Fabrication of porous silicon nitride with high porosity by carbothermal reduction-reaction bonding

By using cheaper Si, SiO₂ and carbon black as starting material, the porous silicon nitride ceramics with high porosity and uniform pore structure were prepared by carbothermal reduction-reaction bonding method. The influences of Si content on the microstructure and mechanical properties of the samples were 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-Si₃N₄phase and glass phase Y₃Si₃O₃N₄ were detected in the samples. 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 the Si content.