Study of the relaxation time for the polarization mechanism in SiO2–SiC/B4C nanowires with broadband absorption of microwave

Abstract

SiO2-supported SiC/B4C (SiO2–SiC/B4C) nanowires were synthesized by using SiO2@C nanospheres, amorphous B powders and catalyst Ni(NO3)2·6H2O as raw materials, and exhibited remarkable microwave absorbing characteristics. The minimum reflection loss of the SiO2–SiC/B4C nanowire/paraffin composite reaches −41.33 dB with an effective absorption bandwidth up to 9.69 GHz. The broadband microwave absorption of SiO2–SiC/B4C nanowires is attributed to the synergistic effect of interfacial polarization relaxation and conduction loss. While conductive loss dominates at low frequencies within 2–8 GHz, polarization loss caused by the heterogeneous interfaces plays an important role at high frequencies, especially between 10 and 16 GHz. The movement of the polarization relaxation peaks to lower frequencies in the composites is further investigated by modeling the relaxation process as a rotating sphere in a viscous fluid. The linear relationship between relaxation time and conductivity indicates that the conductivity is an important factor that affects the electromagnetic wave (EMW) absorption performance not only on the impedance matching and attenuation constant of the materials, but also regulates the relaxation time, and this result provides a new idea for exploring the absorption mechanism of EMW absorbing materials.