Dislocation analysis of a complex sub-grain boundary in UO2 ceramic using accurate electron channelling contrast imaging in a scanning electron microscope

H. Mansour (1) , M. Crimp (2) , N. Gey (1, 3) , X. Iltis (4) , N. Maloufi (1, 3)

1 LEM3 - Laboratoire d'Etude des Microstructures et de Mécanique des Matériaux
2 Michigan State University [East Lansing]
3 Labex DAMAS
4 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)

In this work, accurate electron channelling contrast imaging (A-ECCI) assisted by high resolution selected area channelling patterns (HR-SACP) was used to characterize the structure of a complex low sub-grain boundary in a creep deformed uranium dioxide (UO$_2$) ceramic. The dislocations were characterized using TEM-style g·b = 0 and g·b × u = 0 contrast criteria. Misorientations across the boundary were measured using HR-SACPs with 0.04° precision and high accuracy EBSD. The boundary was determined to be asymmetric and mixed in nature, composed of two distinct regions with different dislocation morphologies and a misorientation below 0.5°. The A-ECCI, HR-SACP, and HR-EBSD results are consistent, confirming A-ECCI as a powerful tool for characterizing even complex dislocations structures using scanning electron microscopy. This is particularly true for UO$_2$, since this material is very difficult to thin, which makes TEM examination of sub-boundaries over the scale of several micrometers difficult. Furthermore, in this study, the change in dislocations arrangement along the breath of the complex low angle sub-grain boundary is related to the misorientation across the boundary.

Mots clés: SACP; EBSD; Accurate-ECCI; Scanning electron microscopy; Crept Uranium dioxide; Sub-grain boundary structure; Dislocations

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique Nucléaire Théorique [nucl-th]

H. Mansour, M. Crimp, N. Gey, X. Iltis, N. Maloufi. Dislocation analysis of a complex sub-grain boundary in UO2 ceramic using accurate electron channelling contrast imaging in a scanning electron microscope. Ceramics International, 2019, 45 (15), pp.18666-18671. ⟨10.1016/j.ceramint.2019.06.091⟩. ⟨cea-02339717⟩