At the same time,the rGO-9 films have excellent electrical conductivity which can achieve 2.54×104 S·m-1.And when the thickness is only 10 ?m,the electromagnetic shielding performance can achieve 39.2 dB,that means the reflection and absorption of electromagnetic wave can reach 99.987%,which has reached the requirement of civil use.