Molten LiCl KCl Eutectic Salt Research Articles

CeCl3 concentration effects on cyclic voltammogram overlap in LiCl-KCl eutectic molten salt

In the present study, cyclic voltammetry was performed to investigate CeCl3 in a LiCl-KCl eutectic molten salt at various concentrations. The results indicate that the overlap degree of cyclic voltammograms at different cycles deteriorates with the increasing CeCl3 concentration in the molten salt. This phenomenon was attributed to higher concentrations of CeCl3, which led to a non-uniform film on the electrode surface. This was evidenced by material characterization of the working electrode after cyclic voltammetry (CV) testing and the simulated cyclic voltammograms of a reversible electrochemical reaction. This study will provide new insights that enhance our understanding of the electrochemistry of the CeCl3-LiCl-KCl system and offer valuable reference for other soluble-insoluble electrochemical systems.

Rotating Disk Electrode Study of Sm(III)/Sm(II) in LiCl-KCl Eutectic Molten Salt

Understanding the redox reactions of fission products in molten salts is crucial for developing pyroprocessing techniques for used nuclear fuel. A rotating disk electrode is useful for investigating the electrochemical reactions with controlled mass transfer conditions, but its application has been limited in high-temperature corrosive molten salts. This study employs a tungsten (W) rotating disk electrode (RDE) to measure the electrochemical and kinetic properties of the Sm(III)/Sm(II) redox reaction in a LiCl-KCl eutectic molten salt. The properties of the Sm(III)/Sm(II) redox reaction, including diffusion coefficients, exchange current densities, charge transfer coefficients, activation energies, and Tafel slopes, were determined over a temperature range of 723–803 K using limiting currents in linear sweep voltammetry at various rotating speeds and mass transfer-corrected Tafel plots. The kinetic parameters obtained using the rotating disk electrode system can be useful for optimizing the design of pyroprocessing techniques.

Investigation of electrochemical behavior of cerium in LiCl-KCl eutectic molten salt by modeling

Investigation of electrochemical behavior of cerium in LiCl-KCl eutectic molten salt by modeling

In situ spectroscopy of Sm(III) and Sm(II) in LiCl–KCl eutectic molten salt

In situ spectroscopy of Sm(III) and Sm(II) in LiCl–KCl eutectic molten salt

(Invited) Electrochemical Synthesis of Diamond from Carbon Dioxide in Molten Lithium Chloride-Potassium Chloride Systems

IntroductionIn order to achieve carbon neutrality by 2050, not only the CO2 capture and storage (CCS) but also the CO2 capture and utilization (CCU) is necessary. Here, electrochemical CO2 conversion technology in molten salt is considered to be one of the promising candidates for CCU [1,2]. In this study, we aimed to convert CO2 into diamond, which is one of the most valuable carbon materials. As a first step, we investigated the electrochemical synthesis of diamond in molten LiCl-KCl systems containing K2CO3 and KOH, based on the premise that CO2 dissolves as CO3 2- in molten salts containing O2-. As a result, micro-Raman spectroscopy and scanning electron microscopy (SEM) confirmed that a part of the deposits obtained by electrolysis were diamonds. As a second step, we attempted the electrochemical synthesis of diamond using CO2 as the actual raw material. Here, H2O was also bubbled in the molten salt in order to produce KOH. The deposits obtained by electrolysis were then analyzed by micro-Raman spectroscopy and SEM, which confirmed the synthesis of diamond.ExperimentalCyclic voltammetry and potentiostatic electrolysis were performed after adding K2CO3 and KOH to LiCl-KCl eutectic melts under an Ar atmosphere at 973 K. The working electrode was a Ni flag (Φ 3 × 0.1 mm) or Ni plate (5 mm × 10 mm × 0.1 mm), the counter electrode was a glass-like carbon rod, and the reference electrode was an Ag+/Ag electrode. The potential was calibrated with Li+/Li potential. After electrochemical measurements were performed, samples were prepared by potentiostatic electrolysis using the Ni plate electrodes. In the case where CO2 was used as a raw material, LiCl-KCl eutectic molten salt containing Li2O was prepared, and CO2 and H2O were bubbled into it in predetermined amounts, respectively. After electrochemical measurements, potentiostatic electrolysis was performed to prepare samples. The obtained samples were analyzed by SEM, EDX, and micro-Raman spectroscopy.Result and DiscussionFirst, electrochemical measurements in baths containing only K2CO3, only KOH, or both indicated that carbon deposition and hydrogen evolution proceed simultaneously in the potential range more negative than 1.2 V. Then, samples were prepared by potentiostatic electrolysis using Ni plate electrodes at 1.0 to 1.2 V (vs. Li+/Li). The charge density was unified at 10 C cm-2. As an example, the surface SEM image of a deposit obtained at 1.1 V in a bath containing 0.05 mol% K2CO3 and 1.0 mol% KOH is shown in Fig. 1(a). The EDX analysis of this area showed that only C and Ni from the substrate were detected. The result of micro-Raman spectroscopy of the sample is shown in Fig. 1(b), which shows a spectrum characteristic of diamond with a sharp peak at 1332 cm-1. Based on the results of these three analyses, the electrochemically synthesized angular particles were identified as diamond.On the day of the meeting, we will also present the results of electrolysis using CO2 as the raw material.AcknowledgmentA part of this work was supported by JSPS KAKENHI Grant Number 21K19024.

