Preliminary List of Abstracts (Alphabetical Order)

2ND INTL. SYMP. ON SUSTAINABLE MOLTEN SALT AND IONIC LIQUID PROCESSING

Refractory metals play crucial roles in our materials based modern civilisation. Currently, industrial production of refractory metals, such as Ti, Si, Ta and Zr, is commonly achieved via the pyrometallurgical process that is often carbon and/or energy intensive. Alternatively, refractory metal extraction might be achieved by electrolysis of their solid oxide minerals in molten CaCl2 with high diffusivity for O2- ions which can then transport to, and discharge at the anode. This mechanism would be ideal if coupled with an inert anode to produce the O2 gas. However, similar to electrolysis of Al2O3 dissolved in cryolite based molten fluorides, the carbon anode will still be the best choice to a commercial process of electro-reduction of solid metal oxides, causing CO2 emission, anode replacement, and other problems, such as shuttle reactions due to the high solubility of CO2 in the CaO containing electrolytes. In this presentation, two new strategies will be explained and discussed on changing the anodic reaction on an inert carbon anode in molten chlorides with negligible or low O2- solubility. One is the electrolysis of solid metal sulfides to metal and elemental S in NaCl-KCl melts with graphite serving as an ideal inert anode, promising clean processes for the metallurgies of sulfide minerals such as molybdenite. The other one is the electrolysis of metal oxides in MgCl2 based melts, showing a completely new mechanism in comparison with that in molten CaCl2. Since the O2- ions cannot transport to anode, the anodic reaction will be the discharge of Cl- ions to Cl2 gas with graphite again serving as an inert anode. This strategy has led to significantly higher current efficiency, and lower energy consumption, and the electrolysis of TiO2, ZrO2, Ta2O5 and SiO2 will be described in detail based on both thermodynamic calculation and experimental results.

To realize the global sustainable society, provisions of scarce functional material resources and energy resources are keen issues. Recently, with these bottom lines, there has been a wide interest in the development of processes for recycling minor metals, such as rare-earths and platinum group metals, because the formers are indispensable for producing high performance magnets, and the latters are used for the production of high density recording media and processing of gas waste from automobiles. Furthermore, the dry processes using molten as reaction media for spent nuclear fuels are recently drawing attention. In this study, alkali metal chlorides, LiCl-NaCl-KCl system for rare earths and NaCl-CsCl system for platinum group metals are chosen as reaction media. In order to develop chemical and electrochemical controls of rare-earth and platinum metal compounds, thermo dynamic stabilities in terms of electric potential and basicity for chemical species of rare earths; La, Ce, Nd, Sm and Dy, and Rh were investigated .The equilibrium potentials as a function of oxide ion concentration were measured. Electrochrmical transient methods such as Cyclic voltammetry, square wave amperometry were also used under the control of the concentration of oxide ions. The mechanism of the reduction processes of the metals were clarified. Then, rare earth containing thin films were prepared. Platinum-Palladium-Rhodium ternary nano and micro sized metal powders were also prepared by the collaboration of dry and wet processes. The powders are expected to be used for oxygen sensors and catalyses of waste gases from automobiles.

The titanium alloys are potential materials for high temperature applications in turbine components due to their very high temperature strength and lightweight properties. The Ti-6Al-4V alloy has been increasingly used in biomedical, aerospace and chemical industries due to their high strength to weight ratio and high corrosion resistance. However, hot corrosion is a life-limiting factor when Ti alloys are exposed to different chemical environments at high temperature. In this study, hot corrosion behavior of Ti-6Al-4V alloy in NaCl-LiF-KCl was investigated at 7400C. The corrosion parameters were calculated by polarization measurements and compared to these of pure Ti. The morphology of the Ti-Al-V was observed by micrograph, X-ray diffraction (XRD), metallographic micrography and AFM. The scale formed on the samples upon hot corrosion was characterized by using XRD, micrographs and AFM analysis to understand the degradation mechanism of the titanium alloy. The information on the exposed surface in the electrolyte and the relative atomic concentration was obtained by XPS analysis method. The XPS analysis shows that TiO2 was the main phase with small amount of V2O5, Al2O3 and TiOCl. The XPS analysis of the electrolyte showed the presence of vanadium in a very low concentration. The binding energies for the formed compounds before and after corrosion were calculated. Even if the corrosion rate of Ti-Al-V is much lower than that of Ti, it is observed that the corrosion rate of titanium alloy is relatively high in molten salt. The degradation occurs due to the chemical reaction of titanium with chloride ions and of aluminium with fluoride ions.

