449 Matching Results

Search Results

Advanced search parameters have been applied.

Continuing development of regenerable sorbents for fluidized-bed combustion. Semiannual technical progress report No. 2, April 1-September 30, 1980

Description: Our efforts were directed primarily to preparation for and/the initial operation of the laboratory-scale hot fluidized bed test system (LSHFB). The initial test sequence in the LSHFB system was performed with a fixed-bed of 100 grams of barium titanate synthetic sorbent. The sorbent bed was alternately sulfated and regenerated five times. Sulfation was accomplished at 900/sup 0/C, with a synthetic flue gas mixture comprising 10.1% CO/sub 2/, 4.95% O/sub 2/, 0.2435% SO/sub 2/ and 84.7% N/sub 2/. Regeneration was performed at 1025/sup 0/C with a gas containing 8.0% CO and 92.0% N/sub 2/. After an initial drop in sulfation performance after the first sulfation/regeneration cycle, performance held steady, or was shown to be improving, during the succeeding four cycles. Although the initial operation of this system proceeded relatively smoothly, the reactor was found to have been irreparably damaged by the end of the initial test sequence. A new reactor was subsequently designed, fabricated, and installed in the unit. Concurrently, sorbent pellet preparation by extrusion was investigated in the Catalyst Preparation Facility at the Baton Rouge Laboratory of Exxon Research and Engineering Company. Preparation of sorbent pellets for use in the LSHFB operation was continued on a laboratory-scale at Linden throughout the reporting period. Cost and time estimates were prepared for operation of the bench-scale fluidized bed coal combustion and regeneration facilities, including preparation of the requisite volumes of synthetic sorbent pellets needed for that program.
Date: January 1, 1980
Creator: Kalfadelis, C D
Partner: UNT Libraries Government Documents Department

Characterization of internal boundary layer capacitors

Description: Internal boundary layer capacitors were characterized by scanning transmission electron microscopy and by microscale electrical measurements. Data are given for the chemical and physical characteristics of the individual grains and boundaries, and their associated electric and dielectric properties. Segregated internal boundary layers were identified with resistivities of 10/sup 12/-10/sup 13/ ..cap omega..-cm. Bulk apparent dielectric constants were 10,000-60,000. A model is proposed to explain the dielectric behavior in terms of an equivalent n-c-i-c-n representation of ceramic microstructure, which is substantiated by capacitance-voltage analysis.
Date: May 1, 1980
Creator: Park, H. D. & Payne, D. A.
Partner: UNT Libraries Government Documents Department

LOADING AND ELUTION CHARACTERISTICS OF SOME NATURAL AND SYNTHETIC ZEOLITES

Description: The cation exchange characteristics of several commercially available zeolites were evaluated, Equilibrium loading characteristics and exchange capacities were determined experimentally in the binary systems cesium-lithium, cesium-- sodium, cesium--potassium, cesium-Tubidium, cesium -- hydrogen, cesium-- ammonium, strontium-- magnesium, strontium-- calcium, strontium-- barium, and strontium-- hydrogen for several zeolites. Exchangeable cation fractions in the equilibrium solutions were varied from 0.2 to 0.00001, while the total normality of the system constituents was held constant. Results were plotted as equivalent fraction of the traced cation on the zeolite at equilibrium vs. the fraction of traced cation remaining in the equilibrium solution. If an influent composition is known, and falls in the system listed above, zeolite column loading may be read directly in univalent-univalent or divalent-divalent systems. However, in the strontium-sodium or strontium-- hydrogen systems, a k value must be used because squared terms appear in the equilibrium expression as follows: 2 Na- zeolite plus or minus Sr-solution in equilibrium 2 Nasolution + Sr-zeolite, or k = (Sr-zeolite)(Na-solution)/ (Na-zeolite)2(Sr-solution). The k for a given cation is a function of zeolite loading with that cation. Several column 50% loading capacities were determined to randomly test the validity of the above curves to predict column capacities, Several columns loaded with known amounts of cesium and strontium radioisotopes were heated to 800 deg C for 24 hours to simulate a zeolite packaging dehydration cycle. Losses of cesium and strontium activity during the 24-hr period were determined. Elution of the remaining activity on the columns was accomplished with various eluting agents including dilute HNO/sub 3/, NH/sub 4/NO/sub 3/, CaCl/sub 2/ and La(NO/su b 3/)/sub 3/, and elution curves were calculated. (auth)
Date: August 10, 1962
Creator: Ames, L.L. Jr. & Knoll, K.C.
Partner: UNT Libraries Government Documents Department