Microelectrode voltammetric analysis of samarium ions in LiCl–KCl eutectic molten salt

A microelectrode is useful to determine electrochemical parameters such as diffusion coefficient, exchange current density, and Tafel slope without the limitations of ion diffusion. This study aims to develop a new microelectrode for use in high-temperature molten salts, which has been evaluated by determining the parameters of the Sm(III)/Sm(II) reaction in a LiCl–KCl eutectic molten salt. The electrochemical and kinetic properties of the samarium ion in the temperature range 723–823 K were calculated using the limiting current from cyclic voltammograms and the Allen–Hickling equation. The results imply that kinetic parameters (exchange current density and charge transfer coefficient) critical for designing pyroprocesses can be obtained using the developed microelectrode.

Temperature and anion ligand field dependence of LnCl3 (Ln = Nd, Dy, Sm) electronic absorption spectra in LiCl–KCl eutectic molten salt

A comprehensive knowledge of the coordination, bonding, and speciation of elements in molten salt mixtures is necessary to understand and predict the chemical and physical properties of the salt. Absorption spectroscopy can yield information about the chemistry of species of interest in alkali halide molten salt mixtures by revealing information about the electronic structure and transitions of those species. In this study, ultraviolet (UV), visible (vis), and near-infrared (NIR) absorption spectroscopy was used to examine changes to the electronic structure of trivalent Nd, Sm, and Dy in LiCl–KCl eutectic molten salt with changes in temperature and the anion composition of the melt. With increasing temperature, changes to spectral features suggest a distortion of the coordination complexes. Changes to lineshape with the substitution of alternative halide anions were examined and analyzed, revealing differences in the coordination for I− versus F− with the lanthanides. Gaussian peak fitting was used to show that the changes in lineshape with the progressive addition of F− anions can be explained by the superposition of a set of absorption bands from complexes with all Cl− anion ligands and a set of blueshifted absorption bands from complexes containing both F− and Cl− anion ligands. This work yields a new method to analyze and interpret change to electronic absorption spectra for f-block elements dissolved in alkali halide molten salts as well as new observations of the interactions of larger and smaller halide anions with lanthanides in Cl−-based molten salts.