We have invented various novel molten salt electrochemical processes, which are available to create new industries in the energy, environment and resources field.They seem promising from both technological and economic aspects, and they are now under development towards industrializations.Among them, in this lecture, the following 4 (four) topics are selected and described in details showing their principles, experimental data and current developmental stages. The result of economical estimations of each process is also presented. (1) Electrolytic synthesis of ammonia from water and nitrogen under atmospheric pressure, which might be able to take place of conventional Haber-Bosch process; (2) Electrochemical formation of various types of carbon film and their practical applications, (3) Plasma-induced discharge electrolysis to produce various metal/alloy nano-particles, and (4)Recycling of rare-metals using "bifunctional" electrode.

Because of the tunable properties of ionic liquids, they are considered perfectly "designed" and "green" solvents. Understanding the physical and chemical properties of ionic liquids is essential for the enormous potential application of ionic liquids in different industrial and technological processes. Although the number of articles on ILs is increasing exponentially, it is obvious some literature discrepancies of basic physical-chemical properties. In this context, the aim of this work is to closely study the volumetric properties of ionic liquids and the molecular interactions between ionic liquids and molecular solvents. Volumetric characteristics of electrolyte solutions are of fundamental importance for the understanding of numerous phenomena occurring in the solutions. These studies can be used to examine the ion-ion, ion-solvent and solvent-solvent interactions. The ion solvation process and the equilibrium involved in different concentration regions in water and many non-aqueous media have been of a great importance due to their commercial applications in many technological areas. The mixtures of IL with lower amides provide potential industrial applications and thus utilization of both IL and amides.

For the pyrochemical reprocessing of nuclear spent fuels, an accurate knowledge of the electrochemical properties is essential, for example the apparent standard potential of actinides and lanthanides dissolved in molten salts. The determination of such quantities is time consuming, especially with radioactive materials at high temperature. The development of computational methods for these properties is a promising alternative. This work is focused on the calculation of the free energy of solvation of uranium-like and americium-like metal chloride in the LiCl-KCl eutectic using a classical model and a three step thermodynamic cycle. The first step involves the oxidation of the metal dissolved in the eutectic to obtain a free energy. The second step computes the free energy resulting from the insertion of a neutral chloride atom into the mixture. The final step reduces the introduced chloride to balance out the charges. This results in an overall reaction of Mn+(eutectic) + Cl0(eutectic) > Mn+1(eutectic) + Cl-(eutectic) . The free energy of solvation resulting from the sum of the three free energy components is plotted against temperature and the entropy so obtained compared with already available experimental data. The calculated entropy of solvation, the diffusion co-efficient and activation energies are in reasonable agreement with the values found experimentally. The radial distribution functions confirm that the model behaves in a physically reasonable fashion. We discuss the possibility of improving the accuracy of the method by using more sophisticated models for the interactions of the ions.This work shows the feasibility of predicting thermodynamic quantities and provides a better local description of the environment of dissolved actinides in molten salts. This method can be further used for metals in more complex mixtures to evaluate the effects of the solvent and can be used as a predictive tool.

Advanced materials can be developed by electrochemical or chemical routes via molten salts. The following topics will be covered: - synthesis of metal matrix composites; - recycling of metal matrix composites; - synthesis of carbon powder and carbon nanotubes; - synthesis of metallic foams; - purification of liquid metals, including silicon; - batteries based on molten salts

Water electrolysis is recognized as an efficient energy storage (in the form of hydrogen) supplement to a renewable energy production. Industrial alkaline water electrolyzers are rather ineffective and space requiring for a commercial use in the energy storage. The most effective modern water electrolyzers are based on the use of a polymeric proton-conducting membrane electrolytes (PEM), e.g. Nafion®. However, there is a great challenge for their widespread commercialization: Very high cost and low abundance of the catalytic materials (Pt, IrO2) and use of Ti or other expensive construction materials.The alternative is to develop an intermediate temperature (200-400C) water electrolyzer without expensive platinum and IrO2 catalysts, and with cheap electrolyte and construction materials. This goal can be achieved by using alkaline metal dihydrogen phosphates (e.g. KH2PO4) as proton-conducting supported liquid phase electrolytes.In this paper, the results of electrochemical study of several metals and transition metals (tungsten, molybdenum and tantalum) carbides in molten KH2PO4 at 260C are presented. All the results were compared to platinum and gold. It has been shown that nickel and high-nickel alloys are corrosion resistant in this electrolyte. These results can be a real breakthrough in the solution of the materials cost problems, because it indicates that nickel and Ni-containing catalysts can be used in the ITWEs. Moreover, all the achievements in this area obtained for the alkaline systems, molten carbonate fuel cells and even SOFCs can be used in the development of the ITWEs.A more important fact was that in molten KH2PO4, at 260C, WC demonstrated better performance than Pt as a catalyst for hydrogen evolution reaction. The catalytic activity of metal carbides decreased in the raw tungsten carbide > molybdenum carbide > tantalum carbide.

