(ANGELL) INTL. SYMP. ON MOLTEN SALT, IONIC & GLASS-FORMING LIQUIDS: PROCESSING AND SUSTAINABILITY

A major question related to the glass transition event is whether there exists an ideal glass temperature T_g,ideal [1,2]. Because the laboratory glass transition T_g is some 40 to 100 K above the putative T_g,ideal it is virtually impossible to perform direct measurements that even approach the true equilibrium state at this temperature. Therefore, it is important to develop methods to finesse the problem and to work in the so-called "unexplored" region of glassy behavior [3] where the non-equilibrium response should be an upper bound to the dynamical behavior of the glass [4,5]. The framework for the study is that of the fictive temperature originally proposed by Tool [6] and that creates a solid framework for understanding the volume or enthalpy vs. temperature behaviors of glass-forming liquids as well as the evolution of the glassy properties during arbitrary thermal histories. In this framework, the fictive temperature T_F of the glass defines a point of intersection of the glass-like behavior with that of the equilibrium liquid. When the temperature T is below T_F, the dynamics are faster than those of the material in the equilibrium state. When T>T_F, the dynamics are slower, i.e., provide an upper bound to the equilibrium relaxation times at T. At T = T_F the equilibrium response should, in principle, be obtained. Therefore, to test concepts such as the possibility that the relaxation times or viscosity diverge at a temperature above absolute zero (possibly at T_g,ideal), as seen in multiple models of glass-forming liquids, the goal became to find or to create glasses with fictive temperatures as far as possible below the glass transition temperature T_g. Then, if one can work in the ''window'' between T_F and T_g, the theoretical predictions or extrapolations from the known equilibrium behavior above T_g can be tested down to T_F. We have addressed this challenge by using a 20 million year old amber [4] having a fictive temperature some 43.6 K below the conventionally measured T_g and were able to determine upper bounds to the relaxation times in the relevant temperature window. We subsequently were able to create an ultra-stable amorphous Teflon through a vapor deposition process that had a T_F some 55 K below the T_g of the same material and very close to the nominal T_g,ideal. In this case, and unlike the amber for which the dynamics could be measured by macroscopic rheological methods, there was an additional challenge. Here the vapor deposition process made only micro-gram quantities of material, at least in a reasonable time of multiple hours. Therefore the challenge was to make dynamic measurements on these ultra-small quantities of material. This we did by using the TTU bubble inflation method [7] of viscoelastic measurements to determine the creep response in the temperature range from just below T_F to T_g and applying time-temperature superposition to estimate the temperature dependence of the relaxation times, again in the upper bound condition. Two important results came from these investigations. The first is that the temperature dependence of the dynamics was found to deviate significantly from the finite temperature divergence given by extrapolation of the equilibrium response obtained for temperatures greater than T_g, thus challenging the idea of an ideal glass transition, at least as seen in the temperature dependence of the dynamics. The second is that the data are good enough to permit the evaluation of more modern theories that do not predict diverging time scales at finite temperature. The comparison with several of these will be shown. It is also of interest that, in spite of the challenge to ideas of an ideal glass transition, the activation energies of these upper bound relaxation times are still extremely high, thus the ''turn over'' from super-Arrhenius to Arrhenius-like behavior does not resolve the conundrum of the high apparent activation energies of the relaxation processes in glass-forming liquids, one of the original motivating factors in the ongoing study of complex fluids [8-11].

Solid-liquid and gas-liquid interfaces play a crucial role in catalysis, electrochemistry, coatings, and separation technology, to name only a view. The extremely low volatility of ionic liquids (ILs) and molten salt systems enables the use of ultra-high vacuum based surface science methods that were originally developed for solids. X-ray photoelectron spectroscopy (XPS) turned out to be a very powerful tool for IL reaction studies, particularly due the possibility to follow changes in chemical state of the IL via XPS chemical shifts. Moreover, angle-resolved XPS (ARXPS) allows for varying the information depth from about 7-9 nm (0° electron emission angle, more bulk-sensitive) down to 1-1.5 nm (80°, more surface-sensitive); in the latter case, about 80% of the overall XPS intensity arises solely from the outermost IL layer. Thus, differences between the top-most layer and the layers underneath can be accessed in great detail by ARXPS. Within the last years, we demonstrated that a large variety of phenomena such as reactions [1] and ion exchange processes [2] at interfaces are accessible when using ARXPS in combination with physical vapor deposition of ILs. The work presented here focuses on processes such as selective adsorption, film growth and stability in ultrathin IL binary mixture films and in IL/porphyrin films grown in situ on solid surfaces. Furthermore, we address the roles of surface free energy versus interface adsorption energy by comparing the surface compositions in the film and the macroscopic mixture systems. Such studies play an important role with respect to thin film / nanoscale applications of ionic systems.

We shall review results of broadband dielectric spectroscopy on supercooled liquids and ion conductors. Our review will cover more than 15 decades of frequency ranging from millihertz to terahertz and in a wide range of temperatures from the low-viscosity liquid to rigid sub-Tg glass [1]. The access to this extremely broad frequency window allows a detailed study of the complexity of glassy freezing and of the ionic and/or molecular dynamics in a large variety of materials. This includes ionic conductors and plastic crystals. Dielectric spectroscopy not only documents the enormous slowing down of the structural relaxation when approaching the glass transition, but also reveals a variety of further dynamic processes. These processes are important to understand the physics of the transition from a supercooled liquid into a rigid glass. We exemplify the phenomenology of glassy dynamics as revealed by these broadband spectra: the structural relaxation, the Johari-Goldstein relaxation, the appearance of a fast process as proposed by the mode-coupling theory, and the boson peak, a well-defined feature in the dielectric loss at THz frequencies. We also will mention the importance of non-linear dielectric spectroscopy to unravel the mystery of the glass transition [2], the significance of sub-Tg experiments like ageing, or the search for fingerprints of the Gardner transition [3]. Finally, we will focus on the charge dynamics in new classes of ionic conductors, like ionic liquids [4], deep eutectic solvents [5], or plastic crystals [6]. Compared to conventional electrolytes, plastic crystals are considered superior concerning ease of preparation, low cost, sustainability, and biocompatibility. Finding better electrolytes is of prime importance for further development of energy-storage and energy-conversion devices like batteries, fuel cells, and super-capacitors. Thus, these devices are a key factor for ensuring the sustainable energy supply of tomorrow. Dielectric spectroscopy is an ideal tool to study the ionic charge transport in these materials and its correlation to their glassy freezing, and to the reorientational dynamics of molecular entities.

Despite a growing number of climate change mitigation policies and increasing investments associated with the capture and storage technologies for CO₂, the anthropogenic emissions of this gas are inexorably growing. [1] Hence, there is a growing interest in finding large-scale commercially viable end-use opportunities for CO₂ utilization. In the last decade, thermal, electrochemical, and photo-reduction of carbon dioxide to CO and/or hydrocarbon derivatives has grown into a blooming field of research. [2, 3] A simple combination of sunlight, aqueous solutions saturated with carbon dioxide, and appropriate photocatalysts may yield CO (reverse semi-combustion) and/or hydrocarbon derivatives (reverse combustion). [4, 5] Ionic liquids (ILs) are known to solubilize and, in some cases, to activate carbon dioxide by stabilizing radical/anionic species [6, 7] and hence, constitute an attractive material for CO₂ capture/reduction.[8] We will present the most recent aspects on CO₂ capture by ILs. This involves the formation of bicarbonate, and its hydrogenation promoted metal nanoparticles to hydrocarbons and formic acid, as well as orgono-photocatalytic and electrocatalytic reduction to carbon monoxide. The basic aspects of the multi-roles of ionic liquids in these transformations will be detailed based on experimental and theoretical evidence, particularly in IL aqueous solutions.

Despite a growing number of climate change mitigation policies and increasing investments associated with the capture and storage technologies for CO₂, the anthropogenic emissions of this gas are inexorably growing. [1] Hence, there is a growing interest in finding large-scale commercially viable end-use opportunities for CO₂ utilization. In the last decade, thermal, electrochemical, and photo-reduction of carbon dioxide to CO and/or hydrocarbon derivatives has grown into a blooming field of research. [2, 3] A simple combination of sunlight, aqueous solutions saturated with carbon dioxide, and appropriate photocatalysts may yield CO (reverse semi-combustion) and/or hydrocarbon derivatives (reverse combustion). [4, 5] Ionic liquids (ILs) are known to solubilize and, in some cases, to activate carbon dioxide by stabilizing radical/anionic species [6, 7] and hence, constitute an attractive material for CO₂ capture/reduction.[8] We will present the most recent aspects on CO₂ capture by ILs. This involves the formation of bicarbonate, and its hydrogenation promoted metal nanoparticles to hydrocarbons and formic acid, as well as orgono-photocatalytic and electrocatalytic reduction to carbon monoxide. The basic aspects of the multi-roles of ionic liquids in these transformations will be detailed based on experimental and theoretical evidence, particularly in IL aqueous solutions.

