Effect Of Graphene And Graphene Nanoribbons Modification On Electromagnetic Properties

Absorbing material is an important military stealth functional materials,graphene material has many excellent properties such as low density,theoretical surface area high electrical conductivity,which is a very promising absorbing material.But Graphene with null band gap is difficult to control his dielectric properties,which cause the application is limited.The bandgap of graphene can be generated by quantum confinement or chemical doping,and the doped heteroatom can effectively regulate its electronic structure and other intrinsic properties.In this paper,the electromagnetic parameters of graphene were controlled from three aspects: nitrogen-doped graphene,different degree of oxidation degree of graphene nanoribbons and nitrogen-doped graphene nanoribbons,finally we can obtained a excellent absorbing materials.Nitrogen-doped graphene(NG)with different nitrogen content was prepared by changing the mass of graphene and urea by hydrothermal reduction using fumed graphene as raw material and urea as nitrogen source.Graphene oxide nanoribbons(GONR)with different degree of oxidation was prepared by longitudinally unzipping multiwalled carbon nanotubes via controlling the ratio of carbon nanotubes and potassium permanganate.Nitrogen-doped graphene nanoribbons(NGNR)was prepared by hydrothermal method with urea as nitrogen source.The microstructure of NG is a kind of porous lamellar structure,which is beneficial to the absorption of electromagnetic waves.The addition of nitrogen and reduction of graphene enriched is carried out at the same time in nitrogen doping process.The interplanar spacing of NG doped with nitrogen becomes smaller,with a large specific surface area.The atomic percent of 10 NG,30NG,50 NG were 8.54%,7.52% and 7.61% respectively.NG contain higher the nitrogen content,and graphene has.the more lattice defects.There are three kinds form nitrogen doping as pyridine type(pyridinic),pyrrole type(pyrrolic)and graphite type(graphitic)in NG materials,and the dominant kind are pyridine type and pyrrole type.GONR with higher degree of oxidation has higher functional group the C = O ratio,and the ribbon opens larger.GONR is reduced during the NGNR nitrogen doping process,whose the edge of the oxygen-containing functional groups greatly reduced,making NG interlayer spacing larger.The nitrogen content of 3NGNR,5NGNR,7NGNR is 3.53 at%,3.76 at%,4.77 at% respectively.The prepared NG,GONR and NGNR were mixed with paraffin and the sample mass fraction was 30%.The inner diameter was 3mm,the outer diameter was 7mm,and the thickness of the ring was about 3mm.The electromagnetic parameters were measured and material loss angle and reflection loss(RL)were calculated.For NG,50 NG with the thickness of 3mm,the RL <-10 dB frequency band is 8.14-12.84 GHz,the effective bandwidth of 4.7GHz,at 9.84 GHz to achieve the maximum absorption of-16.03 dB.For the GONR material,5GONR with thickness of 3mm,RL <-10 d B frequency band is 9.4GHz-18 GHZ,bandwidth of 8.6GHz,the frequency of 12.5GHZ has a maximum reflection consumption of-23 dB.For the NGNR material,7NGNRwith 3mm thick,RL <-10 dB frequency band is from 7GHz to 11 GHz,the bandwidth of 4GHz,the frequency of 9GHZ maximum reflection loss of-45 dB.Compared with graphene,the absorbing properties of nitrogen-doped graphene and graphene nanotubes prepared by quantum confinement or chemical doping are greatly improved,which is favorable for the preparation of high performance absorbing composites.