Pressureless Sintering of Silicon Nitride Porous Ceramics with High Porosity and Bimodal Pore Structure

Abstract

In this paper, silicon nitride porous ceramics with high porosity and bimodal pore structure were prepared using pressureless sintering at 900~1100°C. In these porous ceramics, zirconium phosphate (ZrP2O7) was used as a binder and starch and naphthalene powders were used as pore forming agents. The obtained results showed that the porosity could be controlled in the range of 34 % to 70 % by changing the content of pore forming agents. The pores were formed by the continuous reaction of ZrP2O7 at ~250 °C and burnout of starch at ~550 °C (when starch was used as a pore forming agent), or sublimation of naphthalene at 80°C (when naphthalene was used as a pore forming agent). The bimodal pore structure was produced with pore size of less than 0.5m and ~10 m when using starch as a pore forming agent and the pore size of less than 0.5m and ~30μm when using naphthalene as a pore forming agent.