Preparation and study of porous Si₃N₄ ceramics with high strength by gelcasting

Porous Si₃N₄ ceramics with high strength, uniform structure and relative high porosity were obtained by gelcasting. The mechanical performances and micro-structure of the porous Si₃N₄ ceramics were studied and the reasons were discussed. It was shown that using proper techniques, green bodies with high strength, uniform structure and good machining proparey could be got. Results show that the sintered porous Si₃N₄ ceramics have strength more than 150 MPa and porosity up to 50%. SEM shows that porous are formed by the banding-up of pillar β-Si₃N₄. The uniform porous distribution and pillar structure are the main reasons for good mechanical performances.