In situ studies of the decomposition of ammonium uranyl carbonate in an electron microscope

An electron microscope has been used to study the reduction of ammonium uranyl carbonate (AUC) to UO2. The reactions could be followed both in the diffraction and the lattice image mode. The first intermediate obtained was amorphous UO3. Depending on the experimental conditions, either crystalline UO2 was formed directly from this phase, or several other intermediates were indicated. Properties like crystallinity and crystallite size of final UO2 were found to be a function of experimental conditions. Comparisons with properties of UO2 from the industrial process have been made. (orig.)