Porous Si3 N4 ceramics were prepared by gel casting using agarose additives. By changing the solid
content of the slurries, porous silicon nitride ceramics with different porosities, 茁-Si3 N4 contents, and mechanical
properties were obtained. When solid contents changed from 35vol% to 45vol%, the porosities decreased from
57郾6% to 40. 8%, while the fracture strength increased from 96 MPa to 178 MPa. Many fibrous 茁-Si3 N4 grains
grown from the internal wall of the round pores, the growth mechanisms of fibrous 茁-Si3 N4 grains resulted from the
synergy of solution鄄diffusion鄄reprecipitation and vapor鄄liquid鄄solid. Both elongated 茁-Si3N4 grains and suitable interfa鄄
cial bonding strength contributes to the high fracture strength.