化学气相沉积Hf(Ta)C陶瓷涂层的生长行为与超高温抗氧化机理

In ultra-high temperature environment with oxygen-rich, the ablation protection is the key problem for C/C composite to apply as hot structural component of new generation high-performance spacecraft. HfC ceramic coating can improve the anti-ablation properties of C/C composite significantly. However, the coating surface will form a porous oxide, which can lead to the degeneration of coating resulting from phase transformation of HfO2, and then influence the lifetime and stability of HfC coating. In this project, Ta is used to modify HfC coating for the purpose of increasing the oxidation resistance of HfC coating in ultra-high temperature, by the means of improving the density and stability of HfO2 layer. Chemical vapor deposition was applied to prepare the Hf(Ta)C coating on C/C composites, the influence and action mechanism of Ta on coating structure were investigated, and the growth mechanism of Hf(Ta)C coating was discussed. The effects of composition and structure on the ultra-high temperature oxidation behavior of coating were also investigated. Moreover, the formation mechanism of composite oxides and the collaborative action of the composite oxides during oxidation process were investigated in detail to reveal the anti-oxidation mechanism of Hf(Ta)C coating in ultra-high temperature. This project can be provide theoretical basis for the optimization of structure and performance of Hf(Ta)C coating, as well as the research on the ultra-high temperature ceramic coating for C/C composites.

炭/炭复合材料在超高温富氧环境下的烧蚀防护，是其应用于新一代航天飞行器热结构部件急需解决的关键问题之一。HfC陶瓷涂层可有效改善炭/炭复合材料的超高温抗烧蚀性能，但其表面生成的HfO2层为多孔结构，且相变引起的体积膨胀容易导致涂层快速失效，从而影响HfC涂层的长时使用寿命和可靠性。本项目以改善HfO2产物致密性和稳定性为出发点，利用Ta改性HfC提高涂层的超高温抗氧化性能。采用化学气相沉积在炭/炭复合材料表面制备Hf(Ta)C陶瓷涂层，研究Ta改性对涂层微观结构的影响及作用机理，探讨涂层的生长机制；研究涂层成分、结构对超高温氧化行为的影响；深入研究复合氧化物的形成机制以及复合氧化物在超高温氧化过程中的协同作用，揭示涂层的超高温抗氧化机理，为Hf(Ta)C陶瓷涂层的结构及性能优化，以及炭/炭复合材料超高温陶瓷涂层的研制和应用奠定理论基础。

为改善HfC氧化产物致密性和稳定性，通过添加Ta在碳/碳表面合成了Hf(Ta)C陶瓷涂层，研究了涂层的微观结构、力学性能和超高温抗氧化性能，探明了Ta对涂层结构、力学性能及超高温抗氧化性能的作用机理，揭示了Hf(Ta)C涂层的沉积生长机制和超高温抗氧化机理。本项目取得的研究成果如下：.（1）利用化学气相共沉积合成了不同Ta含量的Hf(Ta)C陶瓷涂层，初步实现了成分和微观结构的可控形成；（2）Hf(Ta)C涂层呈热解炭包覆Hf1-xTaxC结构特征，Ta的固溶可以起到细化晶粒的作用，揭示了涂层的沉积机理和生长机制；（3）建立了Hf(Ta)C涂层结构与力学性能的对应关系，发现涂层呈现高密度位错-颗粒相互作用的蠕变变形机制；（4）Ta的固溶可明显改善HfC涂层的超高温抗氧化性能，建立了涂层成分、结构与烧蚀环境（温度、压力）的内在联系，探明了氧化产物的形成机制及涂层的失效形式；（5）Ta的固溶有助于生成致密氧化物结构，低氧扩散过渡层和低熔点溶体填充HfO2骨架结构是涂层具有优异抗氧化性能的关键；解析了涂层各类界面的高温演变行为，揭示了涂层的超高温抗氧化机理。.本项目三年来总计发表有基金标注的期刊论文4篇，其中SCI收录3篇；参加国际学术交流7人次，国内会议2人次；培养硕士1人。