多层结构C/(SiC-C)n/SiC-ZrB2复合材料界面控制及其高温损伤行为

Thermal protection carbon/carbon (C/C) composite is the important super-high temperature structure material in the high and new technology fields. But the problem of the thermal stress and interfacial debonding exists for the modified and coated C/C composites. In this project, a novel multilayer structure C/(SiC-C)n/ SiC-ZrB2 oxidation-resistance composites are proposed. The multilayer matrix structure of pyrolytic carbon and SiC is prepared in the carbon fiber perform. The internal stress would effectively be transferred and released according to the toughening principle of the laminated interfaces. The SiC-ZrB2 gradient coatings are conducted on the composite surface. The mismatch of the thermal expansion coefficient between ZrB2 and the composites can effectively be relaxed and the interfacial bonding strength between coating and composites can be improved. These processes would contribute to the thermal protection integration of matrix modification and coating methods. The preparation conditions and formation mechanism of the designed C/(SiC-C)n composites and SiC-ZrB2 coatings would be investigated. The interfacial bonding characteristics and interaction mechanism among different matrix layers and the phases in the coatings will be explored. The influence of the thickness and distribution of the matrix layers, the interface state and the kind of pyrolytic carbon on the microstructure and properties of the composites will be discussed. The toughening and failure mechanism of C/(SiC-C)n composites with SiC-ZrB2 gradient coating under different service conditions would be revealed. The above research can lay a theoretical foundation for the application of these composites in the heat-resistant thin and sharp components.

热防护炭/炭（C/C）复合材料是高新技术领域重要的超高温结构材料，但对于基体改性及涂层C/C复合材料构件，存在材料内部热应力聚集崩裂及界面撕裂脱粘等问题。本项目提出一种新型增韧多层结构C/(SiC-C)n/SiC-ZrB2抗氧化复合材料，通过在炭纤维预制体内构筑热解炭与SiC多层基体结构，利用叠层界面强韧化原理，实现材料内部应力的有效转移及释放；通过在复合材料表面制备SiC-ZrB2梯度复合涂层，提高涂层与复合材料间界面结合强度，实现材料基体改性与涂层的一体化多层结构热防护。探索不同基体层之间及涂层组元间界面结合特点及相互作用机制，研究基体层厚度及结构、界面状态及热解炭组织结构对复合材料微观结构与性能的影响规律，阐明梯度涂层沉积过程动力学及其物理化学变化特征，揭示复合材料在服役条件下强韧机制及氧化烧蚀损伤行为，为该复合材料在热防护薄壁和尖角锐形构件的应用提供理论基础。

热防护炭/炭（C/C）复合材料是高新技术领域重要的超高温结构材料，但对于基体改性及带涂层的C/C复合材料构件，存在材料内部热应力聚集崩裂及界面撕裂脱粘等问题。本项目提出一种新型增韧多层结构C/(SiC-C)n/SiC-ZrB2抗氧化复合材料，通过在炭纤维预制体内构筑热解炭与SiC多层基体结构，利用叠层界面强韧化原理，实现了材料内部应力的有效转移及释放；通过在复合材料表面制备SiC-ZrB2复合涂层，提高了涂层与复合材料间界面结合强度，实现了材料基体改性与涂层的一体化多层结构热防护。.研究了不同基体层之间及涂层组元间界面结合特点及相互作用机制，以及基体层界面状态对复合材料微观结构及性能的影响规律，结果发现，通过叠层强韧化，材料的弯曲强度提高了59.5%，断裂韧性增加40%，比强度提升57.1%。对涂层沉积过程动力学及其物理化学变化特征进行了系统研究，揭示了复合材料在超高温条件下的韧化机制及氧化烧蚀损伤行为，研究发现，1500℃等温氧化216h后，SiC-ZrB2涂层试样的失重率仅有0.15%；经历30次“室温↔1500℃”热循环后，C/(SiC-C)n/SiC-ZrB2材料的氧化失重率和弯曲强度保持率分别为1.68%和94%。项目研究成果为该复合材料在薄壁和尖角锐形超高温构件的应用奠定了坚实的理论基础。