Papers by Annabelle LAPLACE
Sealing is a major issue in Solid Oxide Cells (SOC) stacks used for hydrogen production. The spec... more Sealing is a major issue in Solid Oxide Cells (SOC) stacks used for hydrogen production. The specifications that seals must meet are particularly demanding. Glass-ceramics such as materials from the MgO-Al2O3-BaO-SiO2-B2O3 system are used. A preliminary treatment allows the initially amorphous material to set up while partially crystallizing. This paper presents the crystallization study of such a material. The main Ba5Si8O21 and BaMg2Si2O7 crystalline phases are identified and the evolution of crystals morphology with the temperature is followed. The BaxSiyOx+2y surface fraction is determined by image analysis as a function of time and temperature. These data allow accessing the equilibrium crystal fraction. It is then possible to optimize the crystallization treatment and to anticipate the microstructural evolution of the glass-ceramic seal operating in the stack.
Journal of Fluorine Chemistry, 2009
ECS transactions, May 19, 2023
Sealing is a major issue in Solid Oxide Cells (SOC) stacks used for hydrogen production. The spec... more Sealing is a major issue in Solid Oxide Cells (SOC) stacks used for hydrogen production. The specifications that seals must meet are particularly demanding. Glass-ceramics such as materials from the MgO-Al2O3-BaO-SiO2-B2O3 system are used. A preliminary treatment allows the initially amorphous material to set up while partially crystallizing. This paper presents the crystallization study of such a material. The main Ba5Si8O21 and BaMg2Si2O7 crystalline phases are identified and the evolution of crystals morphology with the temperature is followed. The BaxSiyOx+2y surface fraction is determined by image analysis as a function of time and temperature. These data allow accessing the equilibrium crystal fraction. It is then possible to optimize the crystallization treatment and to anticipate the microstructural evolution of the glass-ceramic seal operating in the stack.
ECS transactions, May 19, 2023
Sealing is a major issue in Solid Oxide Cell (SOC) used for hydrogen production. Currently, a slu... more Sealing is a major issue in Solid Oxide Cell (SOC) used for hydrogen production. Currently, a slurry composed of glass powder, organic solvents and adjuvants, is used as a seal. After the deposition of the slurry on the areas to be sealed, a heat treatment allows to obtain a glass-ceramic. This shaping process is very convenient but the obtained material presents porosity. This study aims to understand the evolution of porosity as a function of time and temperature in order to minimize it. A significant increase in porosity is observed when the temperature increases. The porosity evolution is characterized by an increase in pores size and a reduction of pores number, typical of a coalescence phenomenon. At high temperature, the viscosity is low enough to allow pores to rise in the sample. This weakens the upper part of the seal and may cause a loss of sealing.
Journal of Non-crystalline Solids, Apr 1, 2022
Crystals are known to affect bubble behavior in both natural and industrial glass melts. In volca... more Crystals are known to affect bubble behavior in both natural and industrial glass melts. In volcanic systems, high crystal contents (c> 30 vol.%) may drastically increase the suspension viscosity, altering bubble dynamics severely enough to modify eruptive style. During industrial glass production, the presence of crystals can corrupt the process and the final product. In this present work, we investigate how a small crystal fraction of nano-sized RuO2 (c ~ 2.0 vol.%, i.e. 5.0 wt.%) modifies bubble behavior in a molten glass, generating a cyclic gas-release phenomenon. We conduct a series of high-temperature, lab-scale, crucible tests, on a three-phase system composed of a Ce-bearing borosilicate melt, bubbles, and RuO2 crystals. Optical microscopic investigation is performed on the products of thermal treatment at 1000 °C (in air and without agitation) for different dwell times. Based on viscosity measurements on the crystal-bearing melt, contact angle measurements in the melt-RuO2-air system, and numerical simulations of bubblecrystal attachment, we propose a mechanism of entrainment of bubbles carrying crystals to the upper free surface accompanied by crystal aggregation, and followed by an increase in viscosity to explain the phenomenon of cyclic gas-release observed in this system.
