In Situ Liquid Cell Transmission Electron Microscopy Study of Studtite Particle Formation and Growth via Electron...

This study presents in situ observations of studtite (UO₂O₂(H₂O)₂·2H₂O) crystal growth utilizing liquid phase transmission electron microscopy (LP-TEM). Studtite was precipitated from a uranyl nitrate hexahydrate solution using hydrogen peroxide formed by the radiolysis of water in the TEM electron beam. The hydrogen peroxide (H₂O₂) concentration, directly controlled by the electron beam current, was varied to create local environments of low and high concentrations to compare the impact of the supersaturation ratio on the nucleation and growth mechanisms of studtite particles. The subsequent growth mechanisms were observed in real time by TEM and scanning TEM imaging. After the initial precipitation reaction, a post-mortem TEM analysis was performed on the samples to obtain high-resolution TEM images and selected area electron diffraction patterns to investigate crystallinity as well as energy-dispersive X-ray spectroscopy spectra to ensure that studtite was produced. The results reveal that studtite particles form through various mechanisms based on the concentration ratio of uranyl to H₂O₂ and that studtite is initially produced through an amorphous intermediary prior to formation of the crystalline material commonly reported in the literature.