High flexural strength porous silicon nitride ceramics were prepared via nitridation of silicon powder, using silicon powder and Y2O3 as start powder with different forming pressures. The effects of Y2O3 contents and heating programs on nitridation rate were studied. The high nitridation rate was obtained when 9％ Y2O3 was added,which was contributed to Y2O3 reacted with SiO2 at low temperature (1200℃) to transform to Y5Si3O12N and the elimination of SiO2 on Si surface. Under different sintering conditions, the porous Si3N4 ceramics with porosity of 30％-50％ and the flexural strength of 160-50MPa were obtained, respectively. After post-sintering at 1750℃ in 0.5MPa N2 atmosphere, α-Si3N4 was fully transformed into β-Si3N4 by the solution-precipitation process, the rod-like β-Si3N4 promoted the flexural strength of the porous Si3N4 ceramics, and the porous Si3N4 ceramics with a porosity of 46％ and a flexural strength of 140MPa was obtained.%以硅粉(Si)为起始原料,氧化钇(Y2O3)为烧结助剂,利用干压成型工艺制备出不同气孔率的多孔硅坯体,通过反应烧结得到高强度多孔氮化硅(Si3N4)陶瓷.研究了Y2O3添加量在不同升温制度下对于氮化率的影响,以及1500～1750℃后烧结对多孔材料强度的影响.结果表明:添加9%Y2O3的样品具有较高的氮化率,主要是Y2O3与Si粉表面的SiO2在较低的温度下反应生成了Y5Si3O12N.在不同的反应条件下可得到气孔率为30%～50%,强度为160～50MPa的样品.在1750、0.5MPa N2气压下对样品进行后处理,α-Si3N4完全转变成柱状β-Si3N4,晶型转变有利于强度提高,气孔率为46%的多孔Si3N4其强度可达140MPa.
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