A5006771639- Radioactive element chemistry and processing
- Nuclear materials and radiation effects
- Nuclear Materials and Properties
- Chemical Synthesis and Characterization
- Nuclear reactor physics and engineering
- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Radioactive contamination and transfer
- Luminescence Properties of Advanced Materials
- Crystal Structures and Properties
- Extraction and Separation Processes
- Catalytic Processes in Materials Science
- Thermal and Kinetic Analysis
- Advanced Condensed Matter Physics
- Microwave Dielectric Ceramics Synthesis
- Advancements in Solid Oxide Fuel Cells
- Geological and Geochemical Analysis
- Advanced ceramic materials synthesis
- Nuclear and radioactivity studies
- Catalysis and Oxidation Reactions
- Zeolite Catalysis and Synthesis
- Ferroelectric and Piezoelectric Materials
- Geochemistry and Geologic Mapping
- Petroleum Processing and Analysis
- Thermal Expansion and Ionic Conductivity
Institut de Chimie Séparative de Marcoule
2016-2025
Centre National de la Recherche Scientifique
2016-2025
École Nationale Supérieure de Chimie de Montpellier
2016-2025
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2016-2025
CEA Marcoule
2015-2025
Université de Montpellier
2016-2025
Unité Matériaux et Transformations
2014-2020
Aix-Marseille Université
2020
Institut de Physique
2000-2019
Universidad del Noreste
2016
Monazite (Ln3+PO4) and related solid solutions are a well-known source of rare earth elements on earth. They may also accommodate large amounts thorium uranium without sustaining damage to the structure by self-irradiation. Such observations led monazite-type structures being proposed as potential host matrix for sequestering long-lived radionuclides produced during nuclear fuel cycle and/or plutonium americium from dismantled weapons. has two main advantages containment radioactive waste...
Several CeO(2)-based mixed oxides with general composition Ce(1-x)Ln(x)O(2-x/2) (for 0 ≤ x 1 and Ln = La, Nd, Sm, Eu, Gd, Dy, Er, or Yb) were prepared using an initial oxalic precipitation leading to a homogeneous distribution of cations in the oxides. After characterization Ce/Nd oxalate precursors then thermal conversion at T 1000 °C, investigation crystalline structure these was carried out by XRD μ-Raman spectroscopy. Typical fluorite Fm ̅3m obtained for relatively low Ln(III) contents,...
Several La1 − xGdxPO4 solid solutions were prepared in the monazite- or rhabdophane-type structures for various x values using three methods of preparation (direct evaporation, synthesis closed PTFE containers on a sand bath autoclaves). Samples xGdxPO4·nH2O (n ≈ 0.5) at 150 °C only ≥ 0.4. For ≤ 0.3, solids precipitated as monazite-type structure. These results confirmed by study pure rare earth phosphates synthesized under same conditions. By these means, well-crystallized and monophase...
An uranyl isophthalate has been hydrothermally synthesized at 200 °C for 24 h, from a mixture of nitrate, isophthalic acid, and hydrazine in water. It was characterized by single-crystal analysis [triclinic, P ̅1, = 7.3934(3) Å, b 13.3296(5) c 15.4432(5) α 111.865(2)°, β 90.637(2)°, γ 104.867(2)°, V 1355.49(9) Å(3)] different spectroscopic techniques (Raman, IR-ATR, UV-visible). The 3D structure the phase (UO(2))(8)O(2)(OH)(4)(H(2)O)(4)(1,3-bdc)(4)·4H(2)O (1,3-bdc 1,3-benzenedicarboxylate)...
Coffinite, USiO4, is an important U(IV) mineral, but its thermodynamic properties are not well-constrained. In this work, two different coffinite samples were synthesized under hydrothermal conditions and purified from a mixture of products. The enthalpy formation was obtained by high-temperature oxide melt solution calorimetry. Coffinite energetically metastable with respect to UO2 (uraninite) SiO2 (quartz) 25.6 ± 3.9 kJ/mol. Its standard the elements at 25 °C -1,970.0 4.2 Decomposition...
Hydrated rhabdophane with a general formula REEPO4·nH2O (REE: La → Dy) has been always considered to crystallize in the hexagonal system. A recent re-examination of this system by use synchrotron powder data SmPO4·0.667 H2O compound led structure crystallizing monoclinic C2 space group = 28.0903(1) Å, b 6.9466(1) c 12.0304(1) β 115.23(1)°, and V 2123.4 (1) Å3 24 units per unit cell. The consists infinite channels oriented along [101] direction formed connection Sm-polyhedra P-tetrahedra...