A search for a corrosion resistant, electrochemically active electrode material with stable operating characteristics is a pressing task of the electrochemistry. Electrodes from diamond materials meet the above requirements. The advances made in the synthesis and purposeful change of electrophysical properties of diamonds allow them to be used as electrodes in various electrochemistry applications (indestructible anode, diamond metallization). The addition of alloying additives to the diamonds during the synthesis made it possible to increase conductivity by several orders and to obtain electrodes with semiconducting and even semimetallic properties.Another way to change electrophysical properties is the diamond surface modification by various techniques: The implantation of metals into the near surface layer and even in the bulk of crystals, the treatment of diamonds by molten salts, and the partial diamond graphitization when heating in an inert atmosphere. In the present paper, the generalized results are given of the investigation into the electrochemical behavior of electrodes made from monocrystals of dielectric and semiconducting synthetic and natural diamonds, polycrystalline diamond films, compacts from nano- and microdispersed diamond powders in molten salts and aqueous solutions. It is shown that the decisive role in the use of these electrodes is played by the value and type of conductivity of diamond materials, quality (continuity) of films and their resistance to corrosion. Our findings have shown that the use of the studied materials in electrochemical processes has considerable promise. Corrosion, potentiometric and voltammetric investigations of diamond behavior in chloride, chloride-oxide and oxide melts were carried out. On the basis of these studies, new data of halide-oxide systems for obtaining galvanic coatings of refractory metals carbides and carbon coatings at diamonds were elaborated.

Molten salts are known as suitable reaction media for the selective solubilisation or precipitation during chemical reactions and have already been proposed as a possible route for the treatment of raw materials, the production of metals (aluminium, sodium) and the recovery of valuable metals by electrowinning. It is present in significant quantities in ore minerals like monazite or bastnasite but cannot be found in metallic form. The general use of neodymium has to be first refined.Neodymium as "rare earth" belonging to the lanthanide series is becoming increasingly important for current and future industrial components/devices such as computer, LCD screen and laser (YAG:Nd), as well as green technologies (wind turbines and electric cars). Due to the shortage of its availability and the geopolitical issues, fluctuating prices on the markets are observed and it leads to recurrent problem of the raw material supply and makes its use in production unsafe.For the development of electrochemical based processes where Neodymium is involved, its electrochemical properties are needed. As an illustration, Neodymium as fission products in nuclear reactors can be separated from actinides using pyrochemical process.This work summarizes the thermodynamic (phase diagrams) and electrochemical properties (apparent standard potential, effect of electrode) of neodymium in molten salts. It makes an overview about the thermochemical properties of neodymium containing solutions and can be used as design tool for process engineering.

Spent nuclear fuel reprocessing has traditionally utilized liquid-liquid (LLE) extraction techniques, such as the PUREX process. Whilst these processes are well established, they can produce product streams of weapons grade material. Today, the spent fuel reprocessing industry is developing new techniques that will allow for proliferation resistant re-processing methods in closed loop nuclear fuel cycles. Direct electrochemical reduction of the spent oxide fuels coupled with selective electro-refining is one such technique. In this work, the authors have investigated the electrochemical reduction of uranium (IV) oxide and its analogues in the molten lithium chloride-potassium chloride eutectic. The purpose of this work is to ascertain the necessary conditions for the reduction to proceed and to reveal any limitations of the process. Electrochemical techniques, such as cyclic voltammetry and chronoamperometry have been used to investigate the electrochemical reduction. In addition, coupled microstructural characterisation and chemical analysis have been used to ascertain how changes in the microstructure affect the electrochemical reaction pathway as it is proceeding.

We proposed a new separation and recovery process for RE metals from Nd magnet scraps using molten salt electrolysis. The present study focused on the electrochemical formation of RE-Ni (RE=Dy, Nd) alloys in a molten LiCl-KCl system at 723 K. Cyclic voltammetry was conducted using a Ni electrode in molten LiCl-KCl-RECl3(RE=Dy, Nd) systems at 723 K. In cathodic scan, a cathodic current was observed from 1.00 V (vs. Li+/Li) due to the formation of Dy-Ni alloys in a molten LiCl-KCl-DyCl3 system. In contrast, a cathodic current was observed from 0.60 V due to the formation of Nd-Ni alloys in a molten LiCl-KCl-NdCl3 system. On the basis of these results, an alloy sample was prepared by potentiostatic electrolysis at 0.65 V for 1 h using a Ni plate cathode in a molten LiCl-KCl-DyCl3-NdCl3 system. The mass ratio of Dy/Nd in the alloy sample was found to be 72 by ICP-AES.

