Salt Chemistry Research Articles

Development of Neural Network Potentials for Studying Chemical Behaviors of La3+/Nd3+ Ions in Molten LiCl-KCl-CsCl in Combination with Raman Spectroscopy.

The chemistry of molten salts has attracted great research interest owing to their wide applications in diverse fields. In the pyrochemical reprocessing of spent nuclear fuel or molten salt nuclear reactors, lanthanide elements as the principal fission products bring about changes in the composition and properties of molten salts. Herein, we report a comprehensive study on the coordination chemistry of the representative trivalent lanthanide ions (La3+/Nd3+) in LiCl-KCl-CsCl using a multiscale strategy combining Raman spectroscopy, deep learning, and large-scale molecular dynamics (MD) simulations. The neural network potential (NNP)-based MD and Raman spectroscopy studies revealed that La3+/Nd3+ ions prefer to form persistent octahedron complexes with the six-coordinated species as the dominant species at high temperatures. Compared to LaCl63-, NdCl63- shows higher stability with obviously longer lifetimes in LiCl-KCl-CsCl, as confirmed by the observed stronger interaction of Nd3+-Cl- pairs. The total and partial structure factors further indicated the formation of a more stable network structure in LiCl-KCl-CsCl containing NdCl3. Besides, the temperature exerts a larger influence on the local structures of the La3+ species compared to the Nd3+ analogues. According to the potential mean force calculations, the bond dissociation energies follow the order Ln-Cl > Li-Cl > K-Cl > Cs-Cl in LiCl-KCl-CsCl-LnCl3. The NNP-based large-scale MD simulations have been verified to be an efficient and powerful way in molten salt chemistry research.

Tetraarylammonium salts - synthesis, properties and emerging use.

The chemistry of tetraarylammonium salts, first explored in the 1960s Soviet Union, has long been a dormant field of research. This is owing to the inherent difficulty in adding a fourth benzene ring to the nitrogen atom of the sterically demanding and low-nucleophilicity triphenylamine molecule. Only recently have new developments in synthetic methodology made access to tetraarylammonium salts less of a tour de force, and first applications are beginning to emerge. As a consequence, the number of publications in this field of research is growing. The review covers the complete field of research, from the beginnings to the present day.

Development of Optical Sensors Based on Neutral Red Absorbance for Real-Time pH Measurements.

Measuring pH with an optical sensor requires the immobilization of a chemical recognition phase on a solid surface. Neutral red (NR), an acid base indicator was used to develop two different optical probe configurations. The chemistry of aryl diazonium salts was chosen for the elaboration of this chemical phase, as it enables strong covalent bonds to be established on the surface of metallized glass or metallic surfaces. It also allows the formation of a thick film required to obtain an exploitable spectral response. The surfaces of interest (metallized optical fiber and 316 L stainless-steel mirror) are modelized by flat surfaces (metallized glass plates and 316 L stainless-steel plates). The analytical characterizations carried out (IR, XPS, UV-Visible, and profilometry) show that NR was covalently grafted onto the model surfaces as well as on the surfaces of interest. The supports grafted with NR to develop optical pH probes exhibit spectral changes, particularly the values of pKa, the pH range, and the isosbestic point wavelength. The experimental results show that the optical probe can be used for pH measurements between 4 and 8.

An Electrochemical Phase Field Model Applied to Molten Salt Dealloying Corrosion of Ni-Alloys

