Heterostructure Design And Electromagnetic Wave Absorption Of Carbon Matrix Composites

With the development of electronic communication technology,the electromagnetic wave pollution has becoming serious,and the requirements for electromagnetic wave absorbing materials are highly increasing.Carbon-based materials have attracted more and more attention in microwave absorption(MA)applications due to their advantages of simple synthesis process,low density,good electrical conductivity,corrosion resistance,and stable chemical properties.However,due to the single loss mode of the carbon material and the unsatisfactory expansion of the spatial structure,its MA performance has been greatly restricted.In this paper,we describe the latest findings in the MA field and show our recent results about the relationship between designed heterostructure and corresponded MA performance on the two-dimensional transition metal carbides and three-dimensional graphene composites.In this paper,based on the unique accordion structure,large two-dimensional specific surface area and abundant terminal functional groups of Nb2CTx MXene was studied,and Nb2O5-Nb2CTx-Nb2O5 sandwich heterostructure composites were designed and prepared by rapid microwave-assisted hydrothermal method.The introduction of Nb2O5 heterogeneous component could improve the poor impedance matching caused by high conductivity of pure Nb2CTx,change the channel of electromagnetic wave into the absorber,and let more electromagnetic waves into the absorber.On the other hand,Nb2O5 with different morphologies(columnar and irregular granular)was successfully synthesized in situ between the layers of Nb2CTx MXene.Compared with pure Nb2CTx,Nb2O5/Nb2CTx composites exhibited enhanced MA properties,especially for Nb2O5/Nb2CTx composites with columnar Nb205(c-Nb2O5/Nb2CTx).The minimum reflection loss(RL)value reached-44.1 dB at 2.8 GHz with a thickness of 5 mm,indicating that approximately 99.99%of the incident microwaves were absorbed.The special morphology of the columnar heterostructure Nb2O5,the increased lamellar spacing of the Nb2CTx,and the optimized impedance matching characteristic were all important factors that contributed to the enhanced MA performance.In addition,as a traditional two-dimensional dielectric loss material,graphene is often used in MA field.We prepared three-dimensional micro-porous graphene(PG),and then synthesized ZnO/ZnFe2O4/C@PG porous composites by synchronous reflux strategy using porous graphene network and MOF as precursor.As multi-component composites,the component of ZnO/ZnFe2O4/C will provide excellent dielectric loss and certain magnetic loss,while the PG conductive network can create more electronic transmission paths and significant conductive loss.The unique porous structure increases the probability of multiple reflection and scattering,which contributes to the high electromagnetic loss capability of ZnO/ZnFe2O4/C@PG.The minimum reflection loss(RL)value of ZnO/ZnFe2O4/C@PG could reach-54.6 dB at frequency of 9.04 GHz with thickness of 2.7 mm,and the effective absorption bandwidth(RL<-10 dB,EAB)covered as wide as 5.36 GHz.This result demonstrates that ZnO/ZnFe2O4/C@PG composites have promising potential as tunable,broadband and high-performance microwave absorber.