连续SiC(Al)纤维的耐超高温性能及其机理

以有机金属聚合物聚铝碳硅烷为原料, 利用先驱体转化法制备出连续SiC(Al)纤维. 采用一系列分析测试对纤维的组成、结构以及耐超高温性能进行了表征, 通过与Nicalon纤维的比较, 对连续SiC(Al)纤维的耐超高温机理进行了研究. 结果表明, 连续SiC(Al)纤维具有优异的耐超高温性能,在1800 ℃氩气中处理1 h后, 纤维的强度保留率为80%左右; 元素分析和27Al MAS核磁共振等分析表明, 连续SiC(Al)纤维为近化学计量比的SiC纤维, 纤维中微量的铝元素以Al—O和Al—C键两种形式存在; 在超高温条件下, 两种不同存在形式的铝均能够抑制纤维中晶粒的长大. 纤维具有近化学计量比的组成和铝元素在高温条件下对于晶粒长大的抑制, 是连续SiC(Al)纤维具有优异耐超高温性能的原因.

Properties and Mechanism of High Temperature Resistance of Continuous SiC(Al) Fibers

Continuous SiC(Al) fibers were prepared by polymer-derived method using organometallic polymer polyaluminocarbosilane (PACS). The composition, structure, and properties of continuous SiC(Al) fibers were investigated by a series of analyses. The mechanism of high temperature resistance of the fibers was discussed through the comparison between Nicalon fibers and continuous SiC(Al) fibers. The results showed that the fibers exhibited excellent thermal stability. After heat treatment at 1800 ℃ in argon for 1 h, the fibers maintained about 80% of the initial strength. Element analysis and 27Al MAS NMR indicated that the composition of continuous SiC(Al) fibers was close to stoichiometric ratio and the aluminum existed in the form of Al—O and Al—C bonds. The aluminum that existed in different manners could restrain the growth of grain of the fibers at super-high temperature. The high-temperature resistance of continuous SiC(Al) fibers was based on two factors: the near stoichiometric composition and the inhibition of the aluminumto the growth of the grain.