Ionic liquids are thermally stable, low-melting salts (mp. below 100°C), which typically consist of mixed organic and inorganic halogen-containing or halogen–free ions. The exceptionally low melting temperatures are obtained as result of low ion charge densities, which reduce intermolecular forces between the ions.
Ionic liquids are unique compared to all other commonly applied liquids, as they are generally non-volatile and thermally stable in their whole liquid range (often 25-400°C), i.e. below their decomposition temperature. These characteristics enable their replacement for common volatile organic solvents (VOCs), thereby facilitating more environmentally friendly and sustainable technologies.
The non-volatile property of most ionic liquids makes it possible to maintain the liquid intact on the surface of a porous support. This is impossible with almost all other solvents since they will evaporate during use, a scenario that has made a very limited number of industrial SLP (Supported Liquid Phase) catalysts successful so far.
Here we demonstrate that such Supported Ionic Liquid-Phase (SILP) materials, with the catalyst dissolved in the ionic liquid, make heterogenized, homogeneous catalytic processes possible. This is done by turning the cumbersome batch operation into a continuous flow process design without compromising the traditionally high selectivity and heat transfer properties. Thus SILP catalyst processes regarding hydroformylation and alkoxycarbonylation of alkenes, as well as carbonylation of alcoholes, will be highlighted.
In addition, our research shows that due to environmental and climate concern, the gases CO₂, NO and SO₂ can be reversible and selectively absorbed using different ILs and that SILP absorbers. These ILs and SILP absorbers are promising materials for industrial flue gas cleaning, natural and biogas sweetening, and selective separation of gas mixtures. Absorption/desorption efficiency can be tuned by design of the ionic liquid, temperature, pressure and gas concentrations.
The SILP technology dramatically improves the overall kinetics of both catalysis and the gas absorption and desorption processes compared to bulk ionic liquid performance.

Ionic liquids are currently investigated as promising materials for the absorption, storage, and separation of gases, such as CO2 [1], and H₂S [2] among others. Ionic liquids based on the imidazolium cation are intensively studied for these purposes [3]. The possibility of combining distinct cations with different anions permits an easy design of ionic liquids. In an attempt to extract the structure-gas absorption relationship, we performed molecular dynamics computer simulations [4] on ionic liquids containing the 1-butyl-3-methylimidazolium cation and several anions (acetate, prolinate, BF₄^-, Br^-) interacting under typical experimental conditions (298 K, 10 bar gas pressure) with different gases (CO₂, N₂, methane, H₂ S). Two series of simulations have been carried out to characterize the physical absorption of the gases: i) ionic liquids containing 0.25 molar fractions of the gases, and ii) pure ionic liquids interacting with the gas phase.
The first series of simulations revealed that the structure of the ionic liquids is essentially maintained when the gas is dissolved. N₂ and methane are only found in the apolar domains of the ionic liquids presenting a tendency of separating phases, whereas CO₂ and H₂S also enter the polar domains of the ionic liquid producing stable solutions. The second series of simulations demonstrated that the ionic liquids only weakly absorb N₂ and methane, but are able to capture large amounts of CO₂ and, especially, H₂S from the gas phase. In this process of physical absorption of the gases, the small BF₄^- anion, offering several coordination sides for the gas molecules, performs best.

For the production of materials of various functional application based on rare refractory metals, broad prospects are opened when using molten salts. Technological processes have been developed and equipment has been created for obtaining coatings of refractory metals by the electrolytic method in molten salts.
Using this method, a unique rotor design of a cryogenic gyroscope has been created. It consists of a carbopyroceram sphere with a special cut at the equator covered with a superconducting niobium layer of high purity [1].
Biomedical material nitinol/tantalum was obtained by stationary and pulsed electrolysis. The adhesion of tantalum coatings, their porosity, and the corrosion resistance of the nitinol/tantalum composition were measured.
Highly active, stable catalysts of the new generation in the form of nanostructured Mo ₂ C coatings on molybdenum for the water-gas shift reaction (operating temperature 200-550°С) were obtained [2]. A composite material MoSi ₂ -MoB ₄ was created to protect molybdenum microreactors from oxidation in air-water vapor at a temperature of 500-700°C.
By the electrochemical method were produced: carrying devices from copper alloy with a less porous niobium coating for a long-term operation at temperatures up to 1000°С in a high vacuum; Cu-Hf high-temperature solders for diffusion soldering of various refractory metals; heat-resistant material made of niobium alloy with hafnium on borosilicated graphite for operation in an oxidizing environment with an operating temperature of 1700-2200°C [3].

Lithium-ion batteries (LIBs) have been widely used in power devices. For further expanding the usage of LIBs, safety and energy densities must be improved. We have focused on zwitterions, which have positive charge and negative charge in the same molecule [1]. Lithium-ion transport was improved by adding a zwitterion to polymer gel electrolytes [2]. Recently, we found that adding a small amount of zwitterion improved not only the electrochemical stability of oligo-ether electrolytes up to about 5 V [3], but also the charge-discharge cycle stability of cells with oligo-ether electrolytes [4]. We also investigated the effect of zwitterions on electrochemical properties of ionic liquid (IL) electrolytes. Zwitterions showed positive effects in IL electrolytes containing Li salts. Li/LiCoO₂ cells containing the IL/zwitterion electrolyte system exhibited high capacities as compared with those of IL electrolytes without zwitterions [5,6]. The increase in the interfacial resistance between the electrolyte and cathode with cycling was suppressed.
Recently, we have focused on the magnesium secondary battery, which has been attracting much attention as a next generation secondary battery. Magnesium metal has a high theoretical capacity density and low electrode potential, so it is expected to have high energy density. It is, however, difficult to control stripping and plating of Mg because of the formation of the passivation film. We will add zwitterions into IL/Mg electrolytes. The effect of zwitterions on the properties of IL/Mg electrolytes will be introduced.

The aim of this work is to develop a model for the electrical conductivity of complex melts based on the LiCl-KCl eutectic, containing the spent nuclear fuel components. This message is a continuation of our work [1]. In the present study we measured the electrical conductivity of quasi binary melts (LiCl-KCl)_eut., containing CsCl in concentration range 0 - 100 mol.%. Such molten mixtures are also of interest as solvents for various electrochemical applications.
We used in this work a capillary quartz cell with platinum electrodes and the AC-bridge method at the input frequency of 75 kHz. The measurements were carried out at the temperatures up to 900°C. The lowest temperature was 5-10 degrees below the liquidus temperature of all compositions in order to record the onset of the crystallization temperature. The liquidus line of this salt system is built.
It was found that the electrical conductivity of all melts increases with increasing temperature and decreases with increasing CsCl concentration. The specific electrical conductivity (κ, S/cm) of several molten mixture is exemplified below:
κ = -4.4529 + 9.9064*10^-3T - 3.4082*10^-6T² , (671-1173 K) 20 mol.% CsCl;
κ = -3.5257 + 7.5152*10^-3T - 2.4628*10^-6T² , (717-1175 K) 50 mol.% CsCl;
κ = -2.7114 + 5.8676*10^-3T - 1.8094*10^-6T² , (864-1172 K) 80 mol.% CsCl.
In the molten (LiCl-KCl)_eut. - CsCl mixtures the significant negative deviations of electrical conductivity from additive values were observed over the whole concentration range, indicating that the replacement of some alkaline cations by those, significantly different in size, is accompanied by a significant rearrangement of interparticle bonds, which results in different complexation in the system [2].
The electrical conductivity of molten LiCl - KCl - CsCl with a variable ratio of KCl / CsCl concentrations was also measured in [3].
Keywords: Molten salts; Conductivity; LiCl-KCl; CsCl;

Carbamide melts have been discovered as applications as electrolytes for electrochemical treatment of metals [1]. As an example, the possibility of electrodeposition of refractory metals from carbamide melts at 135°С has been examined for tungsten. WO₃ was insoluble in carbamide melts. The solubility of Li₂WO₄, Na₂WO₄, and K₂WO₄ in carbamide melts at 135°С reaches 5 wt.%, which makes it possible to carry out voltammetric studies and electrolysis experiments. Investigation of the electrochemical behaviour of tungsten oxides show the first step as an irreversible change transfer of W(VI) to W(0), followed by an irreversible chemical reation with formation insoluble in carbamide melts, the lower oxidation state of tungsten oxide. When studying the electrochemical behaviour of tungsten oxide and its compounds (Li₂WO₄, Na₂WO₄, and K₂WO₄) in molten carbamide, it can be concluded that maximum limiting currents are typical of the (NH₂)₂CO-Na₂WO₄ system. Micron W coatings on nickel cathodes have been obtained by the electrolysis of the molten system (NH₂)₂CO-Na₂WO₄ at current densities of 10-20 mA/cm².