Metal alloys in contact with molten salts are known to corrode via a dealloying process, wherein the less-noble alloy elements (e.g. Cr) are selectively oxidized and dissolved, leaving behind a corroded structure that is enriched in the more-noble elements (e.g. Ni). In some cases, this can lead to molten salt infiltration into the alloy through discrete channels along specific microstructural features (e.g. grain boundaries). However, in other cases the dealloying process promotes a more full-scale attack of the alloy, generating a fine-scale ligament structure. This process can severely degrade the alloy’s structural integrity, which limits the practicality of these material systems in otherwise promising applications (e.g. molten salt-cooled power reactors).The thermokinetic conditions for dealloying corrosion depend on the salt chemistry and the metal microstructure, which together inform the reaction process occurring at their interface. The salt chemistry and oxidant content set the electrochemical potential for selective oxidation of the less-noble elements. The associated oxidation rate is expected to depend on the presence of an interfacial structure (e.g. double layer) and also on the transport rates of reactants towards the interface (e.g. species diffusion in the metal and oxidizer transport in the salt) and reaction products away from the interface (cation transport in the salt). The corrosion rate and morphology will also depend strongly on the rate of transport laterally along the metal-salt interface, since the reorganization of the more-noble species (Ni) towards ligament formation facilitates the attack of the alloy by the corrosive agent. It has been hypothesized that molten salts enhance this rate of solute diffusion along the metal interface.In this work, we propose an electrochemical phase field model to predict the microstructural evolution of model Ni-alloys undergoing dealloying corrosion in molten fluoride salts. The model incorporates metal oxidation and dissolution via experimentally determined redox potentials and activity coefficients for metal species in the molten salt. We show that the corrosion rate and development of pores is strongly dependent on solute transport rates within the metal and also along their solid-liquid interface. In particular, we reveal a mechanism in which grain boundaries couple with the solid-liquid corrosion front to promote rapid dealloying and molten salt attack. Oxidant content in the salt and double-layer formation at the interface are discussed for their roles in setting the electrochemical potential and reaction rate at the metal-salt interface. Finally, we discuss how the model leverages insights from atomistic modeling and highlight key knowledge gaps in the mesoscale modeling of electrochemical molten salt corrosion.

Investigation of the Relationship between Molten Fluoride Salt Structure and Fluoroacidity Using Chromium As a Probe Redox Ion

Molten fluoride salts have been studied for decades due to their applications in the production of aluminum as well as in the operation of advanced nuclear reactors. Advanced fission and fusion nuclear reactor designs may include molten fluoride salts as coolants, fuel carriers (fission), or fuel breeding blankets (fusion). Relevant to their nuclear applications are the thermophysical and thermochemical properties of the salt. These include viscosity and thermal conductivity, as well as density, vapor pressure, and heat capacity. Underlying these properties are the interactions of the ions constituting the liquid, characterized by their coordination number, correlation times, and the possible formation of polymeric networks in the melt. The composition and structure of a melt, that is, what ions are present and how they interact, dictates the macroscopic properties relevant to reactor operation. Fluoroacidity, or the activity of dissociated fluoride anions, is one metric that may be used to describe the relationship between salt chemistry and structure. Overall, understanding the relationship between molten fluoride salt chemistry and structure enables deeper understanding and, thus, prediction of property changes that may take place throughout a reactor’s lifetime.In this poster, we present cyclic and square wave voltammetry studies of chromium speciation and diffusivity in various molten fluoride salts, connecting results with current understanding of the structure of the melts. Chromium is a thermodynamically favored corrosion product in molten salt systems, and in this study, it serves as a probe ion in different fluoride melts. Chromium trifluoride is added to various fluoride solvents and the diffusion coefficients of its various oxidation states are calculated and interpreted in light of salt structure. Experimental apparatus design and know-how for high-temperature molten salt electrochemistry are also highlighted.

Towards Functionalization of Extracellular Vesicle with Single-Walled Carbon Nanotubes for Long-Term Imaging

In the past years, nanotechnology has been increasingly applied in modern medicine owing to their advantages including high drug loading, increased drug stability, longer circulation time, EPR effect, and lower systemic toxicity compared to small molecular drugs. While most nanomaterials are fabricated synthetically, extracellular vesicles (EVs) present a special class as they are naturally produced by mammalian cells during inward budding of endosomes, which seems beneficial regarding stability, immunotolerance, capacity to cross natural barriers, and inherent targeting properties in vivo compared to synthetically prepared nanomaterials. Although EV-based cancer vaccines are currently tested in clinical phases I and II, a huge gap, preventing broad application of EVs, remains the lack of detailed information concerning the in vivo behavior of EVs. To understand the role of EVs and to optimize their application in future, long-term tracking of EVs is crucial.Single-walled carbon nanotubes (SWCNTs), tube-like, carbon-based nanomaterials with a diameter of around 1 nm and a length of around 100 nm, holding great promise as imaging probes for medical diagnostics owing to their optical properties in the short-wave infrared region. The fluorescent properties of SWCNTs are caused by excitons (bound electron-hole pairs) those energetically favorable dark states result naturally in a low photoluminescence yield. A way to circumvent this effect is oxygen-doping of SWCNT or introduction of sp3 defects which lead to lower energetic states which trap excitons and circumvent dark states. This results in a prolonged photoluminescence lifetime and an emission in the short-wave infrared (SWIR) window allowing imaging with deep optical penetration, reduced scattering, and low autofluorescence. In addition, SWCNTs possess a high photostability, low photobleaching, and negligible fluorescence blinking. The high photostability of SWCNTs in combination with an emission in the SWIR window as well as a size in the nanometer regime, mark SWCNTs as excellent imaging probes for in vivo tracking of extracellular vesicles.To achieve specific labeling of EVs with SWCNTs, we are using bioorthogonal chemistry. Metabolic engineering of cells is an elegant method to equip membrane proteins with bioorthogonal reactive groups. To this end, cells are treated with unnatural sugars which are metabolically incorporated into the glycan chain of proteins. Recently, it was revealed that EVs from metabolically engineered cells also carry unnatural sugars in their membrane proteins. We successfully isolated EVs from MCF-7 cells, which were treated with azide-bearing mannose. Using Cy5-DBCO, we could prove that azide groups present on EVs were able to react with the dye. EVs isolated from metabolically engineered HeLa cells seemed to possess a too low number of azide groups. Hence, EVs were modified successfully with DSPE-PEG-azide. Modification of EVs with Cy5-DBCO enabled in vitro imaging.We followed several strategies to introduce DBCO groups onto SWCNTs to link those to EVs. We were able to successfully functionalize SWCNTs with ssDNA carrying DBCO as an end-group as well as DPSE-PEG-DBCO. However, due to lack of specificity we embarked to use sp3 defects as reactive sites for modification of SWCNTs. Diazonium salt chemistry was used to introduce sp3 defects with a carboxylic acid group which allows further modification using a DBCO end-functionalized PEG linker.Ultimately, we will conjugate DBCO-modified SWCNTs with azid-bearing EVs to enable long-term tracking in vivo.

