Effect of solid content on pore structure and mechanical properties of porous silicon nitride ceramics produced by freeze casting

Porous Si3N4 ceramics were prepared by freeze casting using liquid N2 as refrigerant. The pore structure, porosity, α → β-Si3N4 transformation and mechanical properties of the obtained materials were strongly affected by the solid contents of the slurries. Increasing the solid content would reduce the porosity, decrease the pore size and change the pore structure from the aligned channels with dendrites to the round pores with decreased pore size. The formation of this round pores impeded the α → β-Si3N4 phase transformation, but was beneficial to the mechanical properties of the obtained porous Si3N4 due to its unique pore structure.