高体积分数氮化硼纳米管宏观集成与定向调控机理及其多功能陶瓷基复合材料研究

Owing to excellent mechanical properties, high-temperature stability and radiation shielding capability, boron nitride nanotubes and their composites are considered to have broad applications in space radiation shielding. However, the low volume fraction in the composites and anisotropy of BNNTs lead to the deviation in the expected properties of the composites. Aiming to increase the volume fraction and alignment degree, several factors, such as BNNTs dispersion, macroscopic assembly and accurate alignment control, will be investigated in the proposal. It will develop BNNTs preform with network connected structure, and then prepare BNNTs/BN ceramic matrix composites to fulfill the potential space radiation shielding function by introducing BN as matrix via chemical vapor infiltration method. Effect of dispersion methodology of BNNTs on the macroscopic assembled boron nitride nanotubes with high volume fraction will be studied. To build the relationship between the mechanical stretching process and the alignment degree, the alignment behavior of BNNTs under the dynamical mechanical stretching process will also be investigated. The nanoinfiltration mechanism of chemical vapor infiltration method will be explored in order to realize the fully densification of BNNTs preform, which is the critical factor to obtain high performance BNNTs/BN composites. The expected significance of this research are to develop a space radiation shielding materials system that has high efficacy for shielding radiation, which will provide more security for future long duration manned spaceflight.

由于具有优异的力学性能、高温稳定性和中子辐射屏蔽性能，氮化硼纳米管及其复合材料在空间辐射屏蔽领域具有广阔的应用前景。但现有复合材料存在BNNTs体积分数不足的问题，同时由于BNNTs各向异性特点，导致材料性能低于预期。本项目着眼于提高BNNTs体积分数和定向程度，拟从BNNTs分散、宏观集成和精确定向调控等角度出发，构建具有网络连通结构的BNNTs预制体，并用于制备高性能BNNTs/BN陶瓷基复合材料。首先从BNNTs分散入手，研究不同分散机制对构建高体积分数BNNTs预制体结构的影响；动态研究机械拉伸工艺对BNNTs精确定向调控的作用机制，建立机械拉伸过程与BNNTs定向程度的关联关系。探索纳米孔隙化学气相渗透机理，以实现BNNTs预制体纳米孔隙致密化，获得高致密度高性能BNNTs/BN陶瓷基复合材料制备。本项目的成功实施将有望获得一种高性能辐射屏蔽材料，为未来长期载人航天任务提供可能。

氮化硼纳米管是一种由B和N原子交错排列组成的纳米管状材料，具有优异的力学性能和高温稳定性。将氮化硼纳米管与基体材料结合研制高性能复合材料是实现其宏观应用的主要途径之一。但目前有关氮化硼纳米管及其复合材料的研究水平离理论预测性能仍有较大差距。本项目利用改良高能球磨退火法研究了生长工艺参数对纳米材料合成过程的影响，提出氮化硼纳米材料气-液-固（V-L-S）生长原理，合成了一维氮化硼纳米管与二维氮化硼纳米片。通过改变催化剂尺寸实现了纳米管尺度的控制，利用尺寸均匀的纳米金属氧化物颗粒作为催化剂，合成了管壁尺寸均匀的氮化硼纳米管。以氮化硼纳米管等低维纳米材料为研究对象，提出了构建流体剪切场实现低维纳米材料宏观有序化新思路，利用极性溶液辅助机械拉伸工艺和挤出成型工艺分别实现低维纳米材料有序排列，并获得高性能复合材料。利用3D打印技术，实现三维石墨烯及其复合材料可控制备与结构性能设计。本项目圆满完成了研究目标，研究方法可以拓展到其他低维纳米材料，具有重要的示范意义。相关研究内容发表学术论文19篇，申请专利11项，均达到了预期目标。