LiF-CaF2

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Electrochemical behaviour of thorium(IV) in molten LiF–CaF2 medium on inert and reactive electrodes

Electrochemical behaviour of thorium(IV) in molten LiF–CaF2 medium on inert and reactive electrodes

a b s t r a c t The electrochemical behaviour of the Th(IV)/Th system was examined in molten LiFCaF2 medium on inert (molybdenum), reactive (nickel) and liquid (bismuth) electrodes in the 810–920 ◦ C temperature range by several electrochemical techniques. Experimental results showed that (i) thorium fluoride was reduced in a single step exchanging 4 electrons and limited by thorium ions diffusion in the solution, (ii) the oxide ions induce the precipitation of Th(IV) in the form of thorium oxide (ThO2), in a process involving as intermediate compound a soluble oxifluoride (ThOF2), (iii) the reduction of thorium ions on reactive (Ni and liquid Bi) electrodes yields compounds Ni–Th and Bi–Th with a potential shift of around 0.7 V (for Ni and Bi) more anodic than the reduction of Th(IV) on inert substrate.
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Investigations of Zr(IV) in LiF-CaF2: stability with oxide ions and electroreduction pathway on inert and reactive electrodes

Investigations of Zr(IV) in LiF-CaF2: stability with oxide ions and electroreduction pathway on inert and reactive electrodes

ln D = −2.22(±0.03) − 10765.10(±0.03) T Then, the effect of oxide ions by CaO addition in a LiFCaF2–ZrF4 system has been studied. At 850 ◦ C, the zirconium precipitation is evidenced and the concentration decrease of Zr(IV) with CaO additions indicates that the precipitate is most probably composed of zirconium oxide ZrO 2 and zirconium oxifluoride ZrO 1.3 F 1.4 . On nickel and copper electrodes, Zr(IV) reduction was observed at a more positive potential than pure Zr deposition and zirconium alloys formation (Ni–Zr and Cu–Zr) were evidenced by SEM–EDS. Thanks to the open circuit chronopotentiometry data on the Zr–Cu system, the Gibbs energy of formation of the corresponding inter- metallic compounds (CuZr 2 , CuZr, Cu 10 Zr 7 , Cu 8 Zr 3 , Cu 51 Zr 14 , Cu 5 Zr) were estimated and in good agreement with the SGTE database. Acknowledgement
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Electrochemistry of uranium in molten LiF–CaF2

Electrochemistry of uranium in molten LiF–CaF2

a b s t r a c t This article is focused on the electrochemical behaviour of U ions in molten LiF–CaF 2 (79–21 wt.%) eutec- tic. On a W electrode, U(III) is reduced in one step to U metal and U(III) can be also oxidised to U(IV). Both systems were studied by cyclic and square wave voltammetry. Reversibility of both systems for both techniques was verified and number of exchanged electrons was determined, as well as diffusion coeffi- cients for U(III) and U(IV). The results are in a good agreement with previous studies. On a Ni electrode, the depolarisation effect due to intermetallic compounds formation was observed. Electrorefining of U metal in a melt containing U and Gd ions was carried out using a reactive Ni electrode with promising results.
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Data acquisition in Thermodynamic and electrochemical reduction in a Gd(III)/Gd system in LiF-CaF2 media

Data acquisition in Thermodynamic and electrochemical reduction in a Gd(III)/Gd system in LiF-CaF2 media

Gadolinium is one of the fission products. This work deals with the electrochemical behaviour of gadolinium in the LiF-CaF 2 eutectic in the 800-900°C temperature range with a tantalum electrode. Yang et al. [1] studied Gd (III) reduction in NaCl-KCl at 730°C and in KCl at 800°C. The studies showed that Gd (III) reduction proceeds in a single step, which is diffusion controlled:

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Investigations of Zr(IV) in LiF-CaF2: stability with oxide ions and electroreduction pathway on inert and reactive electrodes

Investigations of Zr(IV) in LiF-CaF2: stability with oxide ions and electroreduction pathway on inert and reactive electrodes

