三维网络碳化硅多孔陶瓷的制备

摘要

The carbon foam template was produced from the mixture of mesophase pitch and 55% Si particles( mass fraction). The SiC porous ceramics were fabricated by infiltrating Si into the carbon foam template at 1500℃ for 1 - 6h in the vacuum furnace under argon atmosphere. The micrograph and identify phase of porous SiC ceramics were observed by means of SEM and XRD respectively. Moreover, the mechanism of reactive infiltration of molten Si into carbon foam was also discussed. The results show that the microstructure of porous SiC ceramics is identical with carbon foam template. The bending strength of porous ceramics is increasing first and then decreasing with holding time prolonged at 1500℃ , however, the porosity is reverse. The porous SiC ceramics obtained at 1500℃ for 4h is composed of the major phase β-SiC. The bending strength and porosity are 26.2MPa and 45% respectively. Both the outer molten Si and inner Si of carbon foam react with C simultaneously to form SiC, and then bonds together to form densest porous SiC ceramics.%以中间相沥青添加55％(质量分数,下同)的Si粉混合物为原料,制备了含Si的炭泡沫模板.在高温反应烧结炉中,氩气气氛下1500℃保温1～6h,结合反应烧结工艺制备了碳化硅多孔陶瓷.利用扫描电子显微镜( SEM)和X射线衍射分析仪(XRD)对碳化硅多孔陶瓷的微观形貌、物相组成进行了观察,并对熔融Si与C的反应机理进行了探讨.结果表明:碳化硅多孔陶瓷的微观结构与炭泡沫模板的微观结构一致,烧结温度1500℃下,随着保温时间的延长,多孔陶瓷的弯曲强度先增大后减小,而孔隙率先减小后增大；在保温4h的条件下制备的碳化硅多孔陶瓷主要由β -SiC相组成,最大弯曲强度为26.2MPa,对应的孔隙率为45％.内部熔融的Si与外部熔融的Si同时与C反应生成SiC,最后两者结合在一起形成致密的SiC多孔陶瓷.