Synthesis of size-controlled UO<sub>2</sub> microspheres from the hydrothermal conversion of U(<scp>iv</scp>) aspartate

Trillaud, V.; Maynadié, Jèrôme; Manaud, Jérémie; Hidalgo, José Manuel Soto; Meyer, Daniel; Podor, Renaud; Dacheux, Nicolas; Clavier, Nicolas

doi:10.1039/c8ce01352g

Cited by 21 publications

(36 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Indeed, after the initial decomposition of the oxalate moieties, the formation of the oxide was likely to occur through the formation of hydroxides, which further rapidly aged to form UO2+x.nH2O. This mechanism was already depicted by several authors 14,39 . Rai et al already reported that such reaction operated at room temperature for pH > 2 40 , while the solubility of amorphous UO2 did not sustain important variation up to 300°C 13 .…”

Section: Effect Of Temperaturementioning

confidence: 72%

Hydrothermal Conversion of Uranium(IV) Oxalate into Oxides: A Comprehensive Study

et al. 2020

Self Cite

View full text Add to dashboard Cite

Within the development of future nuclear reactors, wet chemistry routes have been investigated for the fabrication of advanced oxide fuels. In this frame, a multi-parametric study focused on the hydrothermal conversion of uranium(IV) oxalate U(C2O4)2.nH2O into uranium oxides was undertaken in order to unravel the effects of temperature, pH and kinetics. For pH  1, the lowest temperatures explored (typically from 180 to 200°C) led to stabilize UO2+x/U4O9 mixtures exhibiting a global O/U ratio evaluated to 2.38 ± 0.10 from U M4-edge HERFD-XANES experiments. Higher temperatures (220-250°C) led the oxide stoichiometry to decrease down to 2.13 ± 0.04 which corresponds to a lower fraction of U4O9 in the mixture. Additionally, increasing the temperature of the hydrothermal treatment efficiently improved the elimination of residual carbon species and water. Hydrothermal conversion of U(C2O4)2.nH2O also led to a drastic modification of the powders morphology. With this aim, pH tuning could be used to shift from bipyramidal aggregates (up to pH = 1), microspheres (2 ≤ pH ≤ 5) then to nanometric powders (pH > 5). Finally, a kinetics study showed that uranium oxides can be obtained from the hydrothermal decomposition of oxalate within only few hours. If the samples early collected during the treatment always presented the characteristic XRD lines of UO2+x/U4O9 fluorite-type structure, they were found to be strongly oxidized (O/U = 2.65 ± 0.14) which suggested the existence of a U(VI)-bearing amorphous secondary phase. This latter further tended to reduce through time. Hydrothermal conversion then probably proceeds as a two-step mechanism composed by the oxidative decomposition of uranium(IV) oxalate followed by the reduction of uranium by organic moieties and its hydrolysis. It appears as an easy and efficient way to yield highly pure uranium oxide samples in solution.

show abstract

Section: Effect Of Temperaturementioning

confidence: 72%

Hydrothermal Conversion of Uranium(IV) Oxalate into Oxides: A Comprehensive Study

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…Synthetic UO 2 microspheres (ICSM particles) were analyzed by SEM/EDX in order to characterize their porosity and size distribution. The SEM characterization was carried out on particles deposited on a graphite disk without collodion, as this non‐conductive organic polymer degrades the quality of the SEM pictures.…”

Section: Methodsmentioning

confidence: 99%

“…Preparation of the ICSM particles was based on the initial precipitation of U(IV) aspartate from a mixture of tetravalent uranium in hydrochloric media and aspartic acid. 32 This precursor was then processed under hydrothermal conditions (T = 160°C, t = 30 h) in order to achieve the conversion towards UO 2 and to recover spherical particles. Finally, the resulting powder after this treatment was heated at 600°C under an Ar/H 2 -2% atmosphere in order to eliminate residual organics and water.…”

Section: Sample Preparationmentioning

confidence: 99%

See 1 more Smart Citation

Determination of the isotopic composition of single sub‐micrometer‐sized uranium particles by laser ablation coupled with multi‐collector inductively coupled plasma mass spectrometry

