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Laser‐induced oxidation of UO 2 : A Raman study
Author(s) -
Elorrieta J.M.,
Bonales L.J.,
Naji M.,
Manara D.,
Baonza V.G.,
Cobos J.
Publication year - 2018
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.5347
Subject(s) - raman spectroscopy , laser , analytical chemistry (journal) , materials science , power density , raman laser , laser power scaling , excitation , chemistry , raman scattering , optics , power (physics) , thermodynamics , physics , electrical engineering , chromatography , engineering
A reliable method to probe and characterise the oxidation of actinide oxides by means of Raman spectroscopy is introduced. The present so‐called Raman laser heating method enables studying the behaviour of various compounds at high temperatures and under a given atmosphere with the unique alteration of a small amount of sample, which is certainly advantageous in terms of safety when handling hazardous or radioactive materials. The approach is based on a dual use of the laser beam, which is at the same time employed as excitation source for the Raman analysis and as heating source, by exploiting the possibility to vary the beam power density reaching the sample surface. A high laser power density can lead to a significant increase of the analyte surface temperature by up to several hundred of degrees. A sufficiently low power density allows us to subsequently acquire the corresponding Raman spectrum at the same point without distorting the measurement. In this work, UO 2 powder has been subjected to Raman laser heating in air as a proof of this method's applicability, attaining a sequential acquisition of the characteristic Raman spectra of the different oxides involved in the oxidation from UO 2 to U 3 O 8 . The temperature at which such sequence of phase transformations started to occur was estimated to be around (560 ± 40) K. The temperature at the sample surface was estimated from the Stokes/anti‐Stokes intensities ratio, using a similar set‐up to that used in the Raman laser heating experiments. These results are particularly appealing in remote analyses, like those required in the study of nuclear fuel and nuclear waste.