It is well-known the fact that molybdenum and tungsten carbides coatings on metal and non-metal surfaces significantly improve a corrosion and mechanical resistance of materials.The process of obtaining molybdenum and tungsten carbides coating includes two stages: Co-deposition of molybdenum, tungsten and carbon at simultaneously ions reduction on cathode surfaces; Reaction between atomic Mo, W and C with double carbides (Mo2C, W2C) formation. The process does not require atmosphere protection.We investigated the influence of temperature, concentration of components and the duration of the electrolysis on the structure of (Mo2C, W2C)-coatings.Coatings with best properties are obtained at temperature above 900°C. Crystallites sizes depend on the temperature: The most size-crystals are deposited at temperature above 900°C. Current density was changed in range 0.05-0.1 A/cm2.

Electrochemical synthesis in molten salts has great possibilities for production of various carbon containing compounds (doped, undoped carbon tubes and fibers, tungsten carbides) in one step in the form of coatings and ultra fine powders. Theory and experimental certification of this method for the synthesis of different refractory metal compounds (borides, carbides, silicides of IV-VI groups of metals) were developed in the 1980s at the Institute of General and Inorganic Chemistry of the Ukrainian National Academy of Sciences.The goal of the present paper is the creation of physical-chemical basis for electrochemical synthesis of nanoscale powders of undoped and doped carbon nanotubes and fibers, powders of tungsten and molybdenum carbides in various morphological forms (tubes, fibers and rods). The peculiarities of partial and joint electrochemical reduction of carbon in solid state from CO2 and CO32- anion and tungsten from different ionic forms were studied by cyclic voltammetry. The mechanisms of electrode processes were suggested. Conditions (composition of electrolytic bath, temperature, cathodic current density, bath potential) of electrochemical synthesis of nanoscale carbon materials were determined. Properties of produced carbon-containing compounds were analyzed by XRD, SEM, TEM, Raman spectroscopy, BET. Correlation of product properties against synthesis conditions and parameters have been made.

Although Ionic liquids are meanwhile well accepted in the field of electrochemistry, with a remarkable worldwide output of papers per year, their interfacial behavior, especially under electrochemical conditions, is far from being understood. Depending on the liquid, it can be quite tough to probe by STM the surface of HOPG with atomic resolution, whereas this is a student's exercise with aqueous solutions. Together with Rob Atkin from the University of Newcastle, Australia, we could show that the interfacial behavior of ionic liquids depends on the liquid, on the applied electrode potential and on the level of impurities. A part of the usually wide electrochemical windows of ionic liquids is due to a type of a surface passivation that can be probed both with AFM and STM. As a consequence, the electrochemical behavior of ionic liquids depends on the cation/anion combination, the water content and the level of impurities. LiCl, as an example, has quite a strong effect on the interfacial behavior. This might explain why with one liquid, nanocrystalline materials are obtained whereas with an apparently similar one, microcrystalline materials are obtained under comparable conditions. This lecture will also show that the low surface tension of ionic liquids allows making a variety of macroporous metals and semiconductors as well as of nanowires, like Si, Ge, Al, Zn and conducting polymers. Such materials are potentially interesting for future battery applications but also, if chemically modified, for dye sensitized solar cells, sensors, catalysts and so on.

Experimental investigations and Gibbs energy modelling of KCl-LiCl-UCl3 system employing CALPHAD method are here reported. Gibbs energy modelling of the subsystems KCl-UCl3 and LiCl-UCl3 was carried out primarily using phase diagram data from the literature. For the Gibbs energy modelling of the KCl-LiCl subsystem, new phase boundary data corresponding to the selected terminal compositions obtained through differential thermal analysis data along with thermochemical and phase diagram data from the literature were used. Thermal analysis was also carried out for KCl-LiCl eutectic mixture containing small amounts of UCl3. The liquidus temperatures for these compositions were also determined. Electromotive force data for dilute solutions of UCl3 in the KCl-LiCl eutectic melt, measured in the temperature range 708-833 K in the present work, were found to be in good agreement with the literature data. These data were also used as input for the Gibbs energy modelling of the KCl-LiCl-UCl3 system. In order to improve the quality of the resulting Gibbs energy functions of the quasibinaries and the quasiternary, enthalpies of mixing of the corresponding melts estimated using an empirical correlation based on surrounded-ion model were also used as input. Finally, the generated Gibbs energy functions were used to compute phase equilibria.

