bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elecrochemistry of Uranium and Plutonium in Ionic Liquids
Authors: Chlistunoff Jerzy , Boland Kevin Sean , Gaunt Andrew , Goff George Scott , Runde Wolfgang 
Published: February 2020

Actinides can exist in many oxidation states. The redox potentials for various oxidation states of actinides strongly depend on their electronic structures, but are also affected by the medium properties. The differences between the redox potentials of actinides, most notably uranium and plutonium, have been utilized in the traditional PUREX process (Plutonium Uranium Reduction EXtraction) developed during the 1947. PUREX is based on a nitric acid dissolution of used nuclear fuel followed by liquid-liquid extraction and utilizes hazardous chemicals such as concentrated nitric acid and volatile and hazardous organics like tributyl phosphate and dodecane or kerosene. In spite of the differences in redox chemistries of the actinides, electrochemical methods have never been applied for large scale used nuclear fuel processing. Molten salts (in particular halides) have been demonstrated to be better suited for actinide electrochemistry; however, the practical application of pyroprocessing is limited by the high temperatures and strongly corroding properties of molten salts. Ionic Liquids (ILs) are relatively new media that offer the benefits of molten salts, e.g., high ionic conductivity required for practical operations and wide electrochemical windows, but are also free of the molten salt shortcomings such as the high temperature and corroding properties. Their high ionic conductivity and low reactivity make them especially well-suited for electrochemical applications. While the high conductivity enables for electrochemical reactions at the high current densities required for practical operations, the low reactivity typically translates into a wide potential window, which allows access to electrochemical processes that cannot be accomplished in conventional media. Moreover, ILs offer a wide range of tunable physical properties, which could potentially be utilized not only in the electrochemical but also in numerous other separation techniques relevant to the nuclear industry, including solvent extraction, ion exchange, dissolution, crystallization, etc. The development of separation technologies for spent nuclear fuel in ILs could complement or replace current PUREX and/or high-temperature pyrochemical processing technologies.
The current state of understanding of the electrochemical behavior of actinides in ILs is far from satisfactory. As part of our multi-faceted approach to study the structural, thermodynamic, and kinetic behavior of actinides, we undertook electrochemical studies of uranium and plutonium in selected chloride and bistrifluorosulfonamide based-ILs in order to demonstrate the feasibility of using ILs for electrochemical actinide separations. In this presentation we will summarize our most recent results of those studies.
Development of Carbon Anodes for Use in Electrolytic Reduction of Uranium(IV) Oxide
Authors: Motsegood Perry N , Willit James L , Williamson Mark A. 
Published: February 2020

Recycling of used nuclear fuel using pyrochemical methods involves a series of molten salt processes performed at elevated temperatures and results in the separation of actinides from fission products. The first step in the pyrochemical treatment of light water reactor (LWR) oxide fuel is electrolytic reduction. This electrochemical operation converts used fuel oxides to metal before electrochemical separations can be performed by electrorefining. Conversion of oxides to metal is commonly performed in molten LiCl-Li2O at 650℃. Electrolytic reduction of UO2, the primary component of used nuclear fuel, has been successfully demonstrated at the kilogram-scale using platinum anodes1-2, but progression toward engineering scale presents different anode material requirements.
Carbon, specifically graphite, is commonly used for ore refining in commercial molten salt processes because it is cost effective, readily available, and easily fabricated to meet scale-up requirements. Use of carbon anodes in LiCl-Li2O results in different salt chemistries, with respect to using platinum or other oxygen evolving electrode materials. In particular, the evolved gaseous byproduct of carbon anodes is CO and CO2, which can react with Li2O to form Li2CO3. If the carbonate concentration is allowed to increase, the desired reaction, namely the transport of oxide from the cathode to the anode via Li2O, is replaced by the undesirable transport of carbon from the anode to the cathode via Li2CO3.

This report will discuss use of carbon as an anode material for the electrolytic reduction of UO2 to uranium metal in molten LiCl-Li2O at 650℃. A discussion of the salt chemistry, minimizing Li2CO3 formation, method developments, cell operation, and reduction efficiency will be presented.

