High Temperature Electrochemistry III: Materials Electrochemistry II
Sponsored by: TMS Extraction and Processing Division, TMS: Pyrometallurgy Committee, TMS: Hydrometallurgy and Electrometallurgy Committee
Program Organizers: Prabhat Tripathy, Idaho National Laboratory; Guy Fredrickson, Idaho National Lab; Boyd Davis, Kingston Process Metallurgy Inc

Thursday 8:30 AM
March 2, 2017
Room: 16A
Location: San Diego Convention Ctr

Session Chair: Guy Fredrickson, Idaho National Lab; Prabhat Tripathy, Idaho National Laboratory

8:30 AM  
Electrochemical and Thermodynamic Properties of Gadolinium Chloride in LiCl-KCl Eutectic Salt: Prashant Bagri1; Michael Simpson1; 1University of Utah
    Gadolinium is one of the many constituents of spent nuclear fuel. The behavior of gadolinium in molten eutectic LiCl-KCl needs understanding for pyrochemical processing operations like electrochemical rare earth drawdown and electrorefining. For this paper, the thermodynamic and electrochemical properties of GdCl3 were studied as a function of concentration and the influence of other fission products like cesium were examined and will be reported. Using a two electrode electrochemical cell, the apparent potential and activity coefficient of GdCl3 were studied as a function of concentration of GdCl3 and the influence of cesium on these properties will be reported. Further, relevant phase diagram data were collected and will be presented. The liquidus temperatures for the xGdCl3-CsCl-LiCl-KCl mixtures were determined using a TGA/DSC. Heat capacities (Cp) of these mixtures were also determined using TGA/DSC as a function of concentration of GdCl3, again examining the influence of CsCl on these properties.

9:00 AM  
Electrochemical Synthesis of TaC in Molten Salt: Xin Li1; Xingli Zou1; Shangshu Li1; Kai Zheng1; Yinshuai Wang1; Qian Xu1; Xionggang Lu1; 1Shanghai University
     TaC has been successfully synthesized from Ta2O5/C through electrodeoxidation process in molten CaCl2 at 1000 C and 4.0 V. The electrolysis process utilized a pressed porous Ta2O5/C pellet mixture as the cathode, and a solid-oxygen-ion-conducting membrane (SOM) tube filled with carbon-saturated liquid tin/copper was served as the anode to control the electrodeoxidation process. The obtained cathodic product was analyzed by using X-ray diffraction (XRD) and scanning election microscopy (SEM). The result shows that the possible synthesis pathway can be summarized as the following: (1) CaαTa2βO(α+5β) compounds were firstly formed due to the compounding process (αCaO + βTa2O5 = CaαTa2βO(α+5β)), (2) the generated intermediate compounds would be reduced to Ta through electroreduction process (CaαTa2βO(α+5β) + 10βe- = 2βTa + 5βO2-+ αCaO), (3) the generated Ta reacted with C to form TaC carbide via carbonization process (Ta + C = TaC).Keywords: TaC; electrodeoxidation; molten CaCl2; SOM

9:30 AM  
Thermochemical Properties of Barium-Bismuth Alloys Determined by Emf Measurements: Timothy Lichtenstein1; Nathan Smith1; Hojong Kim1; 1Penn State University
    We present on the thermochemical properties of barium-bismuth alloys determined by emf measurements at temperatures between 450oC and 800oC using binary CaF2-BaF2 (97-3 mol%) electrolyte. Liquid bismuth electrodes exhibit unique electrochemical properties compared to conventional solid-state electrodes due to strong chemical interactions with alkali/alkaline-earth elements in the liquid state. These liquid metal electrodes have been demonstrated to change the deposition potentials of alkali/alkaline-earth elements, to have a high coulombic efficiencies (>98%), and to selectively deposit alkali/alkaline-earth metals. With alkali/alkaline-earth elements making up a substantial portion of the heat density of nuclear waste, we are looking at using liquid metals to separate barium, strontium and cesium out of chloride salts used to process spent nuclear fuels. In order to understand the unique deposition behavior of these alkali/alkaline-earth elements into liquid bismuth, it is necessary to determine the thermochemical properties of these alloys.

10:00 AM Break

10:20 AM  Cancelled
Next-generation Molten Oxide Energy Materials R&D: Valery Belousov1; 1Baikov IMET RAS
    Because of their unique electrochemical properties, metal oxides offer potential opportunities for exploitation in the energy sector. Development of both solid and liquid state ionics for the energy conversion purpose is necessary to address the twin challenges: production of cleaner and sustainable energy sources. Besides, oxide based high temperature electrochemical devices can play a crucial role in reducing the carbon foot print. Current targets of cost and durability necessitate solid oxide fuel cells (SOFCs) to operate in the intermediate temperature range. To achieve these targets, oxygen ionic conductivities of the SOFC ceramic oxide electrolytes need to be increased. The presentation will discuss recent advances made in the development of alterative molten oxides, with relatively higher oxygen ion conductivities, for application in two specific areas, molten oxide fuel cells (MOFC) for electric power generation and molten oxide membranes (MOM) for oxygen separation from air.

10:50 AM  
Effects of Oxide Precursor Preparation Parameters on the Electrochemical Reduction of Tantalum Pentoxide in Calcium Chloride Melt: Maureen Chorney1; Bridger Hurley1; Prabhat Tripathy2; Jerome Downey1; 1Montana Tech of the University of Montana; 2Idaho National Laboratory
    Successful electrochemical reduction of a metal oxide to its constituent metal depends upon two broad unit operations: (i) preparation of the oxide precursor with ideal morphological features and (ii) electrochemical reduction under optimum process parameters. The critical parameters that affect mechanical strength and open porosity of the precursor are oxide particle size; green pellet preparation; and sintering time, temperature, and atmosphere. A judicious combination of these process parameters will produce an ideal precursor for achieving complete reduction. Uniaxial pressing was utilized to prepare 13 mm diameter cylindrical pellets, which were sintered in either oxidizing (air) or reducing atmospheres. Sintered pellets were characterized by XRD, SEM-EDS, and porosity measurement techniques. Electrochemical reduction experiments were performed with a molten calcium chloride electrolyte in a cell with a three electrode configuration. Transient electrochemical techniques were employed to assess the effects of the precursor parameters on the reducibility of the sintered oxide specimens.