In-SEM Raman microspectroscopy coupled with EDX – a case study of uranium reference particles

Abstract

Information about the molecular composition of airborne uranium-bearing particles may be useful as an additional tool for nuclear safeguards. In order to combine the detection of micrometer-sized particles with the analysis of their molecular forms, we used a hybrid system enabling Raman microanalysis in high vacuum inside a SEM chamber (SEM-SCA system). The first step involved an automatic scan of a sample to detect and save coordinates of uranium particles, along with X-ray microanalysis. In the second phase, the detected particles were relocated in a white light image and subjected to Raman microanalysis. The consecutive measurements by the two beams showed exceptional fragility of uranium particles, leading to their ultimate damage and change of uranium oxidation state. We used uranium reference particles prepared by hydrolysis of uranium hexafluoride to test the reliability of the Raman measurements inside the high vacuum. The results achieved by the hybrid system were verified by using a standalone Raman microspectrometer. When deposited on exceptionally smooth substrates, uranyl fluoride particles smaller than 1000 nm could successfully be analyzed with the SEM-SCA system.

Optimizing use of the structural chemical analyser (variable pressure FESEM‐EDX raman spectroscopy) on micro‐size complex historical paintings characterization

“…The disadvantage of this procedure is long‐term electron beam exposure, such that several nondesirable collateral effects arise which can compromise reliable Raman data; these include carbon deposition on samples, and damage induced by the vacuum and the electron. Therefore, depending on the aim of the investigation the analytical sequence can be changed, such that Raman spectra can be acquired first (Stefaniak et al ., ).…”

“…Factors initiating damage processes such as oxidation/reduction and phase transformation causing molecular, elemental or physical changes include the atmosphere (vacuum/air modes), laser beam intensity, sample preparation or particle structure. Laser‐induced damage on pigments analysed with RMS has been widely reported (Burgio & Clark, ; Navas et al ., ) as has damage to particles (aerosols) studied with SEM−SCA (Stefaniak et al ., , ; Worobiec et al ., , ). Worobiec et al .…”

“…In 2003, Renishaw launched the SCA technique and presented the advantages of its use in diverse fields (Williams et al ., ; Brooker et al ., ; Prusnick et al ., ; Brooker et al ., ; Kawauchi et al ., ). Since 2004, in‐SEM Raman analyses have been used to identify bacteria (Jarvis et al ., ), mineral particles and aerosols (Stefaniak et al ., ; Worobiec et al ., ; Worobiec et al ., ), slag (Gómez‐Nubla et al ., ), uranium compounds (Pointurier & Marie, ; Stefaniak et al ., ), metal‐rich particles (Goienaga et al ., ), for criminalistics purposes (Otieno‐Alego, ) and to solve biological problems (Van Apeldoorn et al ., ; Hazekamp et al ., ; López‐Sánchez et al ., ). In the field of heritage science, SEM−SCA has been applied to typify clayey earth pigments (Ospitali et al ., ), archaeological pottery (Bersani et al ., ) and ancient bronzes (Ospitali et al ., ).…”

Characterization of uranium tetrafluoride (UF4) with Raman spectroscopy

“…Previous efforts have utilized the SCA to characterize various uranium oxides in situ within a SEM, but none have published UF 4 particulate measurements. [26,27] Multiple particles were analyzed in this work, and representative Raman spectra are shown in Fig. S2 (Supporting Information).…”

A multimodal microcharacterisation of trace‐element zonation and crystallographic orientation in natural cassiterite by combining cathodoluminescence, EBSD, EPMA and contribution of confocal Raman‐in‐SEM imaging

“…The mirror is connected through a special interface to a conventional μ‐Raman spectrometer. The advantage of such a system has been established for different applications, including forensic applications (Otieno‐Alego, ) and characterisation of individual particles (Worobiec et al ., ; Stefaniak et al ., ; Pointurier and Marie, ; Nelson et al ., ), biological samples (Jarvis & Goodacre, ; Jarvis et al ., ) and mineralogical samples (Stefaniak et al ., ; Maubec et al ., ).…”