References:

Laszlo Redey and Karthick Gourishankar, “Direct Electrochemical Reduction of Metal-Oxides” US Patent US6540902 B1, Granted April 1, 2003

S. D. Herrmann, S. X. Li, M. F. Simpson and S. Phongikaroon, Separation Science and Technology
2006, 41, 1965-1983.

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The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.
(Invited) Designer Ionic Liquids for Improved Magnesium Anode Behavior
Authors: Buttry Daniel A. , Watkins Tylan S , Kumar Ashok 
Published: February 2020

Our group has been involved in studies of the complexation and speciation of Mg2+ in ionic liquids as a means to understand the influence of coordination environment on Mg anode electrochemical behavior.1 In this presentation we will focus on the complexation of Mg2+ by bis(trifluoromethylsulfonyl)imide ionic anion (TFSI-), borohydride anion, glyme-based (i.e. PEGylated) solvents and chelating ionic liquids bearing polyethylene glycol-like chelating groups, and on the influence of such complexation on the reversibility of Mg electrodeposition/dissolution.1,2 Complexation is predominantly studied by Raman spectroscopy, which allows facile differentiation of complexed and free species. We show that the lessons learned from such studies of Mg2+ complexation allow the design of new chelating ionic liquids that show markedly improved Mg2+/Mg0 electrochemical behavior compared to the parent TFSI-based ionic liquids. Specifically, we describe reasonable coulombic efficiency (ca. 90%) and current densities (>1 mA/cm2) that are achievable through judicious choice of the complexation environment and other chemical features of the electrolyte system.
We also discuss more generally the factors that act to suppress facile Mg electrodeposition/dissolution. We provide experimental verification of some of the means by which these various factors influence both chemical and electrochemical reversibility of Mg anode behavior.
These results represent the first demonstration of reversible electrochemical deposition/dissolution of Mg in an ionic liquid specifically designed with this task in mind.

Acknowledgment: We acknowledge support from the Army Research Office grant number W911NF-11-1-0432.
References:

“Determination of Mg2+ Speciation in a TFSI--Based Ionic Liquid With and Without Chelating Ethers Using Raman Spectroscopy”, Watkins, T., Buttry, D. A.; J. Phys. Chem. B, 2015, 119(23), 7003-7014. (DOI: 10.1021/acs.jpcb.5b00339)

“Designer Ionic Liquids for Reversible Electrochemical Deposition/Dissolution of Magnesium”, Watkins, T.; Kumar, A.; Buttry, D.A.; J. Am. Chem. Soc.,
2016, 138(2), 641-650 (DOI: 10.1021/jacs.5b11031)
Availability Evaluation of SiC Anode in Chloride Molten Salt Electrolysis
Authors: Takahashi Yoshihiro , Takenaka Toshihide 
Published: February 2020

INTRODUCTION
Carbon or graphite is commonly used to anode material in molten salt electrolysis because of their stability and reasonable price. However, they are consumed with CO or CO2generation by electrochemical reaction with oxide ion, and the consumption is undesirable in electrolysis in chloride melt. In this study, the anodic behavior of carbide was investigated to develop the inert anode material.
EXPERIMENTAL
A eutectic mixture of LiCl-KCl (41:59 in mole) with Li2O was used as an electrolytic bath. Anode was a silicon carbide (SiC) rod, and a graphite rod was also used for comparison. Cathode was an Al plate, and reference electrode was a Ag/Ag+ couple, and its potential was calibrated with a Li/Li+couple. The electrodes were inserted into the molten salt at 723 K in an Ar atmosphere. Reactions were studied by cyclic voltammetry and potentiostatic electrolysis. The generated gas by potentiostatic electrolysis was analyzed by gas chromatography. After the electrolysis, the specimen was analyzed by SEM-EDX and XRD.
RESULTS and DISCUSSION
Fig.1 shows typical cyclic voltammograms at the SiC and graphite anode. At the graphite electrode, oxidation current increased around 2.65V (vs. Li/Li+, the same hereinafter) and 3.5V, and arose suddenly above 3.8V. At the SiC electrode, oxidation current was increased around 2.65V, 3.2V, 3.5V and arose suddenly above 4.0V. Bubble formation was seen around 3.5V and above 3.8V (4.0V) at both electrodes. The generated gas at 3.5V was identified as CO2
by gas chromatograph, and it was considered that the generated gas above 3.8V (4.0V) was Cl2. Gas was not generated around 3.2V at the SiC electrode, and SiO2was detected on by XRD after potentiostatic electrolysis at 3.2V.
The mass of the SiC electrode increased by potentiostatic electrolysis at 3.2V for 4h and 6h, while it decreased by the electrolysis for 8h, as shown in Table 1. The mass didn’t change by potentiostatic electrolysis at 3.5V for 4h, but it decreased by the electrolysis for 6h and 8h. The mass of the SiC electrode tended to decreased with the electrolysis time at both potentials. The mass decreased by the electrolysis at 4.5V even for 4h.
The O content after the potentiostatic electrolysis at higer potential was smaller than that at lower potential as shown in Table 2. The surface of the SiC electrode after the electrolysis was uneven and a dense SiO2layer was not found at the cross-section.
From the result mentioned above, SiO2 formation occurred below 3.2V at SiC, and CO2 was generated around 3.5V. This result indicate that SiO2 formation precedes CO2 generation at SiC, but that the formed SiO2 cannot prevent the consumption of SiC by CO2 generation. The formed SiO2 layer was still uneven and partially peered out during electrolysis. The formation of a dense and coherent SiO2 layer should be necessary to prevent the consumption of SiC by electrolysis in molten chloride.