CORROSION PERFORMANCE OF PLASMA SPRAYED ALUMINA–40 wt.% TITANIA COATED HIGH-DENSITY GRAPHITE IN MOLTEN LiCl–KCl EUTECTIC SALT

The corrosion performance of plasma sprayed alumina–40[Formula: see text]wt.% titania (A40T) coated high-density graphite was investigated in molten LiCl–KCl eutectic salt at [Formula: see text]C for periods of 500, 1000, and 2000[Formula: see text]h under argon atmosphere. The microstructural and compositional investigations of corrosion-tested A40T coatings by scanning electron microscopy and energy dispersive X-ray spectroscopy showed that the samples exhibited better corrosion resistance up to 500[Formula: see text]h. The poor corrosion behavior and failure of A40T coating from graphite substrate in the long-term (1000 and 2000[Formula: see text]h) immersion was discussed in detail based on the microstructure and composition analysis. The phases existing in the as-sprayed coating ([Formula: see text]-Al2TiO5, [Formula: see text]-Al2O3, R-TiO2, and [Formula: see text]-Al2O3) remained in the detached coating after 1000[Formula: see text]h exposure to the molten salt. The reaction between molten salt and A40T coating was not evident from XRD analysis. A40T coatings with chromium carbide–nichrome (Cr3C2–NiCr) bond coat showed complete spallation of the top coating and oxidation of the bond coat as evident from the X-ray diffraction analysis. Detachment of the A40T coating occurred due to the penetration of the molten salt into the coating through the voids and pores present on the surface, which weakened the adhesion strength between the substrate and the A40T coating or top coat-bond coat interfaces.

Materials Exposure Testing in Chloride Molten Salts for Nuclear Applications

Advanced nuclear reactors using alkali chloride molten salts are actively being developed for deployment as safer next generation reactors. These reactors operate more efficiently and can enable a more flexible nuclear fuel cycle. These designs require the development of the understanding of corrosion at operational conditions. Static corrosion studies fail to capture the effects of flowing electrolyte on the corrosion in these systems. To simulate the effects of flow, we have designed and commissioned an apparatus for such corrosion studies. This study explored the corrosion of alloys in LiCl-KCl eutectic molten salt. After long-term exposure under simulated flow conditions, corrosions samples were evaluated using gravimetric analysis, scanning electron microscopy and energy dispersive spectroscopy, Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy and the results are compared to corrosion under static conditions. Results and analysis of the effects of fluid flow on the corrosion on structural materials will be presented.Acknowledgement:This research is being performed using funding received from the DOE Office of Nuclear Energy's Nuclear Energy University Programs under awards DE-NE0008889 and DE-NE0008236, and the US Nuclear Regulatory Commission (USNRC) under contract 31310018M0032. Dr. Kenny Osborne and Ms. Nancy Hebron-Isreal serve as the program managers for the DOE and NRC awards, respectively.

Near-infrared spectra and molar absorption coefficients of trivalent lanthanides dissolved in molten LiCl–KCl eutectic

Determining the concentration of the dissolved lanthanide species in LiCl–KCl eutectic salt is important to the development of pyrochemical reprocessing of used nuclear fuel. In this process, lanthanide fission products are found dissolved in the electrorefiner electrolyte in their trivalent oxidation state. The presence of dissolved trivalent lanthanides increases the liquidus temperature of the electrolyte mixture and can lead to the formation of insoluble oxide or oxychloride phases and must therefore be continuously monitored and controlled during the operation.Absorbance spectroscopy is a promising method for continuous measurement of the concentration of lanthanides and other elements dissolved in the electrolyte. The absorption of light by elements is linearly proportional to the concentration of the element for relatively dilute solutions according to the Beer-Lambert law. Although measurement of the absorption of ultraviolet and visible range light by lanthanides in LiCl–KCl eutectic molten salt have been explored previously, near infrared (NIR) absorption spectroscopy has received far less attention. It may, however, provide a better analytical signal when insoluble phases are present due to less Raleigh scattering compared to shorter wavelength radiation. Additionally, it may allow for concentration determination for certain elements using NIR absorption features where UV and visible range features are overlapping with features from other species.In this study, we report the UV–Vis–NIR spectra of the trivalent lanthanide chlorides of neodymium, samarium, and dysprosium in LiCl–KCl eutectic. Molar absorption coefficients are reported for analytically useful absorption maxima, with a focus on the molar absorption coefficients for NIR absorption maxima which have not been reported previously. Additionally, we observe a NIR-range absorption band of Nd3+ which was previously predicted but never experimentally observed. We compare the calculated crystal field levels to the newly observed absorbance band and find them to be in good agreement with previous predictions.

