硅液相浸渍反应制备TiC/SiC和TiN/SiC复相陶瓷

以滤纸、酚醛树脂和氧化钛为原料,经过模压成型、固化、碳化及不同条件下渗硅制备了TiC/SiC和TiN/SiC复相陶瓷。通过X射线衍射和扫描电子显微镜研究了TiC/SiC和TiN/SiC复相陶瓷的微观结构和物相组成,测量了复相陶瓷的弯曲强度和断裂韧性。结果表明:真空条件下液态渗硅获得的TiC/SiC复相陶瓷具有多孔的微观结构,其弯曲强度和断裂韧性较小。氮气气氛下液态渗硅制备的TiN/SiC复相陶瓷结构致密,有较高的弯曲强度和断裂韧性。不同反应生成的TiC,TiN陶瓷颗粒对液态硅的润湿性不同,使得生成的复相陶瓷具有不同的微观结构。TiN/SiC复相陶瓷中TiN颗粒的引入,在基体与第二相颗粒间的界面上产生拉应力和压应力,使达到这一区域的裂纹偏转,从而获得增韧效果。

PREPARATION OF TiC/SiC AND TiN/SiC COMPOSITE CERAMICS FROM LIQUID SILICON INFILTRATION

TiC/SiC and TiN/SiC composite ceramics were fabricated by using filter paper,phenolic resin and titania as raw materials through molding,curing,drying,carbonization,and Si infiltration process. The phase composition and microstructure of the TiC/SiC and TiN/SiC composite ceramics were investigated by X-ray diffraction and scanning electron microscopy,and the bending strength and fracture toughness of the composite ceramics were measured. The results show that the TiC/SiC composite ceramic formed from liquid Si infiltration in vacuum has porous microstructure. The dense TiN/SiC composite ceramic formed from liquid Si infiltration at nitrogen atmosphere has higher bending strength and fracture toughness than which of porous TiC/SiC composite ceramic. The different microstructures of these composite ceramics are originated from the different wetting angle of TiC and TiN in liquid silicon. The tension stress and compression stress are formed on the interface between the additive and matrix due to the introduction of TiN particles in TiN/SiC composite ceramic,and the fracture toughness increases as the direction of crack changes in this area.