Figure 1
Currentless Deposition of Niobium-Based Protective Coatings for Application in Molten Salts
Authors: Abramov Aleksandr V. , Polovov Ilya B. , Volkovich Vladimir A. , Rebrin Oleg I. 
Published: February 2020

Molten salts, particularly alkali halides, can be used for developing new methods of rare and refractory metals production and pyrochemical reprocessing spent nuclear fuels. Molten salt nuclear reactor now again attracts attention as one of the prospective power generating systems. Wide scale application of fused salts in various areas of technology is hampered by the problem of finding suitable corrosion-resistant materials. Corrosion of metals in molten salts is electrochemical in nature, and therefore the most suitable constructive materials for these media are electropositive refractory metals, for example, niobium. High cost of these materials and the difficulties associated with the mechanical processing and welding limit their application. A way to overcome this problem is forming a protective layer of a refractory metal on the base material. In the present work a novel method of forming niobium-based coatings by currentless deposition in molten salts is proposed.
Nicrofer 6020, Nicrofer 6616, Hasteloy N, and KhN65MVU nickel based alloys and metallic nickel were chosen as the base materials for the present investigation. Corrosion tests were carried out in NaCl–KCl–NbCln (n=3.5 or 5 wt. % niobium) and NaCl–KCl–UCl3 (1 wt. % uranium) melts at 750 oC. Duration of the corrosion tests was 30 h.
Contacting nickel based alloys with NaCl–KCl–NbCln melt leads to increase of the sample mass due to the formation of an alloy between nickel (the base constituent of the studied alloys) and niobium on the sample surface, Figure. Nickel-niobium alloy is formed as a result of disproportionation of niobium (III) ions, 4Nb3+ + 3Nialloy → Ni3Nb + 3Nb4+. Nb(IV) ions produced in the same reaction can be reduced to Nb(III) by niobium metal placed in the melt. Formation of a Ni-Nb alloy layer on the sample surface decreases the rate of the base alloy corrosion.
This Ni-Nb phase forms a continuous layer on the sample’s surface and, therefore, this phase can protect the studied alloy from further corrosion. Such protection would be very useful for construction materials used for niobium electrorefining in molten chlorides; especially since currently the problem of finding suitable materials is one of the limiting factors in producing high-purity niobium.
The samples of Nicrofer 6616 and 6020 alloys with the formed niobium coatings were tested in NaCl–KCl–UCl3 (around 1 wt.% U) melts (30 h exposure at 750 ºС). Here the weight of the samples covered with Ni3Nb phase decreased and the corrosion rates were comparable with those obtained earlier for uncoated samples in uranium-containing melts.
Figure. Microstructure of Hastelloy N (a), KhN65MVU (b), Nicrofer 6616 (с) and Nicrofer 6020 (d) alloy samples after 30 h contact with NaCl–KCl–NbCln melts (n=3.5, 5 wt. % Nb) at 750 ºС.