The density, viscosity and electrical conductivity of ionic liquid 1,3-diethylimidazolium bis(trifluoromethylsulfonyl)imide, (C₂C₂imTFSI), and 0.5 M solution of LiTFSI in C₂C₂imTFSI were determined at different temperatures. The LiTFSI/C2C2imTFSI system was tested as a possible electrolyte for lithium-ion batteries by using anatase TiO₂ nanotube arrays [1] electrode as anode material for a first time. The electrochemical testing has shown the improvement of lithium-ion insertion/deinsertion properties by increasing temperature. Also the existence of the decomposition of the electrolyte detects the change of colour. The decomposition of electrolyte leads to the formation of a film on the surface of the electrode [2,3] which improves coulombic efficiency during cycling.

By the method of a cyclic voltammetry, the process of electroreduction of oxygen-containing ions of chrome CrO₄^2- and Cr2O72- and processes of their joint electroreduction with fluorborat-ion BF₄^- in equimolar KCl-NaCl melt at temperature 1073 K were studied.
It is shown that the electroreduction of CrO₄^2- and Cr₂O₇^2- ions occurs in two stages with formation of chrome oxide Cr₂O₃ at the first stage. At the second stage, in a case of electroreduction of CrO₄^2- ions Cr₂O₃ forms and a mix Cr₂O₃ and metal chrome forms in a case of electroreduction of Cr₂O₇^2- ions.
It is established that the fluorborat-ion in the equimolar KCl-NaCl background melt can interact with chrome ions Cr₂O₇^2- with formation of oxyfluoride chrome complexes, and boron complexes CrO₂F₄^2-, BOF^2-, and BOF^-.
The possibility of electrochemical synthesis of chrome boride phases in halide-oxide melts by the method of joint electroreduction of oxyfluoride complexes of chrome and boron complexes is showed.

The silicon dioxide electroreduction process in molten salts is of interest both for elemental silicon obtaining and for the electrochemical synthesis of silicides and silicon-based alloys. The most detailed investigation of silica electroreduction processes in chloride-fluoride melts was done in [1, 2], in fluoride melts – in [3], in cryolite melts – in [4]. Chronopotentiometric studies in the Na₃AlF₆-SiO₂ melt have shown that electroreduction process at Ni-cathode surface includes a "weak" pre-dissociation of the complex into the electroactive state followed by 4-electron process of Si (IV) discharge.
This work aim is to find an indifferent electrode material for such systems, to obtain new data on the electrochemical behavior of Si (IV) in molten NaCl-Na₃AlF₆, and to determine conditions of electrodeposition of silicon coatings.
As the main research method, voltammetry with single and cyclic potential sweep was selected. In addition, potentiostatic electrolysis followed by metallographic and X-ray diffraction analysis of deposits was used.
The silica solubility in cryolite melt is caused by the silicon oxifluoride complexes formation. of Current-voltage curves analysis in semilog coordinate system shows that the experimental values of current-voltage dependencies slope are higher than those for reversible four-electron process. The polarization curves slope for the silicon electrode in coordinates lg i - η (n = 2.5-3.2) also exceeds the values for the four-electron reversible process. These experimental facts, as well as presence of two peaks at the anodic dissolution curves, suggesting the possibility of multistage character of the overall process of oxifluoride complex reduction in molten NaCl-Na₃AlF₆ system according to the following scheme:
Si(IV) +2e --> Si(II)+2e --> Si(0)
Coatings were deposited from the NaCl-Na₃AlF₆-0.5-1.0%(wt.)SiO₂ melt at 900ºC at current densities (1-8)∙10^-2 A/cm². Deposition rate within this range of current densities was 10-40 μm/h, and the current yield as a silicon coating was up to 70-80%. Silicon coatings were obtained on samples of glassy carbon, graphite, nickel, copper, molybdenum, tungsten, and steel 3.
Thus, platinum as the electrode material is not indifferent in the systems under investigation. At the current-voltage curves obtained at the glassy-carbon electrode, there is Si (IV) reduction wave stretched along the axis of the potential which potential is close to the potential calculated from thermodynamic quantities. It was shown that the electroreduction of Si (IV) proceeds irreversibly in two stages. Silicon coating on different materials surface were obtained.

We are facing big challenges in developing full-solid Li/Na ion batteries concerning the limited performances and problems of electrodes and solid electrolytes. There are, however, potential possibilities to overcome these challenges. In this presentation, we demonstrate a different route, that is, our disorder/ordering engineering concept [1] to develop high performance cathode/anode/electrolyte materials. The disorder/order engineering refers to two aspects. First, part of the disordered or glass structure in cathode/anode materials is transformed into the ordered domains. Second, the long-range ordered solids are transformed into disordered or amorphous ones. In this talk, we present three case studies concerning the effect of the disorder/order engineering on the electrochemical performances of cathodes, anodes, and solid electrolytes, respectively, for Li/Na-ion batteries.
Case 1: A series of vanadium-tellurite glasses with various V/Te ratios were synthesized via melt-quenching [1,2]. Then, the glass was pulverized and mixed with carbon to make Li-ion battery anodes. The anodes underwent discharging/charging cycles. During cycling, a fascinating phenomenon was observed, i.e., nanocrystals formed in glass matrix. As a consequence, the cycling stability and electronic/ionic conductivity of the anodes were enhanced. This kind of nanocrystal formation has a fundamentally different origin compared to the thermally induced crystallization [1,3].
Case 2: NaFePO₄ with maricite structure, which is a thermodynamically stable phase, was considered to be electrochemically inactive for sodium-ion storage. Recently, we succeeded in creating disorder in the NaFePO4 cathode by a mechanochemical route to enhance electrochemical performances of Na-ion batteries [4]. The derived NaFePO₄ cathodes containing both amorphous and maricite phases exhibit much improved sodium storage performance with an initial capacity of 115 mA h g^-1 at 1 C and an excellent cycling stability of capacity retention of 91.3% after 800 cycles.
Case 3: The crystalline Ag₃PS₄ was transformed into amorphous state via a chemo-mechanical milling process. The Ag⁺ conductivity of the amorphous sample was found to be about three orders of magnitude higher than that of the crystalline counterpart. The amorphous sample exhibits lower activation energy (E_a) for the Ag⁺ migration, and hence, lower Ag+ conductivity compared to the crystalline one. By performing structural characterizations, we explored the origin of the enhanced Ag⁺ conductivity of the amorphous sample. The present study provides valuable information for developing solid electrolytes.

It is known that the density of the most molten salts is well described by linear equations: d = a + b*T, where d is the density of molten salt; a, b are constants; T is the temperature, K. Such equations are convenient for small extrapolations. However, at temperatures near the boiling point and higher, the density of melts deviates markedly from the linear relationship to smaller values.
The technique for the long extrapolation of data on the melts density, which considers the non-linear decrease in density of melts at high temperatures (near and beyond boiling point), was proposed. This technique is based on the use of the Rackett's equation [1-3].
The choice of the equation was based on the comparative analysis of the accuracy of various equations for density calculations. It was found that Rackett's equation is the most precise, the uncertainty,u_r(d), does not exceeds 0.005, which is almost equal to the error of the density experimental determination. The analysis was carried out using the density data on a large amount of molten chlorides (BiCl₃, BeCl₂, ZnCl₂, PbCl₂, InCl₃, ZrCl₄ et. al.) and other inorganic compounds [2,3]. The coefficients A and B in Rackett's equation [1] were calculated using only the low-temperature data on the melts density and then they were extrapolated to the critical temperatures. The critical temperatures values, T_cr., included in the Rackett's equation are available for many molten salts, for example [2,4].
We also considered various ways to estimate T_cr. in the absence of reference data. It is shown that Rackett's equation, in the mathematical sense, is very stable relative to the choice of the value T_cr. This is a significant advantage, since the critical temperature is difficult to determine experimentally and often has to be evaluated.
Thus, the method to extrapolate the density of molten salts to high temperatures, up to T_cr, with a small uncertainty was proposed.
Keywords: Molten salts; Density estimation; Rackett's equation.

In this talk we overview broad literature on temperature dependence of structural relaxation (fragility) in molecular and polymeric systems. We emphasize broad range of known fragility index, from extremely low m~14 in supercooled water to extremely high m ~ 150-200 in many polymers. We ascribe the former to significant quantum effects in dynamics of water [1,2]. To understand better microscopic origin of fragility in non-polymeric systems we performed detailed analysis of the static structure factor S(Q). This analysis reveals that the temperature variations of the width of the main diffraction peak DQ(T) correlates with fragility of these liquids [3]. This observation suggests a direct connection between rather subtle changes in static structure and sharp slowing down of structural relaxation in glass forming liquids. We show that this observation can be rationalized using the Adam-Gibbs approach, through a connection between temperature variations of structural correlation length, lc, and the size of cooperatively rearranging regions. Then we discuss specific case of polymers where chain connectivity leads to many deviations from regularities observed for small molecules [4]. We demonstrate that while segmental relaxation in many polymers exhibits extremely high fragility, the temperature dependence of molecular scale relaxation (chain relaxation in case of polymers) exhibits fragility in the range usual for molecuklar systems, m < 100 [4,5]. We ascribe the extremely high segmental fragility in polymers to non-ergodicity of these systems on segmental time scale [4,5]. At the end we summarize the major microscopic parameters controling steepness of the temperature dependence of structural relaxation in glassforming liquids.