This paper presents a detailed electrochemical study of Zr(IV) ions behaviour in LiF–CaF 2 in the 810–920 ◦ C temperature range on inert electrode (Ta) using several electrochemical techniques (cyclic and square wave voltammetries, chronopotentiometry). Very sensitive to oxide, oxide ions (CaO) have been added into the LiF–CaF 2 –ZrF 4 mixture to investigate the zirconium precipi-

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Electrochemical behaviour of dysprosium (III) in LiF–CaF2 on Mo, Ni and Cu electrodes

Electrochemical behaviour of dysprosium (III) in LiF–CaF2 on Mo, Ni and Cu electrodes

b Université de Toulouse, INPT, UPS, CNRS; Laboratoire de Génie Chimique, Département Procédés Electrochimiques, F-31062 Toulouse Cedex 9, France a b s t r a c t The electrochemical behaviour of dysprosium(III) was investigated in the LiF–CaF 2 eutectic mixture on molybdenum, nickel and copper electrodes in the 840–930 °C temperature range using cyclic voltamme- try, square wave voltammetry and chronopotentiometry. On Mo electrode, the study showed that Dy(III) ions were reduced into Dy metal in a one-step diffusion-controlled process exchanging three electrons: DyðIIIÞ þ 3e ÿ $ Dy: The diffusion coefficients verify the Arrhenius law, allowing the activation energy to
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Electrochemical behavior of plutonium fluoride species in LiF-CaF2 eutectic melt

Electrochemical behavior of plutonium fluoride species in LiF-CaF2 eutectic melt

Among actinides, plutonium was chosen as element of study. In chloride media, electrochemical studies were carried out on PuCl 3 on inert electrode in LiCl-KCl by Serp et al. [ 10 ] and O. Shirai et al. [ 11 , 12 ]. They found that Pu(III) reduction proceeds via a one-step process with 3 electrons exchanged. The system is found to be quasi-reversible and diffusion controlled by both authors. Pu(III) diffusion coef ficient was determined at 733 K by Serp, and the value is found to be 1.6  10 5 cm 2 s 1 . Contrary to chloride media, very limited studies are available in fluoride media. Electrochemical study of PuF 3 in LiF-NaF-BeF 2 was performed at 893 K by Zakirov
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Electrochemistry of uranium in molten LiF-CaF2

Electrochemistry of uranium in molten LiF-CaF2

a b s t r a c t This article is focused on the electrochemical behaviour of U ions in molten LiF–CaF 2 (79–21 wt.%) eutec- tic. On a W electrode, U(III) is reduced in one step to U metal and U(III) can be also oxidised to U(IV). Both systems were studied by cyclic and square wave voltammetry. Reversibility of both systems for both techniques was verified and number of exchanged electrons was determined, as well as diffusion coeffi- cients for U(III) and U(IV). The results are in a good agreement with previous studies. On a Ni electrode, the depolarisation effect due to intermetallic compounds formation was observed. Electrorefining of U metal in a melt containing U and Gd ions was carried out using a reactive Ni electrode with promising results.
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Nitrogen evolution as anodic reaction in molten LiF–CaF2

Nitrogen evolution as anodic reaction in molten LiF–CaF2

a b s t r a c t The electrochemical behaviour of nitride ions has been studied in fluoride melts (eutectic LiF–CaF 2 ) by cyclic voltammetry and square wave voltammetry. The purpose of this work is to propose an alternative way for anodic reaction in molten fluorides processes. Thermodynamical analysis can be used for the evaluation of the anodic material regarding to its oxidation potential and reactivity with nitrogen. Then electrochemical investigations confirm the oxidation of nitride ions into nitrogen in a one-step process exchanging 3 electrons, and let propose several materials usable for nitrogen evolving.
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Nitrogen evolution as anodic reaction in molten LiF-CaF2