Flow Distribution in Molten Salt Receiver Panels at High Flux Gradients

This paper presents a simulation study on critical mass flow distributions in receiver panels of commercial-scale molten salt towers (MST). Despite sophisticated aimpoint optimizations, the flux density distribution on an MST receiver in actual operation contains significant vertical and horizontal gradients. This study investigated how the latter affects the mass flow distribution among the parallel absorber tubes in each panel. A parametric study applied a discretized dynamic thermohydraulic model of a commercial scale receiver design, highlighting at which mass flow rates, flux density gradients and mean flux densities the flow distribution can become critical. Excessive temperature developments were observed, suggesting maintaining appropriate minimal mass flow rates to avoid damaging tube walls and the molten salt chemistry.

Electrolyte Design Enables Rechargeable LiFePO4/Graphite Batteries from -80°C to 80°C.

Lithium iron phosphate (LFP)/graphite batteries have long dominated the energy storage battery market and are anticipated to become the dominant technology in the global power battery market. However, the poor fast-charging capability and low-temperature performance of LFP/graphite batteries seriously hinder their further spread. These limitations are strongly associated with the interfacial Li-ion transport. Here we report a wide-temperature-range ester-based electrolyte that exhibits high ionic conductivity, fast interfacial kinetics and excellent film-forming ability by regulating the anion chemistry of Li salt. The interfacial barrier of the battery is quantitatively unraveled by employing three-electrode system and distribution of relaxation time technique. The superior role of the proposed electrolyte in preventing Li0 plating and sustaining homogeneous and stable interphases are also systematically investigated. The LFP/graphite cells exhibit rechargeability in an ultrawide temperature range of -80°C to 80°C and outstanding fast-charging capability without compromising lifespan. Specially, the practical LFP/graphite pouch cells achieve 80.2% capacity retention after 1200 cycles (2 C) and 10-min charge to 89% (5 C) at 25°C and provides reliable power even at -80°C.

Electrolyte Design Enables Rechargeable LiFePO4/Graphite Batteries from −80°C to 80°C

Lithium iron phosphate (LFP)/graphite batteries have long dominated the energy storage battery market and are anticipated to become the dominant technology in the global power battery market. However, the poor fast‐charging capability and low‐temperature performance of LFP/graphite batteries seriously hinder their further spread. These limitations are strongly associated with the interfacial Li‐ion transport. Here we report a wide‐temperature‐range ester‐based electrolyte that exhibits high ionic conductivity, fast interfacial kinetics and excellent film‐forming ability by regulating the anion chemistry of Li salt. The interfacial barrier of the battery is quantitatively unraveled by employing three‐electrode system and distribution of relaxation time technique. The superior role of the proposed electrolyte in preventing Li0 plating and sustaining homogeneous and stable interphases are also systematically investigated. The LFP/graphite cells exhibit rechargeability in an ultrawide temperature range of −80°C to 80°C and outstanding fast‐charging capability without compromising lifespan. Specially, the practical LFP/graphite pouch cells achieve 80.2% capacity retention after 1200 cycles (2 C) and 10‐min charge to 89% (5 C) at 25°C and provides reliable power even at −80°C.

