烧结温度对SiC纤维结构及性能的影响

Effect of Sintering Temperature on SiC Fiber Structure and Properties

以聚碳硅烷(PCS)为先驱体,采用先驱体转化技术制备出耐高温的连续Si C纤维。研究了烧成过程中温度对纤维结构及性能的影响。结果表明,当纤维的烧成温度低于1 400℃时,纤维的拉伸强度随着温度升高缓慢上升;烧成温度为1 400℃时,氧的质量分数为1.96%,硅碳原子个数比为0.757 6,拉伸强度为2.7 GPa,晶粒尺寸为5.4 nm,惰性气氛下1 800℃处理1 h后,强度保留率为49.63%,空气气氛中1 250℃处理后,拉伸强度仍保留2.24 GPa。烧成温度在1 400℃之后,拉伸强度明显下降。当烧成温度为1 800℃时,拉伸强度为1.32 GPa。这主要是纤维中Si CxOy相分解和晶粒长大两方面的综合因素起作用。烧成温度较高的纤维,惰性气氛中的耐高温性能较好。这是因为其氧含量较低,且纤维的晶粒尺寸增加幅度较小。烧成温度为1 800℃的纤维惰性气氛下1 800℃处理1 h后,强度保留率为72.73%。

High-temperature resistant continuous SiC fibers were prepared by a polymer-derived method with polycarbosilane （PCS） as a precursor. The effect of the sintering temperature on the structure and properties of the fibers was investiagted. The results show that the tensile strength of the fibers increases modestly with the increasing the temperature when the sintering temperature is below 1 400 ℃. At the sintering temperature of 1400 ℃, the fibers have the oxygen mass fraction of 1.96%, atomic ratio of Si and C of 0.757 6, tensile strength of 2.7 GPa and grain size of 5.4 nm. The strength retention rate of fibers processed in inert atmosphere at 1 800 ＂C for one hour is 49.63%. The tensile strength of fibers prepared in air at 1 250 ＂C for half an hour is 2.24 GPa. When the sintering temperature exceeds 1 400 ＂C, the tensile strength of fiber decreases dramatically. It is found that the tensile strength decreases sharply to 1.32 GPa at 1 800 ℃. The main reason for all these phenomena is due to decomposition of SiCxOyphase and the grain growth in the fibles. The fibers with high sintering temperature have a better high-temperature-resistance in inert atmosphere due to their low oxygen content and less degrees of grain growth. The strength retention rate of fibers processed in inert atmosphere at 1 800℃ for one hour is 72.73%.