Sponsored by: LMD Reactive Metals Committee
Co-sponsored by: Canadian Institute of Mining, Metallurgy & Petroleum, Montreal, Canada; The Japan Institute of Metals, Sendai, Japan; Mining & Materials Processing Institute of Japan, Tokyo, Japan; Society for Mining, Metallurgy & Exploration, Littleton, CO
Program Organizers: B. Mishra, Department of Metallurgical & Materials, Engineering., Colorado School of Mines, Golden, CO 80401; G.J. Kipouros, Department of Mining and Metallurgical Engineering, Technical University of Nova Scotia, Halifax, Nova Scotia, Canada B3J 2X4; R.G. Reddy, Department of Chemical and Metallurgical Engineering, University of Nevada, Reno, NV 89557
Co-organizers: W.A. Averill, Rocky Flats, Inc., Golden; R.G. Bautista, University of Nevada - Reno, Reno; M.C. Bronson, Lawrence Livermore Natl. Lab., Livermore; J.A. Sommers, Teledyne Wah Chang Albany, Albany. C.B. Wilson, The Dow Chemical Company, Freeport
Tuesday, PM Room: B9
February 6, 1996 Location: Anaheim Convention Center
Session Chairperson: Dr. R.G. Reddy, Department of Chemical and Metallurgical Engineering, MS 170, University of Nevada, Reno, NV 89557; Dr. D.R. Sadoway, Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 8-109, Cambridge, MA 02139
A NEW ELECTROLYTIC MAGNESIUM PRODUCTION PROCESS: R.A. Sharma, Physical Chemistry Dept., General Motors NAO R&D Center, 30500 Mound Road, Box 9055, Warren, MI 48090-9055
Existing magnesium choride electrolysis and thermal magnesium oxide reduction processes for producing magnesium are described and their limitations are pointed out. There theoretical background of a patented, new process is outlined. In this process, magnesium oxide is dissolved ina rare earth chloride containing electrolyte and electrolyzed to produce magnesium and oxygen like that of alumina in the Hall-Heroult process. It is also shown that the efficiency of the existing magnesium chloride electrolysis process should be improved greatly by adding a rare earth chloride. In both cases, magnesium produced is expected to be free from the detrimental iron, nickel, copper and boron impurities.
INVESTIGATION OF THE SYSTEM Mg-Nd-O-Cl: J.E.Vindstad, H. Mediaas, T. Ostvold: Institute of Inorganic Chemistry, The Norwegian Institute of Technology, N-7034, Trondheim, Norway; G.J. Kipouros, Department of Mining & Metallurgical Engineering, Technical University of Nova Scotia, Halifax, Nova Scotia, Canada B3J 2X4; O. Tkatcheva, High Temp. Electrohemistry Institute, Russian Academy of Sciences, 620219 Ekuterinburg, Russia
The binary phase diagram NdCl3-NdOCl has been measured by thermal analysis (chloride liquidus) and oxide solubility measurements (oxychloride liquidus). the melting point of NdCl3 was determined to be 759+/-1[[ring]]C, in good agreement with the value of 759[[ring]]C cited by Knacke, Kubaschewski, and Hesselmann.1 The eutectic temperature was determined as 739+/-1[[ring]]C. In the pseudo-binary system MgCl2-NdOCl, liquidus temperatures have been measured at up to 15.7 mole % NdOCl. Melt samples have been withdrawn at 850, 800, and 730[[ring]]C, and analyzed for oxide content (Leco TC-436) and Mg/Nd ratio (ICP). The results indicate that a ternary oxygen-containing solid compound precipitates upon addition of NdOCl(s). A stoichiometric equilibrium constant for the equilibrium: MgCl2 (l) + NdOCl (1)->MgO (s) + NdCl3 (1) has been calculated from the melt compositions at the different temperatures.
