170 Matching Results

Search Results

Advanced search parameters have been applied.

Interim Report of the Fuel Processing Group

Description: "This report covers mainly the work completed since the last interim report, HNL Log No. 0-4714. This report includes results from studies of the rare earth distribution in bismuth-uranium and fused chloride and studies of fused chloride behavior."
Date: January 15, 1952
Creator: Bareis, D. W.
Partner: UNT Libraries Government Documents Department

Coated-wire-in-tube processing of bismuth-2223 superconductors

Description: A coated-wire-in-tube (CWIT) process greatly increases the silver/superconductor interface area in silver-sheathed Bi-2223 superconductors. When the performance of CWIT samples is compared to that of conventional monofilaments made with the same powder, critical current density increases significantly with increased silver/superconductor interface area. Benefits of increasing the silver/superconductor interface area are realized only when there is good continuity of the coated wires, and this requires a mechanical deformation sequence to preserve good continuity of the wires.
Date: May 1, 1997
Creator: Dorris, S.E.; Ashcom, N.; Truchan, T.; Vasanthamohan, N.; Burlone, D.A. & Woolf, L.D.
Partner: UNT Libraries Government Documents Department

Fiber-optic wheel rotation sensor. Final report CRADA No. LA93C10086

Description: Two approaches for a fiber optic wheel rotation sensor down to zero RPM have been pursued. The first approach using magnetic domain diffraction of light in a BIG (bismuth iron garnet) material has been demonstrated and the further technical developments to routinely produce a practical product have been identified. The second approach involving Faraday rotation of light within the BIG crystal has been developed and a working sensor has been demonstrated. Both sensors rely on a magnetic tone ring which is mounted within the bearing of the wheel.
Date: April 1, 1997
Partner: UNT Libraries Government Documents Department

Flux pinning in two-dimensional high temperature superconductors

Description: Various types of high temperature superconducting single crystals (TI-2223, Bi-2212, and Y-123 with oxygen contents between 6.4 and 6.64) were investigated by SQUID magnetometry. Both materials show very {open_quotes}low{close_quotes} lying irreversibility lines (Hllc), which follow an exponential law-and rise rapidly below T/T{sub c}=0.5. High critical current P densities are found only at low temperatures, e.g. J{sub c} is about 2.7{circ}10{sup 10}Am{sup -2} at 1 T and 5 K in TI-2223. A comparison of the condensation energy provided by different types of defects with the thermal energy gives evidence for pinning of individual pancakes by the as-grown defect structure.
Date: October 1, 1996
Creator: Brandstaetter, G.; Sauerzopf, F.M.; Weber, H.W. & Veal, B.W.
Partner: UNT Libraries Government Documents Department

Magnetostriction and thermal expansion of the Kondo semiconductor Ce{sub 3}Bi{sub 4}Pt{sub 3}

Description: We report dilatometric thermal expansion ({alpha}) and magnetostriction ({lambda}) measurements on the Kondo semiconductor Ce{sub 3}Bi{sub 4}Pt{sub 3} and its non-magnetic analog La{sub 3}Bi{sub 4}Pt{sub 3} in fields to 100 kOe. The magnetic contribution to the thermal expansion of Ce{sub 3}Bi{sub 4}Pt{sub 3} displays a broad maximum centered at 50 K, close to the temperature where the 4f specific heat is a maximum. The linear magnetostriction is anomalously large in Ce{sub 3}Bi{sub 4}Pt{sub 3}, with values that are characteristic of mixed-valent compounds ({lambda}{sub {perpendicular}} = 3.26x10{sup {minus}5}, {lambda}{sub {parallel}} = -6.24x10{sup {minus}5} in 100 kOe at 4 K). The volume magnetostriction is positive and a factor of ten smaller than the linear coefficients ({lambda}{sub V} = 2.75x10{sup {minus}6} in 100 kOe at 4 K). The volume magnetostriction is temperature-dependent, and peaks at 50 K. The data are considered in terms of a Grueneisen analysis that links the temperature-dependent magnetic susceptibility, thermal expansion, magnetostriction, bulk modulus, and specific heat of Ce{sub 3}Bi{sub 4}Pt{sub 3} via temperature-dependent electronic and magnetic scaling parameters.
Date: May 1, 1995
Creator: Hundley, M.F.; Neumeier, J.J.; Thompson, J.D.; Lacerda, A. & Canfield, P.C.
Partner: UNT Libraries Government Documents Department

