BN纳米片复合SiBN透波纤维调控方法及其服役性能增强机制

连续SiBN透波纤维是高超声速飞行器天线罩/窗研制的关键原材料。随着飞行器飞行速度的进一步增加，SiBN纤维迫切需要优化微结构以提高服役性能。本项目提出采用二维氮化硼纳米片（BNNSs）改性聚硼硅氮烷，继而通过纺丝与无机化构建BNNSs复合SiBN纤维，阻碍纳米孔缺陷诱导的微裂纹扩展和相界面原子的高温迁移，实现宏观力学性能和耐高温性能的双提升。拟首先研究BNNSs与聚硼硅氮烷的结合机理与调控方法，分析维持BNNSs均匀分散的驱动力，探索影响改性聚硼硅氮烷流变学特征的BNNSs含量阈值和尺寸效应；深入研究熔融状态下BNNSs改性聚硼硅氮烷分子链热机械行为，阐释收丝牵伸力对BNNSs的取向作用；系统研究并建立BNNSs含量、尺寸和取向度与复合陶瓷纤维力学和耐高温性能的关联模型，揭示复合陶瓷纤维服役性能多尺度增强的关键机理，建立SiBN透波纤维微结构创新和性能升级的新方法。

Continuous SiBN wave-transparent fibers are the key raw materials for the development of hypersonic vehicle radome/window. With the flight speed of vehicle further increasing, SiBN fibers urgently need to optimize microstructure to improve their service performance. This project puts forward modifying polyborosilazanes with two-dimension BN nanosheets (BNNSs), following to fabricate SiBN fibers combing with BNNSs via spinning and mineralization process. As a result, the crack propagation that induced by the nanoscaled pore-defects, as well as the high-temperature migration of atoms at the interfacial region, can be inhibited, which finally improves both the mechanical and high-temperature properties. It is planned to firstly study the bonding mechanism and regulation method between BNNSs and polyborosilazanes, then analyze the driving force to maintain the uniform dispersion of BNNSs, and explore the BNNSs content threshold and size effect that affect the rheological characteristics of BNNSs modified polyborosilazanes. By in-depth studying the thermomechanical behavior of the molecular chain of modified polyborosilazane in the molten state, the effect of drawing force on the orientation of BNNSs in the condensed-stated raw fibers can be explained. By systematically studying the correlation model between BNNSs content, size, orientation, and the mechanical/high-temperature properties of composite ceramic fibers, we aim to reveal the key mechanism for improving the service performance of composite fibers in a multi-scale. Finally, we expect to establish a new method for microstructural innovation and performance upgrade of SiBN wave-transparent fibers.