Visualizing Non-Classical Growth of f-Element Oxalates with Cryo-TEM

Cryo-transmission electron microscopy (TEM) was utilized to observe the initial stages of <i>f</i>-element oxalate morphologies under varying solution conditions, tracking particle nucleation and growth. U and Pu nitrites were mixed with oxalic acid to produce their respective oxalates. The reaction was stopped by vitrification of the reactants on a TEM grid, enabling the examination of early, meta-stable particle stages. The size and shapes of precipitates were studied over different reaction durations. Chemical analysis of cryo-samples was conducted using EFTEM, while post-mortem STEM-EELS provided more detailed chemical insights into dried samples. Images taken after 10 seconds revealed larger particles formed by the aggregation of smaller particles through particle attachment. Cryo-TEM unveiled the intermediate phases of this non-classical growth process. These findings will be discussed as part of a comprehensive investigation into the complete growth cycle, utilizing a combination of optical and electron microscopy techniques.