Oxidation-Based Sample Preparation of Nuclear Graphite for Transmission Electron Microscopy

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Student Presentation

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Karthik Chinnathambi


Graphite will be used as a moderator and structural material in the next-generation (Gen IV) nuclear reactors. Graphite undergoes drastic structural and microstructural changes under irradiation which negatively affects the in-service lifetime, so it’s important to develop a complete understanding of irradiation-induced structural changes. Transmission electron microscopy (TEM) is a powerful tool with which to both create and monitor damage processes in real-time. Sample preparation for TEM usually involves argon-ion milling which itself introduces damage into the graphite specimen. To ensure that the starting TEM specimens are defect-free, an oxidation-based technique is being developed in which specimens undergo an initial mechanical thinning via dimpling and are then oxidized in a controlled environment to create electron-transparent TEM specimens. In this work, TEM specimens of both NBG-18 and IG-110 grades of nuclear graphite have been prepared. Samples oxidized at around 630 to 640° for 18 to 24 minutes resulted in electron transparent specimens.

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