Study On Low-cost Preparation And Microwave Absorbing Performance Of RGO/CNTs Composite Foam

With the rapid development of information technology,electromagnetic pollution is becoming more and more serious.The main means to prevent and control electromagnetic pollution is to develop electromagnetic shielding materials,reflection and absorption are the two main means.And absorbing materials have attracted much attention because of their advantages of being green and not causing secondary electromagnetic pollution.Among many absorbing materials,carbon material has the advantages of light weight,multipolarization and adjustable dielectric properties,and has become a hot research material in the field of absorbing in recent years.However,in previous studies,carbon materials were prepared with complex molding methods and high costs.At the same time,due to the single absorbing mechanism,the effective absorption bandwidth of carbon materials is narrow,which limits the application of carbon materials in the field of absorbing waves.In this paper,air template method and ice template method will be used to composite one-dimensional carbon nanotubes and two-dimensional graphene to obtain three-dimensional porous sponge,giving full play to the advantages of multipolarization to achieve the preparation of low-cost,broadband absorbing materials.In this paper,surfactant and high speed mechanical stirring were used to introduce air bubbles as templates into GO dispersions,and GO gelated under the action of reducing agent.Following by air drying and high temperature heat treatment,lightweight RGO sponge materials were prepared.The RGO sponge has a self-supporting three-dimensional porous structure characterized by SEM.And Raman spectra showed that there were many defects in the RGO.At the same time,the performance of RGO/CNTs composite sponge with different GO:CNTs ratio was studied.The absolute reflection loss coefficient and effective absorption bandwidth(<10 d B)of the composite sponge are improved after the addition of CNTs.When GO:CNTs is 9:1(wt %),the minimum reflection loss coefficient of the composite sponge at 4.0 mm and 10.478 GHz is-59.366 d B.When GO:CNTs were 7:3(wt %),the effective absorption bandwidth of the composite sponge at 3 mm thickness reached 8.072 GHz(9.928～18.000 GHz).In order to further reduce the sample shrinkage and improve the porosity of the sponge,a three-dimensional RGO /CNTs composite sponge was prepared by inducing ice crystal as the second template,which growth in a low temperature environment after the introduction of air bubbles.When the composite sponge obtained the maximum reflection loss,the frequency moved to high frequency.When GO:CNTs is9:1(wt %),the minimum reflection loss coefficient of the composite sponge at 14.303 GHz is-40.806 d B,and the thickness is 3.0 mm.When GO:CNTs is 7:3(wt %),the effective absorption bandwidth of the composite sponge at 3.0 mm thickness is 8.054GHz(9.946～18.000 GHz).In addition,the prepared RGO/CNTs sponge still has a certain compressive resistance and thermal stability,which further expands its potential application range.