Modified Preparation And Microwave Absorption Properties Of Silicon Carbide Nanoparticles

SiC is a semiconductor material with the advantages of high strength,high hardness,low density,lightweight and high-temperature resistance,making it a potential microwave absorber material.However,due to the disadvantages of low electrical conductivity,unipolarity,and weak magnetic permeability in the microwave region,resulting in poor wave absorption performance,the modification of SiC can effectively improve its wave absorption performance,of which surface modification is a common method of modification.In this thesis,SiC@CN and（SiC/Ni）@CN nanocomposites with the core-shell structure were synthesized by in situ self-polymerization of dopamine（DA）on the surface of SiC nanoparticles,Ni²⁺-mediated in situ self-polymerization of dopamine and heat treatment methods.The phase composition,surface composition,morphological structure,chemical valence,and electromagnetic absorption properties of the samples were examined and analyzed by X-ray diffractometer,transmission electron microscope,scanning electron microscope,Raman spectrometer,and vector network analyzer.The results showed that altering the amounts of DA and Ni Cl₂·6H₂O could effectively modulate the wave absorption properties of the synthesized samples SiC@CN and（SiC/Ni）@CN nanocomposites.The SiC@CN nanocomposites were synthesized by in situ self-polymerization method and heat treatment method,and the synthesized samples have a clear core-shell structure with a core particle size of about 50 nm and shell layer thickness of about 5 nm.The absorption performance was examined,and it was found that when the mass ratio of SiC to DAwas 2:1,the best reflection loss could reach-43.94 d B,corresponding to the frequency and thickness of 7.97GHz and 3.10 mm,respectively.The bandwidth of reflection loss less than-20 d B is 11.32 GHz,and the corresponding thickness range is 1.75-6.00 mm.The（SiC/Ni）@CN nanocomposite was synthesized using Ni²⁺-mediated dopamine in situ self-polymerization and heat treatment techniques.Moreover,when the mass ratio of SiC and Ni Cl₂·6H₂O is 5:2,the optimal reflection loss can reach-45.63 d B,and the corresponding frequency and thickness are 8.99 GHz and 2.67 nm,respectively.The bandwidth for the reflection loss less than-20 d B range is 11.41 GHz,corresponding to a thickness range of1.66-6.00 mm.The results showed that the coating of the N-doped C layer on the surface of SiC nanoparticles caused strong interfacial polarization and defect dipole polarization.Meanwhile,the N-doped C layer modification effectively improved the conductivity of SiC and increased the conductivity loss capability,which led to the enhanced dielectric response of SiC@CN nanocomposites and thus improved the wave absorption performance.Therefore,with appropriate surface modification of SiC by N-doped C layers,SiC@CN nanocomposites can achieve the combined effects of interfacial polarization,defective dipole polarization,conductivity loss,and weak magnetic loss,which balance the relationship between impedance matching and attenuation capability,resulting in excellent microwave absorption properties.The Ni²⁺-mediated in situ self-polymerization of dopamine was introduced to enhance the magnetic loss,and the impedance matching properties of（SiC/Ni）@CN nanocomposites were optimized by the synergistic effect of dielectric and magnetic losses,which further enhanced the wave absorption properties of（SiC/Ni）@CN nanocomposite powders.In conclusion,SiC@CN and（SiC/Ni）@CN nanocomposites have potential applications in the field of electromagnetic wave absorption due to their simple preparation process,rapid synthesis cycle,and outstanding wave absorption properties.