Social Science Research Network, 2022
Journal of Organic Chemistry, Jan 22, 1998
Journal of Nuclear Materials, Jun 1, 2016
Precipitation of Uranium (III) is quantitative in molten salt LiCl-CaCl 2 (30e70 mol%). The salt ... more Precipitation of Uranium (III) is quantitative in molten salt LiCl-CaCl 2 (30e70 mol%). The salt is oxoacid with a water dissociation constant of 10 À4.0 at 705 C. Volatility of uranium chloride is strongly reduced in reductive conditions. Coprecipitation of U(III) and Nd(III) leads to a consecutive precipitation of the two elements.
Journal of Nuclear Materials, 2013
ABSTRACT Co-precipitations of cerium (III) and neodymium (III) at 10 wt.% in LiCl–CaCl2 (30-70 mo... more ABSTRACT Co-precipitations of cerium (III) and neodymium (III) at 10 wt.% in LiCl–CaCl2 (30-70 mol%) molten salt at 705 °C have been achieved using an original way of precipitation, wet argon sparging. Several CeCl3/NdCl3 ratios have been studied, and the isolated powders were analyzed using different characterization methods including XRD investigations. The lanthanides precipitation yields have been determined around 99.9% using ICP-AES analysis. XRD demonstrated that the precipitates mainly contained mixed oxychloride (Ce1−xNdx)OCl and a small amount of the mixed oxide Ce1−yNdyO2−0.5y. Calcination of these precipitates has resulted in the cerium and neodymium mixed oxides. For the precipitation with a Ce/Nd = 50/50 ratio, an hydroxychloride Ln(OH)2Cl and the oxychloride CeIV(Nd0.7Ce0.3)IIIO3Cl have been identified as unexpected intermediate compounds.
Chemical Engineering Science, Mar 1, 2021
The mass transfer of a rising bubble in creeping flow regime is numerically investigated. A rever... more The mass transfer of a rising bubble in creeping flow regime is numerically investigated. A reversible oxidation-reduction reaction is taken into account. Two coupled equations are needed to study the oxygen and reduced species transport. Three dimensionless numbers are involved: the Péclet and Damköhler numbers and the ratio of the diffusion coefficient of the reduced species to the diffusion coefficient of oxygen. Numerical computations are applied to a soda-lime-silica and a borosilicate glass-forming liquids. Results are focused on the determination of the Sherwood number. The mass transfer enhances strongly when the chemical reaction is very fast, i.e. at large value of Damköhler number. Correlations to determine the enhancement factor are proposed in the two limits of small and large Péclet numbers. The Sherwood number enhances when the diffusion coefficient of the reduced species increases. A correlation of the Sherwood number is proposed taking into account advection and reaction.
Nuclear Technology, Sep 1, 2008
The results from a study of U and Pu metal electrodeposition from molten eutectic LiCl-KCl on a s... more The results from a study of U and Pu metal electrodeposition from molten eutectic LiCl-KCl on a solid inert cathode are presented. This study has been conducted using ;50 g of U-Pu together with rare earths (mostly Nd) and 1.5 kg of salt. The introduction of a threeelectrode probe with an Ag/AgCl reference electrode has allowed voltammetric measurement during electrolysis and control of the cathode potential versus the reference. Cyclic and square-wave voltammetric measurements proved to be very useful tools for monitoring the electrolysis as well as selecting the cathode versus reference potential to maximize the separation between actinides and rare earths. The voltammetric data also highlighted the occurrence of back reactions between the cathode deposit and oxidizing equivalents formed at the anode that remained in the molten salt electrolyte. Any further electrolysis test needs to be conducted continuously and followed by immediate removal of the cathode to minimize those back reactions.
Journal of Nuclear Materials, Sep 1, 2009
... For the carbochlorination (Cl 2 + C) test, Cl 2 (Praxair, 99.99%) was introduced through a po... more ... For the carbochlorination (Cl 2 + C) test, Cl 2 (Praxair, 99.99%) was introduced through a porous graphite tube (Carbon Lorraine, ∅ ext-int = 8–3.5 mm, impurities < 200 ppm) shielded in a quartz tube to avoid the gas leakage. ...
