Microwave Absorption Property Of Graphene/Ag Nanowires Composite

The prevalence of digital devices and the rapid development of radar detecting technology can make our life more convenient.But these also generate a large amount of electromagnetic pollution and make a remarkable negative effect on physical health.Microwave absorbing materials can effectively eliminate the harm of electromagnetic waves and provide protection for public safety.In the high-tech field,electromagnetic protection plays a vital role in the development of precision instruments;in the military field,absorbing materials can protect military personnel and weapons from electromagnetic interference to enhance combat effectiveness.However,the traditional absorbing materials have the defects of single loss mechanism,narrow bandwidth and high density.The comprehensive performance of these materials is difficult to meet the requirements of modern commercialization and militarization with the performances of thin thickness,light weight,strong absorption capacity and wide absorption bandwidth.In this paper,a variety of schemes were designed to prepare reduced graphene oxide,and dispersed RGO in epoxy resin matrix to obtain the absorbing materials.A variety of tests and characterizations show that graphene with high degree of reduction has better dielectric loss performance.In addition,nano-surface effect is employed to promote the self-assembly of graphene and silver nanowires to form 3D network nanostructures.The RGO with strong dielectric loss capability and AgNWs with high conductivity can create a synergistic effect.It not only improves the impedance matching characteristics but also enhances the attenuation ability of electromagnetic energy,and a composite material with excellent microwave absorbing properties is obtained.It provides a new idea for the field of electromagnetic wave absorption for graphene and silver.The main contents are as follows:(1)RGO was prepared with VC method and HI method respectively,and the degree of reduction of RGO was controlled by changing the amount of VC.In the VC method,the reduction degree of RGO increases as the amount of VC increases,while the relative content of carbon atoms in the RGO-HI sample is as high as 85.7% which has the highest degree of reduction.The results show that RGO with high degree of reduction has a stronger dielectric loss capability.In the epoxy resin matrix,the RGOHI composite has the most excellent absorbing performance.When the RGO addition is only 1 wt%,the absorber with 2.5 mm thickness has the reflection loss peak-10.1 dB at 16.6 GHz,and its absorbing effect is mainly due to the high reduction degree of RGO,which cause more dielectric loss mechanisms such as electron polarization delay,resistance loss and interface polarization delay.(2)High-purity silver nanowires with uniform size were prepared by ethylene glycol reduction method.The microwave absorbing effect of single-component AgNWs in the resin matrix was not obvious.When the amount of AgNWs reached 15 wt%,the minimum reflection loss of the composite is only-4.2 dB.The silver nanowire has high conductivity but a single electromagnetic loss mechanism,so that the composite material has a high effective permittivity real part and a low imaginary part,resulting in extremely low impedance matching rate of the material,which make it difficult for microwaves to enter the interior of the material.(3)The 3D network nanostructured RGO-AgNWs composite with excellent absorbing performance was prepared by self-assembly of 1D AgNWs and 2D RGO by the nano-surface effect.The absorption capacity of the material increase as the amount of AgNWs increases.When RGO with a content of only 1 wt% was combined with 15 wt% AgNWs,the composite has excellent absorbing properties,and the RGOAgNWs3 absorber with a thickness of 1.8 mm has the strongest absorption peak(-33.2 dB)at 11.5 GHz with an effective absorbing bandwidth of 3.3 GHz(9.9 to 13.2 GHz).This remarkable absorbing effect is due to the synergistic effect of AgNWs and RGO,which greatly improves the dielectric imaginary part of the composite.On the one hand,it effectively increases the impedance matching ratio,and on the other hand,the attenuation ability of the incident electromagnetic wave is greatly enhanced.Therefore,the shortage of AgNWs and RGO alone as the absorbing agent is compensated.