Preparation And Microwave Absorption Property Of Electromagnetic Functionalized Carbon Nanofiber And Its Composites

With the rapid development of contemporary society,electromagnetic wave pollution has become a serious social problem affecting people’s lives.In the military field,the progress of radar detection technology also required that large-scale military equipment on the battlefield be avoided by the enemy and become an important factor in winning modern warfare.Thus,electromagnetic shielding and absorbing material came into being.Since the 1960s,absorbing materials have received widespread attention from researchers.Preparation of absorbing materials with more excellent performance,achieving the overall goal of“thinness,lightness,wideness,and strength”of absorbing materials,has important practical value for civil and military applications.In this paper,an electromagnetically functionalized carbon nanofiber was prepared.Firstly,Fe₃O₄ was coated on the surface of carbon nanofibers by chemical co-precipitation method.Subsequently,the PANI@Fe₃O₄@CNFs nanoparticle with a three-phase heterostructure was prepared by introducing a polyaniline coating by in-situ polymerization.FT-IR,XRD,XPS,SEM and other tests showed that the nanoparticles with good structural stability were successfully synthesized.The epoxy resin with excellent comprehensive performance was selected as the matrix,and PANI@Fe₃O₄@CNFs was used as wave absorbing filler to prepare the wave absorbing composite material.The results showed that with the increase of the filler mass fraction,the wave-absorbing performance of the material also increased.When the filler content was 15 wt%,the minimum RL of the sample occurred at 13.6 GHz,reaching-23.7 dB with a layer thickness of 2 mm,and the corresponding absorption bandwidth（<-10 dB）was approximately 3.7 GHz in the 11.9¹5.6 GHz range.After the polyaniline was coated,it helps to improve the compatibility between the nanoparticles and the epoxy resin,adjusted the impedance matching of the material,enhanced the attenuation loss of the electromagnetic wave inside the nanoparticles,and improved the microwave absorbing performance.Subsequently,the carbonyl iron powder magnetic material and the PANI@Fe₃O₄@CNFs nanoparticle were blended as a microwave absorber to study the microwave absorbing properties of the composite.The results showed that the content of the fixed PANI@Fe₃O₄@CNFs nanoparticles was 5 wt%.With the increase of the mass fraction of carbonyl iron powder,the wave absorbing effect of the composites increased.When the carbonyl iron content was 50 wt%,the minimum RL of the PFC-CIP50 occurred at 11.6 GHz,reaching-15.9 dB with a layer thickness of 2 mm,and the corresponding absorption bandwidth（<-10 dB）was approximately 3.7 GHz in the10.2¹3.9 GHz range.The magnetic losses of materials were mainly natural resonance and eddy current losses.With the introduction of PFC nanoparticles,the dielectric constant of the material was improved under the condition of ensuring the magnetic permeability,and the impedance matching and attenuation characteristics were enhanced,and the density of the material was reduced under the condition of ensuring the wave absorbing effect.Combined with the metamaterial theory,the PFC-CIP50 composite material was selected and its patterning process was designed to design a dual-layer metamaterial broadband absorber（MMA）with an artificial periodic structure.A numerical simulation method was used to study the influence of the periodic structure parameters on the absorber properties of metamaterials.The results show that the absorber of the designed metamaterial has an absorption bandwidth of 11.2 GHz（from 6.8 to 18 GHz）.With the thickness increased,the absorption curve shifted to a low frequency,and the position of the absorption peak can be changed by designed the structural parameters.Subsequently,a square-shaped open metal resonant ring was combined with MMA to realize further widening of the wave absorbing frequency band and controllable design of the C-band absorption peak.