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, β-Si3N4 contents, and mechanical properties were obtained. When solid contents changed from 35vol% to 45vol% , the porosities decreased from 57.6% to 40. 8% , while the fracture strength increased from 96 Mpa to 178 Mpa. Many fibrous B-Si3N4 grains grown from the internal wall of the round pores, the growth mechanisms of fibrous β-Si3N4 grains resulted from the synergy of solution-diffusion-reprecipitation and vapor-liquid-solid. Both elongated β-Si3N4 grains and suitable interfa-cial bonding strength contributes to the high fracture strength.%以琼脂糖作为凝胶物质,采用凝胶注模工艺制备了多孔氮化硅陶瓷,通过改变浆料的固相含量,制备了不同性能的多孔氮化硅陶瓷.结果表明,随着浆料的固相含量从35vol％增加到45vol％,材料的气孔率从57.6％减小至40.8％,弯曲强度从96 MPa增加到178 MPa;大量的长棒状β-Si3N4晶粒从孔壁上生长出来,将气孔填充,其生长方式为溶解-沉淀-析出与气-液-固两种生长机制协同作用的结果.长棒状的氮化硅晶须和恰当的界面结合强度是多孔氮化硅陶瓷具有较高强度的主要原因.
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