Effect of Addition of Silicon on the Microstructures and Bending Strength of Continuous Porous SiC–Si 3 N 4 Composites

The microstructures and mechanical properties of continuous porous SiC–Si 3 N 4 composites fabricated by multi‐pass extrusion were investigated, depending on the amount of Si powder added. Si powder with different weight percentages (0%, 5%, 10%, 15%, 20%) was added to SiC powder to make raw mixture powders, with 6 wt% Y 2 O 3 –2 wt% Al 2 O 3 as sintering additives, carbon (10–15 μm) as a pore‐forming agent, ethylene vinyl acetate as a binder, and stearic acid (CH 3 (CH 2 ) 16 COOH) as a lubricant. In the continuous porous SiC–Si 3 N 4 composites, Si 3 N 4 whiskers like the hairs of nostrils were frequently observed on the wall of the pores. In this study, the morphology of Si 3 N 4 whiskers was investigated with the nitridation condition and silicon addition content. In composites containing an addition of 10 wt% Si, a large number of Si 3 N 4 whiskers were found at the continuous pore regions. In the sample to which 15 wt% Si powder was added, a maximum value of about 101 MPa bending strength and 57.5% relative density were obtained.