Bingying Xie

Electromagnetic wave absorption properties of europium-doped SiCN (Fe) polymer-derived ceramics

A novel material of europium (Eu)-doped SiCN (Fe) ceramics was successfully synthesized by a polymer-derived method. The compositions, microstructure, direct-current electrical conductivity, electromagnetic (EM) properties and microwave absorption properties in the frequency range of 2–18xa0GHz were investigated. Compared to SiCN (Fe) ceramics, Eu-doped SiCN (Fe) ceramics showed the enhanced microwave absorption properties. The existence of Eu increased dielectric loss and magnetic loss, and EM parameters of the ceramics could be tailored by changing the doping amount of Eu2O3. The minimum reflection loss (RL) reached −u200912 dB at 16.8xa0GHz for the Eu-doped SiCN (Fe) ceramics with 25xa0wt% doping amount, exhibiting a promising prospect as microwave absorbing materials.

In Situ Synthesis of ZrB 2 –SiC Composite Powders by Carbothermal Reduction Method

ZrB2–SiC composite powders were synthesized in situ via carbothermal reduction using ZrO2, HBO2 and carbon black as the starting materials. The influences of HBO2 contents (40.6–45.5 wt%), boron sources (HBO2, H3BO3 and B2O3) and carbon sources (black carbon, activated carbon, graphite and petroleum coke) on phase composition and morphology of ZrB2–SiC composite powders were analyzed. The obtained samples were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Results showed that when the HBO2 content was 43.2 wt%, impurity-free ZrB2–SiC composite powders could be successfully produced at 1600 °C for 90 min in argon atmosphere. Meanwhile, columnar ZrB2 and granular SiC particles were combined interactively. Compared with control groups, products fabricated via black carbon revealed the better crystallinity and finer particle size.

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.