Research On The Absorbing Properties Of Fe₃O₄@C And Fe₃O₄@N-C Magnetic Nanocomposites Based On Yolk-shell Structure

In this paper,dielectric/magnetic loss-type Yolk-Shell structure Fe₃O₄@C nanocomposite microspheres and N-doped carbon Fe₃O₄@NC nanocomposite microspheres were designed and prepared according to different electromagnetic wave loss mechanisms.Using X-ray diffractometer,scanning electron microscope and vector network analyzer to analyze the sample’s crystal structure,micro-morphology and absorbing performance,the following results were obtained:（1）Yolk-Shell structure Fe₃O₄@C nanocomposite microsphere system:the magnetic Fe₃O₄composite is prepared by the hydrothermal method;the magnetic Fe₃O₄composite is used as a precursor,and the tetraethyl orthosilicate（TEOS）is determined by the St?ber method The mass ratio is uniformly mixed to construct the Fe₃O₄@Si O₂composite,and then the product is reacted with formaldehyde in an alkaline environment to form the Fe₃O₄@Si O₂@PR nanocomposite microsphere.After heat treatment and etching,the final product Yolk-shell Fe₃O₄@C nanocomposite microsphere.Yolk-shell structure Fe₃O₄@C nanocomposite microspheres have higher dielectric loss capabilities due to interface polarization,dipole polarization and higher conductivity due to surface defects in the carbon layer,which enhances the impedance matching of the composite.In addition,the presence of intermediate holes causes electromagnetic waves to be reflected and refracted many times,which further improves the wave absorbing performance.When the layer thickness is 2.5 mm,the RL value of the compound at 9.7 GHz is-24.9 d B.（2）N-doped carbon Fe₃O₄@C nanocomposite microspheres:By introducing nitrogen element to the Yolk-shell structure Fe₃O₄@C nanocomposite microspheres system,the dielectric properties of the carbon layer are enhanced,and its impedance matching is optimized.The N-doped carbon Fe₃O₄@C nanocomposite microspheres have excellent wave absorption properties.In the presence of nitrogen,nitrogen-doped carbon materials can form lattice defects,which can cause strong dielectric resonance.For the absorbing material,this will effectively improve the impedance matching of the absorbing material and improve the microwave absorption performance of the material.When the layer thickness is 2.5 mm,the RL value of the compound at 11.1 GHz is-34.8 dB.