Neodymium and gadolinium extraction from molten fluorides by reduction on a reactive electrode

This work describes the electrochemical extraction on a reactive cathode (Cu, Ni) of two lanthanides Ln (Ln = Nd and Gd) from molten LiF-CaF2 medium at 840 and 920°C for Nd and 940°C for Gd. Extraction runs have been performed and the operating conditions (cathodic material and temperature) optimised. The titration of the Nd and Gd concentrations in the melt during extraction used square wave voltammetry. At the end of each run, the residual Ln content was checked by ICP-AES; the extraction efficiencies of the two lanthanides were found to be more than 99.8% on both reactive substrates

Electrodeposition of alloys or compounds in molten salts and applications

This article deals with the different modes of preparation of alloys or intermetallic compounds using the electrodeposition in molten salts, more particularly molten alkali fluorides. The interest in this process is to obtain new materials for high technology, particularly the compounds of reactive components such as actinides, rare earth and refractory metals. Two ways of preparation are considered: (i) electrocoating of the more reactive metal on a cathode made of the noble one and reaction between the two metals in contact, and (ii) electrocoating on an inert cathode of the intermetallic compound by coreduction of the ions of each elements. The kinetic is controlled by the reaction at the electrolyte interface. A wide bibliographic survey on the preparation of various compounds (intermetallic compounds, borides, carbides…) is given and a special attention is paid to the own experience of the authors in the preparation of these compounds and interpretation of their results

Cyclic Voltammetric Experiment - Simulation. Comparisons of the Complex Mechanism Associated with Electrochemical Reduction of Zr4+ in LiCl-KCl Eutectic Molten Salt

Nuclear energy increasingly represents an important option for generating largely clean CO2-free electricity and zirconium is a fission product that is expected to be present in irradiated fuels. The present investigation addresses the electrochemical reduction of Zr4+ to Zro in LiCl - KCl eutectic molten salt in the temperature range 425–550◦C using cyclic voltammetry (CV), square-wave voltammetry (SWV) and bulk electrolysis. Simulations of the CV data indicate that the initial reduction proceeds through surface confined steps: Zr4+* + 2e− ↔Zr2+* and Zr2+* + 2e− ↔Zr* processes (* adsorbed species) followed by a peak-shaped complex diffusion controlled step that consists of a combination of closely spaced processes associated with the reactions Zr4+ + 4e− →Zr and Zr4+ + 3e− →Zr+*. Zr+*, probably in the form of ZrCl* is then further reduced to Zro* at even more negative potentials. The simulations provide the first quantitative analysis of the thermodynamics and kinetics of the Zr4+ reduction in the LiCl-KCl eutectic

Interseismic Strain Accumulation on the Himalayan Crustal Ramp (Nepal)

The Departement of Mines and Geology has been monitoring the seismicity of the Central Himalayas of Nepal since 1985. Intense microseismicity and frequent medium‐size earthquakes (mL<4) tend to cluster beneath the topographic front of the Higher Himalaya. This 10–20km deep seismicity also correlates with a zone of localized uplift that has been evidenced from geodetic data. Both microseismic and geodetic data indicate strain accumulation on a mid‐crustal ramp that had been previously inferred from geological and geophysical evidence. This ramp connects a flat decollement under the Lesser and Sub‐Himalaya with a deeper decollement under the Higher Himalaya, and probably acts as a geometric asperity where strain and stress build up during the interseismic period. The large Himalayan earthquakes could nucleate there and probably activate the whole flat‐and‐ramp system up to the blind thrusts of the Sub‐Himalaya

Un Spongiaire Sphinctozoaire colonial apparenté aux constructeurs de récifs triasiques survivant dans le bathyal de Nouvelle-Calédonie

Un second représentant actuel des Sphinctozoaires, importants constructeurs de récifs au Permo-Trias, a été découvert dans la zone bathyale de la NouvelleCalédonie. Contrairement au survivant déjà connu, #Valecetia crypta$, il a conservé le mode de croissance colonial et les capacités constructrices de ses analogues fossiles. Sa croissance est bien plus lente que celle des coraux récifaux actuels. La base d'une construction de 10 cm d'épaisseur a été datée de 700 ans. (Résumé d'auteur

