CVD跨尺度制备定向CNTs/SiC的纳米界面新特性与强韧性规律

Carbon nanotubes (CNTs) with outstanding strength and toughness are optimal nanometer material for ultimate form of fibrous reinforcement. Until now, there are few articles published reporting that the mechanical properties of CNTs reinforced ceramic matrix composites (CMCs) have been greatly improved, because the CNTs reinforced CMCs have many challenges, such as poor dispersion quality, low volume fraction and bad interfacial bonding, to be overcome. In our project, chemical vapor deposition (CVD) method at low temperature is proposed to prepare CNTs/SiC composites on multi-scales with controlled interfaces, high CNTs volume fraction and free damage of CNTs. 1D, 2D and 3D preforms will be prepared with proper orientations, layers and laminations of the aligned CNTs, in which the SiC is then in-situ deposited by CVD to produce nano-, micron-, and millimetric-composites with interfaces of small nano-scale, large suface area, wide distribution and high bonding strength. New strengthening and toughening mode of the CNTs/SiC composites were obtained by reinforcement refinement and matrix refinement. Studying new characteristic of the nano-scale interfaces and its effect on macro-mechanical properties of these composites, building the calculational model and theoretically analyzing the experimental data on each dimension will reveal the transformation mechanism of huge nanometer surface effects of the CNTs to interface effects of the composites, composite rule of the material properties with change in scales and dimensions, and new nano-scale interfacial stress transfer law and toughening characteristic. This study will enrich the fabrication method and the strengthening-toughening theory of CMCs reinforced by nanofibres with very low density and ultra high strength properties.

碳纳米管（CNTs）具有极高强度和韧性，被誉为最理想的纳米增韧材料和纤维类强化相的终极形式。但目前CNTs增强陶瓷复合材料存在CNTs不易分散，体积分数低和界面结合差的缺点，较少有力学性能大幅提高的报道。本项目创新地提出化学气相沉积（CVD）法温度低、界面可控和不损伤CNTs等优点跨尺度制备高体积分数CNTs/SiC。按CNTs取向适当排列、铺层和编织，CVD原位沉积SiC获得纳米级、微米级和毫米级多维复合材料，可形成尺度小、面积大、分布广、结合强的界面，表现出增强体细化和基体细化协同强韧化的新模式。研究界面小尺度新特性与大尺度宏观性能（强度韧性等）的映射关系，逐维建模计算与理论分析，揭示CNTs庞大纳米表面效应向复合材料界面效应的转变机理，材料维数变化与尺度变化的性能复合规律，以及纳米尺度下新的界面应力传递规律与韧化特性。丰富超轻高强纳米纤维增强陶瓷基复合材料制备方法和强韧化理论。

本项目以解决传统碳纳米管(CNTs)增强陶瓷基复合材料制备过程中CNTs难分散、体积分数低和界面结合差等缺点为目的，采用化学气相沉积法(CVD)温度低、界面可控和不损伤碳纳米管(CNTs)等优点结合多维CNTs预制体制备了高体积分数CNTs/SiC复合材料。研究了定向CNTs阵列本征结构及其CVD工艺适应性，测试了CVD法大尺度CNTs阵列/SiC复合材料抗氧化性及力学性能。优化了CNTs二维巴基纸及三维气凝胶制备工艺，表征了浮动催化法二维CNTs膜、三维泡沫微结构。结合CVD法制备了二维高导电及三维各向异性CNTs/SiC复合材料。揭示了纳米级CNTs小尺度、大面积、强结合界面特性与多维大尺度复合材料宏观性能的关系，及材料维数变化与尺度变化的性能复合规律。在此基础上，进一步通过电泳沉积方法将CNTs引入C/SiC复合材料中，研究了电沉积工艺、CNTs引入量与引入位置等工艺参数对CVD法C/SiC复合材料界面性质的影响规律，优化各项参数，匹配了纳米CNTs与微米碳纤维二元面，获得了二元界面控制方法。结合拉伸强度、弯曲强度等性能测试与显微结构、断口形貌分析，研究了界面强弱匹配与强韧性和不同能耗机制之间的关系，揭示二元界面的强韧化机理。同时研究了CNTs电导损耗及界面极化机制对C/SiC复合材料电磁屏蔽性能的影响。研究成果丰富了超轻高强纳米纤维增强结构——功能一体化陶瓷基复合材料制备方法和纳米、微米二元界面强韧化机理。解决的问题具有重要的学术研究价值及应用前景。