Abstract: Porous silicon nitride ceramics with high porosity and uniform pore structure were prepared by carbothermal reduction reaction between low-cost silicon dioxide and activated carbon. The influence of SiO₂ particle sizes on their microstructures was investigated. Microstructures and mechanical properties of porous silicon nitride ceramics were studied by XRD, SEM and three-point bending measurement. XRD analysis showed that only β-Si₃N₄ phase, minor of α-Si₃N₄ phase and glass phase Y₈Si₄N₄O₁₄ were detected. SEM analysis showed that porous silicon nitride ceramics obtained were composed of rod-like β-Si₃N₄ grains and uniform pores. Porous silicon nitride ceramics with different porosities and good mechanical properties were fabricated by changing SiO₂ particle sizes.

Key words: carbothermal reduction method, porous silicon nitride, icrostructure, mechanical properties