Yurun Feng

Electromagnetic and wave absorbing properties of Fe-doped polymer-derived SiCN ceramics

Fe-doped polymer-derived SiCN ceramics were synthesized by a precursor conversion method with different contents of nano-Fe2O3. The phase composition and microstructure were characterized by XRD, SEM and TEM. The results revealed that α-Fe and graphite phases were generated during the synthetic process. The electromagnetic and wave absorbing properties of the Fe-doped SiCN ceramics were analyzed with different amounts of nano-F2O3 over the frequency range of 2–18 GHz. The existence of α-Fe and graphite phases improved the electromagnetic properties of the materials greatly. The reflectance and electromagnetic attenuation coefficient of Fe-doped SiCN ceramics (15 wt% F2O3) reached −11 dB and 325 at 10.5 GHz, respectively, which indicated that the Fe-doped SiCN ceramics possessed excellent absorbing properties.

Microwave Absorbing Performance on Polymer-Derived SiCN Ceramics Doped with Rare Earth Oxides

This study investigated the compositions, dielectric properties, magnetic properties and microwave absorbing properties of polymer-derived SiCN ceramics doped with Dy2O3, Eu2O3, Sm2O3, Y2O3 and Gd2O3 respectively. The complex permittivity and complex permeability were measured at the frequency range of 2–18 GHz. The reflectivity of polymer-derived SiCN ceramics doped with Eu2O3 reaches to the lowest value of −35 dB at 16.4 GHz. While the electromagnetic damping coefficient reaches the maximum value of 653 at 16.1 GHz, which clearly demonstrates that by doping Eu2O3 the wave absorbing performance of polymer-derived SiCN can be enhanced more pointedly than the other samples.

Preparation and Properties of Pressureless-Sintered Porous Si 3 N 4 Ceramics

In this paper, the effect of benzoic acid on the porosity, dielectrical and mechanical properties of porous Si3N4 ceramics prepared by pressureless sintering was investigated. The results showed that the addition of benzoic acid improved the porosity and dielectrical properties of Si3N4 remarkably by pressureless sintering at 1700 ℃ for 60 min. The porosity of sample reached 40.79% with 50 wt% benzoic acid addition and the reflectivity of the sample reached −45 dB at around 12 GHz.