成型温度对多孔SiC陶瓷性能的影响

Effects of Molding Temperature on Properties of Porous SiC Ceramics

以包混工艺合成了核-壳结构的先驱体粉体,并引入少量Al2O3,SiO2和Y2O3作为复合添加剂,通过模压成型、炭化和烧结工艺制备了多孔碳化硅陶瓷;研究了成型温度对样品的孔隙率、密度、热膨胀系数、抗弯强度和热震性能的影响。结果表明:成型温度对多孔碳化硅陶瓷的孔隙率、密度、抗弯强度及热震性能均产生了显著影响,对热膨胀系数影响较小。在80℃成型的多孔碳化硅陶瓷综合性能较佳,过低的成型温度使包覆在核-壳结构先驱体粉体外层的钡酚醛树脂不能充分流动,使最终多孔碳化硅陶瓷样品结构松散、强度降低;而过高的成型温度使钡酚醛树脂过分流动,对添加剂粉体形成包覆再经过炭化后阻碍了添加粉体的充分接触,未能起到烧结助剂的作用。

The core-shell structure precursor powders were synthesized through coat mix process,and a small amount of Al2O3,SiO2 and Y2O3 composite additives was added.A series of porous silicon carbide ceramics were produced after molding,carbonization and sintering.The porosity,density,thermal expansion coefficient,bending strength and thermal shock resistance of porous silicon carbide ceramics were analyzed.The results show that the porous silicon carbide ceramic with molding temperature 80℃ possesses best general performance.When the molding temperature is very low,the barium phenolic resin coated over the core-shell structure precursor powders can not flow adequately,leading a loose structure and lower strength for the final porous silicon carbide ceramic.While the phenolic resin flows too much with excessive high molding temperature,some of composite additives are coated by phenolic resin and can not touch each other adequately,thereby the effect of composite additive is weaken.