Management and bioremediation of hydrocarbon-polluted soils in Antarctica

Until a few years ago, the Antarctic continent was considered a pristine place. However, human activity there changed that condition, being hydrocarbon pollution a concerning and attention-drawing issue. Soils around scientific stations show different levels of pollution caused by oil-derived fuels, such as gasoil. Bioremediation is a tested, effective technique to remove contaminating hydrocarbon from the soil. Biostimulated biopiles is the most effective, tested strategy for Antarctic soils that makes use of the microorganisms’ catabolic potential; ecopiles, in turn, seem to be a better alternative that brings more complex biological systems into the process, such as vascular plants, in order to obtain higher removal levels. Finally, a reflection is made that appropriate, specific logistics are needed to reduce execution times of these innovative bioremediation treatments.Fil: Ruberto, Lucas Adolfo Mauro. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Martinez Alvarez, Lucas Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Massot, Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Nanobiotecnología. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Nanobiotecnología; ArgentinaFil: MacCormack, Walter P.. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentin

Experimental and simulation study of the electrode reaction mechanism of La3+ in LiCl-KCl eutectic molten salt

Nuclear energy increasingly represents an important option for generating largely clean CO2-free electricity. The present investigation addressed the electrochemical reduction of La3+, a rare earth element, in LiCl - KCl eutectic molten salt in the temperature range 450–550°C using transient techniques such as cyclic voltammetry (CV) and square-wave voltammetry (SWV). Simulation of the CV data suggested a reaction mechanism in which lanthanum reduction occurred in a single three-electron step (La3+ + 3e− → La°). The rate constant, k° was determined to be 5.7 x 10−3, 14.6 x 10−3 and 31.7 x 10−3 cm/s and the Matsuda et al.1 dimensionless parameter Ʌ was 0.82, 1.52 and 2.89 for temperatures of 450, 500 and 550°C, respectively and therefore it was concluded that the was process quasi reversible

A multimaterial based on metallic copper and spinel oxide made by powder bed laser fusion: A new nanostructured material for inert anode dedicated to aluminum electrolysis

Coherent 3D parts of cermets, made of spinel ferrite and metallic copper, are prepared in a nitrogen atmosphere by powder bed additive manufacturing of a mixture of oxide and metallic powders. The cermets obtained are constituted by the association of blocks of about 500 μm, which create between them, a relatively large porosity (# 35%). Each block is subdivided into intimately nested zones that are either predominantly metallic or predominantly oxide type. In the metal parts, a dispersion of oxide crystals is observed, whose size varies from ten nanometers to a few micrometers. A similar distribution of metal particles in the oxide zones is also demonstrated. The chemical compositions of metallic and oxide phases are slightly different from those in the initial powders. Due to the high energy density of the laser, the melting temperature of the metal and oxides could be reached and therefore this could explain the chemical composition variations in the phases and the shape of oxide and metallic nanometric grains. The process used can therefore be described as powder bed fusion. These nanostructured cermets have been used as "inert" anodes for the electrolysis of aluminum in molten cryolite. Although penalized by a high porosity, 5 mm in diameter anodes allowed to carry out an electrolysis for 4 h. Since Spark Plasma Sintering can greatly reduce their porosity, while retaining their specific microstructure, the implementation of additive manufacturing for producing "inert" anodes is therefore of real interest

Phase diagram of neutron-rich nuclear matter and its impact on astrophysics

Dense matter as it can be found in core-collapse supernovae and neutron stars is expected to exhibit different phase transitions which impact the matter composition and equation of state, with important consequences on the dynamics of core-collapse supernova explosion and on the structure of neutron stars. In this paper we will address the specific phenomenology of two of such transitions, namely the crust-core solid-liquid transition at sub-saturation density, and the possible strange transition at super-saturation density in the presence of hyperonic degrees of freedom. Concerning the neutron star crust-core phase transition at zero and finite temperature, it will be shown that, as a consequence of the presence of long-range Coulomb interactions, the equivalence of statistical ensembles is violated and a clusterized phase is expected which is not accessible in the grand-canonical ensemble. A specific quasi-particle model will be introduced to illustrate this anomalous thermodynamics and some quantitative results relevant for the supernova dynamics will be shown. The opening of hyperonic degrees of freedom at higher densities corresponding to the neutron stars core modifies the equation of state. The general characteristics and order of phase transitions in this regime will be analyzed in the framework of a self-consistent mean-field approach.Comment: Invited Talk given at the 11th International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1, 2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference Series (JPCS