Properties and Processing of Porous Si sub(3)N sub(4) Ceramics

Porous silicon nitride (Si sub(3)N sub(4)) ceramics green were prepared by sol-gel and freeze drying processing. Al sub(2)O sub(3) and MgO were selected as sintering additives. Porous Si sub(3)N sub(4) ceramics were sintered at 1200~1300 [degrees]C. The porosity of porous Si sub(3)N sub(4) ceramics reached 60~80%, the pore size of porous Si sub(3)N sub(4) ceramics dried by freeze drying is less than 5 mu m. Two kinds of pores were formed, including open pores with pore size of l~5 mu m and closed pores pore size with the nanometer level. The compression strength of porous Si sub(3)N sub(4) ceramics was 15~25MPa. Thermal conductivity of porous Si sub(3)N sub(4) ceramics was 0.08-0.1 W/m-K.