Broadband Mircowave Absorption Fe₃O₄/C Nano-composite Design And Mesoscopic Ordered Structure Control

When electromagnetic wave(EMW)communication technology is widely used by mankind at contemporary era,the resulting EMW pollution has a huge negative impact on social production.At the same time,in military the continuous upgrading of stealth and electronic countermeasure technology has spawned and stimulated the development of electromagnetic wave absorption(EMA)materials.Fe₃O₄,as a traditional ferrite material,has been used in the field of EMA very early.However,as time goes by,Fe₃O₄gradually cannot meet the modern requirements of"thin absorber thickness,light weight,wide absorption frequency bandwidth and strong absorption".Therefore,this paper studies the related research literature,summarizes and proposes improved methods for nanometerization,carbon composite and microstructure design.But the absorption range of Fe₃O₄/C composites is mostly located at high frequencies,and there is currently a lack of structural explanations for the broadband absorption performance.Therefrom,this project is guided by theory and simulation,and designed the electromagnetic parameters of the required materials.Then the results guided the preparation of mesoscopically ordered Fe₃O₄/C nano-composites(F/C-O),and obtained broad and strong absorption performance at low frequency.Finally,by analyzing the material composition,structure and electromagnetic theory support,a suitable mechanism explanation of the structure and performance is proposed.The design simulation believes that the material must have multiple magnetic resonance peaks in the low frequency band and have strong magnetic loss.The electromagnetic loss must be dominated by the magnetic loss in the low frequency band which is very important for the goal of low frequency and wide absorption.This guides the preparation of the material from the aspect of magnetic loss.F/C-O preparation studies have shown that the morphology and properties of the materials are significantly affected by the preparation process.The determined reaction time of the precursor is 90 min,the heat treatment temperature is 500?and the mass fraction of the coaxial ring sample is 50 wt.%.According to the final F/C-O morphology and structure characterization,the Fe₃O₄ particle size is 12?14 nm and the thickness of the coated carbon layer is 1?2 nm,the carbon content is 12 wt.%.F/C-O has good EMA performance.With a matching thickness of 4.0 nm,a maximum reflection loss(RL)value of-51.51 d B appears at 9.44 GHz,achieving a strong absorption target.The effective absorption bandwidth under the same thickness is 6.72GHz(4.00?10.72 GHz),covering the C-band and most of the X-band.While achieving broadband absorption,the absorption range is broadened to the C-band,completing the absorption at low frequencies.By comparing the preparation of comparative samples and F/C-O,it is believed that the effective combination of Fe₃O₄ and carbon adjusts the electromagnetic parameters of the overall composite material,thereby improving the absorbing performance;the mesoscopically ordered structure design of the material makes the F/C-O has the characteristics of broadband absorption.F/C-O has the best impedance matching and attenuation constant in the entire test frequency band,which is one of the important reasons for broadband absorption.The quarter-wavelength theory can explain the strong absorption and low frequency absorption of ordered F/C-O.Among the factors of F/C-O loss ability,the dielectric loss mainly comes from the conductivity loss.The magnetic loss is provided by the resonance loss in the S and C bands.The eddy current loss is dominated by the loss in the X band.The strong magnetic loss plays a vital role in the absorption of low frequency,and the conclusion of the simulation is applied.Finally,this subject proposes a reasonable attenuation mechanism of electromagnetic waves that gradually decreases,and successfully establishes the relationship between structure and performance.