Figure 1
On the Formation of Clusters of Li8 in Molten Solutions of LiCl-Li
Authors: Merwin Augustus , Phillips William , Chidambaram Dev 
Published: February 2020

Numerous base metals can be obtained via electrolytic reduction of their respective oxides in molten LiCl-Li2O electrolytes. In these processes, often times, Li+ is co-reduced to metallic Li. The formation of Li0 is undesirable and leads to a loss of current efficiency and therefore is of significant interest. In spite of its importance, molten mixtures of LiCl and Li are still poorly understood and previous research has demonstrated a variety of phenomena that are seemingly unexplainable. We have custom built a unique setup to conduct in-situ Raman spectroscopy of such molten mixtures. In this work, we show that a Raman active phase forms in the fused salt when Li is electrochemically reduced from Li2O in LiCl. The spectrum was comprised of three fundamental features at 285.5, 302.8, and 318.2 cm-1, with overtones of decreasing intensity at approximately integer multiples of these Raman shifts as Shown in Figure 1. This spectrum was found to be consistent with previously-reported characteristic spectrum of the lithium cluster Li8. The presence of a colloidal suspension of lithium clusters in the molten salt is hypothesized to be the reason behind anomalous physical behavior of LiCl-Li solutions.
Acknowledgements: This work was performed under the auspices of the Department of Energy (DOE) through grant DE-NE0008262, and the US Nuclear Regulatory Commission (NRC) under contracts NRCHQ-11-G-38-0039, NRC-38-10-949 and NRC-HQ-13-G-38-0027. Mr. Kenny Osborne serves as the program manager for the DOE awards and Ms. Nancy Hebron-Isreal serves as the grants program officer for the NRC awards.

Figure 1
Pd Nanoparticle Formation during Constant Potential Electrodepositions in Ionic Liquids
Authors: Shrestha Sujan , Nagib Miyan , Biddinger Elizabeth J 
Published: February 2020

Electrodepositions in ionic liquids (ILs) allow for opportunities to improve deposited morphologies, access redox potentials that cannot be achieved in aqueous baths, and utilize less hazardous bath compositions. The driver to utilize ILs for Pd electrodeposition is to minimize hydrogen embrittlement challenges commonly associated with Pd electrodeposition in aqueous electrolytes. Generally, the resulting Pd deposits in ILs are thin films, loosely adhered fine powders or dendritic structures, depending upon the IL selected and the electrochemical parameters used(1, 2). Recently, it has also been shown that electroreduction of Pd in ILs can result in nanoparticles being formed in solution, rather than on an substrate electrode when high overpotentials are used(3).
Previously, we showed Pd nanosphere formation can be controlled through potentiostatic pulse deposition in 1-butyl, 3-methylimidazolium chloride [Bmim][Cl] onto Ni electrode substrates(4). The nanosphere size was found to be a function of cycle time. In contrast, using 1-buty, 1-methylpyrrolidinum dicyanamide [Bmpyrr][DCA] under constant potential conditions, thin film Pd layers on nickel electrode substrates were obtained(5).
We will present how, upon further investigation, these Pd “thin films” formed from constant potential deposition in [Bmpyrr][DCA] are actually agglomerates of nanoparticles that can be scraped off the Ni substrate and dispersed in solution in an unagglomerated state. These nanoparticles have an average size of 6.3 ± 1.6 nm when deposited at -2.3V vs. Fc/Fc+. Further investigation into the conditions for electrodeposition in ILs where it was thought that thin films were formed will also be discussed to better understand if the resulting deposits were truly thin films and not nanoparticle agglomerations.

References

1. M. Jayakumar, K. A. Venkatesan and T. G. Srinivasan, Electrochimica Acta, 52, 7121 (2007).
2. I. W. Sun and C. L. Hussey, J. Electroanal. Chem., 274, 325 (1989).
3. Y. Katayama, Y. Oshino, N. Ichihashi, N. Tachikawa, K. Yoshii and K. Toshima, Electrochimica Acta, 183, 37 (2015).
4. S. Shrestha, M. Nagib and E. J. Biddinger, Journal of The Electrochemical Society, 163, D74 (2016).
5. S. Shrestha and E. J. Biddinger, Electrochimica Acta, 174, 254 (2015).
Electrochemical Deposition of Aluminum and Aluminum-Manganese Alloys in Ionic Liquids
Authors: Ispas Adriana , Vlaic Codruta Aurelia , Camargo Magali Karina , Bund Andreas 
Published: February 2020