Corrosion studies of SS 316H and Alloy 617 in thermally purified molten NaF‐KF‐UF4‐UF3 salts

AbstractThe study investigates salt chemistry and corrosion behavior of SS 316H and Alloy 617 in thermally purified molten NaF‐KF‐UF4‐UF3 salts (UF4/UF3 initial ratio 12–14) at 800°C for 120, 72, and 32 h. UF4/UF3 ratio increases after corrosion tests. Cr species concentration in salts keeps increasing. Fe, Co, Ni, and Mo species increase first, then decrease. Cr/Mn oxides are formed along grain boundaries in SS 316H. Cr near the surface of Alloy 617 is completely depleted. A thin layer composed of Fe, Co, Ni, and Mo is observed on the Alloy 617 surface in 72‐h and 32‐h tests.

Nanostructured MoS2 grafted by anthraquinone for energy storage

Two-dimensional materials such as molybdenum disulfide (MoS2) can be employed as an electrode material in energy systems due its good electrical conductivity and high reachable capacity/capacitance. We demonstrate the concept of a covalent modification of nanostructured MoS2 with anthraquinone (AQ) molecules through diazonium salt chemistry for electrochemical capacitors and lithium-ion storage. AQ molecules are chemically bonded to MoS2 which was proved experimentally by spectroscopic techniques. Here, AQ is grafted (ca. 20 wt%) to the outer surface of nanostructured MoS2, but also confined within the MoS2 interlayer spacing. Modified AQ-MoS2 exhibited faradaic response which improved the overall charge stored from 191 F g−1 (461 F cm−3) to 263 F g−1 (631 F cm−3) at 0.2 A g−1 in 1 M H2SO4. The process of intercalation of ions within interlayer spacing of AQ-MoS2 was not hindered by the presence of confined AQ molecules. Impedance spectroscopy and voltammetry analysis revealed comparable non-diffusion limited response of MoS2 before and after modification. The MoS2 modification was likely conducted on the defect sites limiting the catalytic activity of MoS2 towards hydrogen evolution improving stability of electrodes. In organic medium, the pseudocapacitive response of MoS2, enhanced by additional redox reactions of grafted AQ was observed during lithium-ion storage.

Mechanistic study of moisture corrosion of FeCr alloys in molten salts by ab-initio molecular dynamics simulations

Molten salts are promising for various energy applications including fuel and solar cells and nuclear energy. These applications face a common challenge: corrosion of structural materials by impurities such as H2O. This work employs ab-initio molecular dynamics simulations to study H2O induced corrosion of FeCr alloys in molten NaF and NaCl salts. H2O is found highly stable in both salts, with infrequent, reversible dissociation into OH− and H+ along with HF or HCl formation. The dissociation tendency correlates positively with the electronegativity and negatively with the size of halogen atoms. Accordingly, H2O reaches the salt/metal interface as a molecule before reacting with metal. Reduction of H+ is found to occur without simultaneous oxidation of specific metal atoms such as Cr, suggesting sequential instead of the commonly proposed concurrent reduction and oxidation. The reduced H atoms prefer to stay at the interface and may re-enter NaF but not NaCl, highlighting the influence of salt chemistry.

Environmentally-assisted cracking of electropolished 316L stainless steel in molten FLiNaK salt

Environmentally-assisted cracking is a well-known and extensively studied phenomenon in light water reactor environments but remains relatively unexplored in proposed molten salt reactor systems where the mechanisms at play are expected to be quite different. Here, slow strain rate testing has been performed on 316L stainless steel tensile specimens during simultaneous exposure to a molten LiF-KF-NaF eutectic salt environment at 600°C with a strain rate between 1E-5 to 1E-7 s-1. Sample ductility and ultimate tensile strength were both observed to decrease for slower strain rates/longer salt exposures. Post-mortem characterization of fractured specimens revealed Fe deposits and Cr- and O-rich precipitates decorating surface grain boundaries and crack surfaces, suggesting a cracking mechanism driven by embrittlement of the crack tip due to oxide formation. Unlike previous studies, intergranular Cr corrosion into the bulk was not observed, and distinct differences in surface morphology between electropolished and non-electropolished sample surfaces are reported. Trace metal salt chemistry measurements showed accumulation of 316L alloying elements over the course of the tests. It appears likely that the surface oxide layer induced by electropolishing, in addition to oxygen and moisture impurities in the salt, led to the formation of LiCrO2 which had a net passivating effect that prevented significant bulk corrosion, though some interplay between mechanical and environmental stressors is still observed.