The chemistry of thorium phosphate reported in the literature has been found to be erroneous. It was reconsidered terms careful chemical preparations and specific analytical methods. Special attention paid atom ratio value referred r = thorium/phosphorus, which experimentally fixed order obtain correct composition final compound. A new compound with formula Th4(PO4)4P2O7, derived from crystal structure determination, obtained. unit cell parameters were obtained powder single-crystal X-ray...
On the basis of optimized grinding/heating cycles developed for several phosphate-based ceramics, preparation brabantite and then monazite/brabantite solid solutions loaded with tetravalent thorium, uranium, cerium (as a plutonium surrogate) was examined versus heating temperature. The chemical reactions transformations occurring when initial mixtures AnO2/CeO2, CaHPO4·2H2O (or CaO), NH4H2PO4 were identified through X-ray diffraction (XRD) thermogravimetric/differential thermal analysis...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTU(UO2)(PO4)2, a New Mixed-Valence Uranium Orthophosphate: Ab Initio Structure Determination from Powder Diffraction Data and Optical X-ray Photoelectron SpectraP. Benard, D. Louer, N. Dacheux, V. Brandel, M. GenetCite this: Chem. Mater. 1994, 6, 7, 1049–1058Publication Date (Print):July 1, 1994Publication History Published online1 May 2002Published inissue 1 July...
The dissolution of Th1–xCexO2 solid solutions samples prepared by thermal conversion oxalate precursors was studied varying independently several parameters (such as chemical composition, leachate acidity, leaching temperature, firing and crystallization state). relative effects these on the normalized rate were examined. Either obtained partial order related to proton activity (n = 0.50 ± 0.01) or activation energy (EA 57 6 kJ.mol–1) suggested that mainly driven surface reactions occurring...
To underline the potential links between crystallization state and microstructure of powdered cerium-neodymium oxides their chemical durability, several Ce(IV)(1-x)Nd(III)(x)O(2-x/2) mixed dioxides were prepared in various operating conditions from oxalate precursors then leached. The samples first examined through physicochemical properties (crystallization associated crystallite size, reactive surface area, porosity...). dependence normalized dissolution rates on parameters (including...
A systematic study of the solubility rhabdophanes LnPO 4 · 0.667H 2 O (Ln = La–Dy) was performed through oversaturation and undersaturation experiments at different temperatures (298–363 K) to demonstrate reversibility equilibria. The structure neoformed phase controlled carefully over entire temperature range enable unambiguous attribution products derived thermodynamic data rhabdophane phases. log K ° s,0 (298 values for ranged from –25.6 ± 0.8 (Pr) –24.9 1.7 (Eu), minimum were Pr Sm,...
Evolution of sintered Ce<sub>1−x</sub>Ln<sub>x</sub>O<sub>2−x/2</sub>samples during dissolution tests in acidic media was followed the same zone by environmental scanning microscopy.
The determination of activities thorium, uranium, plutonium, americium, and curium at very low levels has been performed by a new α liquid scintillation system (PERALS, name registered to Ordela, Inc.). limit detection determined for these nuclides with calculated values often lower than those obtained other methods, like ICPMS/HP/Mistral, time-resolved laser-induced spectrofluorometry, spectrometry. All the results show that PERALS is promising method levels. However, its energy resolution...
Extended X-ray absorption fine structure (EXAFS) has been utilized to investigate the local atomic around Th, U, and Pu atoms in polycrystalline mixed dioxides Th(1-x)M(x)O2 (with M = Pu) for x ranging from 0 1. The composition dependence of two first-coordination-shell distances was measured throughout entire range both solid solutions. first-shell vary slightly across solid-solution with values close those pure dioxide parents, indicating a bimodal cation-oxygen distribution. In contrast,...
To study the simultaneous incorporation of both tri- and tetravalent actinides in phosphate ceramics, we prepared several β-TUPD/monazite-based radwaste matrices through two different chemical routes (called dry wet routes) involving initial precipitation crystallized precursors each phase, i.e., TUPHPH solid solutions on one hand, rhabdophane (LnPO4·xH2O) other. The final material was obtained after heating above 1000 °C, no additional phase detected from elementary analyses XRD. Moreover,...