14 research outputs found
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X-ray reflectivity studies of the metal/solution interphase
We have designed an electrochemical cell that permits x-ray scattering studies in a transmission geometry under in-situ electrochemical control and have performed x-ray specular reflectivity studies of several metal/solution interphases as a function of electrochemical potential. For the copper/solution interphase, we found that the reflectivity changes upon oxidation and reduction, indicating a phase transition between copper and copper oxide at the interphase. We also found that the thickness of the pure copper and the roughness of the interfaces exhibited electrochemical irreversibility that is consistent with the potentials for the oxidation waves in the anodic sweep and the reduction waves in the cathodic sweep of the voltammogram. A standard Fresnel expression for the x-ray specular reflectivity was applied in the data analysis, and a smoothly varying Lorentzian interface profile was used for the individual rough interfaces. Furthermore, an incoherent average was used to include the effect of correlated roughness between a pair of interfaces. Preliminary results are also presented for the silver/solution and platinum/solution interphases. 14 refs., 9 figs., 2 tabs
Palladium/Hydrogen Membrane Electrode for High Temperature/High Pressure Aqueous Solutions
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Argonne National Laboratory Reports
The available thermodynamic information is reviewed for three categories of materials that meet essential criteria for use as breeding blankets in deuterium-tritium (D-T) fueled fusion reactors: liquid lithium, solid lithium alloys, and lithium-containing ceramics. The leading candidate, liquid lithium, which also has potential for use as a coolant, has been studied more extensively than have the solid alloys or ceramics
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Electrochemical cell
This invention is comprised of an electrochemical cell has a layer-type or sandwich configuration with a Teflon center section that houses working, reference and counter electrodes and defines a relatively narrow electrolyte cavity. The center section is surrounded on both sides with thin Teflon membranes. The membranes are pressed in place by a pair of Teflon inner frames which are in turn supported by a pair of outer metal frames. The pair of inner and outer frames are provided with corresponding, appropriately shaped slits that are in plane generally transverse to the plane of the working electrode and permit X-ray beams to enter and exit the cell through the Teflon membranes that cover the slits so that the interface between the working electrode and the electrolyte within the cell may be analyzed by transmission geometry. In one embodiment, the center section consists of two parts, one on top of the other. Alternatively, the center section of the electrochemical cell may consist of two intersliding pieces or may be made of a single piece of Teflon sheet material. The electrolyte cavity is shaped so that the electrochemical cell can be rotated 900 in either direction while maintaining the working-and counter electrodes submerged in the electrolyte
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Experimental studies of processing conditions for liquid lithium and solid lithium alloy fusion blankets
A 50-gallon-capacity liquid lithium loop (Lithium Processing Test Loop, LPTL) has been constructed and brought into operation at the Argonne National Laboratory. This system contains experimental assemblies to study (a) lithium processing technology based on molten salt extraction, cold trapping, and getting trapping and (b) on-line hydrogen monitoring. An efficient electrolytic method, employing a porous sparged electrode, has been developed to recover hydrogen isotopes from the types of molten salts (e.g., LiF-LiCl-LiBr) selected for use in the salt-processing system on the LPTL. This method, when tested under realistic conditions, has demonstrated the potential for recovering tritium (from lithium) at the sub-wppm level. Results of cold-trap tests on the LPTL and of getter-trap tests on both the LPTL and a much smaller lithium loop have provided some evidence that these types of processing methods can be used to control oxygen and nitrogen levels in lithium. Studies of the hydridation of solid Li-Al and Li-Pb alloys have provided data on activity coefficients and phase boundary locations for these binary systems as functions of temperature and composition. The Sieverts' constants for dilute hydrogen solutions in LiAl (in wppm/Torr/sup 1/2/) were found to be 10/sup 3/ to 10/sup 4/ times smaller than those for hydrogen in pure lithium at the same temperature
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Argonne National Laboratory Reports
Physicochemical and thermodynamic studies of liquid-lithium-containing systems have continued. Pressure-composition isotherms for the lithium-hydrogen system measured by a gravimetric technique are found to be in reasonably good agreement with earlier tensimetric results. Plateau-pressure studies of the lithium-hydrogen, lithium-deuterium, and lithium-tritium systems have been made at temperatures above and below the monotectic. The observed isotope effects were found to be near the predicted values. Measurements of the solubility of the lithium-deuterium in liquid lithium gave results in good agreement with prior data for the solubility of lithium-hydrogen in lithium and confirmed that the limits on cold trapping of lithium hydrides from lithium are too high for protected fusion reactor applications. Determination of the solubility of lithium dioxide in liquid lithium is nearing completion. Solubility values measured to date are slightly lower than, but in the range of, prior measurements
Temperature Dependence of the Heterogeneous FerrousāFerric Electron Transfer Reaction Rate: Comparison of Experiment and Theory
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Argonne National Laboratory Reports
The hydrogen permeabilities of selected metals, alloys, and multiplex preparations that are of interest to fusion reactor technology are being characterized. A high-vacuum hydrogen-permeation apparatus has been constructed for this purpose. A program of studies has been initiated to develop design details for the tritium-handling systems of near-term fusion reactors. This program has resulted in a better definition of reactor-fuel-cycle and enrichment requirements and has helped to identify major research and development problems in the tritium-handling area. The design and construction of a 50-gallon lithium-processing test loop (LPTL) is well under way. Studies in support of this project are providing important guidance in the selection of hardware for the LPTL and in the design of a molten-salt processing test section