Ronzani

Hubert

Pointurier

et al. 2019

Rapid Comm Mass Spectrometry

View full text Add to dashboard Cite

Rationale A multi‐collector inductively coupled plasma (MC‐ICP) mass spectrometer coupled to a UV ns‐laser ablation (LA) system was used to measure uranium isotopic ratios (234U/238U, 235U/238U and 236U/238U) in single uranium particles of various sizes and isotopic compositions, including home‐made sub‐micrometric natural uranium particles of narrow size distribution (415 ± 60 nm). Methods The LA‐ICP mass spectrometer was operated in wet plasma conditions thanks to simultaneous injection of the laser aerosol and water vapor through a desolvating nebulizer. The isotopic ratios were corrected for mass bias and gain factors between detectors. The 236U/238U ratios were also corrected for the presence of 235U hydrides and tailing of the 238U+ peak. Results 236U/238U ratios were successfully measured in micrometer‐sized particles from the NBS U050 certified standard material with a 236U/238U ratio of ~5 × 10−4. The analysis of 77 natural uranium sub‐μm‐sized particles yielded a very good trueness with respect to the expected 234U/238U and 235U/238U ratios, while the measurement errors for single particles ranged from −2.7% to +2.1% for 235U/238U and from −17% to +33% for the 234U/238U ratios. Their relative combined standard uncertainties ranged from 3.3% to 32.8% and from 0.4% to 4.0% for 234U/238U and 235U/238U ratios, respectively. In addition, extremely low detection limits, in the attogram range, were achieved. Conclusions This study demonstrates that coupling of a ns‐laser ablation system with a MC‐ICP mass spectrometer allows measurements of the isotopic composition in natural uranium particles of a few hundreds of nm with very good trueness, average combined standard uncertainties of ~1% for 235U/238U ratios and 12% for 234U/238U ratios, and detections limits of a few ag for minor isotopes.

show abstract

“…Both thermal ionization (TIMS) and secondary ion mass spectrometry (SIMS) are primary particle characterization tools for these analyses, but representative particulate (reference and proficiency testing) materials have been historically limited and/or unavailable. This material need is recognized by the IAEA as urgent; with our team and others pursuing the R&D required to reproducibly produce single and mixed element reference particulates [2][3][4][5]. Initial efforts focused on U/Ce as a convenient test surrogate for U/Th and U/Pu materials.…”

mentioning

confidence: 99%

Towards the Synthesis of Mixed Actinide Particulate Reference Materials: Microscopy and Spectroscopic Characterization of U/Ce-containing Specimens

et al. 2019

View full text Add to dashboard Cite

Synthesis of size-controlled UO₂ microspheres from the hydrothermal conversion of U(iv) aspartate

Cited by 21 publications

References 43 publications

Hydrothermal Conversion of Uranium(IV) Oxalate into Oxides: A Comprehensive Study

Hydrothermal Conversion of Uranium(IV) Oxalate into Oxides: A Comprehensive Study

Determination of the isotopic composition of single sub‐micrometer‐sized uranium particles by laser ablation coupled with multi‐collector inductively coupled plasma mass spectrometry

Towards the Synthesis of Mixed Actinide Particulate Reference Materials: Microscopy and Spectroscopic Characterization of U/Ce-containing Specimens

Contact Info

Product

Resources

About

Synthesis of size-controlled UO2 microspheres from the hydrothermal conversion of U(iv) aspartate

Cited by 21 publications

References 43 publications

Hydrothermal Conversion of Uranium(IV) Oxalate into Oxides: A Comprehensive Study

Hydrothermal Conversion of Uranium(IV) Oxalate into Oxides: A Comprehensive Study

Determination of the isotopic composition of single sub‐micrometer‐sized uranium particles by laser ablation coupled with multi‐collector inductively coupled plasma mass spectrometry

Towards the Synthesis of Mixed Actinide Particulate Reference Materials: Microscopy and Spectroscopic Characterization of U/Ce-containing Specimens

Contact Info

Product

Resources

About

Synthesis of size-controlled UO₂ microspheres from the hydrothermal conversion of U(iv) aspartate