多层结构SiCNW/(BN/SiC)n/ZrB2-SiC复合涂层界面控制及高温氧化烧蚀机理研究

To prevent carbon/carbon (C/C) composites from oxidation and ablation at the elevated temperature, a multi-layer SiCNW/(BN/SiC)n/ZrB2-SiC composite coating will be developed by a feasible three-step method in the present project. Firstly, a porous SiC nanowire layer is deposited on the surface of C/C composites by thermal evaporation reduction method. Secondly, the (BN-SiC)n interphase is deposited on the surface of the SiC nanowires by chemical vapor deposition method. Lastly, ZrB2-SiC multi-phase ceramic is deposited by supersonic plasma spraying technology into the porous structure layer composed by (BN-SiC)n interphase and SiC nanowires to obtain a dense multi-layer SiCNW/(BN/SiC)n/ZrB2-SiC composite coating. The project is aimed at getting high purity SiC nanowires, making full use of the enhancement of the alternating multi-layer interphase, achieving significantly the most toughening effect of SiC nanowires. In the project, the fabricating technologies and formation mechanism of the coating will be studied systematically. The effect of the SiC nanowires and (BN-SiC)n interphase on the microstructure, the mechanical properties, oxidation and ablation resistance of the coating will be investigated. The reinforcement mechanism of the (BN-SiC)n interphase coated SiC nanowires in the coating will be also revealed. The relationship between the microstructure of the coating and its oxidation and ablation resistance will be established. In addition, the oxidation and ablation mechanism of the coating in different service environments will be revealed. The research results of the project can provide the theoretical foundation for broadening the applications of C/C composites exposed to the high temperature and high gas velocity environment.

本项目针对碳/碳复合材料高温易氧化烧蚀难题，开发一种多层结构SiCNW/(BN/SiC)n/ZrB2-SiC复合涂层，拟首先采用热蒸发还原法在碳/碳复合材料表面制备SiC纳米线多孔层，再采用化学气相沉积法在SiC纳米线表面引入(BN/SiC)n界面相，最后利用超音速等离子喷涂技术将ZrB2-SiC陶瓷填充于由(BN/SiC)n界面相与SiC纳米线形成的多孔层中，进而获得致密的多层结构复合涂层。旨在制备高纯纳米线，充分利用交替多层界面相的增强作用，发挥纳米线的最大强韧化效果。系统研究涂层的制备工艺和形成机理，探讨纳米线、界面相对涂层微观结构、力学性能和抗氧化烧蚀性能的影响规律，明确带有界面相的纳米线在涂层中的增韧机理，建立涂层微观结构与抗氧化烧蚀性能之间的关系，揭示涂层在不同服役环境中的氧化烧蚀机理，为碳/碳复合材料在高温高质流冲刷环境中的应用提供理论基础。

为解决碳/碳复合材料高温易氧化烧蚀的难题，本项目开发了一种多层结构SiCNW/(BN/SiC)n/ZrB2-SiC复合涂层，首先采用热蒸发还原法在碳/碳复合材料表面制备SiC纳米线多孔层，再采用化学气相沉积法在SiC纳米线表面引入(BN/SiC)n界面相，最后利用超音速等离子喷涂技术将ZrB2-SiC陶瓷填充于由(BN/SiC)n界面相与SiC纳米线形成的多孔层中，进而获得致密的多层结构复合涂层。旨在发挥纳米线的最大强韧化效果，为碳/碳复合材料在高温高质流冲刷环境中的应用提供理论基础。.通过研究发现，SiCNW/(BN/SiC)n/ZrB2-SiC涂层中复合界面相层数为1时，其抗烧蚀性能最佳，线烧蚀率和质量烧蚀率分别为-0.29±0.06 μm/s和-1.90±0.46 mg/s。一方面，在烧蚀过程中BN/SiC界面相能通过多级环装裂纹扩展和拔出机制缓解涂层的热应力集中，另一方面，复合涂层在烧蚀过程中能生成具有良好自愈合效果的Zr-Si-B-O玻璃相，抑制了涂层的机械剥蚀，并阻止氧化性气氛向内扩散，大幅度提升了涂层的抗氧化烧蚀性能。