TEM/STEM observation of ZrC coating layer for advanced high temperature gas cooled reactor fuel, 3

Aihara, Jun ; Ueta, Shohei   ; Yasuda, Atsushi; Takeuchi, Hitoshi; Sawa, Kazuhiro; Motohashi, Yoshinobu*

We report in this study the microstructural change of the ZrC coating layers with annealing. We already reported the microstructures of as-fabricated ZrC coating layers last year. ZrC coated particles were annealed at about 1800 C for 1 hour to simulate the sintering process of the real HTGR fuel. With annealing, ZrC grains were slightly grown especially near the surface regions and kept their orientation. The free carbons and/or voids cohered at the grain boundaries. The cohered free carbons and/or voids were appeared to form the clods of the free carbon ribbons. In addition, IPyC/ZrC boundary structure changed. Fibrous carbon texture was found at IPyC/ZrC boundary even in the specimen of the batch of which that texture was not observed in the as-fabricated specimen.