The determination of electrochemical reactivity and sustainability on individual hyper-stoichiometric UO2+ grains by Raman microspectroscopy and scanning electrochemical microscopy

He, Heming; Ding, Zhifeng; Shoesmith, David W.

doi:10.1016/j.elecom.2009.07.013

Cited by 21 publications

(15 citation statements)

References 14 publications

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“…Measurements were repeated at different points on the surface of each sample to confirm that the recorded spectra were representative of the whole sample. A loss of relative intensity in the T 2g band would indicate deviations from the perfect cubic fluorite structure, consistent with the formation of oxygen vacancies in the lattice …”

Section: Resultsmentioning

confidence: 86%

“…A loss of relative intensity in the T 2g band would indicate deviations from the perfect cubic fluorite structure, consistent with the formation of oxygen vacancies in the lattice. 41 The characteristic 1150 cm À1 2LO band of UO 2 was observed only for (U 0.94 La 0.06 )O 1.97 sample ( Fig. 4) and it disappeared when increasing the La content of the sample.…”

Section: July 2015mentioning

confidence: 90%

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Raman and X‐ray Studies of Uranium–Lanthanum‐Mixed Oxides Before and After Air Oxidation

et al. 2015

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UO 2 samples doped with 6, 11, 22 mol% lanthanum were examined before and after air oxidation. To verify the formation of uranium-lanthanum-mixed oxide solid solutions, powder X-ray diffraction (XRD) analyses of the crystalline phases in the materials were carried out. The presence of oxygen vacancies in the La-doped UO 2 samples was identified by Raman spectrometry. It was evidenced by changes induced in the Raman spectra by air oxidation. This latter was carried out either by increasing the Raman laser power or by thermally treating the samples at 500 K for 370 h. In addition, oxidation behavior differences of pure and La-doped UO 2 samples were reported by comparing XRD and Raman results of the samples before and after air oxidation. It was shown that the concentration of the M 4 O 9 (M: U, La) phase increased with increasing content of La, whereas inhibition for the formation of M 3 O 8 phase was observed.

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Section: Resultsmentioning

confidence: 86%

Section: July 2015mentioning

confidence: 90%

Raman and X‐ray Studies of Uranium–Lanthanum‐Mixed Oxides Before and After Air Oxidation

et al. 2015

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“…The peak at ~ 1150 cm -1 , originally claimed to be associated with electronic origin [46] can be assigned to be an overtone (2LO) of the LO phonon mode at ~575 cm -1 [45]. This peak behaves as a characteristic "finger print" [47] of the hyper-stoichiometric of uranium dioxide UO 2+x with the x value less than 0.09, and the peak intensity gradually decreases and eventually disappears with the change of stoichiometry from UO 2 to UO 2.09 . On the other hand, the T 2g model shifts to a higher angle and its intensity is weakened by excess oxygen being incorporated into UO 2 structure, resulting in a transition from fluorite to tetragonal phases.…”

Section: Fuel Chemistry and Stoichiometry By Xrd And Raman Analysismentioning

confidence: 98%

“…Another peak, located at ~ 630 cm -1 , displayed noticeable intensity changes which can attributed to cuboctahedra constituting U 4 O 9 phase [47,49]. However, this assignment has been questioned recently since this peak can also be observed at stoichiometric SIMFUEL UO 2 (simulated high burn-up fuel) [48].…”

Section: Fuel Chemistry and Stoichiometry By Xrd And Raman Analysismentioning

confidence: 99%

TiO2 doped UO2 fuels sintered by spark plasma sintering

Yao¹,

Scott²,

Xin³

et al. 2016

Journal of Nuclear Materials

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UO 2 fuels doped with oxide additives Cr 2 O 3 and TiO 2 display larger grain size, improving fission product retention capability and thus accident tolerance. Spark plasma sintering (SPS) was applied to consolidate TiO 2 -doped UO 2 fuel pellets with 0.5 wt % dopant concentration, above its solubility, in order to induce eutectic phase formation and promote sintering kinetics. The largest grain achieved is up to 80 µm by sintering at 1700 °C for 20 mins, and liquid U-Ti-O eutectic phase occurs at the triple junction of grain boundaries and significantly improves grain growth during sintering. The oxide additive also impedes the reduction of the initial hyperstoichiometric fuel powders to more stoichiometric pellets upon SPS. Thermal-mechanical properties of the sintered doped pellets including thermal conductivity and hardness are measured and compared with undoped pellets. The enlarged grain size (80 µm) and densification within short sintering duration highlight the immense possibility of SPS in fabricating large grain UO 2 fuel pellets to improve fuel performance.

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“…For example, SECM has been associated with a variety of optical/spectroscopic techniques: optical microscopy [18,23], single-molecule fluorescence spectroscopy [24], infrared spectroscopy [21,22] and with surface plasmon resonance [25,26]. SECM has also been successfully combined with Raman spectrometry [27][28][29]. More recently, SECM measurements with shear-force regulation of the probe position have been reported under a confocal Raman microspectrometer in order to study local corrosion phenomena [20].…”

Section: Introductionmentioning

confidence: 99%

Dual microelectrodes decorated with nanotip arrays: Fabrication, characterization and spectroelectrochemical sensing

Bombail

Garrigue

Goudeau

et al. 2019

Electrochimica Acta

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Gold microelectrodes decorated with nanotips were developed for spectroelectrochemical experiments. These new dual probes were fabricated by combining fabrication processes of scanning near-field optical microscopy with photolithography. A nanotip array was produced at the surface of a coherent optical fiber bundle by a wet chemical etching step. The resulting nanostructured surface was sputter-coated with a thin gold layer. This gold film conferred plasmonic properties to the sharp nanotips and served as well as the electrode material to enable electrochemical reactions. A photolithographic process was used to define on the bundle surface nanotips-decorated microelectrodes with tunable dimensions (radii ranging between 20 μm and 3.5 μm) individually or in an array format. The resulting microelectrodes with a regular nanotip pattern were characterized first by cyclic voltammetry. Numerical simulation was used to assess the electrochemical properties of these platforms and the influences of the recessed geometry and of the nanotips. Approach curves were recorded in negative and positive feedback modes of scanning electrochemical microscopy (SECM) on insulating and conducting substrates. Finally, spatially resolved Raman imaging allowed us to detect a mercaptobenzoic acid monolayer adsorbed on the microelectrode surface, demonstrating a surface-enhanced Raman scattering (SERS) effect induced by the gold-coated nanotips with a typical enhancement factor of~7 × 10 4. Such an approach introduces a reproducible method to fabricate promising SERS-active platforms with microelectrode behavior for SECM experiments.

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The determination of electrochemical reactivity and sustainability on individual hyper-stoichiometric UO2+ grains by Raman microspectroscopy and scanning electrochemical microscopy

Cited by 21 publications

References 14 publications

Raman and X‐ray Studies of Uranium–Lanthanum‐Mixed Oxides Before and After Air Oxidation

Raman and X‐ray Studies of Uranium–Lanthanum‐Mixed Oxides Before and After Air Oxidation

TiO2 doped UO2 fuels sintered by spark plasma sintering

Dual microelectrodes decorated with nanotip arrays: Fabrication, characterization and spectroelectrochemical sensing

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