Microstructure and mechanical properties of porous Si_3N_4 ceramics prepared by freeze-casting

摘要

Porous silicon nitride (Si_3N_4) ceramics were prepared from water-based Si_3N_4 slurries via a freeze-casting process. The green body shows good replica of ice dendrites with uniform pore channels. The microstruc ture of porous Si_3N_4 ceramics could be controlled by the freezing temperature. After sintering, porous Si_3N_4 ceramics with uniform microstructure was obtained. At low freezing temperature, the pore size dis tribution was narrower and concentrated with pore morphology from tree-like to vimineous channels. Porous Si_3N_4 ceramics with a porosity of 51%, flexural strength of 77 MPa, and aspect ratio (AR) of 5.20 was obtained at 1850 °C with 3% sintering additives.