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Electrochemically induced reconstruction of the Au(001) surface: An x-ray scattering study

Description: In-situ x-ray specular reflectivity and glancing incident angle x-ray diffraction measurements have been performed in the Au(001) surface in two solutions under potential control in an electrochemical cell. In both the 0.01 M HCl0{sub 4} and 0.01 M KBr solutions a ``(5 {times} 20)`` reconstruction is formed at sufficient negative potentials. The reconstruction is similar to that obtained for the clean surface in vacuum.
Date: December 31, 1991
Creator: Ocko, B. M. & Wang, Jia
Partner: UNT Libraries Government Documents Department

Gamma scattering in condensed matter with high intensity Moessbauer radiation. Final technical progress report, January 16, 1993--January 15, 1996

Description: Progress is reported on work with high intensity radiation. Moessbauer radioisotopes of exceptional high intensity have been the source of photons for most experiments. Topics include lattice dynamics, studies of glass forming liquids, and line-shape and it`s role in finding materials and nuclear parameters.
Date: June 1, 1997
Partner: UNT Libraries Government Documents Department

Characterization of low-melting electrolytes for potential geothermal borehole power supplies: The LiBr-KBr-LiF eutectic

Description: The suitability of modified thermal-battery technology for use as a potential power source for geothermal borehole applications is under investigation. As a first step, the discharge processes that take place in LiSi/LiBr-KBr-LiF/FeS{sub 2} thermal cells were studied at temperatures of 350 C and 400 C using pelletized cells with immobilized electrolyte. Incorporation of a reference electrode allowed the relative contribution of each electrode to the overall cell polarization to be determined. The results of single-cell tests are presented, along with preliminary data for cells based on a lower-melting CsBr-LiBr-KBr eutectic salt.
Date: May 1, 1998
Creator: Guidotti, R.A. & Reinhardt, F.W.
Partner: UNT Libraries Government Documents Department

Performance of LiAlloy/Ag(2)CrO(4) Couples in Molten CsBr-LiBr-KBr Eutectic

Description: The performance of Li-alloy/CsBr-LiBr-KBr/Ag{sub 2}CrO{sub 4} systems was studied over a temperature range of 250 C to 300 C, for possible use as a power source for geothermal borehole applications. Single cells were discharged at current densities of 15.8 and 32.6 mA/cm{sup 2} using Li-Si and Li-Al anodes. When tested in 5-cell batteries, the Li-Si/CsBr-LiBr-KBr/Ag{sub 2}CrO{sub 4} system exhibited thermal runaway. Thermal analytical tests showed that the Ag{sub 2}CrO{sub 4} cathode reacted exothermically with the electrolyte on activation. Consequently, this system would not be practical for the envisioned geothermal borehole applications.
Date: October 18, 1999
Creator: GUIDOTTI,RONALD A. & REINHARDT,FREDERICK W.
Partner: UNT Libraries Government Documents Department

Re-evaluation of the eutectic region of the LiBr-KBr-LiF system

Description: The separator pellet in a thermal battery consists of electrolyte immobilized by a binder (typically, MgO powder). The melting point of the electrolyte determines the effective operating window for its use in a thermal battery. The development of a two-hour thermal battery required the use of a molten salt that had a lower melting point and larger liquidus range than the LiCl-KCl eutectic which melts at 352 C. Several candidate eutectic electrolyte systems were evaluated for their suitability for this application. One was the LiCl-LiBr-KBr eutectic used at Argonne National Laboratories for high-temperature rechargeable batteries for electric-vehicle applications. Using a custom-designed high-temperature conductivity cell, the authors were able to readily determine the liquidus region for the various compositions studied around the original eutectic for the LiBr-KBr-LiF system. The actual eutectic composition was found to be 60.0 m/o LiBr-37.5 m/o KBr-2.5 m/o LiF with a melting point of 324 {+-} 0.5 C.
Date: May 1, 1996
Creator: Redey, L. & Guidotti, R.A.
Partner: UNT Libraries Government Documents Department