Arylthianthrenium Salts as the Aryl Sources: Visible Light/Copper Catalysis-Enabled Intermolecular Azidosulfonylation of Alkenes.

The difunctionalization of alkenes using aryl thianthrenium salts as the aryl sources has been reported sporadically. However, the four-component difunctionalization of alkenes on the basis of aryl thianthrenium salts has not been reported thus far and still remains a challenge. Herein, a visible light/copper catalysis-enabled four-component reaction of aryl thianthrenium salts, DABCO·(SO2)2, alkenes, and TMSN3 is presented, which affords a facile approach to β-azidosulfones in good yields with broad substrate scope and excellent functional group tolerance. This strategy indirectly realizes the method for the synthesis of β-azidosulfones through site-selective aryl C-H bond functionalization and alkene difunctionalization. This developed method is an important complement to thianthrenium salts chemistry.

Complex Structure of Molten FLiBe (2 LiF – BeF 2 ) Examined by Experimental Neutron Scattering, X-Ray Scattering, and Deep-Neural-Network Based Molecular Dynamics

The use of molten salts as coolants, fuels, and tritium breeding blankets in the next generation of fission and fusion nuclear reactors benefits from furthering the characterization of the molecular structure of molten halide salts, paving the way to predictive capability of the chemical and thermophysical properties of molten salts. Due to its neutronic, chemical, and thermochemical properties, 2LiF-BeF2 is a candidate molten salt for several fusion- and fission-reactor designs. We performed neutron and x-ray total-scattering measurements to determine the atomic structure of liquid 2LiF-BeF2. We also performed and neural-network molecular-dynamics simulations to predict the structure obtained by neutron- and x-ray-diffraction experiments. The use of machine learning provides improvements to the efficiency in predicting the structure at a longer length scales than is achievable with simulations at significantly lower computational expense while retaining near accuracy. We found that the NNMD simulations accurately predicted the BeF42− oligomer formations seen in the experimental first-structure-factor peak. Our combination of high-resolution measurements with large-scale molecular dynamics provided an avenue to explore and experimentally verify the intermediate-range ordering beyond the first-nearest neighbor that has posed too many experimental and computational challenges in previous works. With a deeper understanding of the salt structure and ion ordering, the evolution of salt chemistry over the lifetime of a reactor can be better predicted, which is crucial to the licensing and operation of advanced fission and fusion reactors that employ molten salts. To this end, this work will serve as a reference for future studies of salt structure and macroscopic properties with and without the addition of solutes. Published by the American Physical Society 2024

Effect of Brain-Based Learning on Conceptual Change in Acid, Base and Salt among Chemistry Students of Varied Cognitive Ability in Onitsha Education Zone

The study investigated the effect of brain-based learning on conceptual change in acid, base and salt among chemistry students of varied cognitive ability in Onitsha Education Zone. Three research questions guided the study and five hypotheses were tested at 0.05 alpha level. Quasi-experimental design was used in the study, specifically, the pretest-posttest non-equivalent control group design. The study population comprised 3, 103 SS2 students offering chemistry in Onitsha Education Zone, out which 108 students were selected using random and purposive sampling techniques. The instruments used for data collection were Test of Logical Thinking (TOLT) adopted from Tobin and Capie (1981) and Chemistry Students’ Conceptual Change Test (CSCCT) adopted from Zudonu (2013). Data was generated for the study by administering the instruments as pretest and posttest. Research questions were answered using mean and standard deviation while analysis of covariance was used to test the null hypotheses. The findings of the study showed that students taught acid, base and salt chemistry using brain-based learning had significantly higher mean conceptual change scores than those taught using lecture method. Also, there was a significant influence of cognitive ability level and gender on students’ conceptual change. It was recommended that seminars and workshop should be organized for chemistry teachers by school administrators to acquaint them with the effective ways of integrating brain-based learning into the teaching process of chemistry.

