Electromagnetic wave absorption properties of hot-pressed Si3N4-SiC ceramic nanocomposites

High-density Si3N4-SiC ceramic nanocomposites have exceptional mechanical properties, but little is known about their electromagnetic wave absorption (EMA) capabilities. In this paper, the effects of sintering temperature and starting material compositions on the dielectric and EMA properties of hot-pressed Si3N4-SiC ceramic nanocomposites were investigated. The real and imaginary permittivities of Si3N4-SiC ceramic nanocomposites increase with increasing sintering temperature or SiC content, particularly at the sintering temperature of 1850 degrees C and SiC content of 50 wt.%. This is primarily due to the improvement of interfacial and defect polarizations, which is caused by the doping of nitrogen into the SiC nanocrystals during the solution-precipitation process. The real and imaginary permittivities of Si3N4-SiC ceramic nanocomposites show decreasing trends as sintering aid content increases. Si3N4-SiC ceramic composites have both good EMA and mechanical properties when they are sintered at 1850 degrees C with 30 wt.% SiC and 5-8 wt.% sintering aids. The minimum reflection loss and maximum flexural strength reach -58 dB and 586 MPa, respectively. Materials with multilayered structural designs have both strong and broad EMA properties.