Critical current density enhancement in rolled multifilament Bi-2223 HTS composites

Description: At 77 K and self-field, we report transport critical density (J{sub c}) of 58 kA/cm{sup 2} in rolled 19 and 85 filament Bi-2223 HTS tapes. For an 85-filament tape with transport J{sub c} of 50 kA/cm{sup 2}, transport J{sub c} of greater than 80 kA/cm{sup 2} electrical performance, increasing the number of the strong links between the 2223 colonies is believed to be the most important factor. Microstructure studies on these samples suggest that there is still great potential for further J{sub c} enhancement.
Date: December 31, 1997
Creator: Li, Q.; Riley, G.N. Jr. & Parrella, R.D.
Partner: UNT Libraries Government Documents Department

Adsorption-controlled growth of ferroelectric PbTiO{sub 3} and Bi{sub 4}Ti{sub 3}O{sub 12} films for nonvolatile memory applications by MBE

Description: Epitaxial PbTiO{sub 3} and Bi{sub 4}Ti{sub 3}O{sub 12} thin films have been grown on (100) SrTiO{sub 3} and (100) LaAlO{sub 3} substrates by reactive molecular beam epitaxy (MBE). Titanium is supplied to the film in the form of shuttered bursts each containing a one monolayer dose of titanium atoms for the growth of PbTiO{sub 3} and three monolayers for the growth of Bi{sub 4}Ti{sub 3}O{sub 12}. Lead, bismuth, and ozone are continuously supplied to the surface of the depositing film. Growth of phase pure, c-axis oriented epitaxial films with bulk lattice constants is achieved using an overpressure of these volatile species. With the proper choice of substrate temperature (600--650 C) and ozone background pressure (P{sub O{sub 3}} = 2 {times} 10{sup {minus}5} Torr), the excess of the volatile metals and ozone desorb from the surface of the depositing film leaving a phase-pure stoichiometric crystal. The smooth PbTiO{sub 3} surface morphology revealed by atomic force microscopy (AFM) suggests that the PbTiO{sub 3} films grow in a layer-by-layer fashion. In contrast the Bi{sub 4}Ti{sub 3}O{sub 12} films contain islands which evolve either continuously or around screw dislocations via a spiral-type growth mechanism.
Date: September 1, 1997
Creator: Theis, C. D.; Yeh, J.; Schlom, D. G.; Hawley, M. E. & Brown, G. W.
Partner: UNT Libraries Government Documents Department


Description: Improvements in Glendenin's procedure for the determimation of fission product ruthenium have been made. The distillation from perchloric acid has been replaced by ABSTRACTS a more rapid distillation from a dilute suifuric acid- sodium bismuthate mixture. Conditions for the quantitative volatilization and collection of the tetroxide, as well as reduction to the dioxide, have been established. Reduction to the metal for a yield determimation is no longer necessary. The analysis time has been halved and the precision has been improved by a factor of three. (auth)
Date: December 1, 1957
Creator: Larsen, R.P.; Ross, L.E. & Kesser, G.
Partner: UNT Libraries Government Documents Department


Description: Commercially available specimens of polycrystalline nand p-type lead telluride and n- and p-type bismuth telluride were irradiated in the Engineering Test Reactor. Total integrated flux times of 1.5 x 10/sup 20/ neutrons/cm/sup 2/ (thermal) and 1.6 x 10/sup 19/ neutrons/cm/sup 2/ (fast, i.e., for neutrons having energies greater than 1 (Mev) were accumulated by the specimens during irradiation. The specimen temperature during irradiation was 60 plus or minus 20 deg C. The effects of the irradiation on the thermoelectrical properties of these materials were found to be due almost entirely to fast neutrons insofar as most of the damage is healed during heat treatment. Increases in the electrical resistivity for irradiated n type PbTe and Bi/sub 2/Te/sub 3/ were found to anneal at temperatures below 200 deg C. Measurements of the electrical resistivity and Seebeck coefficient as a function of temperature for irradiated and unirradiated samples cut from the same ingot are given for all materials except p type PbTe. For the latter sample only the measurements of the Seebeck coefficient are given. (auth)
Date: April 1, 1960
Creator: Corelli, J. C. & Frost, R. T.
Partner: UNT Libraries Government Documents Department

