High Temperature Electrochemistry V: Session III
Sponsored by: TMS Extraction and Processing Division, TMS: Hydrometallurgy and Electrometallurgy Committee
Program Organizers: Prabhat Tripathy, Batelle Energy Alliance (Idaho National Laboratory); Guy Fredrickson, Idaho National Laboratory
Tuesday 8:00 AM
March 21, 2023
Room: 28B
Location: SDCC
Session Chair: Prabhat Tripathy, Batelle Energy Alliance (Idaho National Laboratory)
8:00 AM Introductory Comments
8:05 AM Invited
The Impact of Moisture on the Electrochemical Behavior of Molten Calcium Chloride: Marah Fuller1; Devin Rappleye1; 1Brigham Young University
The presence of moisture in molten salts impacts their electrochemical and corrosion behavior. However, systematic studies on the effect of moisture on the electrochemical behavior of molten salts using electroanalytical techniques are lacking. This work seeks to provide an analysis of moisture within molten calcium chloride through various electrochemical methods. Cyclic voltammetry, square wave voltammetry, and chronoamperometry are performed and their associated relations are applied to characterize the behavior of hydrogen ions in molten calcium chloride. Also, Karl Fischer titration and electrochemical signals are also investigated as a potential ex-situ and in-situ methods, respectively, to quantify the moisture content of various samples from pure, molten CaCl2 containing differing amounts of moisture.
8:45 AM
Electrochemical Reduction of Nd2O3+Fe2O3 Mixed Oxide Precursors in Calcium Chloride Melt: Kunal Mondal1; Prabhat Tripathy1; 1Idaho National Laboratory
Alloys of transition metals and rare earth elements are widely used as magnet materials in many industries including the clean energy sector. Currently, these magnets are prepared by a mixing-cum-melting technique. Efforts are currently underway to develop innovative ways to cut down the overall manufacturing costs of these magnets. Two of these efforts include preparation of these magnets by an electrochemical technique directly from their mixed oxide precursors and recycling of spent magnets. In the present research, an attempt was made to fabricate the neodymium iron (NdFe) master alloy directly from the mixed oxide precursors (Nd2O3 and Fe2O3 respectively) by cathodic polarization of the sintered precursors in a pool of molten calcium chloride at a temperature of 800oC. The presentation will discuss detailed experimental approaches pertaining to the fabrication of the oxide precursors and their subsequent electrochemical polarization to the alloy phase.
9:05 AM
Oxide Ion Ceramic Sensor in Molten CaCl2 for Real Time Monitoring of the Direct Oxide Reduction Process: Olivia Dale1; Forest Felling1; Michael Simpson1; 1University of Utah
The direct oxide reduction (DOR) process is used to reduce actinide oxides into metals. Molten CaCl2 is commonly used as the electrolyte for this reaction. As the DOR reaction proceeds, CaO will accumulate in the salt and must be measured in real-time to know when the reaction has gone to completion. Open circuit potential (OCP) was tested in this study between tungsten working electrodes and Ni/NiO/MgO reference electrodes. As a solid piece of CaO slowly dissolved in the salt over several hours, the OCP was measured and steadily decreased from -0.25 V to a minimum plateau of -0.69 V. CaO concentrations were separately measured via sampling and acid-base titration. A plot of OCP versus concentration of CaO fits the Nernst Equation at the higher end of the CaO concentration range. Scanning electron microscopy showed that magnesia was stable in the salt system with little degradation to the membrane.
9:25 AM
The Demonstration and Optimization of Thin-cell Electrochemical Measurements in Molten LiCl-KCl Eutectic: Cameron Vann1; Tyler Williams1; Devin Rappleye1; 1Brigham Young University
While solvation limits low temperature electrochemistry to primarily dilute samples, molten salt electrochemistry has no such limitations. For processes such as monitoring an electrorefiner or molten salt reactor, sensors that operate in highly concentrated regimes need to be developed. To this end, thin-cell apparatuses and techniques have been developed for use in molten salts. These thin-cell sensors can make concentration measurements of dilute and concentrated samples with short measurement times. Even chronocoulometric measurements have low latency because thin-cells isolate a few µL from the solution for analysis. The accuracy of these sensors has been tested in concentrations from 1 to 50 wt%.