Modification of LiCl-LiBr-KBr electrolyte for LiAl/FeS{sub 2} batteries

Description: The bipolar LiAl/FeS{sub 2} battery is being developed to achieve the high performance and long cycle life needed for electric vehicle application. The molten-salt (400 to 440 C operation) electrolyte composition for this battery has evolved to support these objectives. An earlier change to LiCl-LiBr-KBr electrolyte is responsible for significantly increased cycle life (up to 1,000 cycles). Recent electrolyte modification has significantly improved cell performance; approximately 50% increased power, with increased high rate capacity utilization. Results are based on power-demanding EV driving profile test at 600 W/kg. The effects of adding small amounts (1--5 mol%) of LiF and LiI to LiCl-LiBr-KBr electrolyte are discussed. By cyclic voltammetry, the modified electrolytes exhibit improved FeS{sub 2} electrochemistry. Electrolyte conductivity is little changed, but high current density (200 mA/cm{sup 2}) performance improved by approximately 50%. A specific feature of the LiI addition is an enhanced cell overcharge tolerance rate from 2.5 to 5 mA/cm{sup 2}. The rate of overcharge tolerance is related to electrolyte properties and negative electrode lithium activity. As a result, the charge balancing of a bipolar battery configuration with molten-salt electrolyte is improved to accept greater cell-to-cell deviations.
Date: June 1, 1996
Creator: Kaun, T.D.; Jansen, A.N.; Henriksen, G.L. & Vissers, D.R.
Partner: UNT Libraries Government Documents Department

Characterization of the LiSi/CsBr-LiBr-KBr/FeS(2) System for Potential Use as a Geothermal Borehole Power Source

Description: We are continuing to study the suitability of modified thermal-battery technology as a potential power source for geothermal borehole applications. Previous work focused on the LiSi/FeS{sub 2} couple over a temperature range of 350 C to 400 C with the LiBr-KBr-LiF eutectic, which melts at 324.5 C. In this work, the discharge processes that take place in LiSi/CsBr-LiBr-KBr eutectic/FeS{sub 2} thermal cells were studied at temperatures between 250 C and 400 C using pelletized cells with immobilized electrolyte. The CsBr-LiBr-KBr eutectic was selected because of its lower melting point (228.5 C). Incorporation of a quasi-reference electrode allowed the determination of the relative contribution of each electrode to the overall cell polarization. The results of single-cell tests and limited battery tests are presented, along with preliminary data for battery stacks tested in a simulated geothermal borehole environment.
Date: October 18, 1999
Creator: GUIDOTTI, RONALD A. & REINHARDT, FREDERICK W.
Partner: UNT Libraries Government Documents Department

He atom-surface scattering: Surface dynamics of insulators, overlayers and crystal growth. Progress report, May 1, 1991--April 30, 1994

Description: This progress report describes work carried out in the study of surface structure and dynamics of ionic insulators, the microscopic interactions controlling epitaxial growth and the formation of overlayers, and energy exchange in multiphonon surface scattering. The approach used is to employ high resolution helium atom scattering to study the geometry and structural features of the surfaces. Experiments have been carried out on the surface dynamics of RbCl and preliminary studies done on CoO and NiO. Epitaxial growth and overlayer dynamics experiments on the systems NaCl/NaCl(001), KBr/NaCl(001), NaCl/KBr(001) and KBr/RbCl(001) have been performed. They have collaborated with two theoretical groups to explore models of overlayer dynamics with which to compare and to interpret their experimental results. They have carried out extensive experiments on the multiphonon scattering of helium atoms from NaCl and, particularly, LiF. Work has begun on self-assembling organic films on gold and silver surfaces (alkyl thiols/Au(111) and Ag(111)).
Date: April 1, 1994
Creator: Safron, S. A. & Skofronick, J. G.
Partner: UNT Libraries Government Documents Department

Electrochemically induced reconstruction of the Au(001) surface: An x-ray scattering study