Geometric structure of four T-x-y diagrams, forming the T-x-y-z diagram of the quaternary system Li,Na,Th,U||F have been thoroughly analyzed, and 3D models of 4 space diagrams have been assembled. On the basis of data for the structure of the bounding binary and ternary systems, a scheme of mono and invariant states for the quaternary system has been formed. This scheme is the basis for the topological forecast of the geometrical structure of the Т-х-y-z diagram for LiF-NaF-ThF₄ -UF₄ (А-B-C-D) system. Nineteen binary compounds R(J) and 30 invariant transformations (2 peritectic, 20 quasiperitectic and 8 eutectic ones) are characterized this quaternary diagram. It is expected that within the quaternary system, 10 invariant reactions involving the melt (6 of quasiperitectic type and 4 of peritectic type) should run. The Т-х-y-z diagram will be formed by 17 hypersurfaces of liquidus. Seven of them correspond to the primary crystallization of lithium and sodium fluorides (A and B) and solid solutions С(D), R2(R11), R4(R12), R7(R15), R8(R16). Ten of them correspond to the primary crystallization of compounds R1, R3, R5, R6, R9, R10, R13, R14, R17, R18. Compound R10 on the edge LiF-UF4 (A-D) has, in both ternary adjoining systems, LiF-NaF-UF4 (A-B-D) and LiF-ThF4-UF4 (А-C-D), the liquidus surfaces of the wedge type. Compound R10 participates only in 2 phase reactions Q14: L+R10→A+R2(R11) and E7: L→A+R10+R2(R11). Therefore, it is assumed that in the Т-х-у-z diagram, the dots Q14 and E7 are joined without the quaternary invariant dot. On the scheme of mono and invariant states, they are joined by a line, corresponding to the reaction L→A+R10+R2(R11). Thus, a liquidus hypersurface of the compound R10 has a counter eR10R11pAR10E7Q14.

Certain molten solvates of Li salts can be regarded as solvate ionic liquids [1, 2]. A typical example is equimolar mixtures of glymes (G3: triglyme and G4: tetraglyme) and Li[TFSA]([TFSA]=[NTf₂]) ([Li(glyme)][TFSA]). The amount of free glyme estimated by Raman spectroscopy and MD simulation was found to be a few percent in [Li(glyme)][TFSA]^-, and thereby could be regarded as solvate ionic liquids. The activity of Li⁺ in the glyme-Li salt mixtures was also evaluated by measuring the electrode potential of Li/Li⁺ as a function of concentration. At a higher concentration of Li salt, the amount of free glyme diminished in the solvate ionic liquids, leading to a drastic increase in the electrode potential. Unlike conventional electrolytes, the solvation of Li⁺ by the glyme forms stable and discrete solvate ions ([Li(glyme)]⁺) in the solvate ionic liquids. This anomalous Li⁺ solvation had a great impact on the electrolyte properties and electrode reactions [1].
The electrochemical oxidation of glyme in [Li(glyme)][TFSA] is greatly enhanced due to the donation of lone pairs of ether oxygen atoms to the Li⁺ cation, resulting in the HOMO energy level lowering of a glyme molecule. This anomalous Li⁺ solvation induces interesting transport properties when interfacial electrochemical reactions proceed, which is not transport of solvated ions based on Stokes' law but a ligand (solvent)-exchange transport. Another intriguing aspect of the solvate ionic liquids is unusual solubility, which leads to the stable operation of the Li-S battery due to very low solubility of the discharge products (Li₂S_x). Li⁺-intercalated graphite was electrochemically formed in [Li(G3)₁][TFSA]. In contrast, the cointercalation of G3 and Li+ (intercalation of solvate [Li(G3)₁]⁺ cation) into graphite occurred in [Li(G3)_x][TFSA] electrolytes containing excess G3 (x > 1). In the solvate ionic liquid, the activity of the free solvent is very low, which would make the solvate ion unstable and the desolvation possible at the interface.
Very recently, we demonstrate that Li⁺ hopping conduction, which cannot be explained by conventional Stokes' law, emerges in highly concentrated molten solvate electrolytes composed of LiBF₄ and sulfolane (SL) [3]. In the concentrated electrolytes with molar ratios of SL/LiBF₄ < 3, Li⁺ diffused faster than SL and BF₄^-, and thus the evolution of Li⁺ hopping conduction was found.

Glassforming liquids with emphasis on the ionic liquids have been on my mind, since my early graduate student days. At that time (1950’s) the molten silicates and sulfides of Chemical Metallurgy (where they served as scavengers for unwanted components in the metals extraction processes) were still regarded as molecular mixtures in institutions as august as MIT. Then John Bockris and students at Imperial College of Science, London, measured the ionic conductivity, and introduced the term “ionic liquids” for the first time. My M.Sc. Advisor in Chemical Metallurgy at Melbourne University, Mervyn Willis, told me this was the way to go, so I dropped the PbO-Fe2O3 -SiO2 4D phase diagram project I had been working on and joined Bockris’ group (then at the University of Pennsylvania) in 1956. That started a long journey through liquid silicates, molten salts, concentrated aqueous and non-aqueous solutions and molecular liquids and finally back to ionic liquids, touching many personalities and countries. I will try to give some feeling for the highlights of the journey.

Misfolded proteins form protein aggregates and it is hard to dissolve in aqueous buffer solutions. Some denaturants such as guanidine hydrochloride and urea are usually used to dissolve these protein aggregates in the refolding process. Excess amount of denaturants, however, prevent proteins from refolding, and prevent activity recovery even after dialysis or dilution. Furthermore, re-aggregation of protein occurs at high rate in the dialysis step. Development of re-naturation methods have been desired for a long time. Hydrated ionic liquids (Hy ILs), which have been reported as a potential solvent to stabilize proteins and enzymes [1], are expected to provide a matrix for re-naturation of aggregated proteins [2]. In this study, we have analysed the effects of component ion and water content on the dissolution followed by refolding behaviour of aggregated proteins in Hy ILs.
Aggregated concanavaline A (Con A), a sugar chain recognition protein, was prepared by heating at 70°C for 10 minutes. ILs, which have different component structures, were mixed with aggregated Con A. The solubility and folding state of Con A in Hy ILs were measured with fluorescence spectroscopy. The solubility of aggregated Con A was affected by cation structure. Furthermore, the solubility of aggregated Con A was decreased with the increase of water molecules in Hy ILs [3]. In Hy ILs composition of selected cations and anions resulted in the aggregation of Con A, showing strong solubility properties, as well as refolding behaviour. Dissolved Con A in some Hy ILs showed recovery of the binding ability of the sugar chain after dilution with the buffer.

The possibility to distill the lithium chloride-based electrolyte from metallized products of pyrochemical operations is experimentally verified. The study was carried out in connection with the development of promising options for the industrial method of metallization of uranium dioxide, which is the main component of spent nuclear fuel after its voloxidation. The electrolyte was distilled off from metallized tablets and powders based on uranium dioxide with their continuous vacuuming at 700-900°C [1]. Powders or tablets (4-40 % porosity) of UO₂ or UO₂ + 5-15 wt% La₂O₃, CeO₂, and Nd₂O₃, after electrolytic reduction with lithium in the molten LiCl-Li₂O (0.8-1.5 wt% Li₂O) mixture, were used as the distillation samples.
Metallized powders or tablets were placed in nickel or molybdenum containers. Distillation was carried out in quartz tubes under continuous evacuation (P = 1.2-2.5 mPa) for 1-3 hours. The temperature was 700-900°C. The Li, U, La, Ce, and Nd concentrations in metallized products and in vapor condensates were determined with an atomic emission spectrometry using an Optima 4300DV ICP-OES spectrometer before and after distillation.
It was found that lithium chloride is the main component of sublimates, the content of rare earth elements and uranium is negligible. In our experiments with the electrolyte content of 10-36 wt.%, lithium compounds (98.8-99.9%) were almost completely removed at 780-850°C for 1.5-3.0 hours. After distillation under such (optimal) conditions, the lithium content (mainly Li₂O) in the metallized products decreased to hundredths of a percent. At lower temperatures the fraction of distilled lithium (in the form of LiCl) decreases, and the use of higher temperatures as compared to the optimal conditions is not recommended, since an undesired back reaction of metallic uranium oxidation to UO₂ by residual lithium oxide occurs:
U + 2Li₂O = UO₂ + 4Li.
Keywords: Molten salts; UO₂; U; LiCl; Vacuum distillation;

