posted on 2023-12-05, 17:04authored byNick Kurtyka, Brian van Devener, Brandon W. Chung, Luther W. McDonald
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.