Description: In-situ x-ray specular reflectivity and glancing incident angle x-ray diffraction measurements have been performed in the Au(001) surface in two solutions under potential control in an electrochemical cell. In both the 0.01 M HCl0{sub 4} and 0.01 M KBr solutions a (5 {times} 20)'' reconstruction is formed at sufficient negative potentials. The reconstruction is similar to that obtained for the clean surface in vacuum.
Date: January 1, 1991
Creator: Ocko, B.M. & Wang, Jia.
Partner: UNT Libraries Government Documents Department

Optical, mass, and auger spectra from e-bombarded KBr

Description: We have measured the mass spectrum and optical emission lines of neutral potassium atoms ejected from KBr at T = 300/degree/K and 443/degree/K bombarded by 2-keV electrons. The room-temperature data may be complicated by the nonstoichiometry of the alkali-enriched sample surface and seem difficult to interpret. The high-temperature sample, which maintains the proper stoichiometry, produces data in support of gas-phase excitation of alkali atoms desorbed from the surface. 15 refs., 4 figs.
Date: January 1, 1988
Creator: Arakawa, E.T. & Kamada, M.
Partner: UNT Libraries Government Documents Department

Temperature measurements of shocked translucent materials by time-resolved infrared radiometry

Description: Infrared emission in the range 2 to 5.5 ..mu..m has been used to measure temperatures in shock-compressed states of nitromethane, cyclohexane and benzene and in polycrystalline KBr. Polymethylmethacrylate shows anomolous emission probably associated with some heterogeneity.
Date: June 4, 1981
Creator: Von Holle, W.G.
Partner: UNT Libraries Government Documents Department

A shuttle mechanism for molten-electrolyte lithium batteries

Description: The lithium-transport rates arising from a lithium shuttle mechanism (LSM) were examined by potentiometric control of a lithium-alloy electrode in a temperature range of 400 to 515{degrees}C in three electrolytes: LiCl-KCl, LiCl-LiBr-KBr, and LiF-LiCl-LiBr. Lithium transport in Li/FeS{sub x} cells by LSM was found to occur by diffusion of reduced lithium species across the separator layer, which was controlled by the Li-activity of the Li-alloy electrode. Solubility of lithium was strongly affected by electrolyte composition, especially K{sup +} content, which in turn regulated the lithium transport rate. As evidenced by LSM rates, the solubilized lithium would appear to form dimers (e.g. Li{sub 2}{sup +} or LiK{sup +}). The half-cell self-discharge rates, which were measured, correlate well with self-discharge rates in developmental cells ranging from 0.1 to 10 mA/cm{sup 2}. Innovative application of the LSM has led to the development of overcharge tolerant Li/FeS{sub x} cells. A bimodal self-discharge characteristic (a 20-fold increase toward the end of charge) results from a 150-250 mV step increase in lithium activity of a two-phase Li-alloy electrode (Li-Al plus Li-Al{sub 5}Fe{sub 2}). Three versions of the battery cell (100 cm{sup 2} separator area) have been demonstrated: LiAl+Li{sub 5}Al{sub 5}Fe{sub 2}(10% of capacity)/LiCl-LiBr-KBr(MgO)/FeS{sub 2}, as well as a FeS-type, (both operated at 400{degrees}C) and LiAl+Li{sub 5}Al{sub 5}Fe{sub 2}(10% of capacity)/LiF-LiCl-LiBr(MgO)/FeS (operated at 475{degrees}C). These cells exhibit a unique combination of overcharge capacity and extended trickle-charge tolerance at 2-5 mA/cm{sup 2}. Additionally, Li/FeS{sub 2} cells having overcharge tolerance have operated with stable performance for greater than 500 cycles. The overcharge tolerance rates are sufficient for battery cells to exhibit built-in charge/equalization capability by way of full-battery trickle charging.
Date: November 1, 1993
Creator: Kaun, T. D. & Nelson, P. A.
Partner: UNT Libraries Government Documents Department