ABSTRACT Pyrolytic graphite (PyG) coatings on high-density graphite (HDG) substrates were deposited by chemical vapour deposition using propane and methane as precursor gas at aprocess temperature of 1800°C. Upon cooling to room temperature, cracking and delamination were observed in the PyG layer at certain edges of flat substrates deposited in propane cycle, attributed to large thermal expansion mismatch stresses. The PyG coatings deposited using different precursor hydrocarbon sources were characterised using polarised light microscopy, scanning electron microscope, X-Ray diffraction analysis, Laser Raman Spectroscopy and X-ray Photoelectron Spectroscopy. Microstructure analysis revealed coarse structure cones grown with larger cone angles. The large deposition rate, associated growth and thermal stress in the case of propane cycle have led to the cohesive delamination of the PyG coating. Nickel melting studies to simulate the uranium melting was carried out in PyG coated HDG crucibles whichshowed reactive dissolution of PyG at the Ni/crucible interface.

中文翻译：

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以丙烷和甲烷为前驱体的 CVD 热解石墨涂层的微观结构和相表征

摘要 使用丙烷和甲烷作为前体气体，在 1800°C 的工艺温度下，通过化学气相沉积在高密度石墨 (HDG) 基材上沉积热解石墨 (PyG) 涂层。冷却至室温后，在丙烷循环中沉积的平坦基板的某些边缘处的 PyG 层中观察到开裂和分层，这归因于大的热膨胀失配应力。使用偏光显微镜、扫描电子显微镜、X 射线衍射分析、激光拉曼光谱和 X 射线光电子光谱对使用不同前体烃源沉积的 PyG 涂层进行表征。微观结构分析揭示了以较大锥角生长的粗结构锥。沉积速率大，在丙烷循环的情况下，相关的生长和热应力导致了 PyG 涂层的内聚分层。在 PyG 涂层 HDG 坩埚中进行模拟铀熔化的镍熔化研究，显示出 PyG 在 Ni/坩埚界面处的反应溶解。