Development of regenerable sorbents for fluidized bed combustion. Quarterly progress report No. 1, September-December 31, 1979

Description: In the initial work on the current program, equipment employed in the original pioneering study, including a thermogravimetric analyzer, an associated gas-mixing panel, and sorbent pellet preparation and conditioning hardware, was accumulated, tested for operability, refurbished, reinspected and recalibrated for future use. Specifications were prepared for the fabrication of a laboratory-scale hot fluidized bed test unit, and a design for this system was completed by our Mechanical Division. As a means to reinitiate the laboratory program and to test our equipment, new formulations incorporating the calcium aluminate cements (CAC) and barium titanate (BaTiO/sub 3/) materials, which were found to be the most promising sorbent candidates in the original study, were prepared and tested. Titanium dioxide, when incorporated into calcium aluminate cement formulations, produced an improvement in SO/sub 2/ absorption performance and, up to a level of about 5 weight percent, did not degrade crush strengths appreciably. Incorporation of carbon black and/or flyash into TiO/sub 2/-containing CAC formulations produced additional absorption improvement, but significantly reduced sorbent crush strengths. Several promising leads were pursued in the reformulation of barium titanate compositions. But it is apparent that this line of research must be considerably extended to achieve improvements of the type desired.
Date: January 1, 1979
Creator: Kalfadelis, C D & Gaydos, T
Partner: UNT Libraries Government Documents Department

The formation and analysis of thin film high temperature superconductors

Description: Thin films of high temperature superconductors have been fabricated using a variety of physical vapor deposition techniques. Recent results of HTS thin films produced by coevaporation, sputtering and laser deposition will be briefly reviewed. In addition some examples of the utility of high energy ion backscattering for the analysis of film stoichiometry will be given. 34 refs., 6 figs.
Date: January 1, 1989
Creator: Nastasi, M.; Muenchausen, R.E. & Arendt, P.N.
Partner: UNT Libraries Government Documents Department

A review of basic phenomena and techniques for sputter-deposition of high temperature superconducting films

Description: The processes involved in plasma and ion beam sputter-deposition of high temperature superconducting thin films are critically reviewed. Recent advances in the development of these techniques are discussed in relation to basic physical phenomena, specific to each technique, which must be understood before high quality films can be produced. Control of film composition is a major issue in sputter-deposition of multicomponent materials. Low temperature processing of films is a common goal for each technique, particularly in relation to integrating high temperature superconducting films with the current microelectronics technology. It has been understood for some time that for Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} deposition, the most intensely studied high-{Tc} compound, incorporation of sufficient oxygen into the film during deposition is necessary to produce as-deposited superconducting films at relatively substrate temperatures. Recent results have shown that with the use of suitable buffer layers, high quality Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} sputtered films can be obtained on Si substrates without the need for post-deposition anneal processing. This review is mainly focussed on issues related to sputter-deposition of Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7} thin films, although representative results concerning the bismuth and thallium based compounds are included. 143 refs., 11 figs.
Date: January 1, 1990
Creator: Auciello, O. (Microelectronics Center of North Carolina, Research Triangle Park, NC (USA) North Carolina State Univ., Raleigh, NC (USA). Dept. of Materials Science and Engineering); Ameen, M.S.; Kingon, A.I.; Lichtenwalner, D.J. (North Carolina State Univ., Raleigh, NC (USA). Dept. of Materials Science and Engineering) & Krauss, A.R. (Argonne National Lab., IL (USA))
Partner: UNT Libraries Government Documents Department

Some reduced ternary and quaternary oxides of molybdenum containing strong metal-metal bonds. [Molybdates of ScZn, LiZn, Zn, Ba, and Na]

