Hydrothermal conversion of mixed uranium(IV)-cerium(III) oxalates into U1-CeO2+·nH2O solid solutions
S Benarib1, N Dacheux1, X F Le Goff1
1ICSM, Univ Montpellier, CEA, CNRS, ENSCM, Marcoule, France. nicolas.clavier@icsm.fr.
Dalton Transactions (Cambridge, England : 2003)
|July 25, 2023
Summary
Hydrothermal conversion of uranium-cerium oxalate precursors yields mixed uranium-cerium oxide solid solutions. The pH influences morphology, while reaction time affects homogeneity, creating a viable synthesis for plutonium-surrogate materials.
Area of Science:
- Materials Science
- Inorganic Chemistry
- Radiochemistry
Background:
- Uranium-cerium oxide solid solutions are important for nuclear waste management and as surrogates for plutonium.
- Hydrothermal synthesis offers a controlled method for producing advanced ceramic materials.
Purpose of the Study:
- To develop a hydrothermal synthesis route for uranium-cerium oxide solid solutions.
- To investigate the influence of pH and reaction time on the structure, morphology, and homogeneity of the resulting oxides.
- To explore the feasibility of cerium incorporation within the uranium oxide matrix.
Main Methods:
- Hydrothermal conversion of mixed U(IV)-Ce(III) oxalate precursors.
- Varying initial pH and reaction duration (1-48 hours) at 250 °C.
- Characterization using Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy with Energy Dispersive Spectroscopy (TEM/EDS).
- Thermodynamic calculations and O/M ratio analysis.
Main Results:
- Fluorite-type U1-xCexO2+n·nH2O solid solutions were successfully synthesized.
- Initial pH significantly impacted morphology: acidic pH yielded microspheres, alkaline pH produced nanocrystallite agglomerates.
- Single-phase mixed oxides formed within 3 hours, with cationic distribution narrowing over time, leading to high homogeneity.
- Formation was possible for cerium incorporation rates (x) between 0.1 and 0.75.
Conclusions:
- Hydrothermal conversion is an effective method for preparing homogeneous uranium-cerium oxide solid solutions.
- Control over pH and reaction time allows tailoring of oxide morphology and homogeneity.
- The study provides insights into the redox behavior of uranium and cerium during hydrothermal processing.
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