"Unlike charges attract, but like charges repel". We recently challenged This conventional wisdom for ionic liquids (ILs). Here, we show that like-charged ions attract each other despite the powerful opposing electrostatic forces. In principle, cooperative hydrogen bonding between ions of like-charge can overcome the repulsive Coulomb interaction while pushing the limits of chemical bonding [1-11]. The key challenge of this solvation phenomenon is to establish design principles for the efficient formation of clusters of like-charged ions in ionic liquids. For that purpose, we combined weakly coordinating anions with polarizable cations, which are all equipped with hydroxyl groups for possible H-bonding. The formation of H-bonded cationic clusters can be controlled by the interaction strengths of the counterions and the delocalization of the positive charge on the cations [1-4]. Strongly interacting anions and localized charges on the cations result in hydrogen bonded ions of opposite charge, whereas weakly coordinating anions and delocalized charge on the cations lead to the formation of H-bonded cationic clusters up to cyclic tetramers. If we increase the distance between the hydroxyl groups and the positive charge centre on the cation we can further support the cationic cluster formation. These clusters are observed by bulk infrared (FT-IR) and cryogenic vibrational spectroscopy, and interpreted by density functional theory (DFT) calculations on neutral and ionic clusters [1-11]. The formation of cationic clusters is also reflected in NMR coupling parameters and relaxation times. Additional molecular dynamics simulations (MD) provide information about the lifetimes of the hydrogen bonds in the cationic clusters compared to those in the typical ion pairs [9]. Moreover, we show that cationic clustering influences the phase behavior of ionic liquids. These ILs can be supercooled and form glasses.[6]

Layered carbon nitrides based on a polytriazine imide (PTI) sheet structure crystallize as 50-100 nm particles with hexagonal columnar morphology following synthesis from precursors such as dicyandiamide (DCDA) in molten salt (LiCl/KCl or LiBr/KBr eutectic) solutions [1,2]. When the crystals are exposed to aprotic polar liquids including DMSO, DMF and NMP as well as H₂O they dissolve spontaneously forming few-layered crystalline 2D nanosheets in solution. The solutions are photoluminescent and photocatalytically active [3,4]. Following solvent evaporation the layered nanomaterials re-stack in a crystalline arrangement giving rise to a broad range of emission wavelengths extending throughout the visible range [3,5]. We will present new results for the dissolution process and the 2D nanoparticles in solution using high energy X-ray and neutron scattering techniques. We also discuss the glass forming ability of the solutions to provide few-layered crystalline nanoparticles with tunable photoluminescence properties held in a solid matrix.

All the NdBr₃-MBr binary systems (M = Li, Na, K, Rb, Cs) are characterized by negative enthalpies of mixing [1]. The minimum of molar mixing enthalpy is shifted towards the alkali bromide-rich composition and located in the vicinity of x(NdBr₃) of about 0.3-0.4. Ionic radius of the alkali metal influences the magnitude of mixing enthalpy as well as the minimum position. The smaller the alkali metal ionic radius, the smaller the absolute value of mixing enthalpy and the minimum more shifted towards the alkali bromide-rich composition. Comparison with other LnX₃-MX binary systems (Ln = lanthanide, X = Cl, Br, I) showed that mixing enthalpy depends also on lanthanide and halide ionic radii. Its absolute value increases with decrease of lanthanide ionic radius and decreases with increase of halide ionic radius. In all the NdBr₃-MBr binary systems, the value of interaction parameter λ, which represents energetic asymmetry of the melts under investigation, is negative. Its absolute value increases significantly with ionic radius of alkali metal cation. All the systems show more negative values of the interaction parameter in the alkali halide-rich compositions. Starting from potassium bromide a broad minimum appears to exist at a molar fraction of neodymium bromide x(NdBr₃) of about 0.2-0.3. This minimum can be undoubtedly ascribed to the formation of NdBr₆^3- octahedral complexes in the systems under investigation. Conclusion concerning octahedral complexes formation in investigated melts is confirmed by the results of electrical conductivity measurements of NdBr₃-MBr liquid mixtures.
Temperatures and molar enthalpies of phase transitions of all the M₃NdBr₆ congruently melting compounds (M = K, Rb, Cs) were determined and compared with data obtained for analogous chloride and bromide compounds of other lanthanides [2]. This comparison showed that M₃NdBr₆ compounds could be divided into two groups: compounds, which are formed at higher temperatures from M₂NdBr₅ and MBr, and compounds, which are stable or metastable at ambient temperature. Moreover, compounds formed at higher temperatures can exist at ambient temperature as metastable phases when cooled with high rate. On subsequent heating thermograms exothermic effect related to the decomposition of “undercooled” decomposition occurs abruptly. The heat capacities of M₃NdBr₆ compounds were fitted by equations, which provides a satisfactory representation up to temperature of the Cp discontinuity [3]. Electrical conductivity of solid phase of M₃NdBr₆ compounds correlates well with their heat capacity [3]. Specific behavior of the heat capacity and electrical conductivity dependence on temperature of solid M₃NdBr₆ compounds is undoubtedly connected with disordering of cationic sublattice formed by alkali metal cations.

The principal ideas will first be reminded. Then, the basic scientific research steps will be clarified in the very beginning of the first nuclear era, in the repetition of this effort in the so-called renaissance of this scientific region, in the frame of global collaboration, and also in the national research area in the Czech Republic (former Czechoslovakia).
The first stage is the period from the 1940s up to the 1960s, when this field of research was mostly performed in the USA, namely in the Oak Ridge National Laboratory [1]. The second stage is the period from the 1960s up to the 1980s, when higher activity in this field started during that time in the Soviet Union. The Soviet Union was closely collaborating with Czechoslovakia, namely in the field of spent nuclear fuel reprocessing.
The developed regeneration process was based on the fluorination of uranium and plutonium by elementary fluorine to volatile hexafluoride. This process has been developed to fit the level of the demonstration laboratory equipment, where mechanically disintegrated spent fuel in powder form is converted, by fluorination, to UF₆ and PuF₆. Volatile and non-volatile fission products are separated by fluorination or by distillation of UF₆. The whole technological line is operated in the hot chamber with a remote control. The capacity of the entire technological equipment is 1-2 kg of heavy metal / day.
The fluorinator of the flamboyant type, including the entire device, is made by nickel, resp. by MoNel metal. The condensers, separation columns, and distillation are provided with control elements, valves, flow meters, and pressure gauges. This allows remote control directly from the control panel. The principle of technology and the entire procedure, including the operational experience, are applicable to reprocessing of spent fuel from reactors operating in the thorium-uranium fuel cycle.
This activity was stopped after the Chernobyl accident and started again in the 1990s when a renaissance of this effort started in the US Los Alamos National Laboratory, in the frame of the so called ADTT (Accelerator Driven Transmutation Technology) [2]. The scientific and technological research of this concept based on MSR systems was performed in the frame of a close collaboration of the scientific capacity of the USA, Russian Federation, and the Czech Republic. Since the beginning of the 2000s, it was incorporated in the global activity of the development of the nuclear reactors of the 4^th generation [3] and the preparation of the entrance in the second nuclear era.

During the last decade, the problem of the greenhouse effect is widely covered in the media and scientific literature. Among the all pollutants in the earth's atmosphere, carbon dioxide plays a key role in climate changes. It absorbs the long-wave radiation and is one of the factors contributing to the greenhouse effect in the atmosphere. Therefore, the problem of the effective disposal of carbon dioxide is an urgent task of scientists around the world. In order to reduce CO₂ emissions, the technologies for its capture and utilization are being developed [1-3]. Many methods of carbon dioxide utilization are discussed. They are aimed at converting CO₂ into commercially beneficial products such as chemicals, polymers, building materials, fuel, etc.
High-temperature electrochemical synthesis (HTES) in molten salts is one of the promising methods due to the simplicity of hardware implementation and mild synthesis conditions. Also, HTES is a low cost method. It was shown [4] that the electro-reduction of carbonates anions in chloride melts occurs with kinetic difficulties (the previous chemical reaction of the acid-base type) and the electrochemically active particle is CO₂.
In the present work, the results of the cyclic voltammetry study in the molten salt system Na,K|Cl - xLi₂CO₃ (x = 1*10^-4 - 2*10^-3 mol/cm³ Li₂CO₃ concentration) against Pt and Pb|PbCl₂ reference electrodes at temperature 750 ^oC in air and argon atmosphere are presented. The composition and morphology of the cathode products obtained under varied experimental parameters were investigated.
There are two cathodic waves (K₁ and K₂) observed at CV curves at the potentials of -1.25 and -1.5 V against Pb|PbCl₂ reference electrode in argon atmosphere.
Potentiostatic electrolyzes at potentials of the first and second waves were carried out. According to results of XRD method the cathodic product of both waves is carbon. The results of SEM showed that the morphology of the product produced at different potentials is not the same. Samples obtained at a potential of the first wave contain particles with plate form. Other ones (electrolysis at second wave) contain spherical carbon particles of very high dispersity. This may indicate the different nature of the electrochemically active particles that are involved in electrode reactions. The mechanism of electrode processes based on acid-base interactions occurring in melts is proposed.