Modeling Potential and Species Distribution in a Li||Bi Liquid Metal Battery Using the Finite Volume Method

To match the growing demand for grid scale energy storage in order to balance out renewable energies, the liquid metal battery (LMB) technology is highly promising. Key elements of these batteries are the liquid electrodes, which require LMBs operating at elevated temperatures. Hereby, the electrolyte can be liquid or solid state. Based on density differences, the battery is self-assembling since the components self-segregate when the system is heated. Additionally, many of the possible materials are earth-abundant and not expensive. This results in a very cost effective technology. Moreover, the molten electrodes feature superior kinetics and transport properties as well as high voltage efficiencies at high current densities. Otherwise, the liquidity has the disadvantage that high operating temperatures are necessary. Further, there is a risk of corrosion, self-discharge and short-circuiting. The latter makes the battery not applicable for portable applications [Kim, H. et al. Chem. Rev. 113 (3) (2013)]. Among all LMBs, the Li||Bi cell has been investigated to a large extend and therefore, most material properties are readily available. This is the reason why the present study focuses on this material pairing. A schematic of this cell during discharge is shown in figure 1a. Here, the anode metal Lithium is oxidized and the ion crosses the electrolyte layer. Then it alloys with the molten Bismuth. At charge, this process is reversed. A picture of a real cell can be found in figure 1b. Nevertheless, there are other very promising cell chemistries such as NaZn batteries [Xu, J. et al. J. Power Sources 332 (2016)].For theoretical investigations and numerical simulations, electromagnetic fields, electrochemistry and fluid dynamics need to be considered. Coupling of the corresponding fundamental equations and the different regions in the battery is challenging. Further, there are multiple fluid flow phenomena – like surface instabilities, Tayler instability, electro-vortex flow, thermal convection,solutal convection or Marangoni convection [Kelley, D. H. and Weier, T. Appl. Mech. Rev. 70 (2) (2018)] – that might occur when the battery is operated. To determine the operating voltage of a cell, overpotentials need to be investigated. Generally, there are three types of overpotentials: the ohmic loss, the mass transfer and the charge transfer overpotential. However, the latter can be neglected [Newhouse, J. M. Ph.D. thesis, MIT (2014)]. Determining the ohmic overpotential is quite straightforward using Ohm’s law, while the concentration overpotential requires the calculation of the species distribution in the electrolyte and the positive electrode.The present study will focus on the electrochemical behavior of an all liquid Li||Bi battery and neglects fluid flow. Hereby, the whole cell is modeled using the parent-child-mesh technique from Weber et al. [Weber, N. et al. Computers & Fluids 168 (2018)]. This implies that the species distribution in the electrolyte and the distribution of the dissolved species in the cathode are calculated locally and the potential and current density distribution are calculated globally. The equations to solve are coupled between the used meshes. To account for the potential distribution, it is necessary to consider the electrochemical double layer at the electrode-electrolyte interfaces. Macroscopically, the latter can be described as a potential jump at both interfaces in accordance to the Nernst equation. Weber et al. [Weber, N. et al. Electrochim. Acta 318 (2019)] introduced to model this jump using a source term. In the present study, the approach to use internal jump boundary conditions for modeling the potential jump is proposed. To the best knowledge of the authors, species distributions in the electrolyte have not been investigated previously. When there is no mixing of the electrolyte of LMBs, concentration gradients of each species might be significant [Vallet, C. E. et al. J. Electrochem. Soc. 130 (12) (1983)]. Based on the solution for the species distribution, the potential jump at each interface can be calculated. Further, the charge transfer overpotentials can be obtained.The equations are solved quasi-one-dimensional using the finite volume method and are implemented in the open source library OpenFOAM. To validate this new approach, a comparative study with Comsol is performed. Lastly, an application case is simulated, which confirms that concentration layers in the electrolyte are indeed present. This is, for the case of an Li+ ion in a LiCl-KCl eutectic molten salt, exemplarily shown in figure 1d. Further, as it can be seen in figure 1c, the simulation is able to solve the potential distribution in the cell with respect to the potential jump at the interface.Acknowledgment: This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 963599. Figure 1