SOLUBILITY OF MgO IN MgCl2-NaCl-NaF MELTS: H. Mediaas, J.E. Vindstad, T. Ostvold, Institute of Inorganic Chemistry, The Norwegian Institute of Technology, N-7034, Trondheim, Norway
The solubility of MgO in MgCl2-NaCl-NaF melts have been measured for melts with constant and varying concentration of Mg2+ with addition of NaF. The fluoride-chloride melt samples have been analyzed by Leco TC-436 for total oxide content, and the different complexes have been quantitatively separated. The oxide content in the binary melt (MgCl2-NaCl) has also been analyzed by Iodoetric titration. The increase is smaller when NaF is added to a binary MgCl2-NaCl melt, compared to when MgCl2 is added together with NaF to keep the Mg2+ concentration constant. It seems to be possible to distinguish between two different oxide containing complexes in the ternary MgCl2-NaCl-NaF melt. The fluoride-containing complex oxidizes carbon at higher temperatures than the "MgOCl" complex. An introduction of 1.7 mole % NaF in industrial electrolytes does not seem to have any effect on the oxide solubility.
3:15 pm BREAK
ANODIC OVERVOLTAGE ON GRAPHITE IN Li2CO3-LiF-CaF2 MELTS: P.T. Velu, R.G. Reddy: Department of Chemical and Metallurgical Engineering, MS 170, University of Nevada, Reno, NV 89557
The anodic overvoltage on graphite anode during electrolysis of Li2CO3 in LiF-CaF3 melts at 1093 K was measured. A steady state current-voltage metod was used. The experimental results plotted with anodic overvoltage as a function of log current density, showed a straight line relationship given as [[alpha]]s [[eta]]= 4.17 + 1.38 log i. A two electron controlled charge transfer reaction between the complex oxyfluoride and graphite anode is proposed. The limiting current density in the melt is determined to be 0.011 A/cm2.
AN IN-BATH LIQUIDUS TEMPERATURE MEASUREMENT FOR MOLTEN SALTS AND SLAGS: E.J. Grimsey, N. Li, X.Y. Yan, Western Australian School of Mines, P.O. Box 597, Kalgoorlie WA, Australia 6430; A. Warczok, T.A. Utigard, University of Toronto, Toronto, Ontario, Canada M5S1A4
A technique is being developed to provide a rapid liquidus measurement for salts and especially metallurgical slags. A copper or nickel cylinder is immersed into a molten bath and a computer based data-logging system is used to record the heating profile of a type K thermocouple centered within the cylinder. The heat transfer is affected initially by the presence of a thin crust on the cylinder surface which freezes from the bath. When the crust melts, the rate of heating shows a subtle increase. Numerical differentiation is used to detect the on-set of this increase so as to provide an indication of the liquidus temperature of the melt. This paper outlines the technique and its application to a number of molten salts and slags. Factors which affect the sensitivity of the measurement are discussed also.
CaO INSULATOR COATINGS AND SELF-HEALING OF DEFECTS ON V-ALLOYS IN LIQUID LITHIUM AND LITHIUM-CALCIUM: J.-H. Park, T.F. Kassner: Energy Technology Division, Argonne National Laboratory, 9700 S Cass Avenue, IL 60439
Electrically insulating and corrosion-resistant coatings are required at the
liquid metal/structural interface in fusion first-wall/blanket applications.
The electrical resistance of CaO coatings produced on V-5%Cr-5%Ti by exposure
of the alloy to liquid lithium that contained 0.5-85 wt.% dissolved calcium was
measured as a function of time and temperatures between 250 and 600[[ring]]C.
The solute element, Ca in liquid Li, reacted with the alloy substrate at
400-420[[ring]]C to produce a CaO coating. Resistance of the coating layer
measured in-situ in liquid Li was ~106 [[Omega]] at
400[[ring]]C. Thermal cycling between 300 and 700[[ring]]C changed the coating
layer resistance, which followed insulator behavior. These results suggest that
thin homogeneous coatings can be produced on variously shaped surfaces by
controlling the exposure time, temperature and composition of the liquid metal.
The technique can be applied to various shapes (e.g. inside/outside of tubes,
complex geometrical shapes) because the coating is formed by liquid-phase
reaction. Examination of the specimens after cooling to room temperature
revealed no spallation, but homogeneous crazing cracks were present in the CaO
coating. Additional tests to investigate the insitu self-healing behavior of
the cracks indicated that rapid healing occurred at 360[[ring]]C. This work
has been supported by the US Department of Energy, Office of Fusion Energy
Research, under contract W-31-109-Eng-38.
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