Presence of Li Clusters in Molten LiCl-Li

Merwin, Augustus; Phillips, William; Williamson, Mark A.; Willit, James L.; Motsegood, Perry; Chidambaram, Dev

doi:10.1038/srep25435

Cited by 30 publications

(22 citation statements)

References 49 publications

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“…It is widely known that a “metal fog” (colloidal metal) could be formed around the deposited Me without mechanical stirring, if a suitable emulsifier is present 23–27 . Electrochemically deposited colloidal Me in molten salt has been considered to be particles formed by Me x molecular clusters 28–30 . Despite its importance, however, there is only limited knowledge about the behaviour of colloidal Me due to the difficulty of in-situ observation 31–37 .…”

Section: Introductionmentioning

confidence: 99%

Spontaneous colloidal metal network formation driven by molten salt electrolysis

Natsui

Sudo

Kaneko

et al. 2018

Sci Rep

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The molten salt-based direct reduction process for reactive solid metal outperforms traditional pyrometallurgical methods in energy efficiency. However, the simplity and rapidity of this process require a deeper understanding of the interfacial morphology in the vicinity of liquid metal deposited at the cathode. For the first time, here we report the time change of electrode surface on the sub-millisecond/micrometre scale in molten LiCl-CaCl2 at 823 K. When the potential was applied, liquid Li-Ca alloy droplets grew on the electrode, and the black colloidal metal moved on the electrode surface to form a network structure. The unit cell size of the network and the number density of droplets were found to depend on the applied potential. These results will provide important information about the microscale mixing action near the electrode, and accelerate the development of metallothermic reduction of oxides.

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Section: Introductionmentioning

confidence: 99%

Spontaneous colloidal metal network formation driven by molten salt electrolysis

Natsui

Sudo

Kaneko

et al. 2018

Sci Rep

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“…The electrode guides on the insulation cap were machined in line with an electrode mounting plate at the end of a motorized stage which helps make the experiments repeatable by ensuring electrodes are immersed in a consistent and perpendicular orientation. 17 A threeelectrode setup consisting of a tungsten plate working electrode, graphite counter and silver wire quasireference was employed for electrochemical reduction experiments. Cyclic voltammetry (CV) was conducted to identify a reducing potential for Sm 2+ formation.…”

Section: Spectroelectrochemical Apparatusmentioning

confidence: 99%

“…30 Therefore, Sm 0 will not be thermodynamically stable in the system and is likely to spontaneously reduce Li + and/or Na + (Na is the major impurity inn Li salts) impurities in solution as observed by our group earlier. 17,18 Figure 5 shows the formation and disappearance of divalent samarium Raman modes over the course of 60 minutes, in 10minute intervals, after the addition of an equimolar amount of samarium metal. The disappearance of divalent modes suggests the divalent samarium is indeed re-equilibrating into some other ionic form.…”

Section: Chemical Reductionmentioning

confidence: 99%

“…10 Our group designed and built an in situ Raman spectroscopy system to study molten salts and successfully employed it study the nature of Li in LiCl-Li 2 O. 17,18 The design reported in this manuscript is based off the previous design but with several improvements such as laser power and polarizability. Previous research conducted by our group, using the in situ Raman system reported here, has produced high quality Raman spectra from nitrate salts in open atmosphere.…”

Section: Introductionmentioning

confidence: 99%

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In situ Raman spectroscopy of samarium ions in molten LiCl-KCl eutectic

Singh¹,

Bruneau²,

Chidambaram³

2019

Preprint

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A fiber-based Raman spectroscopy system was commissioned in an inert atmosphere for in situ analysis of high temperature molten salts. Speciation of samarium chloride was studied in the LiCl-KCl eutectic system at 500 °C. Raman spectra indicated trivalent samarium forms an octahedral SmCl63- complex with two detectable vibration modes. Chemical reduction experiments were conducted to investigate the coordination of divalent samarium in the same eutectic salt. The resulting spectra are reported and discussed in terms of complex formation and behavior of divalent samarium ions. Trivalent samarium was electrochemically reduced in situ and Raman spectra obtained were compared with those resulting from chemical reduction experiments. The spectra suggest divalent samarium ions form in LiCl-KCl only temporarily and spontaneously disproportionate into a mixture of trivalent samarium ions and metallic samarium.