Electrochemical Behaviors and Thermodynamic Properties of Ce on Liquid Bi, Sn, and Zn Electrodes in Molten LiCl-KCl Salt

This study presents the electrochemical behaviors and thermodynamic properties of Ce on liquid Bi, Sn, and Zn electrodes in molten LiCl-KCl eutectic salt. First, the Ce-metal binary systems on the solid tungsten electrode were investigated to determine the formation of Ce-metal intermetallic compounds during the electrowinning process. In these experiments, the formation of five Ce–Bi intermetallic compounds, eight Ce–Sn intermetallic compounds, and nine Ce–Zn intermetallic compounds was confirmed from the oxidation peaks of cyclic voltammetry. The standard Gibbs free energy of formation of each intermetallic compound was calculated from plateaus of the open-circuit chronopotentiometry. Subsequently, the electrochemical behaviors of Ce were investigated on liquid Bi, Sn, and Zn electrodes using cyclic voltammetry. In particular, while the reduction potentials of Li and Ce were too close to differentiate on the liquid Bi and Sn electrodes, they were not on the liquid Zn electrode. Peak potentials from cyclic voltammetry were utilized to calculate the activity coefficients of Ce in the liquid Bi, Sn, and Zn electrodes, which were 3.16 × 10−14, 1.82 × 10−12, and 9.05 × 10−10, respectively.

In Situ Corrosion Monitoring of the T91 Alloy in a Molten Chloride Salt Using a Miniaturized Electrochemical Probe for High-Throughput Applications.

Corrosion sensing is essential to monitor and safeguard materials' health in molten salts. The present study developed a three-electrode-array minisensor for high-temperature molten salt corrosion monitoring. By using the developed sensor, the impurity-driven corrosion of T91 by a fission product, europium, in the LiCl-KCl eutectic molten salt has been studied. The developed minisensor was validated to be an ideal probe for in situ corrosion monitoring in the high-temperature molten salt via the comparisons on concentrations of the dissolved corrosion products detected using this device and inductively coupled plasma mass spectroscopy. To analyze the large volume of data measured using the minisensor during in situ corrosion experiments, an algorithm has been developed to achieve the high-throughput data analysis. The well-designed minisensor can be potentially used for high-throughput corrosion experiments. Combined with the developed algorithm for high-throughput analysis, this study provided a platform to explore the application of electrochemical sensors for the in situ corrosion monitoring of materials in high-throughput molten-salt corrosion experiments.

The Electrochemical Behavior of Tellurium Tetrachloride in LiCl-KCl Eutectic Molten Salt at 450 ºC

Cyclic voltammetry CV), square wave voltammetry (SWV), and electrochemical impedance spectroscopy measurements were carried out in 1 and 5 wt% TeCl4 containing LiCl-KCl eutectic molten salt at 450 °C using tungsten and glassy carbon as working electrodes. Reduction of Te(IV) to Te(0) occurred in three steps at potentials more negative than −0.4 VAg/AgCl. The Te(0) was further reduced to Te2− at more negative potentials. Formation of Te2− was observed at potentials more negative than −2.2 VAg/AgCl. Diffusivities of Te4+, Te2+, and Te2− and their formal potentials were estimated from the CV data. The diffusion coefficients of Te4+, Te2+ and Te2− were 0.9 × 10−5, 3.8 × 10−5, and 1.5 × 10−5 cm2 s−1, respectively in the 1 wt% TeCl4 containing LiCl-KCl molten salt. The diffusivity of Te species generally decreased with increase in the concentration of TeCl4.

