基于气溶胶微空间的超长SiC纳米线生长及其连续纤维纺丝

The continuous SiC fibers which are used as important reinforcements for silicon carbide matrix composite have many promising applications in some high-tech fields. Recently, the spinning of the continuous carbon nanotube fibers is becoming a rapidly emerging field of material research. This spinning method accomplished by integrating bottom-up carbon nanotube self-assembly provides a new way for the fabrication of the new continuous SiC fibers. Based on our previous research work on SiC nanowires, the continuous growth of the ultralong single-crystalline SiC nanowires in the micro space of the carbon aerosol will be studied, and the continuous SiC nanowire fibers will also be spun directly from the as-synthesized SiC nanowire aerosol. The growth mechanism of SiC nanowires in the micro space of the aerosol will be clarified. The key technology and process control parameters will be confirmed. The effects of the post-processings on the mechanical and physical properties of the fibers will be investigated. SiC nanowire ceramic fibers will also be fabricated via polycarbosilane infiltration and pyrolysis technique. Two key problems, the continuous fabrication of SiC nanowires and the direct spinning of the continuous SiC nanowire fibers, will be resolved. The new spinning technique for SiC nanowire fibers will provide a new strategy toward materials design and fabrication for the research and development of the continous SiC fibers.

连续SiC陶瓷纤维是高强度SiC陶瓷基复合材料不可缺少的增强体，在多个高技术领域具有广泛的应用前景。近几年，关于连续碳纳米管纤维纺丝的研究方兴未艾，这种由碳纳米管自下而上组装成宏观纤维材料的方法为新型连续SiC纤维的制备提供了新的研究思路。申请人拟在前期SiC纳米线研究的工作基础之上，研究碳气溶胶微空间超长单晶SiC纳米线的持续生长，并将生成的SiC纳米线气溶胶经直接纺丝获得连续SiC纳米线纤维。研究将澄清气溶胶微空间SiC纳米线的生长机理，确定SiC纳米线生长的关键制备技术和工艺参数。研究牵引、加捻和浸润等后处理工艺对纤维力学与物理性能的影响，并探讨通过液相聚碳硅烷浸渍工艺制备连续SiC纳米线陶瓷纤维。研究将重点解决气溶胶微空间SiC纳米线的持续稳定生长及SiC纳米线纤维的直接纺丝两个关键问题。这种新型SiC纳米线纤维的纺丝可为今后SiC纤维的研究与开发提供材料设计思想和关键制备技术。

受化学气相沉积法制备连续碳纳米管纤维的启发，项目开展了由SiC纳米线自下而上组装成宏观连续SiC纳米线纤维的制备研究。. 研究了碳热还原化学气相沉积法制备SiC纳米线的反应热力学，明确了Si-C-O体系SiO/CO气体生成、SiC晶核形成、SiC纳米线生长涉及到的关键热力学反应，提出了两步气-固反应模式及氧辅助螺型位错生长机理。热力学分析有利于优化SiC纳米线制备的温度、气体压强和原料类型等参数，为SiC纳米线的可控制备、宏量制备与产业化奠定了理论基础。.提出了微空间生长纳米线的研究方案，并开发了高产率SiC纳米线制备技术。采用不同碳源/硅源和处理工艺获得微空间，并通过提高SiC形核数量、调控气体过饱和度，实现了超长纳米线宏量制备，同时实现了SiC纳米晶须/纤维制备的工程化，实现了在管式炉开放体系中SiC纳米线的生长。微空间生长纳米线的思路与制备技术对其他一维纳米材料的宏量制备也具有重要指导意义。. 采用浮动化学气相沉积法制备了碳纳米管纤维，提出碳纳米管筒状物“sock”的“沉积-飘浮-自组装”D-F-A (deposition-float-assembly)形成机理，研究对化学气相沉积SiC纳米线纤维的纺丝具有指导意义。同时，通过湿法纺丝技术制得连续碳化硅纳米线-海藻酸复合纤维。. 超长单晶SiC纳米纤维具有高强度、超塑性，耐高温腐蚀和耐烧蚀性好等特性。采用真空抽滤/滚压法制备了由超长SiC纳米线组成的SiC纳米纤维纸/无纺布，可加工为无纺布、纸或毡，柔顺可折叠弯曲。SiC纳米纤维及纳米纸作为新型增强体，在高强度高韧性SiC/SiC陶瓷基复合材料、陶瓷/金属基复合材料、热气过滤、高温电磁波吸收及催化等领域具有应用前景。