先驱体转化原位制备表面富BN的SiBN纤维的机理与性能研究

With development of the aerocraft possessing ultra-high velocity above speed of sound, the demand for fibers with high heat resistance, load bearing and wave transparence is increasingly pressing. The aim of the project is to decrease the requirement of humidity for polymeric precursor's melt spinning and improve the high temperature resistance, interfacial performances and dielectric properties. Based on materials design, the polycarbosilane (PCS) with good stability in air and melt-spinnability, will be taken as main precursor and poly(alkylaminoborazine) with low molecular weight as additive. After melt spinning of the mixed polymeric precursor in air, the polymer fiber is pre-treated to control phase separation of the low molecular weight PPAB from PCS to form compositional gradient (bleed out). Then the gradient fiber will be cured and pyrolyzed in ammonia to be nitrified and carbon impurity in precursor will be removed to form SiBN fiber with BN rich surface. The SiBN fiber and functional surface layers will form without obvious interface at the same time. The mechanism of pre-treated on elemental distribution in the radial direction of polymer fiber, control of BN surface thickness and influence of composition/structure of SiBN fiber on mechanical property, interface property, high temperature resistance and dielectric properties will be researched primarily. Furthermore, the SiBN fiber's property will be regulated and the relation of composition-structure-property will be established. The project is of benefit to the development of novel ceramic fiber and structural/functional composite parts due to its significance in theory and application in reality.

高超声速飞行器的发展对耐高温/承载/透波陶瓷纤维的需求日益迫切，本项目拟结合先驱体法和原位转化法的优势，以降低先驱体对环境湿度的要求、提高SiBN纤维的耐高温性能、界面性能和介电性能为目标，基于材料设计，利用聚碳硅烷（PCS）不易水解、可纺性好的特点，以其为本体先驱体，添加较低分子量的聚烷氨基环硼氮烷（PPAB）经空气中熔融纺丝后，控制熟化条件使PPAB从PCS中析出形成径向化学成分梯度，再经不熔化、氨气氮化除碳无机化原位制备表面富BN的SiBN纤维，陶瓷本体和功能表面层同时形成且无明显界面。重点研究熟化工艺对原丝径向化学成分分布的影响机制、BN层厚度控制，SiBN纤维组成结构对力学、界面、耐高温和介电性能的影响规律，进而调控纤维性能，建立SiBN纤维的组成-结构-性能间的关系规律并揭示其机理。本项目对新型陶瓷纤维的研制以至先驱体转化原位制备结构/功能复合材料器件具有重要理论和现实意义。

依据研究计划，对SiBN纤维的制备开展了工作。基于SiC纤维，在此基础上拓展了原位制备具有无明显界面“第二相”表面层复合纤维（如ZrO2/SiC梯度纤维）种类。同时，针对原位制备的复合纤维在部分催化反应（光催化、电催化）中的应用进行了研究。主要思路如下：结合先驱体法和原位转化法的优势，以简化制备路线、提高纤维性能为目标，基于材料设计，以聚碳硅烷（PCS）为本体先驱体，添加较低分子量化合物经纺丝后，控制熟化条件使低分子量化合物从PCS中析出形成径向化学成分梯度，再经不熔化和氨气氮化除碳无机化等方法原位制备表面富第二相的复合纤维，陶瓷本体和功能表面层同时形成且无明显界面。重点研究熟化工艺对原丝径向化学成分分布的影响机制、纤维组成结构性能的影响规律，进而调控纤维性能，建立复合纤维的组成-结构-性能间的关系规律并揭示其机理。本项目对新型陶瓷纤维的研制以至先驱体转化原位制备结构/功能复合材料器件具有重要理论和现实意义。. 超额完成了研究任务，取得了一系列基于先进纤维材料的创新成果。三年来，共发表SCI论文22篇（原计划发表论文8-10篇），其中Journal of Materials Chemistry A 2篇、Nano Research 3篇、Chemical Communication 1篇、Scientific Reports 1篇。影响因子累计约83，论文引用次数约160余次，单篇最高引用次数为25。受邀参加国际、国内学术会议6次并做报告5次，申请国家发明专利2项。项目负责人获2014年度湖南省优秀博士学位论文作者，入选学院青年拔尖人才培养对象。