Description: ScZnMo/sub 3/O/sub 8/, LiZn/sub 2/Mo/sub 3/O/sub 8/, and Zn/sub 3/Mo/sub 3/O/sub 8/ were synthesized and crystal structures were determined for the latter two. These oxides contain the same type of triangular molybdenum atom clusters found in Zn/sub 2/Mo/sub 3/O/sub 8/, but each of the trimeric clusters has available one or two additional electrons for participation in metal-metal bonding. Another new ternary oxide containing discrete metal atom clusters is Ba/sub 1/ /sub 14/Mo/sub 8/O/sub 16/. The structure of this compound consists of molybdenum-oxide cluster chains extended parallel with the c axis. The new compound NaMo/sub 4/O/sub 6/ contains infinite chains which are comprised of Mo/sub 6/O/sub 12/ clusters fused at opposite edges by removal of two edge-bridging oxygen atoms, and sharing of the metal and remaining oxygen atoms between cluster units. Another new compound, whose structure is closely related to that of NaMo/sub 4/O/sub 6/, is Ba/sub 0/ /sub 62/Mo/sub 4/O/sub 6/. This material also exhibits a sperlattice ordering of barium ions within the channels. Other compounds that have been prepared and also characterized are K/sub 2+x/Mo/sub 12/O/sub 19/, Na/sub 2+x/Mo/sub 12/O/sub 19/, and CaMo/sub 5/O/sub 8/.
Date: October 1, 1981
Creator: Torardi, C.C.
Partner: UNT Libraries Government Documents Department

Radium and uranium determination in samples of Utah Roses geothermal water

Description: The method of direct alpha counting on separated elements was used for the analysis of geothermal water. The radium and thorium were separated from uranium by chemical means and both were collected for gross alpha counting on barium sulfate. Results are presented and discussed. The procedure is described in the appendix. (MHR)
Date: June 1, 1980
Creator: Willis, C.P.
Partner: UNT Libraries Government Documents Department

A fermi liquid electric structure and the nature of the carriers in high-T/sub c/ cuprates: A photoemission study

Description: We have performed angle-integrated and angle-resolved photoemission measurements at 20 K on well-characterized single crystals of high-T/sub c/ cuprates (both 1:2:3-type and 2:2:1:2-type) cleaved in situ, and find a relatively large, resolution limited Fermi edge which shows large amplitude variations with photon energy, indicative of band structure final state effects. The lineshapes of the spectra of the 1:2:3 materials as a function of photon energy are well reproduced by band structure predictions, indicating a correct mix of 2p and 3d orbitals on the calculations, while the energy positions of the peaks agree with calculated bands only to within /approx/0.5 eV. This may yet prove to reflect the effects of Coulomb correlation. We nevertheless conclude that a Fermi liquid approach to conductivity is appropriate. Angle-resolved data, while still incomplete, suggest agreement with the Fermi surface predicted by the LDA calculations. A BCS-like energy gap is observed in the 2:2:1:2 materials, whose magnitude is twice the weak coupling BCS value (i.e., 2/Delta/ = 7 KT/sub c/). 49 refs., 11 figs.
Date: January 1, 1989
Creator: Arko, A.J.; List, R.S.; Bartlett, R.J.; Cheong, S.W.; Fisk, Z.; Thompson, J.D. et al.
Partner: UNT Libraries Government Documents Department

Photoemission spectroscopy of single crystal HTSC materials: A Fermi liquid electronic structure

Description: Photoemission spectra from HTSC materials (primarily 123-type), cleaved and measured at 20K, reveal a rich DOS structure which compares favorably with a calculated band structure, except for a residual 0.5 eV shift which may reflect some correlation effects. Band dispersion is observed throughout the valence bands, with clear evidence for a 0.2 eV wide band dispersing through E/sub F/. The orbital character at E/sub F/ is a mix of Cu-3d and O-2p. There is unambiguous evidence for a large BCS-like gap (2..delta.. greater than or equal to 4kT/sub c/). 25 refs., 5 figs.
Date: January 1, 1989
Creator: Arko, A.J.; List, R.S.; Bartlett, R.J.; Cheong, S.W.; Olson, C.G.; Yang, A.B. et al.
Partner: UNT Libraries Government Documents Department

High-frequency cavity applications and measurements of high-temperature superconductors