Nitrogen evolution as anodic reaction in molten LiF-CaF2

a b s t r a c t The electrochemical behaviour of nitride ions has been studied in fluoride melts (eutectic LiF–CaF 2 ) by cyclic voltammetry and square wave voltammetry. The purpose of this work is to propose an alternative way for anodic reaction in molten fluorides processes. Thermodynamical analysis can be used for the evaluation of the anodic material regarding to its oxidation potential and reactivity with nitrogen. Then electrochemical investigations confirm the oxidation of nitride ions into nitrogen in a one-step process exchanging 3 electrons, and let propose several materials usable for nitrogen evolving.
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Electrochemical behavior of plutonium fluoride species in LiF-CaF2 eutectic melt

Electrochemical behavior of plutonium fluoride species in LiF-CaF2 eutectic melt

Diffusion coef ficients (D) were calculated in the 1093e1153 K temperature range, using equation (6) . For instance, at T ¼ 1113 K and m 0 ¼ 0.086 mol kg 1 , the diffusion coef ficient is found to be 3.3 ± 0.1  10 5 cm 2 s 1 . In comparison with cerium which is usu- ally used to simulate plutonium because of its similar physico- chemical properties (melting point, conductivity, redox potential, oxidation number …) [ 25 ], the Ce(III) diffusion coef ficient deter- mined by Gibilaro et al. [ 26 ] in LiF-CaF 2 melt at 1113 K is 2.64 ± 0.43  10 5 cm 2 s 1 and is in the same order of magnitude than the Pu(III) one. The linear relationship between ln D and the inverse absolute temperature, plotted in Fig. 8 , demonstrates that the variation of the diffusion coef ficient obeys to an Arrhenius' type law:
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Time-resolved measurement of concentration fluctuations in a confined bubbly flow by LIF

Time-resolved measurement of concentration fluctuations in a confined bubbly flow by LIF

of 250 Hz. A spectrometer is used to analyse the light issued from the observation volume and to dis- tinguish the fluoresced light from other light sources. Simultaneously, the bubble distribution around the observation volume is imaged with a high speed camera synchronised with the spectrometer in order to assess the LIF technique in bubbly flow. Thanks to the good time resolution, rapid and intense concen- tration fluctuations corresponding to dye patches passing through the observation volume are recorded and are superimposed to a slow global evolution. This slow global evolution shows first an increase of the concentration and then an exponential decrease due to the mixing by bubble-induced agitation. This exponential decay, which is incompatible with a diffusion process, is consistent with the transport by dye capture in bubbles wakes that are quickly dampened by the shear-stress at the walls. The one-point statistics of the concentration fluctuations (probability density function and spectrum) also point out that mixing in a confined bubbly flow is intermittent and convective.
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Expression of leukemia inhibitory factor (LIF) and its receptor gp190 in human liver and in cultured human liver myofibroblasts. Cloning of new isoforms of LIF mRNA.

Expression of leukemia inhibitory factor (LIF) and its receptor gp190 in human liver and in cultured human liver myofibroblasts. Cloning of new isoforms of LIF mRNA.

vivo . Cloning of new isoforms of LIF mRNA In order to test whether myofibroblasts transcribed all the alternatively spliced D, M or T first exons, a first set of RT- PCR experiments was carried out using the forward prim- ers chosen in the alternative D, M or T first exons (hLIF- D3, hLIF-M3 and hLIF-T5), and a common reverse primer chosen in exon 3 (hLIF-N4) (Table 1 and Fig. 5). As shown in Fig. 2B, PCR with D- or M-specific primers was positive. Moreover, it always yielded a second, shorter, PCR prod- uct in addition to the expected amplified product (Fig. 2B). Similar results were obtained with other primer sets specific for either LIF-D (hLIF-D) or LIF-M (h-LIFM5) combined with hLIF-3N (data not shown), which strengthened the previous observation. No amplification products were obtained with the T primer. Then, we designed a reverse primer within exon 2 (hLIF-2N) that
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Dislocation mobility study of heavy ion induced track damage in LiF crystals

Dislocation mobility study of heavy ion induced track damage in LiF crystals

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignemen[r]

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Development of a sensitive CE-LIF method for the analysis of synthetic cathinones.

Development of a sensitive CE-LIF method for the analysis of synthetic cathinones.