Carbon has been used in contact with molten salts for over a century since Hall and Heroult, independently, electrolysed aluminium from molten cryolite. In molten salt nuclear reactors, carbon is purely used as a container material, but in the electrolysis of alumina, dissolved in cryolite, or the electro-deoxidation of nuclear waste, the evolved oxygen reacts with the carbon to form carbon dioxide. In other cases where the electrolyte is a chloride, as in magnesium, lithium and sodium production, the anodic reaction is the evolution of chlorine and provided there are no oxides in the electrolyte, there is no reaction with the carbon anodes. If graphite is made the cathode in lithium chloride, lithium intercalates into the structure and pushes out graphene sheets which can roll up to form either nanoscrolls or nanoparticles, depending on the temperature and the grain size of the graphite. If tin or silicon chlorides are present in the salt, these metals will deposit preferentially on the graphite and subsequently form lithium silicon or lithium tin alloys which will be incorporated into carbon nanotubes and nanoparticles. These materials may find applications in lithium ion batteries.Simply heating graphite in lithium chloride will lead to a breakdown in the structure of the graphite and, under certain conditions, can lead to the production of graphene sheets, a method which may be more appealing than laborious mechanical methods. Furthermore, intercalation of ionic liquids into graphite has also led to the formation of graphene.Carbon can also be extracted cathodically from carbonate containing melts below about 700oC to form nanosized carbon particles which are ideal as the anode in lithium ion batteries. Above about 700oC, the cathodic product is carbon monoxide, which is the stable phase at this temperature. In addition, it is known that carbon dioxide has a high solubility in lithium oxide containing melts and this may offer a way of both extracting carbon dioxide from polluting gases or even the environment and, at the same time, converting it to high value nanosized carbon particles for lithium ion batteries.These varied and diverse applications of the interaction of carbon with molten salts will be discussed in this paper.

It was not until 2005 that the rather obvious compatibility of ionic liquids with ultra-high vacuum (UHV)-based spectroscopies was fully realised. Since that time, an ever-increasing portfolio of UHV based techniques including XPS, UPS, SIMS, TPD, SEM, TEM, and related synchrotron based experiments have been applied to the study of both pure ionic liquids and solutions thereof. UHV techniques give tremendous insight into many aspects of ionic liquid properties and the role that they play in chemical reactions and processes. Since 2005 we have developed a series of robust spectroscopic protocols that allow the direct comparison of spectroscopic data, and more critically allows the investigation of subtle changes in binding energy that result from chemistry within the sample itself.The chemistry of ionic liquid mixtures is an emerging area of research that offers tremendous potential in applied fields, particularly those that are based upon the electrolytic properties of the liquid itself. The direct combination of different ions could provide a fine tuned balance between electrochemical stability, viscosity, conductivity and melting points. We explore the nature and local electronic environments within simple ionic liquid mixtures by direct XPS measurement. Common cation mixtures based upon both dialkyl imidazolium and dialkyl pyrollidinium8 based liquids are investigated and XPS data will be used to illustrate speciation and bulk structure in mixed anion-based systems as a function of molar fraction. The experiments illustrate opportunities to tune the electronic environment within ionic liquid mixtures and highlight a strategy that may be used to develop a palette of ionic liquids that may be blended to produce mixtures with tuneable chemical properties that could potentially impact upon catalytic performance. This lecture will review progress using laboratory based XPS instrumentation employing both monochromatised Al KI± and Ag LI± X-rays.

Industrial applications of noble and refractory metals and non-metals and their compounds define further development and improvement of existing technologies and development of new and more effective ones, more effective and ecologically safe. The use of molten ionic electrolytes as reaction medium can solve these problems. To achieve the objectives stated, the following points are necessary: - electrolyte suitable for this purpose; - corresponding electrochemical properties of metals and non-metals; - targeted scientifically substantiated approach to the implementation and control of mechanism and kinetics of electrode processes.The relevance of the topic is due to its importance for modern melts electrochemistry. From a theoretical point of view, the following issues are of great importance:1. Mechanism and kinetics of electrode processes of noble and refractory metals and non-metals in low-temperature melts.2. Study of the melt state after anodic dissolution of metal (ions oxidation state, complexation etc.).3. Theoretical study of anodic dissolution of metals in multicomponent electrolytes with complexation.4. Investigation of processes occurring at the interface metal/melt (passivation, adsorption etc.) in steady state and during polarization.5. Investigation of the mechanism and kinetics of co-deposition of refractory metals with other metals and non-metals in the medium-temperature melts.From a practical point of view, the following topics are important: 1. Electro-deposition of metals and metal alloys from ionic melts.2. Possibility to control a form of cathodic deposits (powders, galvanic coatings etc.).3. Electrochemical synthesis of binary and ternary compounds of refractory metals with non-metals.4. Possibility of metals separation during processing of their joint raw materials.5. Electrochemical processing and refractory metals surface polishing.

