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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
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
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

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

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

Mechanism of catalytic gasification of coal char. Quarterly technical report No. 5, October 1 to December 31, 1981

Description: The purpose of this study is to determine the mechanisms involved in the catalytic reactions of coal char and to identify the specific reaction steps and the parameters that control the catalytic process. The mode of action of the catalyst can be viewed in two ways. In one view, the catalyst participates in a reduction/oxidation cycle. The initial reaction between the carbon and the catalyst reduces the KOH to potassium accompanied by the gaseous reactant (H/sub 2/O or CO/sub 2/), producing further gaseous products (CO and H/sub 2/) and regenerating the initial state of the catalyst. In an alternative view, the catalyst initially forms an alkali metal addition compound with the carbon network of the char. The carbon-carbon bonds are altered by the formation of the metal-carbon linkage, possibly by electron transfer from the alkali metal atom to the carbon structure. As a result, the carbon structure is more readily attacked by the gaseous reactant (CO or H/sub 2/O) to produce the products of gasification. The following areas were investigated to provide experimental evidence for these catalytic modes of action: chemical kinetic measurements; thermodynamic measurements; free radicals in reacting carbon; electrical conductivity measurements. A detailed discussion on the catalyst-carbon interaction and on the reaction intermediate is provided.
Date: February 26, 1982
Creator: Wood, B. J.; Sancier, K. M.; Sheridan, D. R.; Chan, B. L. & Wise, H.
Partner: UNT Libraries Government Documents Department

He atom surface scattering: Surface dynamics of insulators, overlayers and crystal growth

Description: Investigations have focused primarily on surface structure and dynamics of ionic insulators, epitaxial growth onto alkali halide crystals and multiphoton studies. The surface dynamics of RbCl has been re-examined. We have developed a simple force constant model which provides insight into the dynamics of KBr overlayers on NaCl(001), a system with a large lattice mismatch. The KBr/NaCl(001) results are compared to Na/Cu(001) and NaCl/Ge(001). We have completed epitaxial growth experiments for KBr onto RbCl(001). Slab dynamics calculations using a shell model for this system with very small lattice mismatch are being carried out in collaboration with Professor Manson of Clemson University and with Professor Schroeder in Regensburg, Germany. Extensive experiments on multiphoton scattering of helium atoms onto NaCl and, particularly, LiF have been carried out and the theory has been developed to a rather advanced stage by Professor Manson. This work will permit the extraction of more information from time-of-flight spectra. It is shown that the theoretical model provides a very good description of the multiphoton scattering from organic films. Work has started on self-assembling organic films on gold (alkyl thiols/Au(111)). We have begun to prepare and characterize the gold crystal; one of the group members has spent two weeks at the Oak Ridge National Laboratory learning the proper Au(111) preparation techniques. One of our students has carried out neutron scattering experiments on NiO, measuring both bulk phonon and magnon dispersion curves.
Date: January 1, 1992
Partner: UNT Libraries Government Documents Department

Investigation of sorption interactions between organic and mineral phases of processed oil shale

Description: Minerals and organic compounds representative of oil shale processing wastes were analyzed for potential sorption interactions. The analysis consisted of Fourier Transform Infrared spectroscopy, high performance liquid chromatography, thermogravimetric and differential scanning calorimetry, and laser Raman spectroscopy. Montmorillonite clay was used as a representative of the smectites found in raw and spent shales, and hematite was used as a representative of iron oxide found in spent shales. Benzene, 2,2,4-trimethylpentane, benzoic acid, sodium benzoate, and pyridine were used as representatives of oil shale process organic wastes. In addition, isopropylamine and dimethyl methylphosphonate, a pesticide model, were studied. A preparation methods comparison study was performed and established the validity of the solid state KBr sample preparation technique upon FTIR spectral quality. The results of this study illustrate the utility of fourier transform infrared spectroscopic analysis to establish and describe the potential for sorption interactions between inorganic and organic phases of oil shale processing wastes. Experimentation with the laser remain system shows promise for significant contributions in this field of research. 43 refs., 3 figs., 6 tabs.
Date: November 1, 1987
Creator: Blanche, M. S. & Bowen, J. M.
Partner: UNT Libraries Government Documents Department