Adaptation potential of Miscanthus in a solonetz agricultural landscape

The aim of the study was to assess the ecological adaptability of Miscanthus cv. Soranovsky to saline agricultural landscapes and the phytomeliorative effect of the plant on saline soils. Location and time of the study. The field experimental part of the research was carried out in 2018-2020 in the central forest-steppe in the Barabinsky agrolandscape region (Experimental Research Station of the Siberian Federal Center for Agrobiotechnologies). Methods. The common methods of field and vegetation experiments, chemical analysis of soils and plant samples were used in the study. Results. Miscanthus can grow on solonetzic soils, providing a biomass yield of up to 5 t/ha under dry growing season conditions. The removal of nutrients from the soil by the biomass of Miscanthus stems was found to be low (8.2 kg/ha of nitrogen, 1.4 kg/ha of phosphorus and 9.7 kg/ha of potassium per year) due to their annual reutilization into rhizomes. This fact allow to avoid the danger of soil depletion during long-term cultivation of crops. Growing Miscanthus on meadow-chernozem solonetz for an average of three years led to changes in soil properties such as a decrease in pH, and changes in salts chemistry in the soil solution, manifested as a decrease in sodium bicarbonate content. Conclusions. Miscanthus as a crop has wide adaptation capabilities in relation to the marginal lands of the solonetz zone of West Siberia. Miscanthus plantings have a beneficial environment-forming effect on solonetz soils, due to the enrichment of soils with mineral nutrition elements and improvement of soil chemical properties.

Transition-metal-catalyzed enantioselective C-N cross-coupling.

Chiral amine scaffolds are among the most important building blocks in natural products, drug molecules, and functional materials, which have prompted chemists to focus more on their synthesis. Among the accomplishments in chiral amine synthesis, transition-metal-catalyzed enantioselective C-N cross-coupling is considered one of the most efficient protocols. This approach combines traditional C(sp2)-N cross-coupling methods (such as the Buchwald-Hartwig reaction Ullmann-type reaction, and Chan-Evans-Lam reaction), aryliodonium salt chemistry and radical chemistry, providing an attractive pathway to a wide range of structurally diverse chiral amines with high enantioselectivity. This review summarizes the established protocols and offers a comprehensive outlook on the promising enantioselective C-N cross-coupling reaction.

Revisiting the phosphonium salt chemistry for P-doped carbon synthesis: toward high phosphorus contents and beyond the phosphate environment.

The introduction of phosphorus and nitrogen atoms in carbo-catalysts is a common way to tune the electronic density, and thereby the reactivity, of the material, as well as to introduce surface reactive sites. Numerous environments are reported for the N atoms, but the P-doping chemistry is less explored and focuses on surface POx groups. A one-step synthesis of P/N-doped carbonaceous materials is presented here, using affordable and industrially available urea and tetrakis(hydroxymethyl)phosphonium chloride (THPC) as the N and P sources, respectively. In contrast to most of the synthetic pathways toward P-doped carbonaceous materials, the THPC precursor only displays P-C bonds along the carbon backbone. This resulted in unusual phosphorus environments for the materials obtained from direct thermal treatment of THPC-urea, presumably of type C-P-N according to 31P NMR and XPS. Alternatively, the in situ polymerization and calcination of the precursors were run in calcium chloride hydrate, used as a combined reaction medium and porogen agent. Following this salt-templating strategy led to particularly high phosphorus contents (up to 18 wt%), associated with porosities up to 600 m2 g-1. The so-formed P/N-doped porous materials were employed as metal-free catalysts for the mild oxidative dehydrogenation of N-heterocycles to N-heteroarenes at room temperature and in air.

Effect of Fission Products on Molten Salt Corrosion for Nuclear Reactor Applications

Molten halide salts are used in various technologically important applications like molten salt reactors and concentrated solar power. A major challenge of molten salts is their corrosivity towards structural materials. However, most of the complex interfacial phenomena related to molten salt corrosion are not well understood, primarily due to the complex impact of salt chemistry on structural material interface. Structural material corrosion is influenced by salt redox potential, fission product buildup, presence of impurities and moisture. Given the huge dependence of operations on salt chemistry, understanding the interactions between soluble fission products and structural alloys is of great importance. EuCl3 is one of the primary fission products and shown EuCl3 to cause accelerated corrosion of structural alloys in molten chloride salts. Given the more positive formal oxidation potential of Eu(III)/Eu(II) compared to nickel, iron, and chromium that are major components of the structural alloys, Eu(III) species act as a strong oxidant to cause the dissolution of these metals. This talk will highlight utilization of novel in situ optical spectroscopy technique to study time-dependent evolution of corrosion damage of metals in presence of EuCl3 as well as the EELS technique to identify changes in oxidation states of dissolved alloying elements.