Angewandte Chemie, Jun 14, 2004
There is a rise in interest in the rational design of new surfactants that possess various chemic... more There is a rise in interest in the rational design of new surfactants that possess various chemical or biological functionalities and self-assemble into tunable and predictable aggregate structures. In the past few years new amphiphiles (many of which are chiral and ...
ChemInform, May 31, 2012
Molten Salt Synthesis of a Mixed-Valent Lanthanide(III/IV) Oxychloride with an Unprecedented Sill... more Molten Salt Synthesis of a Mixed-Valent Lanthanide(III/IV) Oxychloride with an Unprecedented Sillen Structure: Ce1.3Nd0.7O3Cl.-The new title compound is precipitated under wet argon from NdCl3 and CeCl3 in a molten LiCl/CaCl2 (30:70) mixture (705°C, 4 h). The samples are characterized by powder XRD, SEM, and XPS. The compound crystallizes in the space group P4/nmm with Z = 2 with a new Sillen-type structure. Fluorite-type layers [M 4 O 6 ], containing Ce IV in "inner" sublayers and both Ce III and Nd III in "outer" sublayers, alternate with double-halide ion sheets.
Chemical Engineering Journal, 2023
The two-phase flow dynamics involving mass transfer and coalescence is investigated. The model is... more The two-phase flow dynamics involving mass transfer and coalescence is investigated. The model is specifically developed to describe the dynamics of bubble population dispersed in glass forming liquids. The amounts of gas dissolved in the liquid are determined using the chemical equilibrium involving oxidation-reduction reactions. The gravitational bubble rising is used to write the coalescence kernel for which a collision efficiency is also introduced. Based on a Direct Quadrature Method of Moments (DQMOM), a numerical method is developed. This numerical tool is applied to melting of borosilicate glass beads for which temperature and residence time of the sample in a crucible are investigated. The bubble density decreases sharply at short times. This early stage decrease is well explained and quantified when the coalescence is taken into account in numerical computations. The bubble size density is very well described with a log-normal distribution. Using the first three moments, the bubble size distribution obtained numerically is in good agreement with experimental data. Numerical computations are also applied to soda-lime-silica glass in which the bubble release is driven by the mass transfer between the two phases. The faster decrease of bubble density than would be expected by temperature is reproduced by the numerical computation. The enhancement of the bubble release rate is mainly due to the increase of dissolved gas species with temperature.
Journal of Alloys and Compounds, Aug 1, 2019
The vitrification is a possible treatment for the conditioning of the metallic Long-Lived Interme... more The vitrification is a possible treatment for the conditioning of the metallic Long-Lived Intermediate-Level nuclear waste. This process is characterised by the presence of immiscible oxide and metallic liquids that react each other. A thermodynamic model using the Calphad method is then required to predict the composition of the treated waste and the speciation of uranium in this complex system. The quaternary Cu-Fe-Si-U is chosen as the most representative to describe the metallic liquids that appear at high temperature. Key subsystems of this quaternary are experimentally investigated and thermodynamically modelled. The description of the liquidus in the Si-rich corner of the binary Cu-Si is improved. The Cu-U is assessed with the Calphad method for the first time; it is characterised by a large miscibility gap in the liquid phase. Some new ternary isotherms of the ternary Cu-Fe-Si are then proposed: a large liquid miscibility gap appears also in this system in agreement with the observed behaviour of the metallic liquid during the experimental investigations. The Cu-Si-U system is characterised by three ternary intermetallic compounds: CuSiU, Cu2Si2U and Cu4Si4U3. A first description is proposed, but more data are still required to improve the thermodynamic modelling of this system.
