Research On Absorbing Characteristics Of Boron And Nitrogen Co-doped Carbon Nanotubes Coated Metal Nanoparticles/Reduced Graphene Oxide

Due to its high thermal conductivity,moderate dielectric constant,and large specific surface area,graphene has attracted widespread attention in the field of electromagnetic wave(EMW)absorption.However,graphene has only dielectric loss and almost no magnetic loss,and its poor impedance matching limits its practical application in EMW absorption.Many functional groups are attached to the surface of graphene,which makes it have a certain degree of dispersibility in aqueous or organic solutions,so other functional materials can be easily anchored or grown on the surface.Therefore,combining nanomaterials with magnetic loss or dielectric loss with graphene to form a graphene-based nanocomposite can greatly improve the EMW absorption property of graphene.In this paper,boron-nitrogen co-doped carbon nanotubes wrapped the metal nanoparticles/reduced graphene oxide composites were successfully prepared by means of room temperature chemical synthesis and annealing treatment,and the structure characterization and EMW absorption properties of these composites were studied.The main contents are as follows:1.The precursor Cobalt-based borate nanosheets(Co-Bi NS)and Fe-based borate nanosheets(Fe-Bi NS)composite materials were prepared by the room temperature chemical synthesis method,and then heat treatment was carried out.During this process,these materials were reduced to Co and Fe nanoparticles and acted as catalysts to form boron and nitrogen co-doped carbon nanotubes.After freeze-drying treatment,boron and nitrogen co-doped carbon nanotubes coated Co Nanoparticles/reduced graphene oxide(Co@BNCNT/rGO)and boron and nitrogen co-doped carbon nanotubes coated Fe Nanoparticles/reduced graphene oxide(Fe@BNCNT/rGO)nanocomposites were obtained.2.These samples were characterized to explore their morphology,structure,and other information.Previous reports found that boron-nitrogen co-doped carbon nanotubes could grow uniformly on the reduced graphene oxide sheet,and most of the metal nanoparticles were wrapped in the boron-nitrogen co-doped carbon nanotubes with good crystallinity.Co@BNCNT/rGO shows a good morphology with the average diameter of Co nanoparticles and carbon nanotubes are about 20 and 25 nm,and the tube wall thickness is between 2-9 nm.In addition,Raman measurement shows that there are many defects in Co@BNCNT/rGO,which can cause defect polarization.It is also found that Co@BNCNT/rGO has good ferromagnetic properties by vibrating sample magnetometer,which is beneficial to EMW absorption.3.Co@BNCNT/rGO has high conductivity,a large number of defects,and a three-dimensional structure with multiple interfaces.Experimental results show that the introduction of rGO can adjust the dielectric loss and impedance matching characteristics of Co@BNCNT/rGO.Density functional theory was used to investigate the charge arrangement of the structural system for Co@BNCNT/rGO.It was found that the electron could transfer from the metal Co to the boron nitrogen doped carbon nanotubes,created a spatial electric field in the interface region,and causes the interface polarization relaxation,which is beneficial to improve EMW absorption properties of Co@BNCNT/rGO.4.The electromagnetic parameters and reflection loss of Co@BNCNT/rGO and Fe@BNCNT/rGO were performed.After mixing 20 wt% of the nanocomposite with a paraffin matrix,the Co@BNCNT/rGO has a minimum reflection loss of-42.31 d B at the matching thickness of 2.5 mm,and the effective absorption bandwidth is 3.28 GHz under the matching thickness of 2.0 mm;the reflection loss value ranging from 1.5 to 5.0 mm are all less than-20.0 d B.Fe@BNCNT/rGO has a minimum reflection loss of-43.55 d B and effective absorption bandwidth of 3.28 GHz at the matching thickness of 2.5 mm,and the mass ratio of nanocomposite into paraffin matrix is 40 wt%.The above results all indicate that Co@BNCNT/rGO and Fe@BNCNT/rGO have good EMW absorption properties.In summary,in order to obtain a "thin,light,wide,and strong" EMW absorbing material,this paper adopts a simple method to controllable synthesis of several graphene-based nanocomposites,which all show strong EMW absorption characteristics.The research content of this paper provides new ideas for graphene-based nanocomposites in the field of EMW absorption.