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“…116 Should Li clusters be miscible with molten LiCl, a well-defined solubility limit of Li in LiCl may not exist due to the dispersion mechanism of colloidal suspension in addition to physical dissolution. In this case, the quantity of Li that may be suspended or dispersed under a given set of conditions would be highly dependent upon experimental factors such as thermally induced mixing of the melt or mechanical agitation.…”

Section: -29mentioning

confidence: 99%

Review—Metallic Lithium and the Reduction of Actinide Oxides

Merwin

Williamson

Willit

et al. 2017

J. Electrochem. Soc.

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Extensive research and process development has been conducted on the electrolytic reduction of actinide oxides in molten LiCl-Li 2 O. It is now accepted that the reduction of these metal oxides occurs via two separate reduction mechanisms: direct electro-chemical reduction and mediated chemical reduction by metallic lithium. The deposition of metallic lithium at the cathode (mediated chemical reduction mechanism) during the process is known to be essential in order to achieve high process throughputs and reduction yields, and yet a knowledge gap exists regarding the nature of metallic lithium in this system. This review summarizes the formation of lithium during the process and its dispersion into the molten salt electrolyte. Previously reported aspects of the physical chemistry of the LiCl-Li 2 O-Li system are presented with a specific focus on the dispersion of Li in the solution. Finally, issues regarding the effect of the presence of lithium on the electrolytic reduction process are discussed. Evidence shows that electrochemically generated metallic lithium is likely a significant source of experimental uncertainty, low current efficiency and Li 2 O consumption in the oxide reduction process. The reduction of uranium, plutonium and minor actinide oxides to a metallic form is an important nuclear fuel cycle process.2-9 The ability of metallic lithium to reduce various uranium oxides, importantly UO 2 and U 3 O 8 , has been known for many years.10 A molten salt metalothermic reduction process employing metallic lithium (Li) as a reductant dissolved in molten LiCl was first developed by Argonne National Laboratory (ANL) to consolidate a variety of forms of actinide oxides for integration into a single electrometallurgical reprocessing system. 11-13 An electrolytic process, often referred to as electro-deoxidation or simply oxide reduction, was subsequently developed as a more controllable method of reducing metal oxides. A feasibility study conducted by Poa et al. demonstrated that oxides of uranium and plutonium could be reduced electrochemically in molten salts as long as the reduction potential of the metal oxide in question was more noble than the cation of the electrolyte.14,15 This approach was further developed by Gourishankar et al. to better understand processes chemistry and develop the electrolytic cell technology. 13,[16][17][18][19][20] Independent research conducted by Fray, Farthing, and Chen (FFC) applied the principles of electrochemical reduction in molten salt electrolytes to a variety of metal oxide reduction processes. 21,22 The FFC process has been the subject of several literature reviews.23-25 While these review articles address the processes associated with the reduction of nuclear fuel in LiCl, they focus on the electro-deoxidation phenomena and the CaCl 2 -CaO system. Additionally, the process engineering of the electrolytic reduction of nuclear fuel, and experience in incorporating oxide fuel into pyroprocessing, has been the focus of a recent review article. 26 The current review wi...

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Presence of Li Clusters in Molten LiCl-Li

Cited by 30 publications

References 49 publications

Spontaneous colloidal metal network formation driven by molten salt electrolysis

Spontaneous colloidal metal network formation driven by molten salt electrolysis

In situ Raman spectroscopy of samarium ions in molten LiCl-KCl eutectic

Review—Metallic Lithium and the Reduction of Actinide Oxides

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