Copper smelting plant in Bor operates over hundred years, treating copper ores and copper concentrates in order to extract metal copper by pyro metallurgical process. During that processing a great amount of copper slag has been generated. Copper contents in the slag is about 0.4 up to 0.7%, and like this, the secondary source for metal copper re-utilization is presented. Microscopy analyses were widely carried out on various samples of copper slag in order to determinate its micro structure. The main goal of this investigations was to find a possibility for re-extraction remaining copper in slag. According to phase occurrences in slag, there are possibilities to apply flotation technic for utilization of that remaining copper.

Molten salts and ionic liquids are solvents with great potential for carrying out chemical reactions in a more sustainable way regarding e.g. Process design, energy consumption, product selectivity, reaction rates, loss of solvent and waste production. The talk will highlight molten salts and ionic liquids already in use or very promising for future sustainable production of bulk chemicals and environmental protection.Thus, ongoing or future production of bulk chemicals, like sulfuric acid, acetic acid, aldehydes, acid esters, methyl methacrylate and selective absorption of pollutants in industrial off-gases, which are important for the environmental protection and the climate will be addressed.

This paper reports thermodynamic calculations on the LaBr3, CeBr3 compounds and MBr-LaBr3, MBr-CeBr3 binary systems over the entire temperature and composition range. The Gibbs energies of LaBr3 and CeBr3 were evaluated using an independent polynomial to fit the experimental heat capacity. A two sub-lattice ionic solution model (M+)P : (Br-, LnBr6-3, LnBr3)Q (Ln=La, Ce) was adopted to describe the liquid phase and the thermodynamic parameters for each phase in the MBr-LaBr3 and MBr-CeBr3 systems were reassessed by using available experimental information on phase diagram and thermodynamic properties. A comparison between the calculated phase diagram and thermodynamic quantities of the MBr-LaBr3 and MBr-CeBr3 systems was made and a discussion was provided.

Present-day trends in material science of halide scintillators are connected with the improvement of their quality by the use of halide raw of high purity. The common way of purification consists in the treatment of the corresponding melts in reactive gas atmosphere containing free halogens or hydrogen halides that provide the removal of oxygen-containing products in the gaseous phase. However, the use of these methods is rather limited because of the high corrosion activity of the mentioned agents.We report methods providing the precipitation of oxygen-containing admixtures as solid phase by cation dopants destructing oxide-containing anions and fixing the formed oxide ions.The connection between physicochemical parameters of cation dopants (Be, Eu, Mg, Ni and Y) and their purification ability is considered an example of cesium iodide, which is widely used as a scintillator for high-energy physics.The radioluminescence spectra and time profiles of the scintillation pulse of undoped and cation scavenged CsI single crystals are analyzed. The treatment of molten CsI by the dopants results in the suppression of afterglow that makes the material faster.The efficiency of the studied cations depends, mainly, on the solubility of the formed oxide, which is the function of the melting point of the formed oxide. The density ratio of the formed oxide and the melt treated should be taken into consideration too, from the industrial use of the cation dopants perspective.Mg and Y cations are the most effective for the purification since they form refractory oxides possessing extremely low solubility. Their use permits obtaining the materials with the fraction of the fastest components more than 80 %.

It was found that low-temperature melts based on urea, acetamide, imidazole and tetraalkylammonium chlorides are stable and have low melting point (<100oC).Based on study results of electrochemical behavior of noble and refractory metals in these melts, a relationship between the passivation properties of these metals and their electrochemical behavior was established. Metals which are not passive (Ag, Cu, Pt, and Pd) are deposited on cathode in form of powder or galvanic coating. Galvanic coatings of Pt (from urea), Pd (from acetamide), Cu, Ag (from urea, acetamide, and imidazole) of different thickness were deposited with good adhesion to substrate. Pd powders were deposited from urea having spherical and needle structure. The electropolishing of such metals is unprofitable due to a high consumption of metal during unimpeded dissolution.Metals which are poorly passive (Ru, Rh, Ir, Ti, Mo, and W) are deposited on cathode in form of metal or metal-like deposit containing mainly oxihalide complexes and small amount of pure metals. In case of metals which are well passive (Nb and Ta), it is not possible to obtain a cathode deposit.Metals which are passive are suitable for electropolishing. The passivation degree of metal is the lowest, the process efficiency (polishing conditions - time, current density, and surface quality) is the highest. With weak passivation of metal, the metal-like deposit is deposited on cathode (containing small amount of metal and mainly its insoluble compounds). The relationships obtained allow predicting the possibility of applying solutions realization, i.e. Obtaining a cathodic deposit and its purity and also efficiency of anodic surface treatment of metals.

