New insight into UO2F2 particulate structure by micro-Raman spectroscopy

Abstract

h i g h l i g h t s " Uranyl fluoride particles prepared via hydrolysis of UF 6 were deposited on metallic substrates for micro-Raman spectroscopy." New substrates enhanced Raman signal from the particles of the size below 1 lm." Raman shift of U-O symmetric stretching appeared at values 847/842/839 cm À1 due to gradual water absorption by UO 2 F 2 . " The smooth substrates fa cilitated the process of water saturation of deposited particulate uranyl fluoride. " UO 2 F 2 particles deposited of metallic surfaces appeared very stable under long-term exposure of a laser beam. a b s t r a c tUranyl fluoride particles produced via hydrolysis of uranium hexafluoride have been deposited on different substrates: polished graphite disks, silver foil, stainless steel and gold-coated silicon wafer, and measured with micro-Raman spectroscopy (MRS). All three metallic substrates enhanced the Raman signal delivered by UO 2 F 2 in comparison to graphite. The fundamental stretching of the U-O band appeared at 867 cm À1 in case of the graphite substrate, while in case of the others it was shifted to lower frequencies (down to 839 cm À1 ). All applied metallic substrates showed the expected effect of Raman signal enhanceme nt; however the gold layer app eared to be most effective. Application of new substrates provides more infor mation on the molecular structure of uranyl fluoride precipitation, which is interesting for nuclear safeguards and nuclear environmen tal analysis.

Identifying anthropogenic uranium compounds using soft X-ray near-edge absorption spectroscopy

“…Methods that can non-destructively detect and characterize these compounds would be highly desirable to monitor process chemistry and to chemically identify any environmental contamination. While a variety of spectroscopic probes exist for detecting uranium, including fluorescence spectroscopy [9,10] and Raman spectroscopy [11,12], X-ray absorption techniques are advantageous in that they are element-specific and highly sensitive to physical and chemical structure. Soft X-rays-X-rays with an energy below 1 keV-are particularly useful because absorption edges in this regime show minimal lifetime broadening (0.1-0.3 eV) [13][14][15], and as a result sharper absorption peaks and greater chemical information can be obtained.…”

Identification of Uranyl Minerals Using Oxygen K‐Edge X‐Ray Absorption Spectroscopy

“…Micro‐Raman spectroscopy has been used to identify specific markers for UO 2 , UO 4 •4(H 2 O) and U 3 O 8 , among other compounds (Pointurier and Marie , Stefaniak et al . ). For uranyl compounds, the vibrational spectra can change subtly depending on the co‐ordination environment in the equatorial plane (Liu et al .…”

“…, Stefaniak et al . ). Synchrotron X‐ray imaging and spectromicroscopy have been used previously to analyse uranium debris.…”

“…Spectromicroscopy can be used to study these localised components specifically in situ. Furthermore, microscale studies of the structure and composition of uranium particles and deposits can often serve as clues to the sample's storage conditions (Hanson et al 2005, Stefaniak et al 2013. Synchrotron X-ray imaging and spectromicroscopy have been used previously to analyse uranium debris.…”

Morphologic and chemical characterization of products from hydrolysis of UF6

“…However, UOF 4 was detected by FT-IR following hydrolysis of UF 6 conducted in an argon matrix, a potential trap for reaction intermediates, or in solid films of UF 6 /H 2 O mixtures prepared at 12 K and slowly annealed to 242 K [5,18]. Raman spectra collected from UF 6 hydrolysis products on stainless silver foil, stainless steel, or goldcoated silicon wafers revealed that the signals from UO 2 F 2 products were enhanced compared to the signals from UO 2 F 2 products deposited on graphite [19].…”