Progress in the development of BSCCO-2212 superconductors

Description: BSCCO-2212 powders were uniformly dip coated on silver ribbons of 1 meter lengths. Short sample sandwiches of various combinations of silver and the dip coated ribbon were reacted to form possible conductor geometries for characterization and testing. Optical and Scanning Electron Microscope (SEM) examination of surfaces and cross sections showed good but still not ideal microstructure. Representative critical current densities at 6 T and 4.2 K ranged from 8 {times} 10{sup 3}A/cm{sup 2} for sandwich samples to 2 {times} 10{sup 4}A/cm{sup 2} for open-faced samples.
Date: November 1, 1992
Creator: Walker, M. S. & Dietderich, D. R.
Partner: UNT Libraries Government Documents Department

Anisotropy of the critical current density in Bi-2223/Ag tapes

Description: The effect of thermomechanical processing on texture in Bi-2223 Ag-sheathed tapes as determined from the anisotropy of the critical current density J{sub c} in an applied magnetic field will be discussed. Model calculations for a distribution of grain orientations in the tape produce good fits to the data and allow characterization of the degree of long-range texture. There is a qualitative correlation of J{sub c} with global texture, but other factors, such as intergrain connectivity, are also important.
Date: May 1, 1994
Creator: Willis, J. O.; Coulter, J. Y.; Maley, M. P.; Daemen, L. L.; Rupich, M. W. & Riley, G. N. Jr.
Partner: UNT Libraries Government Documents Department

Solution based temperature of Perovskite-type oxide films and powders

Description: Conventional solid state reactions are diffusion limited processes that require high temperatures and long reaction times to reach completion. In this work, several solution based methods were utilized to circumvent this diffusion limited reaction and achieve product formation at lower temperatures. The solution methods studied all have the common goal of trapping the homogeneity inherent in a solution and transferring this homogeneity to the solid state, thereby creating a solid atomic mixture of reactants. These atomic mixtures can yield solid state products through {open_quotes}diffusionless{close_quotes} mechanisms. The effectiveness of atomic mixtures in solid state synthesis was tested on three classes of materials, varying in complexity. A procedure was invented for obtaining the highly water soluble salt, titanyl nitrate, TiO(NO{sub 3}){sub 2}, in crystalline form, which allowed the production of titanate materials by freeze drying. The freeze drying procedures yielded phase pure, nanocrystalline BaTiO{sub 3} and the complete SYNROC-B phase assemblage after ten minute heat treatments at 600{degrees}C and 1100{degrees}C, respectively. Two novel methods were developed for the solution based synthesis of Ba{sub 2}YCu{sub 3}O{sub 7-x} and Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10}. Thin and thick films of Ba{sub 2}YCu{sub 3}O{sub 7-x} and Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} were synthesized by an atmospheric pressure, chemical vapor deposition technique. Liquid ammonia solutions of metal nitrates were atomized with a stream of N{sub 2}O and ignited with a hydrogen/oxygen torch. The resulting flame was used to coat a substrate with superconducting material. Bulk powders of Ba{sub 2}YCu{sub 3}O{sub 7-x} and Bi{sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10} were synthesized through a novel acetate glass method. The materials prepared were characterized by XRD, TEM, SEM, TGA, DTA, magnetic susceptibility and electrical resistivity measurements.
Date: April 1, 1995
Creator: McHale, J.M. Jr.
Partner: UNT Libraries Government Documents Department

Fabrication and properties of hot pressed bismuth tungstate

Description: Bi/sub 2/WO/sub 6/ is a synthetic polar material that is a possible candidate for energy conversion and detection systems. Previous research on this material has been concerned with crystal growth and sintering characteristics of polycrystalline compacts. This study involves itself with the fabrication of polycrystalline compacts by hot pressing techniques. Densities approaching theoretical crystal density were achieved by hot pressing at 850/sup 0/C for one hour with pressures exceeding 35 MPa. Before hot pressing, the sintering range was determined by high temperature dilatometry of unfired Bi/sub 2/WO/sub 6/ ceramics. Hot pressed discs were characterized by scanning electron microscopy, differential scanning calorimetry, and x-ray diffraction. Electrical properties were determined by dc resistivity, capacitance, and conductance measurements, ac poling, dc poling, and current-voltage measurements.
Date: January 1, 1978
Creator: Streicher, W.L.
Partner: UNT Libraries Government Documents Department

Structure of liquid trivalent salts

Description: Total neutron scattering measurements have been made on three trivalent molten salts: InCl[sub 3] (605C), BiCl[sub 3](300C) and BiI[sub 3] (420C). Results are discussed in the general context of ordering, bonding and macroscopic properties of trivalent molten salts.
Date: April 1, 1993
Creator: Price, D. L.; Saboungi, M. L.; Howells, W. S. & Tosi, M. P.
Partner: UNT Libraries Government Documents Department