Real-Time Monitoring for Electrochemical Analysis in Molten LiCl-KCl Eutectic Salt

Molten salts are one of the promising alternative classes of new materials for electrochemical processing. They have high chemical stability and offer much wider electrochemical window than conventional aqueous media. This enables various electrochemical reactions to be conducted without decomposing background media. In addition, the high operation temperature of molten salt boosts the mass transfer of reactant of electrochemical reaction, so that the processing time is shortened. Owing to such advantages, the molten salt media have intensively dealt with the electrowinning of metal and electrochemical separation processes. However, knowing the chemical behavior of electrodes during such processes is crucial to understanding the mechanism of electrochemical reactions that occur during the process. One of the most powerful methods of examining the system is to monitor the visual status of electrodes in real time while the electrochemical process is running. However, due to some practical limitations, it has rarely been applied to the molten salt electrochemical system.In the present work, the real-time monitoring system for molten LiCl-KCl eutectic salt medium is set up. Instead of an optically opaque ceramic crucible, a cylindrical quartz tube is chosen for the electrochemical cell of our experimental system. With four optically accessible quartz windows mounted on the electrical furnace, a commercially available CMOS camera can be installed externally to monitor the molten salt system without any special modifications.Real-time monitoring was carried out to investigate the electrode behavior in various electrochemical systems. First, the deposition behavior of cobalt in molten CoCl2-LiCl-KCl system (1wt% CoCl2) is compared on a tungsten working electrode. As shown in Figure 1, there is a clear morphological structural difference in the cobalt deposit between the galvanostatic and the potentiostatic electrodeposition. While the metallic cobalt was deposited evenly on the surface of the working electrode by galvanostatic electrodeposition, rapid growth of the dendritic structure was observed using the potentiostatic electrodeposition. This suggests that the structural properties of deposits can vary significantly due to the nature of the electrodeposition methods.In electrochemical experiments in molten salt system that do not produce solid phase products, it is difficult to elaborately understand the behavior of chemical species during the experiment. However, real-time monitoring enables noteworthy observation from these experiments. During the galvanostatic lithium reduction in the molten LiCl-KCl system, the liquefied metallic lithium formed the oval bulge on the surface of the tungsten working electrode. At the same time, the unknown indigo-colored flow was observed on the surface of the deposited metallic lithium. The clear mechanism remains to be explored, but it appears to be related to the re-oxidization of metallic lithium to Li(I) ions. In the molten ZrCl4-LiCl-KCl system (1wt% ZrCl4) with tungsten working electrode, the reduction of Zr(IV) ions to Zr(III) ions during the potentiostatic electroreduction was visualized and identified by the formation of brown-colored flow near the surface of the working electrode. This confirms the result of our previous work and suggests that Zr(IV) is reduced to Zr(III) with a brown color in the first step of CV [1].Furthermore, with the video signal from the CMOS camera to the PC that controls the potentiostat, the visual changes can be synced with the measured current or potential during the experiment. This enables us to compare the visualized morphological properties on the surface of the working electrode under different applied potential conditions during the CV experiment (Figure 2).[1] H. L. Cha, J.-I. Yun, Electrochem. Commun. 84, 86 (2017) Figure 1

Real-Time Monitoring for Electrochemical Analysis in Molten LiCl-KCl Eutectic Salt

In the present work, a real-time monitoring system for molten LiCl-KCl eutectic salt medium is set up with optically accessible quartz windows mounted on the furnace and the CMOS camera. Based on the designed system, the real-time monitoring was carried out to investigate the electrode behavior in various electrochemical systems, such as (1) differences in Co morphology deposited in molten CoCl2-LiCl-KCl system by various electrochemical deposition methods, (2) a reoxidation behavior of electrochemically reduced lithium, and (3) a reduction of Zr(IV) ions to Zr(III) ions in the molten ZrCl4-LiCl-KCl system. By delivering the video signal from the CMOS camera to the PC which controls the potentiostat, the visual changes can also be synced with the measured current or potential during the experiment. This enables us to compare the visualized morphological properties on the surface of the working electrode under different applied potential conditions during the application of electroanalytical methods.

