The Preparation And Electromagnetic Wave Absorption Performance Of Iron Cobalt Metals/Carbon Composites

Electromagnetic wave absorption materials?EMAMs?have attracted more and more attention in recent years,they play core roles in the fields of electromagnetic pollution precaution and information security,as well as military stealth technology.Magnetic carbon-based composites are promising EMAMs with both dielectric and magnetic loss.Rational adjustment and construction on chemical composition and microstructure has gradually developed into an effective method to prepare the new type of magnetic carbon based EMAMs.The magnetic carbon-based composites described in this paper were prepared by the following strategy.Firstly,preparing the mixture of magnetic precursors and polymers in the first step,and then transform the mixture to final magnetic carbon-based composites through high-temperature pyrolysis under an inert atmosphere.The effects of chemical composition and microstructure on electromagnetic properties and electromagnetic wave absorption performance of these composites are investigated in detail,revealing that the attenuation ability and impedance matching characteristics,as well as electromagnetic wave absorption performance of these materials are determined by their chemical composition and microstructure.FeCo@C nanoparticles with core-shell structure were encapsulated in carbon nanocages?CNGs?derived from polydopamine?PDA?,obtaining the FeCo/C composites.The mass ratio of dopamine?DA?to FeCo Prussian blue analogs?FeCo PBAs?will affect the carbon contents and microstructure of resulting composites.PDA coating is greatly helpful to suppress the microstructure collapse of FeCo PBAs during high-temperature pyrolysis.The formation of CNGs adjusts and improves the electromagnetic?EM?properties and impedance matching characteristics of these composites,and their attenuation ability toward incident EM waves can be significantly enhanced.When the mass ratio of dopamine?DA?to FeCo PBAs reaches 0.75,the obtained composite will exhibit excellent electromagnetic wave absorption performance.The strongest reflection loss intensity is located at-67.8 dB at 15.8 GHz,and the effective bandwidth covers 11.0-16.3 GHz with the thickness of 2.0 mm.Porous three-dimensional?3D?carbon nanofoams decorated with cobalt nanoparticles?Co-CNFx?are synthesized by a metal nitrate-assisted polymer-blowing process.During this procedure,the relative contents of Co and carbon in the final composites can be adjusted by changing the mass ratio of Co?NO₃?₂·6H₂O to polyethylene pyrrolidone?PVP?,and the formation of porous 3D carbon framework depends on huge volume of the gas released from the rapid decomposition of cobaltous nitrate at high temperature.Analyzing the attenuation abilities and impedance matching characteristics,it is found that the appropriate Co/C ratio and unique microstructure of Co-CNFx endow it excellent electromagnetic wave absorption performance.When the mass ratio of Co?NO₃?₂·6H₂O to PVP reaches 1.5,the obtained composite will exhibit desirable electromagnetic wave absorption performance.The strongest reflection loss intensity is located at-76.5 dB at16.8 GHz with a match thickness of 1.5 mm,and the effective bandwidth covers 5.0 GHz?12.3-17.3 GHz?with the thickness of 2.0 mm.