Mix with ionic surfactants Low % of solvents In the present project, we developed a capillary electrophoresis separation method coupled to laser induced fluorescence detection (CE-LIF) to analyze most frequently observed SCs. Due to their lack of native fluorescence, analytes were labeled using fluorescein isothiocyanate isomer I (FITC). The labeled-compounds present closely related structures, some of them being isobaric (identical mass and charge). To tackle this analytical challenge in terms of separation, various additives in the background electrolyte were investigated.

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Etude de la spectroscopie LIF à deux photons de la molécule CO pour des mesures en flammes à haute pression

Etude de la spectroscopie LIF à deux photons de la molécule CO pour des mesures en flammes à haute pression

La molécule CO a été mesurée dans des milieux en combustion par CARS [ 46 , 47 , 53 , 54 ] et TDLAS [ 15 , 17 – 20 , 103 , 104 ]. A titre d’exemple, à l’ONERA, des mesures de concentration de CO par TDLAS ont été effectuées dans une flamme CH 4 -O 2 -NH 3 à basse pression [ 15 ]. Contrairement à NO qui est sondé par LIF à un photon, la molécule CO est sondée par LIF à deux photons compte tenu des longueurs d’onde d’absorption dans l’ UV lointain. Le premier état électro- nique est situé à 48687,40 cm −1 , ce qui correspond à une absorption à un photon de longueur d’onde 205 nm depuis l’état fondamental. Le tableau 1.3 résume quelques expériences pertinentes de LIF -CO en flammes. Hormis dans les études de Sullivan et Crosley [ 112 ], et Mosburger et Sick [ 113 ], l’excita- tion laser à deux photons est à 230,1 nm. En 2010, Mosburger et Sick [ 113 ] ont montré la possibilité de détecter simultanément CO et le radical OH au moyen d’une longueur d’onde d’excitation com- mune égale à 283,7 nm avec une détection de la fluorescence entre 200 et 240 nm. De nombreuses études [ 7 , 114 – 116 ] ont été réalisées au Sandia National Laboratories dans l’équipe de Barlow en col- laboration avec d’autres laboratoires. Dans ces travaux, différentes techniques de diagnostics laser (diffusion Raman et diffusion Rayleigh et LIF -CO) ont été combinées pour caractériser les flammes à pression atmosphérique et valider des modèles de combustion. On citera notamment l’étude de Fuest et al. [ 7 ] dans une flamme turbulente de diffusion dimethyl ether/air où des mesures simultanées de température (diffusion Rayleigh) et de concentration des espèces majoritaire H 2 , O 2 , N 2 , CO 2 , H 2 O et C 2 H 6 O (diffusion Raman spontanée) et de CO ( LIF à deux photons) sont présentées. D’autres instituts de recherche ont également appliqué la technique LIF afin de déterminer les profils de concentration de CO dans des flammes laminaires ou turbulentes [ 117 , 118 , 120 – 122 ]. On remarque que seule l’étude de Kim et al. [ 119 ] a été réalisée pour des pressions supérieures à 1 bar dans un moteur diesel.
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Distributed synaptic weights in a LIF neural network and learning rules

Distributed synaptic weights in a LIF neural network and learning rules

2.1 Structured Noisy LIF model We consider a heterogeneous population of homogeneous neural networks structured by their synaptic weights w ∈ (−∞, +∞), negative sign stands for inhibitory neurons and positive sign for excitatory neurons. We have chosen to use a signed parameter σ, instead of a system of two equations for excitatory and inhibitory neurones, because this leads to a simpler formalism and avoids boundary conditions in w = 0. We assume that each homogeneous subpopulation, with synaptic weight w, is governed by the classical mean field noisy integrate and fire equation, widely used for large neural networks [7, 6, 5]. Moreover, we assume that the subpopulations interact via the total firing rate ¯ N (t) defined as the mean activity for all the subpopulations. Setting v the value of the action potential, V F > V R the values of the firing and reset potentials, we consider the classical equation
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Interaction ions-surfaces : étude de la pulvérisation du fluorure de lithium LiF par technique d'imagerie XY-TOF-SIMS

