Preparation and study of porous Si₃N₄ ceramics with high strength

Porous Si₃N₄ ceramics with high strength and high porosity were obtained by the addition of small amount of carbon. The effects of carbon content, sintering temperature and reaction time on porous Si₃N₄ ceramics were studied. It was showed that SiC particles could pin the β-Si₃N₄ grains boundaries and had an effective reinforcing effect, which formed through reaction of the added carbon with SiO₂ on the Si₃N₄ surface or with the Si₃N₄ particles themselves. Sintered Si₃N₄ porous ceramics with 100 MPa strength and >40% porosity were obtained when the carbon content was 5 wt%, and the sintering temperature was 1 780°C.