Predoctoral training grant in the area of physical sciences. Final technical report, October 1989--October 1993

Description: This final technical report represents the results of the research in nonlinear optics (optical phase conjugation) obtained by five (5) predoctoral students in the department of physics at Alabama Agricultural and Mechanical University (AAMU).
Date: November 1, 1993
Creator: Venkateswarlu, P.
Partner: UNT Libraries Government Documents Department

Synfuel (hydrogen) production from fusion power

Description: A potential use of fusion energy for the production of synthetic fuel (hydrogen) is described. The hybrid-thermochemical bismuth-sulfate cycle is used as a vehicle to assess the technological and economic merits of this potential nonelectric application of fusion power.
Date: January 1, 1979
Creator: Krakowski, R.A.; Cox, K.E.; Pendergrass, J.H. & Booth, L.A.
Partner: UNT Libraries Government Documents Department

Two bismuth sulfate-sulfuric acid hybrid thermochemical hydrogen cycles. Some experimental work related to the cycles and their possible improvement. Outline of a proposed antimonyl sulfate cycle in which sulfur dioxide and oxygen are separately evolved

Description: Thermochemical hydrogen production topics discussed include: equilibrium pressures in the decomposition of Bi/sub 2/(SO/sub 4/)/sub 3/ and ..cap alpha..-and ..beta..-Bi/sub 2/O(SO/sub 4/)/sub 2/; survey experiments on the thermal decomposition of Bi/sub 2/(SO/sub 4/)/sub 3/; hydrates sorption of H/sub 2/SO/sub 4/ solutions by the solids; and possible simplification of the SO/sub 3/-SO/sub 2/-O/sub 2/ separation problem with a sulfuric acid-antimonyl sulfate hybrid cycle.
Date: January 1, 1982
Creator: Jones, W.M.
Partner: UNT Libraries Government Documents Department

LASL thermochemical hydrogen program status on October 31, 1977. [Cycles using sulfuric acid as an intermdiate]

Description: The LASL Hydrogen Program is continuing its investigation of practical schemes to decompose water thermochemically for hydrogen production. Efforts were and are being devoted to process improvements in cycles that use sulfuric acid as an intermediate. Sulfuric acid-hydrogen bromide cycles are being studied as a means of overcoming the heat penalty in drying acid solutions. An alternate approach involves the use of insoluble bismuth sulfate that is precipitated from acid solution. Preliminary energy balances indicate a significant increase in cycle efficiency for both these options.
Date: January 1, 1977
Creator: Cox, K.E. & Bowman, M.G.
Partner: UNT Libraries Government Documents Department

LASL thermochemical hydrogen status on September 30, 1979

Description: The work described in this report was accomplished during the period October 1, 1978 to September 30, 1979. Most of the effort was applied to a study of the Los Alamos Scientific Laboratory (LASL) hybrid bismuth sulfate cycle. The work included a conceptual design of the cycle and experimental work to verify the design conditions. Key findings were: a 50.8% efficiency was obtained when an improved cycle design was coupled to a fusion energy source at 1500 K; experimental results showed an endothermic heat requirement of +172 kJ/mol for the decomposition of Bi/sub 2/O/sub 3/.2SO/sub 3/ to Bi/sub 2/O/sub 3/.SO/sub 3/, and SO/sub 3/; reaction times for bismuth sulfate decomposition were determined as a function of temperature. At 1240 K, < 1.5 min were required for the first two stages of decomposition from Bi/sub 2/O/sub 3/.3SO/sub 3/ to Bi/sub 2/O/sub 3/; tests made to determine the feasibility of decomposing Bi/sub 2/O/sub 3/.2SO/sub 3/ in a 1 inch diameter rotary kiln showed that Bi/sub 2/O/sub 3/.2SO/sub 3/ could be decomposed continuously. In related work, support was given to the DOE Thermochemical Cycle Evaluation Panel (Funk). The Second Annual International Energy Agency (IEA) Workshop on Thermochemical Hydrogen Production from Water met on September 24 to 27, 1979 at Los Alamos.
Date: January 1, 1979
Creator: Cox, K.E.
Partner: UNT Libraries Government Documents Department

