含铝碳化硅纤维耐高温性能

HIGH-TEMPERATURE RESISTANCE PROPERTIES OF SILICON CARBIDE FIBERS CONTAINING ALUMINUM

通过合成陶瓷纤维先驱体聚铝碳硅烷,制备了具有耐高温性能的含铝碳化硅SiC(Al)纤维。SiC(Al)纤维的化学组成为SiC1.15O0.026·Al0.013,主要结构是平均晶粒为95nm的βSiC,O和游离C含量均大大低于nicalon纤维,同时含有微量的Al和少量的αSiC。SiC(Al)纤维的平均直径为13μm,平均抗拉强度为2.3GPa。1400℃氩气中处理1h后,抗拉强度是原始强度的95%以上;1800℃氩气中处理1h后,抗拉强度保留率为71%。纤维的高温稳定性高于nicalon,Hi nicalon等商品SiC纤维,但低于TyrannoSA商品SiC纤维,并且SiC(Al)纤维的高温抗蠕变性能明显高于nicalon纤维。SiC(Al)纤维的高温稳定性取决于其低氧含量、低富碳含量以及异元素Al的助烧结和在高温下抑制SiC晶粒长大的作用,良好的抗蠕变性能决定于其高结晶度和低含量的SiCxOy相。

Fibers of SiC(Al) with superhigh-temperature resistances were prepared by ceramic precursor polyalumicarbosilane (PACS). The composition of SiC(Al) fibers is described as SiC1.15O0.026A10.013 in which there are mainly β-SiC grains in size of 95 nm, small amount of α-SiC, aluminum, SiCxOy phase and free carbon. The average tensile strength of SiC(Al) fibers is 2.3 GPa, with the average fiber diameter of 13 μm. The initial tensile strength of the fibers remains 95% after heat treatment at 1400°C for 1 h in argon. After SiC(Al) fibers were sintered at 1800°C for 1 h in argon, the tensile strength changed to 71% of initial tensile strength. The stability of the SiC(Al) fibers at high-temperature is better than that of nicalon and Hi-nicalon (trade name) , but more inferior than Tyranno SA (trade name). The creep resistance of SiC(Al) fibers at high temperature is obviously better than that of nicalon. Low contents of oxygen and free carbon, the introduction of hetero-elements aluminum acting as both sintering aids and inhibitors to prevent coarseness of SiC crystalline at high temperature are responsible for the high-temperature resistance properties of SiC(Al) fibers. Unique creep resistances of SiC(Al) fibers are related to high crystallinity and low contents of SiCxOy phase.