Molten blast furnace slag systems viz Al2O3, SiO2, CaO, FenO, MgO, MnO etc. Are comprised of ionic network structure. These slag systems possess silicate network structure. Silicate slags are built up of Si4+ cations, surrounded by 4 oxygen anions in the form of a regular tetrahedron. These (SiO4)4-tetrahedra are joined together in chains or rings by bridging oxygen. The mobility of ionic species present in the slag affects the slag rheology. However, the mobility is, in turn, dependent on the nature of the chemical bond, inter-ionic forces of the ions involved. The stronger inter-ionic forces leads to higher slag viscosities. The paper examines slags possessing high silica contents and discusses the effect of its polymeric anions on the rheology of slag system. It shows that as the metal oxide concentrations increase, Si-O bonds break down and decrease the slag viscosity. In high alumina blast furnace slags; Alumina is present as (AlO4)5-forming polymeric units with (SiO4)4. Thus, alumina acts as a network former. The cations of basic oxides viz lime, magnesia, titania act as a network breakers and oxygen providers. They result in de-polymerization of the melt and the basic cations tend to balance the charges to maintain the electrical neutrality. This phenomena interestingly affects the slag rheology. The paper discusses the effect of alumina on the slag viscosity at high temperatures. The ionic network structure of the slag determines the heat levels in the blast furnace operations to maintain the adequate slag rheology. The paper discusses the high temperature rheological experimentation of some molten blast furnace slag containing high alumina and its effect in slag rheology. The paper also describes some results of a model study of the momentum transfer to the blast furnace slag systems possessing ionic network structure.

Our long term electrochemical investigations of halide-oxyfluoride molten systems resulted in the electrochemical synthesis of early unknown in literature compounds of niobium and tantalum. These elements are to a certain extent chemical analogs. Nevertheless, the cathodic products of electrolytic processes carried out in similar Nb-and Ta-containing melts are very different.For the Nb-containing melts the most typical cathodic products are low valence compounds: Nb, Nb(O), NbO', Nb4O5, tetragonal suboxide Nb6O, rombohedral suboxide NbxO (x. For Ta-containing melts, the most characteristic cathodic products are metal-like conducting oxide bronzes of three structural types: Cubic, tetragonal and hexagonal for the potassium compounds K1-xTaO3, K6-xTa10.8O30 and K6Ta6.5O15+xF6+y respectively while the cesium phases, with pyrochlore type lattice, have the general formula Csn+2+zO5+yF1-y.For the first time by electrochemical synthesis from NaCl-KCl-NaF-GdF3-KBF4 melt at temperature 1023 K and with utilization of molybdenum cathode, the gadolinium hexaboride nanotubes were synthesized. Most likely GdB6 nanotubes formation is ruled by intercalation mechanism.Nanoneedles of TaO with tetragonal crystal lattice were obtained by electrolysis of CsCl melt, containing monooxofluoride complexes of tantalum. It was determined the correlation between the redox potential of molten system, temperature and stability of tantalum monoxide.A new generation of highly active and stable nanostructured catalytic coatings for the water-gas shift reaction by high-temperature electrochemical synthesis in molten salts has been developed.

Due to the low toxicity, high conductivity and a significant electrochemical stability, ionic liquids can be used as green solvents and as a replacement for volatile organic solvents in many industrial processes. They are often called designed solvents. It is possible to synthesize ionic liquid with required properties in order to obtain the most suitable solvent. In this work, several ionic liquids with different inorganic anions such as nitrate, bromide and tetrafluoroborate were synthesized. Density, viscosity, electrical conductivity and thermal stability were also measured. Some ionic liquids were tested as solvents and media for different chemical reactions.Although the green attributes of ionic liquids have helped scientist to develop many green and technologically safer processes, their impact on the environment is still under discussion. For new chemicals, such as ionic liquids, it is very important to evaluate their environmental impact, degradation and stability. Thus, the efficiency of different advanced oxidation processes for the removal of ionic liquid was studied. An attempt was also made to identify the reaction intermediates formed during the photo-oxidation process, using the LC-ESI-MS/MS and 1H NMR techniques.

It is hypothesized that the electrical conductivity polytherms of all molten salts pass through a maximum in the temperature range from the melting point to the critical point. However, direct experimental evidence supporting this idea is very limited. This paper describes the electrical conductivity measurements of a number of molten salts (BeCl2, ZnCl2, SnCl2, TeCl4, etc.) over a wide temperature range with the vapor pressure of the salts reaching tens of atmospheres at high temperatures. In some cases, the cupola of electrical conductivity was reached. The conductivities of some salts (InCl3, ZrCl4, HfCl4) were found to decrease with increasing temperature. The densities of the melts were estimated and molar conductivities and activation energies were calculated at the same temperatures. The reasons for the appearance of maxima on the conductivity polytherms of molten salts are discussed. Some correlations between the physical-chemical properties of these salts are suggested.

