Structure of UC2 and U2C3: XRD, 13C NMR and Exafs Study

Abstract

In this study, uranium dicarbide (UC2) has been prepared by arc melting and heat treated under vacuum to form uranium sequicarbide (U2C3) in the presence of a second phase UC2-z. Both samples, as cast and heat treated, have been characterised by chemical analyses, X-ray diffraction (XRD), 13C magic angle spinning nuclear magnetic resonance (MAS-NMR) and by extended X-ray absorption fine structure (EXAFS). The composition, the purity, the various environments of both U and C atoms as well as the bonds length with the coordination number have been determined. By combining a long-range order method (XRD) and short-range order spectroscopy techniques (EXAFS and NMR), a unique view on the microstructure of UC2, before and after heat treatment, and of U2C3 phase has been achieved.