Carbon nanomaterials have been widely used in modern devices and high tech [1-2]. This is the reason why the obtaining of carbonaceous materials in molten salts has attracted great interest among researchers. Various carbon products such as carbon nanotubes, carbon nanofibers, carbon nanoparticles, and graphene have been successfully prepared in molten salts by electrochemical reduction processes [3-5].
This paper is devoted to the physicochemical substantiation of the choice of composition of the electrolytic bath and the electrode materials for the generation of carbon nanostructures of different morphologies from molten salts, based on the thermodynamic calculation of the decomposition voltages of various carbonates and analysis of the metal - carbon, and metal carbide - carbon state diagrams.
An analysis of the decomposition voltages of lithium, sodium, potassium, calcium, barium, and magnesium carbonates with different versions of cathode products (elemental carbon, carbon monoxide, metal and carbide) in the range of 300-1900 K have showed that for K₂CO₃ deposition of alkali metals on the cathode is a most energetically profitable process at all temperatures. For Na₂CO₃, it is possible to obtain carbon at T < 1000 K. With temperature increase, the predominant process is the reduction of alkali metals. For Li₂CO₃, CaCO₃, BaCO₃, and MgCO₃ at T < 950 K, carbon deposition will be more advantageous at higher temperatures including reduction up to CO. The decomposition of CO₂ flows at more positive potentials compared with carbonate systems. However, low activity of CO₂ in carbonate-containing melts will prevent the significant contribution of this reaction to the electrode process. Thermodynamic calculations of the dependence of the carbon deposition potentials from carbonate anion on the acidity of the melt (concentration of oxide ions) show the possibility of displacing this potential up to 0.8 V. This can be done by changing the acid-base properties of the melt. On the basis of the analysis of binary phase diagrams of Me-C and MeC-C, criteria for selecting the cathode material for generation of the tubular structure of graphite are established. The diagrams should contain: (1) solid solutions of C-Me at a temperature of 700-900°C and sufficient solubility of carbon (up to ~ 1 at.%) in the metal should be observed; (2) after saturation of the solid solution with carbon, the precipitation of graphite from the metal should occur without the formation of intermediate carbide phases; (3) in the case of the formation of carbides, the diffusion of carbon in the solid С-Ме solution, and in the MeС carbide phase should flow with high speed and quickly reach the concentration of carbon saturation for graphite deposition.

The largest anthropogenic contribution to climate change is the fossil fuel burning resulting in huge carbon dioxide (CO₂) emissions. Reduction of CO₂ emissions is imperative to mitigate environmental impacts. CO₂ separation can help global warming mitigation as well as provide CO₂ for other processes such as carbon capture and utilization (CCU) and enhanced oil recovery (EOR). Yet CO₂ is an abundant nontoxic resource that can be used in several applications. Chemical absorption processes for CO₂ capture using aqueous amine solutions have been extensively studied and used in industry for decades. They have, however, some operational drawbacks. Ionic liquids have been proposed as the next generation of solvents for a selective CO₂ separation. These compounds are versatile and less harmful to the environment than conventional organic solvents. They present unique properties such as negligible vapor pressure, non-flammability, high thermal stability, and tunability (myriad of possible combinations of cations and anions). Nevertheless, these solvents suffer from high viscosity and high production costs when compared to aqueous amines solutions. Poly(ionic liquid)s (PILs) appear as an alternative to RTIL for CO₂ capture and utilization. PILs represent an emerging subclass of the polyelectrolytes, were each repeating unit is ionic and connected through a polymeric backbone forming a macromolecular structure[1]. PILs combine the good features of RTILs with good mechanical stability, processing and tunable macromolecular design of polymeric material. PILs present higher CO₂ sorption capacity and sorption/desorption velocity than RTIL. PILs, materials with smart designs, can be used for CO₂ separation from the flue gas (CO₂/N₂), and natural gas purification (CO₂/CH₄), besides being active as catalyst for cyclic carbonate production from the reaction of CO₂ and epoxide. The aim of this presentation is to give a concise overview of PILs described in literature, as well as the research published by our group[1-5]. In addition, PLIs syntheses routes, as well as the influence of PILs backbone, anions type, and modification in CO₂ sorption capacity and catalyst activity will be discussed.

Polymer electrolytes have been an active field of research since the late 70's. This has culminated in the commercial launching of lithium metal polymer electrolytes batteries powering a fleet of cars since 2011 in different cities in France ^[1]. The poly(ethylene oxide) - PEO-based as 'solvent' for a low lattice energy salt has been the key to obtain decent conductivities. The operational temperature, however, is a ≈ 70°C, i.e. 10°C above the melting point of crystalline PEO and 100°C above the T_g of the resulting melt. These systems are coupled (diffusion with segmental motion) and can be called "fragile" according to Angell definition ^[2]. Besides, the fraction of the current carried by the cations (Li⁺, Na⁺), the only important species in the electrodes processes, expressed as T+, is only 0.2 to 0.3.
We will discuss here the strategies to improve the performances of such ionic conductors in the hopes to meet the requirement for the dearly sought after high energy density battery operating at/close to room temperature, and safer and longer cycling than the present ones using flammable liquid electrolytes technology.
Without resorting to modify PEO, the modification of the solute (salt) is one fruitful strategy. The introduction of the extensively delocalized fluorinated imides (R_fSO₂)₂N^- (R_f = F, CF₃) anions where the charge is spread on 5 centers and importantly possess a a"hinge", with the flexible S-N-S "pia" bonds lowering the T_g of the resulting solid solution with PEO, have revolutionized the field. This is also true for ionic liquids, in majority based on these anions.
The concept can be pushed further with the "super imide" family, where the charge is further delocalized and the number of "hinges" extended. The first example is [(CF₃SO₂N)₂S(O)(CF₃)] with two S-N-S "pi" bonds. The T_g for the polymer-salt complex is thus further lowered (Fox equation). Besides, when this salt is tethered to a polymer to immobilize the anion, this results in the highest conductivities reported for a single-ion conductor (T₊ = 1) ^[3].
Manipulation of the simple anions, while still keeping the flexible imide linkage, allows the increase of T+ to ≈ 0.5 by simply removing one fluorine from (CF₃SO₂)₂N to (CF₂HSO₂)(CF₃SO₂)N , resulting in H bond formation with the ether oxygens, slowing the negative charge correspondingly ^[4]. Alternatively, the (CF₃SO₂)N( )SO₂- moiety can be kept, attached to either long alkyl chains or short EO units. The former anions result in nanophase separation with the formation of micelles; for the latter, the CH₂CH₂O units attached to the imide center plasticize the polymeric chains without participating in the solvation. Both systems results in much decreased anion mobility, keeping the Li⁺ diffusion at a high value. Both salts seem to, for the first time, exhibit some decoupling.
The salt aspect as well as that of new alternatives to PEO will be discussed.

Since the beginning of this century, an important idea of density scaling (DS) has been developing successfully. This idea relates macroscopic properties of supercooled liquids to an effective short-range intermolecular Lennard-Jones-type potential and bears hallmarks of universality in cases of different quantities (structural relaxation time, viscosity, segmental relaxation time, Debye-like relaxation time, conductivity relaxation time, dc-conductivity, and diffusivity) and various materials. This includes van der Waals liquids, polymer melts, protic and aprotic ionic liquids, and liquid crystals[1].
According to the basic DS law, the dynamic quantities typically measured in isobaric or/and isothermal conditions can be plotted onto one master curve as a single-variable function f(Gamma), where the scaling variable Gamma=density^gamma/temperature and the scaling exponent, gamma, is a material constant related to the exponent of the repulsive part of the effective intermolecular potential. An additional advantage of the DS law consists in its powerful predictive capabilities, remaining in effect in both the supercooled and normal liquid states [1-3]. Recently, we have shown that the DS based transformation from the temperature-pressure domain to the temperature-density domain enables to reveal some invariant quantities, including a new invariant that is the ratio of dynamic and thermodynamic moduli in both the supercooled and normal liquid states [1,2]. Very recently, we have established that the inflection points observed in isothermal dependences of dynamic quantities, reported first by Herbst et al. in Nature in 1993, can be numerically predicted for different materials from the DS law [1,3]. This surprising finding has resulted in an even more spectacular outcome that is a breakdown of the Arrhenius law regarded, since the end of the 19th century, as a standard rule. This rule is valid for various physicochemical processes, including the thermodynamic evolution of dynamic quantities (such as primary relaxation time, viscosity, and dc-conductivity) in the normal liquid state in isobaric conditions. Combining numerical and analytical arguments based on experimental data measured at ambient and high pressures, we have justified that the standard Arrhenius law, log(X) ~ E_act/temperature, considered for a dynamic quantity X on the assumption of constant apparent activation energy E_act, cannot generally be valid, not only in the supercooled liquid state characterized by super-Arrhenian cooperative molecular dynamics, but also between the boiling and melting points in isobaric conditions, including ambient pressure, at least if the DS law is satisfied [1,3].