Many metal production and refining processes are limited by transport properties of melts: Diffusion, viscosity, ionic conductivity, etc. The molecular dynamics method demonstrates that in a conventional computer model, the "substance of the melt" has both kinetic and mechanical properties of a dense gas or simple fluid over all temperature range, including the area near absolute zero. The rigid network of the melt or the crystal lattice is not formed at ordinary interactions of atoms and their classical motion, and, thus, the liquid solidification does not occur. In such model, the energy barriers EA, surmounted at atomic rearrangements, are relatively small compared to the thermal energy RTm, where Tm is the melting temperature.The present work proposes a new model that considers the influence of occurring quantum effects on the melt solidification. This model naturally describes the solidification process, the appearance of stable and rigid crystal structures and large real activation energies (e.g., E ~ 40RTm) of transport properties. In this model, the increase in viscosity and solidification results from the increasing fraction of the quantum "freezing out" of atoms. The "frozen out" atoms are motionless because they are located on the zero energy level. Normally, the fixation of a few atoms is sufficient to form the rigid lattice. This fixation is equivalent to the loss of some atomic degrees of freedom.

Lanthanides are fairly used in a number of applications, such as lanthanide or lanthanide alloys production, recycling of spent nuclear fuel, waste processing, lighting industry, etc. Many industrial processes, that are molten salt-based, involve rare earth halides and their mixtures with alkali halides. The present work focuses on the thermodynamic properties of europium (II) bromide-alkali bromide melts. By opposition to most lanthanide compounds, which correspond to the valence state (III), europium is one of the few rare earth metals together with samarium and ytterbium that forms stable compounds in the valence state (II). Several experimental techniques were used complementarily to acquire the corresponding physicochemical data that are also required for process development. Also, numerical approaches were applied to the above systems.A critical thermodynamic description on MBr-EuBr2 systems was carried out by the CALPHAD method. A two-sublattice ionic solution model for the liquid, denoted as (M+)P : (Br-, EuBr42-, EuBr2)Q, was employed to represent phase diagram and enthalpy of mixing data. To reach a self-consistent thermodynamic description for the constituent phases in the system, the experimental heat capacity data of the intermediate compounds M2EuBr4 and MEu2Br5 were evaluated.

This article summarizes the main characteristics of the FFC-Cambridge process for the molten salt electrolytic winning of metals from metal oxides, presents the key features of in-situ resource utilization and lunar geology, discusses the recent identification of anodes capable of evolving oxygen, and finally highlights the new LunarRox process for the combined molten salt electrolytic winning of metal and oxygen from oxidic lunar materials.

Potential modeling studies on ionic liquids using local structure analysis have an important role in understanding the liquid structure. The ultimate target of these studies is to find a good potential for Molecular Dynamics (MD) simulations that can be transferable between different systems. MD simulation studies, which employ two-body interionic polarizable potentials obtained by experimental data fitting, gave successful structural and spectral results with real systems. In this talk, it will be shown that in certain cases, where two-body interactions are inadequate to fully describe the system properties, ab initio density functional calculations might be very helpful in the local structure analysis part of the potential modeling studies. Using case studies, it is also aimed to compare the results of the MD simulations, where polarizable interaction potentials are derived from ab initio calculations with the simulation results where empirical polarizable ion interaction potentials are used. Structural and spectral results will be discussed comparatively using the examples of liquid cryolite, AuCl3 and halides of the Group 12 metals.

Concentrating solar power (CSP) plants offer the key advantage of reliable and dispatchable power generation through the use of thermal energy storage (TES). CSP parabolic trough plants use organic heat transfer fluids (HTF) to generate turbine steam at 393°C. Power towers use molten salts to generate steam at 565°C. This higher steam temperature increases the power generation efficiency of the power plant. The current binary nitrate salt mixture of sodium and potassium nitrate (NaNO3/KNO3) has a maximum operating temperature of about 580°C and an average heat capacity of 1.5 J/g.K. Next-generation CSP plants will require advances in HTF and TES systems to generate higher temperatures in the range from 500° to 800°C so they can provide thermal energy to advanced power cycles such as supercritical carbon dioxide (CO2) and improve the thermodynamic efficiency of the power plant. We selected several candidate molten salt systems that operate at these higher temperatures using thermodynamic databases. The selection criteria were heat capacity, heat of fusion, melting temperature, thermal stability, and cost. These thermal properties as well as the thermal conductivity of the candidate molten salts were evaluated and reported. Measurement methods include differential scanning calorimetry, laser flash diffusivity and thermogravimetry.

« Back To Technical Program