Porous Silicon Nitride Ceramics Prepared by Reduction–Nitridation of Silica

A new method for preparing porous silicon nitride ceramics with high porosity had been developed by carbothermal reduction of die‐pressed green bodies composed of silicon dioxide, carbon, sintering additives, and seeds. The resultant porous silicon nitride ceramics showed fine microstructure and uniform pore structure. The influence of SiO 2 particle size and sintering process (sintering temperature and retaining time) on the microstructure of sintering bodies was analyzed. X‐ray diffractometry demonstrated the formation of single‐phase β‐Si 3 N 4 via the reaction between silicon dioxide and carbon at high temperature. SEM analysis showed that pores were formed by the banding up of rod‐like β‐Si 3 N 4 grains. Porous Si 3 N 4 ceramics with a porosity of 70–75%, and a strength of 5–8 MPa, were obtained.