The conventional polymer-electrolyte membranes used in low-temperature fuel cells are limited to operating temperatures below about 120 celsius, as they must be fully hydrated to facilitate proton transport. Protic ionic liquids (PILs) are ionic liquids formed by transferring protons from Brønsted acids to Brønsted bases, and it has recently been shown that some ammonium-based PILs inherently exhibit high proton conductivities. Consequently, PILs have been proposed for use as electrolytes in non-humidified fuel cells that can operate above 120 celsius (at intermediate temperatures).^1-3 While they nominally consist entirely of ions, however, PILs can often contain a significant quantity of neutral species (either molecules or ion clusters) that can affect the physicochemical properties of the liquids.
In this contribution, we first describe an electroanalytical method for detecting and quantifying residual Brønsted acids in a series of ammonium-based PILs. Ultramicroelectrode voltammetry reveals that some of the accepted methods for synthesizing PILs can readily result in the formation of nonstoichiometric PILs containing up to 230 mmol/L residual acid. We will then show that residual acids in PILs can have a drastic effect on the electrocatalytic oxygen reduction reaction (ORR) in the PILs. For example, the potential at which the ORR occurs at Pt in the PIL diethylmethylammonium trifluoromethanesulfonate, [dema][TfO], decreases linearly as the strength of the proton donor in the liquid decreases. In pure [dema][TfO], in which the proton donors during the ORR are the cations of the PIL (pK_a = 10), the onset potential of the ORR is the same as that of the hydrogen oxidation reaction (HOR) in the PIL. These observations have significant implications for the use of PILs as electrolytes in fuel cells and indicate that the best PILs are highly "acidic" liquids that can support oxygen reduction at high potentials.

Most of reactive metals and their alloys are produced by fused salt electrolysis or metallothermic reduction in molten salts. The feed material for both of these processes is the anhydrous chloride of the metal under consideration produced by the dehydration of the form of hydrate. A critical step in the production of most reactive metals requires rigorous thermodynamic analysis. Thermodynamic data for most of the reactive metal chloride hydrates have not been measured. Improper dehydration of the metal chloride hydrate may lead to a prohibitive amount of hydroxychloride, oxychloride, and finally oxide. To prevent hydrolysis, a certain pressure of hydrogen chloride must be maintained to supress or reverse hydrolysis. In this investigation, it is demonstrated that by careful application of the phase rule, sigma function, and utilization of prediction and estimation techniques will lead to a reliable technique for the estimation of the hydrate vapour pressure. These techniques will also lead to prediction of the necessary hydrogen chloride presence to avoid hydrolysis. Thermodynamic data, including heat capacities, standard entropies, and enthalpies, are estimated/predicted for all conceivable intermediate hydrate compounds. Estimations are based on published data, as well as trends proven in similar systems. The thermodynamic estimations and predictions have been published for magnesium chloride, neodymium trichloride, dysprosium chloride and is a continuous program for rare earth metal chlorides.

Rare earths (RE) elements are becoming very important for current and future industrial products, such as computers, LCD screens and lasers, but also for so-called "green technologies", such as wind turbines, electric cars and bicycles [1]. Due to highly volatile markets, the high environmental impacts, and the geopolitical challenges of raw material supply and production, many efforts are made worldwide to develop new recycling processes. Only a few countries have access to neodymium; China dominates the world production with above 90 % of the whole market. According to a recent study of the European Union [2] and the US Department of Energy [3], the RE elements are the most critical raw material resource. Despite extensive research activities in this field, only about 1 % of the RE elements are currently recycled. [4]
Currently, different processes are used or investigated for the recovery of neodymium, such as hydrometallurgy, glass-based method, and direct melting.
In this work, we investigate the selective recovery of neodymium by using pyrochemical based processes. Anodically, Nd is dissolved selectively from the NdFeB matrix and metallic Nd is recovered at the cathode. It was shown that electrolyte composition is crucial as it impacts the electrolysis efficiency significantly. Mass balance and Nd recovered analysis confirms the results of the electrochemical investigations and electrolysis runs.

Spent salts coming from pyrochemical processing are composed of mixtures of NaCl, KCl, and CaCl₂ with various dissolved/precipitated species according to the process used and the storage time and conditions.
In order to stabilize these materials, a pyrochemical treatment has been developed by CEA Valduc. It consists in carrying out two steps: pyro-oxidation [1] and distillation [2, 3].
Pyro-oxidation, also known as oxidation-chlorination, allows oxidizing An into a stable oxide: AnO₂. This requires the use of Cl₂ gas to remove excess carbonate through the exhaust of CO₂ and O₂ gases:
Ongoing work is underway on the stability of carbonate in salt mixtures. Preliminary results and literrature [4] suggest that carbonates ions can be completely decomposed into carbon dioxide and a stable oxide by simply changing the composition of the molten bath. Indeed, salts containing CaCl₂ showed quick and total decomposition of carbonates.
Follow-up work will have to verify the experimental conditions for which the chlorination step can be replaced by a simple stirring or addition of CaCl₂ to remove excess carbonates.

Molten halide salts are of interest for applications as heat transport fluids (HTF) in concentrated solar power plants due to their excellent resilience at high temperatures. Application as HTF requires a combination of properties including high heat capacity, low vapor pressure and low viscosity to optimize fluid flow through heat-exchanger networks. A fundamental understanding of viscous behavior in halide salts in relation to their structure is therefore of interest for optimizing HTF formulations. Here we perform a combination of modeling (ab-initio molecular dynamics) [1] and spectroscopic analysis (Raman) [2] of tetrahedral zinc chloride melts as a function of temperature. It is found that the ratio of edge- to corner-sharing tetrahedra varies with temperature and that it can be correlated with the viscous behavior through configurational entropy considerations. More interestingly, it is observed that a fragile-to-strong transition occurs at high temperature which can also be correlated with a change in structural behavior [3]. This behavior is compared with that of other tetrahedral melts and found to be related to changes in multiple physical properties such as heat-capacity, density, compressibility etc.

The vitreous state (bulk glasses and amorphous films) remains a challenging problem in physics owing to the lack of a regular crystalline background. Thus, most scientists approach this state from the liquid side, at high temperatures, where theoretical physics is quite well established. In this talk, I will present the embryo of an approach that looks at the glass transformation region from the low-temperature, solid-state side. I shall attempt, at the same time, to provide a reasonable description of the structure and ensuing physical properties of the glassy-state itself. This is mainly for silicates, but also for other classes of amorphous materials, including semiconductor films.
The surprising picture that is emerging is that the vitreous state appears to be a novel type of solid state, rather than a "dynamically arrested" liquid state, in that an amount of residual quasi-regular structure is still remaining in the highly-disordered medium. This is seen, however, only at the mesoscopic scale where the amorphous solid appears to be rather like a failed poly-crystalline medium. Important differences with true poly-crystalline solids is that, in-between the grains, there appear to be remnants of liquid-like regions and the grains themselves are only quasi-ordered.
This scenario is being investigated and developed by means of a phenomenological theory that takes its moves from the lowest temperatures phenomena, where bizarre magnetic effects have been reported which have been explained satisfactorily by means of this new theory. Presently, I have been able to conduct new experiments on glasses at temperatures up to 315 K and in a magnetic field. The analysis of the data corroborates the new approach and theory with surprising accuracy.
I will review this new theory and scenario, surveying the results obtained so far at the lower temperatures, and present the new results at higher temperatures. An embryo of the new approach's resulting description of the glass transformation will also be presented.

The balance between the attractive and repulsive forces between the ions in room temperature ionic liquids (RTILs) and their high-melting molten salts (MSs) analogs is responsible for their cohesive energy density (ced), their internal pressures (P_int) and their surface tensions (σ). Therefore, definite relationships exist between these quantities pertaining to the ionic liquids. For 33 RTILs and 53 MSs for which all the data are available, the relationships are linear and take the form ced = a + b(σV^-1/3) and P_int = p + q(σV^-1/3). The quantity σV^-1/3, called the Gordon parameter, has the dimension of a pressure, as do ced and Pint. The slopes b ≈ 67 and q ≈ 25 are the same for these two kinds of ionic liquids, because the electrostatic interactions between the ions are the dominant attractive forces. The internal energy of the ionic liquid is inversely proportional not to its volume, but to a higher power of it, so that the cohesive (or internal) energy divided by the volume (the ced) is more than twice its volume derivative (the internal pressure, P_int). The established relationships can help estimate unknown quantities among the three dealt with here from the other two.