Nuclear Technology, Sep 1, 2008
Pyrochemical separation processes [1,2] are considered for the treatment of spent nuclear fuel an... more Pyrochemical separation processes [1,2] are considered for the treatment of spent nuclear fuel and particularly for the separation of fission products from actinides. In order to estimate the efficiency and selectivity for various extraction processes based on a molten salt/solvent metal separation technique, we have to know the properties of the elements to be extracted in each solvent, notably their activity coefficients in the two phases. The classical way to measure the activity coefficient of an element in a liquid metal is to use a concentration cell whose the electromotive force (emf) is measured. This type of cell involves 2 electrodes (i) the element investigated in its pure metallic form and (ii) the element solvated in the solvent metal. The electrolyte used for this study is a chloride melt which contains the element under consideration as a solute. In this paper, an effort was made to measure activity coefficients in liquid metals by means of electrochemical techniques rather than potentiometric technique. The experimental protocol was optimized by measuring the activity coefficient of gadolinium in liquid gallium (solvent metal) γ(Gd/Ga) at 530°C for several amounts of gadolinium in gallium and logγ(Gd/Ga) was determined to be equal to-10.17 (mole fraction scale). Then, the temperature dependence of the activity coefficient was determined in the range of 535-630°C. It appears that logγ(Gd/Ga) varies linearly with the reciprocal value of T, thus following the theoretical variation. The electrochemical method was also performed to the determination of activity coefficient of plutonium in liquid gallium at 560°C. The value of logγ(Pu/Ga) so obtained is equal to-8.04 (mole fraction scale). This value was confirmed using electrochemical and potentiometric measurements with a plutonium saturated gallium electrode.
Inorganic Chemistry, Mar 19, 2012
A new cerium neodymium oxychloride, Ce 1.3 Nd 0.7 O 3 Cl, has been synthesized by precipitation i... more A new cerium neodymium oxychloride, Ce 1.3 Nd 0.7 O 3 Cl, has been synthesized by precipitation in a LiCl−CaCl 2 molten salt by humid argon sparging. Chemical and structure characterization have been undertaken by powder X-ray diffraction, scanning electron microscopy, hightemperature X-ray diffraction, thermogravimetric analysis, and X-ray photoelectron scattering. This oxychloride crystallizes in space group P4/nmm, a = 3.9848(3) Å and c = 12.467(2) Å, in a new Sillen-type phase represented by the symbol X 2 4 where "quadruple" fluorite-type layers [M 4 O 6 ], containing Ce IV in "inner" sublayers and both Ce III and Nd III in "outer" sublayers, alternate with double-halide ion sheets. The structure is also described as a stacking of LnOCl and fluorite-type blocks and constitutes the term n = 2 of a possible series (MO 2) n (NdOCl) 2 .
Journal of Alloys and Compounds, Sep 1, 2019
Several processes are designed to treat different type of metallic waste. It is common to find el... more Several processes are designed to treat different type of metallic waste. It is common to find elements like copper, iron and silicon in such systems; the prediction of their behaviour in different conditions can help in improving the efficiency of these treatments. In the present work, the thermodynamic reassessments of the binary Cu-Si and the ternary Cu-Fe-Si systems are proposed. Differential Thermal Analysis and Scanning Electron Microscopy are the techniques adopted to collect new experimental data regarding the transition temperatures and phase equilibria of the investigated systems. The Calphad approach is used to model the phase diagrams of the binary Cu-Si and the ternary Cu-Fe-Si, starting from the new obtained data and the ones available in literature.
Journal of The Electrochemical Society, 2004
ABSTRACT The physical and chemical properties of zirconium chlorides have been studied in fused L... more ABSTRACT The physical and chemical properties of zirconium chlorides have been studied in fused LiCl-KCl eutectic at 823 K using an electrochemical cell containing two platinum-oxygen electrodes with a solid electrolyte membrane. The first is used as indicator electrode and the second as an oxygen pump which allows us to vary the of the ionic melt by electrolysis. Titration of Zr(IV) chlorocomplex by ions demonstrated the precipitation of and The solubility constants of these compounds were calculated. A Pourbaix type diagram, which summarizes the properties of zirconium species in the melt, was determined. © 2004 The Electrochemical Society. All rights reserved.
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Papers by Annabelle LAPLACE