A Controllable Preparation And EMI Shielding Performance Of Flexible Three-dimensional Conductive Graphene Sponge

Graphene is the hottest two-dimensional carbon material at present,owing to its unique sheet structure and super performance in the acoustics,optics,electronics,thermal and mechanics.Three-dimensional graphene material is a form of graphene application.It is of great significance to study high performance three-dimensional graphene materials for its wide use in electromagnetic shielding,pressure sensor,catalytic adsorption and etc.This paper introduces and analyzes the related research and fabrication process of three-dimensional graphene sponge.We propose an improved two-step reduction method to reduce Graphene oxide(GO)precursor,successfully getting a flexible three-dimensional conductive composite of graphene/polyurethane(PUG)sponge with excellent functions in mechanical electrical and electromagnetic shielding.This product has not only remained good electrical conductivity and high specific surface area of graphene sponge,but also inherits the flexibility and stability of the polyurethane sponge.The three dimensions graphene plays an important role of the PUG sponge as an efficient conductive filler.The main work of this thesis consists of three parts.(1)Firstly,the difference between one-step hydrothermal reduction method and direct reduction of graphene oxide was studied in theory and experiment.Then we use this two-step pre-frozen method to gain partially reduced the graphene oxide(PRGO)nanosheets and controllable adjustment was applied to the intermediate product,which can increase the binding force of the?-?bond between the graphene nanosheets owing to the reduction of partly graphene oxide.The ice template was introduced to provide an external regulation to make sure the three-dimensional conductive network is ordered and compacted in the graphene sponge.After lyophilization,we obtained the related PUG sponge product and characterized it by morphology and structure test.The characterization results show that this method can not only efficiently reduce graphene oxide,but also can effectively control the reduction process thus taking control of the PUG sponge.(2)Secondly,we characterized PUG sponge after preparing the three-dimensional PUG sponge.The characterization results show that the three-dimensional graphene structure prepared by this method has uniform pore size,the same element and functional group distribution as reduced graphene oxide in literature.Similarly,it is proved that the PUG sponge prepared by this method has excellent microstructure and high degree of reducibility.At the same time,we also tested the conductivity,pressure resistance effect and cycle performance of the PUG sponge and found that it exhibited a good correlation between electrical conductivity and approximately linear pressure resistance.This property makes the PUG sponge have an adjustable resistivity which could be used to detect pressure.(3)Finally,we did a related test on the electromagnetic shielding performance of the PUG sponge in the X-band.We tested the thickness of the material,the content of graphene,the frequency band of the electromagnetic wave,etc.The final experiment showed that the PUG sponge showed a superior electromagnetic shielding performance,the electromagnetic shielding effect per unit density is654-789dB.cm~2/g.What is more,we compared it with similar graphene and similar electromagnetic shielding products reported recently,getting the fact that it processed superior EMI shielding performance than most products,low density,excellent flexibility.It exhibited a bright future in EMI shielding for many military and civilian occasions.