The polymer-derived SiC fibers have broad application prospects in the fields of aerospace, nuclear industry and high-tech weapon. Oxygen plays an essential role in adjusting the composition, structure and tensile strength of SiC fibers. Our studies have found that introducing too much oxygen during air curing process will form the skin-core structure in nearly stoichiometric polycrystalline SiC fibers. In order to reveal the formation mechanism of the skin-core structure, gradient oxygen was introduced into the fibers. The morphologies, phase distributions and defects of the fibers were well characterized. By strictly controlling the introduction of oxygen, the polycrystalline product fiber exhibits intragranular fracture behavior and excellent high-temperature resistance. The retention rate of its tensile strength can reach up to 91% and 61% after exposure at 1800 °C for 1 h and 10 h, respectively. The present results give valuable insights into the structural optimization of the nearly stoichiometric polycrystalline SiC fibers.

源自聚合物的SiC纤维在航空航天，核工业和高科技武器领域具有广阔的应用前景。氧气在调节SiC纤维的组成，结构和拉伸强度方面起着至关重要的作用。我们的研究发现，在空气固化过程中引入过多的氧气会在接近化学计量的多晶SiC纤维中形成皮芯结构。为了揭示皮芯结构的形成机理，将梯度氧引入到纤维中。纤维的形态，相分布和缺陷得到了很好的表征。通过严格控制氧的引入，多晶产品纤维表现出晶内断裂行为和优异的耐高温性。在1800°C暴露1 h和10 h后，其拉伸强度的保留率可分别达到91％和61％。本研究结果为近乎化学计量的多晶SiC纤维的结构优化提供了宝贵的见识。