Aluminum and aluminum-manganese alloys were electrodeposited on low carbon steel substrates from 1-ethyl-3-methyl imidazolium chloride with AlCl3 and MnCl2 salts. We could show that the applied current density influenced drastically the morphology of the deposits. More uniform and smooth deposits were obtained at current densities above 6 mA/cm², while at lower current densities the morphology of the deposits was in the form of plates, which grown parallel to the substrate. The morphology and the composition of the deposited films were characterized by SEM and EDX. X-Ray diffraction (XRD) measurements showed that the Al and some of the AlMn layers have a crystalline structure. The thicknesses of the deposits, and in the case of the AlMn their composition, were estimated from X-Ray Fluorescence measurements.
The corrosion behavior of the layers having different thicknesses (up to 30 µm) was studied by electrochemical impedance spectroscopy and linear polarization in 3.5% NaCl solution. We could show that the AlMn coatings had superior corrosion resistance compared to the pure Al layers.
Combining Mechanical Tension with Natural-Fiber-Welding Treatments of Cellulose Yarns
Authors: Fahey Patrick J , Fox Eric T , Durkin David P. , De Long Hugh C , Trulove Paul C 
Published: February 2020

Natural-fiber welding (NFW) is an ionic-liquid based treatment method that partially dissolves a fibrous structure’s polymer chains to allow subsequent polymer-chain entanglement between adjacent fibers. NFW treatments can beneficially alter the tensile properties of treated fibrous structures through this polymer entanglement [1]. Up until now fibrous-structure samples were held in place during NFW treatments by applied force to ensure contact with heated platens or to prevent deformation and warping. This new study, however, purposefully applies force during the NFW treatments to evaluate the effect of applied force upon the resulting material properties of the treated fibrous structure. Understanding what additional effects tension has upon NFW treatments is vital to evaluating not just how to best control warping of experimental samples, but also how to design scaled-up NFW treatment processes that rely upon applied tension for pulling continuous feeds of yarn and cloth through equipment.
To test the effect of mechanical forces during NFW treatment, tension was applied to natural fiber yarns in their axial dimension. The three main variables evaluated were (1) the magnitude of tensile force, (2) the time at which this tensile force began during the course of the NFW treatment, and (3) the NFW treatment parameters previously known to be vital like temperature, time duration, and ratio of 1-ethyl-3-methylimidazolium acetate to yarn. In this presentation we will present results of our investigations of these variables using tensile testing, infrared spectroscopy, con-focal fluorescence microscopy, and scanning electron microscopy.

[1]
L. M. Haverhals, W. M. Reichert, H. C. De Long and P. C. Trulove, "Natural Fiber Welding," Mcromolecular Materials and Engineering, 295, 425-430 (2010).
Potential Dependent IR/Visible Double Resonance Sum Frequency Generation Spectroscopy to Probe Electronic Structure at Electrochemical Interfaces
Authors: Noguchi Hidenori , Yang Shuo , Uosaki Kohei 
Published: February 2020

To understand the mechanism and improve the efficiency of processes at solid surfaces both in gas phase such as heterogeneous catalytic reactions, and in liquid phase such as electrochemical reactions, it is essential to have in situ, real time information of geometric structure and electronic structure of the solid/gas or solid/liquid interface, and molecular structures of reactant, product, intermediate, and solvent at the interface. While many techniques to obtain such information are available for solid/gas interfaces, most of them are not applicable to solid/liquid interfaces because of the presence of liquid, mostly water, which interacts strongly with probe such as electron.
Double resonance sum frequency generation (DR-SFG) spectroscopy, which is a highly surface-sensitive nonlinear optical technique with the tunable frequencies of both incident fundamental lights, i.e., visible and IR, can provide information of surface molecular and electronic structures, which is not obtained by traditional surface vibrational technique. Here, we employed DR-SFG technique to probe potential-dependent electronic structure of CO/Pt interface in acid electrolyte solution. SFG signal due to C-O stretching was observed and was dependent on frequency of visible light as a result of the energetic coupling of electronic transition with the input visible photon and/or output SF photon, i.e., double resonance effect. Furthermore, resonant visible energy linearly depended on electrode potentials. Thus, the electronic resonance could be explained by the transition from Fermi energy, Ef, of Pt to the unoccupied 5anti-bonding state of CO.
The present work showed that SFG spectroscopy can probe not only the molecular structure but also the electronic structure of electrochemical interface, which is difficult to be determined by other methods.