Our previous review articles [1] evidenced the relation of thermodynamic data with the Periodic Law. A strict relationship could be established between the enthalpy of formation, melting point and the components atomic numbers in the semiconductor A^IIIB^V phases, with diamond-like structures of sphalerite and wurtzite types. The proposed model was used to critically assess the thermodynamic properties of isostructural compounds. The relationship between the reduced enthalpy, standard entropy, reduced Gibbs energy and the sum of the atomic numbers (Z_i = Z_A + Z_B) has been used to critically assess the thermodynamic properties of A^IIIB^V phases.
For the A^IIIB^V in the solid-state, the Similarity method was applied to critically analyse heat capacities. For these A^IIIB^V phases (sphalerite and wurtzite types), heat capacities relationship with the logarithm of elements atomic numbers was used to estimate the continuum above 298 K [2].
The Similarity Method was also used for the specific heat critical analysis for the fourth group (C, Si, Ge, Sn), A^IIIB^V and A^IIB^VI isostructural phases in the solid-state. The dependence of the heat capacities from 0 to 1500 K follows certain regularity. Phases with the same element atomic numbers (Z) sum, such as BN (hex) Z=12 and glassy pure carbon Z=6; BP and AlN (Z=20); AlP (Z=28) and pure Si (Z=14); BAs and GaN (Z=38); AlAs and ZnS (Z=46); AlSb, GaAs, InP (Z=64) and pure Ge (Z=32); GaSb, InAs, and CdSe (Z=82); InSb, CdTe (Z=100) and pure grey Sn (Z=50); have the same heat capacity experimental values in the solid-state within the experimental uncertainty [3].
This rule can be applied to different isostructural compounds.

Our previous review articles [1] evidenced the relation of thermodynamic data with Periodic Law. A strict relationship could be established between the enthalpy of formation, melting point and the atomic numbers of components in the semiconductor AIIIBV phases, with the diamond-like structure of sphalerite and wurtzite types. The proposed model was used for the critical assessment of the thermodynamic properties of isostructural compounds. The relationship between the reduced enthalpy, standard entropy, reduced Gibbs energy and the sum of the atomic numbers (Zi = ZA + ZB) has been used for the critical assessment of the thermodynamic properties of AIIIBV phases. The Similarity method was applied for the critical analysis of heat capacities for the AIIIBV in the solid-state [2]. The relationship of the heat capacities of AIIIBV phases vs. the logarithm of the sum of elements atomic numbers the AIIIBV phases (sphalerite and wurtzite types) was used to estimate the continuum above 298 K [2].
So, the Similarity Method was used for the critical analysis of specific heats for the fourth group (C, Si, Ge, Sn), AIIIBV and AIIBVI isostructural phases in the solid-state. The dependence of the heat capacities from 0 to 1500 K follows certain regularity. Phases with the same sum of the atomic numbers of elements (Z), such as BN (hex) Z=12 and glassy pure carbon Z=6; BP and AlN (Z=20); AlP (Z=28) and pure Si (Z=14); BAs and GaN (Z=38); AlAs and ZnS (Z=46); AlSb, GaAs, InP (Z=64) and pure Ge (Z=32); GaSb, InAs, and CdSe (Z=82); InSb, CdTe (Z=100) and pure grey Sn (Z=50); have the same heat capacity experimental values of the solid-state within the experimental uncertainty [3].
We can apply this rule for different isostructural compounds.
Keyword: Semiconductors (AII-BVI, AIV, AIII-BV), heat capacity, entropy, Debye’s functions

For conventional engineering alloys (which are of course polycrystalline), thermomechanical processing is routinely applied to change their microstructure and optimize their properties. Thermomechanical processing is not applied to conventional glasses, which are generally considered to be brittle. In contrast, metallic glasses formed by liquid quenching have a range of possible states. This range is remarkably extendable by thermomechanical processing [1]. Plastic deformation at room temperature leads to relaxation or rejuvenation. A notched sample in compression shows extreme rejuvenation at the notch root: locally, the hardness and enthalpy match those for a glass cooled at 10¹⁰ K/s, 10⁷-10⁸ times faster than for the original glass [2]. Effects of loading in the nominally elastic regime, whether quasi-static or cyclic, are also reviewed [3,4]. Cryogenic thermal cycling (CTC) reduces the initial yield load in nanoindentation and increases plasticity in macroscopic compression, partially reversing the effects of annealing [5]. Yet CTC has little effect on other properties such as elastic moduli. CTC may stimulate soft spots in a matrix that itself is largely unaffected. Combined treatments, e.g. annealing with CTC, can have dramatic effects, e.g. glasses that are harder and stiffer, yet more plastic. Prospects for further modification of metallic glasses will be considered, outlining useful property changes that may be achieved.

Recently, studies on ions and ionic interactions in solution have raised as a leading research direction of culminating importance.[1] In medicine, pharmacy and drug development, including sports supplementation, ionizable molecules are required for better bioavailability in the organism.[2] The main problem in medicine and the food industry is the implementation of substances which have a tendency to create polymorphs since each form shows different solubility and biological activity.[3] The most promising strategy to avoid this issue, can be observed in the field of ionic liquids (ILs), compounds which are usually composed of large asymmetric cations and organic/inorganic anions, and exist as a liquid at temperatures below 100°C. ILs have numerous advantages that may be applied in medicine and food industry such as good solubility in water, which leads to improved bioavailability, designed lipophilicity which allows easier transport of the desired compounds through the cell membrane and possibility of ILs synthesis with synergistic cation and anion performances.[4] Unique dynamic micro- and nanoheterogeneous structuring of these substances has been shown to have a significant effect on physicochemical and biological properties of ILs. Until now, a large number of ILs with different pharmacologically and biological active anions (amino acids, Krebs cycle molecules, etc.) were synthesized, but the selection of cation is mostly dedicated to choline as a widespread biological nutrient.[5] The extensive search in the field of ionic liquids started for new, biologically active cation besides choline. One of the possible solution can be agmatine, endogenous polycationic amine derived from L-arginine through enzymatic decarboxylation.
Six new agmatine bioinspired salts, agmatine citrate, agmatine ascorbate, agmatine glutamate, agmatine m-hydroxybenzoate, agmatine nitrate, and agmatine chloride, and three ionic liquids, agmatine ibuprofenate, agmatine salicylate, and agmatine nicotinate were synthesized. For all newly synthesized compounds the glass transition temperature, melting and decomposition temperature were determined using thermogravimetric and DSC analysis. The cytotoxicity on MRC-5 and HT-29 cell lines was tested also, where results indicate lower toxicity of examined compounds compared to ascorbic acid on the human non-tumor cell lines. Densimetric and viscosimetric measurements of their aqueous solutions were performed, supported by molecular dynamics simulation. From obtained results, it can be concluded that all investigated compounds have a structrure-making properties. The effect of the anion nature on the conformation of agmatine cation is negligible in the investigated concentration range.

The phase-change materials (PCMs) such as Ge-Sb-Te alloys can be reversibly switched between amorphous and crystalline states on a timescale of nanoseconds. The phase switch provides the material basis for next-generation non-volatile phase-change memory devices. I show experimental studies of PCM kinetics spanning over 1000 K in temperature and 16 orders of magnitude in timescales. In the (supercooled) liquid states, this class of materials exhibits a variety of anomalous behaviors in thermodynamics and kinetics, such as heat capacity and density maxima, dynamic crossovers, and a breakdown of the Stokes-Einstein relations. These anomalies are related to a high- to low-density and metal-to-semiconductor liquid-liquid transition hidden below the melting temperature obscured by fast crystallization. I will bring the idea of tuning this transition through adjusting metallicities to attain desired switching kinetics for faster and more reliable phase-change memory applications.

Previously, [1] the possible options for the system Li,Na,U||F,Cl polyhedration were considered. The system LiF-NaCl is eutectical [1] (eutectic 0.415 mole LiF at 685°С), so within the reciprocal system Li,Na,U||F,Cl , diagonal LiF-NaCl is stable. It is also known [2, Р. 88] that a NaF-UF4 system is characterized by 3 eutectics (0.215 mole UF4 at 618°С; 0.28 mole UF4 at 623°С and 0.56 mole UF4 at 680°С), 2 peritectics (0.325 mole UF4 at 648°С and 0.37 mole UF4 at 673°С, 2 congruently melting compounds (R1=3NaF-UF₄, R2=7NaF-6UF₄), and 2 incongruently melting ones (2NaF-UF₄, 5NaF-3UF₄). As a result, it is possible to consider 3 variants of polyhedration: two with the stable diagonal LiF-UCl₃ (LiF-UCl₃, NaF-UCl₃ and LiF-UCl₃, NaCl-UF4), and one with the diagonals LiCl-UF₄, NaCl-UF₄. In the case of polyhedration with the stable diagonals LiF-UCl₃ and 3 diagonals from the apex NaCl, the initial prism of the reciprocal system consists of 5 tetrhedra: LiF-NaF-NaCl-R₁, LiF-UF₄-NaCl-UCl₃, LiF-UF₄--NaCl-R₂, LiF-LiCl-NaCl-UCl₃, and LiF-NaCl-R₁-R₂. When all stable diagonals are of the eutectic type, then the tetrahedron LiF-LiCl-NaCl-UCl₃ is bounded by 5 eutectic binary systems and by LiCl-NaCl. This includes the continuous rows of solid solutions. Systems LiF-NaF-NaCl-R₁, LiF-NaF-NaCl-UCl₃ , and LiF-NaF-UCl₃-R₁ are bounded by 6 binary and 4 ternary eutectic systems.
This work has been performed under the program of fundamental research SB RAS (project 0336-2016-0006) and partially supported by the RFBR project 17-08-00875.