Interaction ions-surfaces : étude de la pulvérisation du fluorure de lithium LiF par technique d'imagerie XY-TOF-SIMS

Tout d’abord, nous décrirons dans le deuxième chapitre l’interaction ions lourds-matière. Nous y ferons alors le point sur les connaissances actuelles de l’interaction ion-matière ainsi que sur les paramètres importants à prendre en compte lors de notre étude. La description de la technique d’analyse utilisée pour effectuer ce travail fera l’objet du troisième chapitre. Nous présenterons le fonctionnement de spectromètre XY-TOF sur la ligne SME du GANIL et le système de TOF sur l’accélérateur Van de Graaff de Rio de Janeiro. Nous terminerons ce chapitre par l’étude de la méthode de la “ligne de gaz“ qui permet d’étalonner le système de mesures en temps et en positions ainsi la vérification des paramètres expérimentaux. Dans le quatrième chapitre, nous présenterons les résultats expérimentaux obtenus sur la ligne SME-GANIL (Caen) et sur l’accélérateur Van de Graaff (Rio). Nous montrerons les distributions en masse des ions secondaires émis de LiF pour différents projectiles. Nous démontrerons le rôle important de la préparation de l’échantillon (surface propre).
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Etude expérimentale des processus multi-électroniques lors de collisions d'ions en incidence rasante sur une surface de LiF(001)

Etude expérimentale des processus multi-électroniques lors de collisions d'ions en incidence rasante sur une surface de LiF(001)

Etude expérimentale des processus multi-électroniques lors de collisions d'ions en incidence rasante sur une surface de LiF(001) Ce manuscrit présente différentes études expérimentales des collisions en incidence rasante (< 3 degrés) sur LiF(001) d'ions simplement chargés tels que le néon et le fluor de basses énergies (< 3 keV). Le faisceau incident est pulsé. Le produit de la diffusion après une analyse en charge entre des plaques électrostatiques est détecté sur un détecteur sensible en position. Les particules secondaires (électrons ou ions) sont recueillies sur un détecteur composé de 16 unités de détection (2 galettes microcanaux) couvrant 2 π stéradian au dessus de la surface. La technique de mesure de perte d'énergie (spectroscopie de translation) associée à la détection des particules diffusées en coïncidence avec les électrons émis de la surface lors de la collision d'ions néons simplement chargés, a permis de mettre en évidence des états excités de la surface. Ces états excités, localisés sur les ions fluors négatifs de la surface, sont soit centrés autour d'une seule lacune (les excitons), soit autour de 2 lacunes, ce dernier, complexe à 3 corps est connu dans la littérature sous le nom de trion. On trouvera dans ce manuscrit la première caractérisation de ces états par impact d'ions. Dans le cas du néon la capture correspond à une neutralisation Auger
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Simultaneous Temperature and Velocity measurements by LIF and PIV in a complex geometry

Simultaneous Temperature and Velocity measurements by LIF and PIV in a complex geometry

Un colorant est un composant nécessaire à la LIF. L’aptitude d’un colorant est basée sur un spectre d’absorption compatible avec la longueur d’onde d’excitation laser. Le traceur fluorescent doit être solu- ble dans l’eau avec une efficacité quantique élevée de sorte que la force du signal soit maximisée. Il doit présenter une dépendance à la température suffisante sur une plage de température appropriée et doit être photostable dans des conditions expérimentales qui produisent une émission détectable. De plus, l’absorption et l’émission du colorant doivent être séparées spectralement. La technique de LIF à un col- orant est la méthode dans laquelle un seul colorant fluorescent et une bande de détection spectrale sont utilisés. En général, la linéarité du signal de fluorescence par rapport à l’énergie laser incidente et la concentration de colorant est rapportée. De telles expériences ont été les premières à être menées dans le domaine de la mesure de la température. A partir de ces expériences, les chercheurs ont pu identifier les caractéristiques des colorants organiques tels que la longueur d’onde d’excitation, le pourcentage d’émission dépendant de la température et la plage de température.
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