LASL bismuth sulfate thermochemical hydrogen cycle

Description: The LASL bismuth sulfate cycle is one of a generic class of solid sulfate cycles in which a metal sulfate is substituted for sulfuric acid in a hybrid (partly electrochemical) cycle. This technique avoids the serious materials and heat penalty problems associated with the handling of concentrated acid solutions, and if the electrolyzer is operated at acid concentrations below 50% it may, in principle, lead to a lower cell voltage with subsequent energy savings. Experiment verification of all steps in the cycle has been obtained, particularly for the decomposition of normal bismuth sulfate and lower bismuth oxysulfates. For the substance, Bi/sub 2/O/sub 3/ 2SO/sub 3/, an endothermic requirement of 172 kJ/mol was obtained, which is considerably less than that for other metal sulfate systems. A rotary kiln was used for continuous experiments and our results show decomposition of this compound to Bi/sub 2/O/sub 3/ SO/sub 3/ in under 8 minutes residence time at 1023 K. Preliminary analysis of the cycle's energy balance shows an overall thermal efficiency of greater than 50% when the maximum cycle reaction temperature is 1500 K. The cycle has potential for hydrogen production when coupled with an energy source such as solar or fusion energy.
Date: January 1, 1980
Creator: Cox, K.E.; Jones, W.M. & Peterson, C.L.
Partner: UNT Libraries Government Documents Department

LASL thermochemical hydrogen program status on September 30, 1980

Description: The work described here was accomplished during the period October 1, 1979-September 30, 1980. Highlights of the experimental program were: a solids decomposition facility was constructed and used to study the handling of bismuth oxysulfates and the kinetics of their decomposition; and the results of our kiln experiments showed that a substantial amount of bismuth oxysulfate decomposition occurs with residence times under 2 min. at temperatures between 973 and 1143/sup 0/K. The LASL bismuth sulfate sub-cycle thus appears a candidate for hydrogen production utilizing a solar heat source. In the evaluation phase of our work, the technoeconomics of the hybrid sulfur cycle were determined and compared with several published results as well as compared to the technoeconomics for water electrolysis processes for hydrogen production. We aided the efforts of the Department of Energy (DOE) Thermochemical Cycle Evaluation Panel in reviewing the Lawrence Livermore Laboratory (LLL) zinc selenide cycle as well as the General Atomic (GA) sulfur-iodine cycle.
Date: January 1, 1980
Creator: Cox, K.E.; Peterson, C.L.; Jones, W.M. & Bowman, M.G.
Partner: UNT Libraries Government Documents Department

Initial characterization of a BGO-photodiode detector for high resolution positron emission tomography

Description: Spatial resolution in positron emission tomography is currently limited by the resolution of the detectors. This work presents the initial characterization of a detector design using small bismuth germanate (BGO) crystals individually coupled to silicon photodiodes (SPDs) for crystal identification, and coupled in groups to phototubes (PMTs) for coincidence timing. A 3 mm x 3 mm x 3 mm BGO crystal coupled only to an SPD can achieve a 511 keV photopeak resolution of 8.7% FWHM at -150/sup 0/C, using a pulse peaking time of 10 ..mu..s. When two 3 mm x 3 mm x 15 mm BGO crystals are coupled individually to SPDs and also coupled to a common 14 mm diam PMT, the SPDs detect the 511 keV photopeak with a resolution of 30% FWHM at -76/sup 0/C. In coincidence with an opposing 3 mm wide BGO crystal, the SPDs are able to identify the crystal of interaction with good signal-to-noise ratio, and the detector pair resolution is 2 mm FWHM. 32 references, 7 figures, 3 tables.
Date: November 1, 1983
Creator: Derenzo, S.E.
Partner: UNT Libraries Government Documents Department

Monte Carlo calculations of the optical coupling between bismuth germanate crystals and photomultiplier tubes

Description: The high density and atomic number of bismuth germanate (Bi/sub 4/Ge/sub 3/O/sub 12/ or BGO) make it a very useful detector for positron emission tomography. Modern tomograph designs use large numbers of small, closely-packed crystals for high spatial resolution and high sensitivity. However, the low light output, the high refractive index (n=2.15), and the need for accurate timing make it important to optimize the transfer of light to the photomultiplier tube (PMT). We describe the results of a Monte Carlo computer program developed to study the effect of crystal shape, reflector type, and the refractive index of the PMT window on coupling efficiency. The program simulates total internal, external, and Fresnel reflection as well as internal absorption and scattering by bubbles.
Date: October 1, 1981
Creator: Derenzo, S.E. & Riles, J.K.
Partner: UNT Libraries Government Documents Department