Evaluation of Li Electrodeposition into Al from LiCl–KCl Electrolyte

This study investigated the effects of temperature and the current density on the production of an Al–Li master alloy using electrolysis. The current efficiency and the specific energy consumption were calculated according to Faraday’s law to determine optimal conditions for production of the Al–Li master alloy. Solid aluminum and graphite were used as the cathode and the anode, respectively. The LiCl–KCl eutectic molten salt was used as a lithium-containing electrolyte. Different current densities were applied to obtain the optimum condition. In addition, different temperatures were investigated at the optimum current density during the deposition of lithium. Scanning electron microscopy, optical microscopy, and the X-ray diffraction analysis were used to investigate the microstructure and phase compositions. Atomic absorption spectroscopy was used to measure the existing lithium. The results showed that electrolysis at 620°C and a current density of 0.9 A/cm2 at 4 V for 3 h leads to the formation of an Al–17.43 wt % Li master alloy. The current efficiency and the specific energy consumption for the optimum conditions were found to be 96% and 16.08 kWh/kg, respectively.

Electrochemical Studies on the Redox Behavior of Zr(IV) in the LiCl-KCl Eutectic Molten Salt and Separation of Zr and Hf

Electrochemical behavior of Zr(IV) in LiCl-KCl-ZrCl4 molten salt on molybdenum electrode was systematically studied by a series of electrochemical techniques such as cyclic voltammetry, square wave voltammetry and chronopotentiometry. It was investigated that the Zr(IV) was first reduced to Zr(III) in this system, which is different from most studies in which Zr(IV) is first reduced to Zr(II). The activation energy of Zr(IV) converted to Zr(III) was calculated to be 24.6 kJ mol−1 by measuring the diffusion coefficients of Zr(IV) at 450 °C, 500 °C, and 550 °C. Through research, the nucleation of zirconium belongs to the progressive nucleation on molybdenum electrode in LiCl-KCl-ZrCl4 (0.0359 mol L−1) at 500 °C at −3.0 V vs Cl2/Cl−. Constant current electrolysis (Current density 0.52 A cm−2, duration 500 min) was carried out in LiCl-KCl-ZrCl4 system and the electrolytic product was porous metallic zirconium. More importantly, it is found that the difference in decomposition potential between Zr(II) and Hf(II) is the largest by calculation and test compared with their trivalent and tetravalent states, and they may be separated by electrolysis, which provides a theoretical reference for the electrolytic preparation of nuclear grade zirconium.

Corrosion assessment of 9Cr-1Mo steel in molten LiCl-KCl eutectic salt by electrochemical methods

Ferritic chromoly steels are being considered for the process crucibles for the electrorefining of the pyrochemical reprocessing of spent metallic fuels in India. Pyrochemical reprocessing uses molten LiCl-KCl salt at 500–600 °C under an inert argon atmosphere for the electrorefining. The corrosion assessment of the 9Cr-1Mo steel in LiCl-KCl molten salt at 500 °C under inert argon atmosphere has been attempted using electrochemical measurements such as open circuit potential (OCP), linear polarization resistance and electrochemical impedance spectroscopy (EIS). The OCP of the sample was shifted towards noble direction during the total duration of 98 h. The linear polarization resistance, measured at regular intervals of exposure of 9Cr-1Mo steel to molten salt, increased with the increase of the exposure duration. The electrochemical impedance technique has been used to evaluate and monitor the molten salt-corrosion processes of the base metal. The EIS results showed the formation of a large semi-circle, with the characteristics of double loops capacitance attributed to the nature of intermittent oxide film over the surface. The surface oxide films are mostly composed of iron and chromium oxides confirmed by XRD and SEM-EDS analysis. It is also evident from the EDS analysis that depletion and enrichment of Cr and Mo across the surface of the 9Cr-1Mo steel. This work indicated that the electrochemical techniques show considerable promise for the monitoring of high-temperature molten salt corrosion processes.

Synthesis of uranium trichloride salt using ZnCl2

We report a method for preparing uranium trichloride, UCl3, by reacting ZnCl2 with U in a molten LiCl–KCl eutectic salt at 500 °C. Cyclic voltammetry indicated the formation of UCl3 as the reaction proceeded. After 30 h, the reaction was terminated and the final product was confirmed to contain 13.2 wt% UCl3–LiCl–KCl salt by the ICP-OES method.