Abstract: 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 showed 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 150MPa 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.

Key words: gelcasting, porous ceramics, silicon nitride