沉积在核石墨IG-110基体上的热解炭涂层微观结构

摘要

采用化学气相沉积技术，以甲烷作为碳源，在核石墨IG-110基体上制备层状热解炭涂层。利用偏光显微镜、扫描电子显微镜( SEM)、透射电子显微镜( TEM)以及同步辐射掠入射X 射线衍射( GI-XRD)研究热解炭涂层的微观结构和生长特性。结果表明，热解炭涂层具有大锥体、小锥体和再生锥体三种生长锥微观结构，热解炭片层间结合紧密，生长锥间结合密实。热解炭涂层存在光滑层和再生层两种织构，每种织构都含有两种晶面间距不同的相结构，平滑层主要含有低石墨化度相，而再生层主要含有高石墨化度相。热解炭涂层致密的微观结构和仅存在的纳米级别的微孔使其可以作为气体阻隔涂层。%The molten salt reactor ( MSR) is one of the six Generation IV reactors that is being reexamined today, owing to its unique fuel cycle capabilities and safety characteristics. IG-110 nuclear graphite a candidate material for constructing a MSR. However, the existence of large pores at its surface is a big problem due to the impregnation of molten salts and the diffusion of fission product gases into the graphite through the pores. A pyrolytic carbon ( PyC) coating can act as a barrier coating on the nuclear graphite. Investigation of the microstructure and growth characteristics of PyC is very important for an understanding of the relationship between microstructure and performance. In this study, polarized light microscopy, scanning electron microscopy, transmission electron microscopy and synchrotron based grazing incidence X-ray diffraction were used to study the microstructure and growth characteristics of the PyC coating. Results show that the PyC coating shows three growth cones ( a large cone, a smaller one and a regenerative cone) and exhibits a wave-like layered structure. The resulting structure is fairly dense. There are two kinds of textures in the PyC coating:smooth laminar and regenerative laminar, each of which contains two crystal structures with different interlayer spacings. The smooth laminar carbon has mostly a low degree of graphitization, while the regenerative laminar structure mainly has a high degree of graphitization. The PyC coating is a perfect barrier to gas infiltration due to its compact structure and it containing only nanopores rather than large pores.