Description: A potentially important application of high-temperature superconductors will be high-frequency accelerating cavities. Currently these materials are not competitive with Nb at liquid helium temperature or with Cu at room temperature. However, available data on high-quality single crystals suggest that the relatively poor rf properties (high surface resistance and low surface magnetic field) of bulk and film specimens are due to materials properties that can be eliminated by improved processing techniques. Recent progress in the fabrication of thin films, for example, demonstrates that this is indeed the case. 27 refs., 10 figs., 1 tab.
Date: January 1, 1989
Creator: Cooke, D.W. & Gray, E.R.
Partner: UNT Libraries Government Documents Department

Improved CO sub 2 enhanced oil recovery -- Mobility control by in-situ chemical precipitation

Description: The overall objective of this study has been to evaluate the feasibility of chemical precipitation to improve CO{sub 2} sweep efficiency and mobility control. The laboratory experiments have indicated that carbonate precipitation can alter the permeability of the core samples under reservoir conditions. Furthermore, the relative permeability measurements have revealed that precipitation reduces the gas permeability in favor of liquid permeability. This indicates that precipitation is occurring preferentially in the larger pores. Additional experimental work with a series of connected cores have indicated that the permeability profile can be successfully modified. However, Ph control plays a critical role in propagation of the chemical precipitation reaction. A numerical reservoir model has been utilized to evaluate the effects of permeability heterogeneity and permeability modification on the CO{sub 2} sweep efficiency. The computer simulation results indicate that the permeability profile modification can significantly enhance CO{sub 2} vertical and horizontal sweep efficiencies. The scoping studies with the model have further revealed that only a fraction of high permeability zones need to be altered to achieve sweep efficiency enhancement. 64 refs., 30 figs., 16 tabs.
Date: June 1, 1991
Creator: Ameri, S.; Aminian, K.; Wasson, J.A. & Durham, D.L.
Partner: UNT Libraries Government Documents Department

Single crystal NMR studies of high temperature superconductors

Description: The authors report Cu NMR studies in the normal state of a single crystal of the T/sub c/ = 90 K superconductor YBa/sub 2/Cu/sub 3/O/sub 7/minus/delta/. The authors have measured the magnetic shift tensor, the electric field gradient tensor, the nuclear spin-lattice relaxation rate tensor, and the time dependence and functional form of the transverse decay. From these data they obtain information about the charge state and magnetic state of the Cu atoms, and the existence and size of the electronic exchange coupling between spins of adjacent Cu atoms. 18 refs., 3 figs., 2 tabs.
Date: January 1, 1989
Creator: Pennington, C.H.; Durand, D.J.; Zax, D.B.; Slichter, C.P.; Rice, J.P.; Bukowski, E.D. et al.
Partner: UNT Libraries Government Documents Department

Advanced Thermionic Technology Program progress report No. 3

Description: Research progress is reported. A BaO collector was subjected to Auger and scanning electron microprobe analyses. Experiments measuring the work function of promising collector materials at high cesium impingement rates were continued. Evaluation of the tungsten oxide converter, barium oxide converter, and guarded converter continued. Results are given and discussed. (WHK)
Date: September 1, 1975
Partner: UNT Libraries Government Documents Department

Chemical Engineering Division thermochemical studies. Annual report, July 1974--June 1975

Description: Standard enthalpies of formation were determined for the following compounds: Cs$sub 2$U$sub 2$O$sub 7$(c), $beta$-Na$sub 2$UO$sub 4$(c), BaUO$sub 4$(c), HI(aq), CsNO$sub 3$(c), Cs$sub 2$CO$sub 3$(c), CsCl(c), RbCl(c), Cs$sub 2$CrO$sub 4$(c), and Cs$sub 2$Cr$sub 2$O$sub 7$(c).Preliminary reaction calorimetric studies of WS$sub 2$ and Li--Al alloys are described. High- temperature enthalpies and other thermodynamic properties are reported for $alpha$- and $beta$-Na$sub 2$UO$sub 4$(c), Cs$sub 2$UO$sub 4$(c), and Al$sub 2$O$sub 3$(c). (auth)
Date: January 1, 1975
Creator: O'Hare, P.A.G.; Johnson, G.K.; Ader, M.; Hubbard, W.N.; Fredrickson, D.R.; Cafasso, F.A. et al.
Partner: UNT Libraries Government Documents Department

Investigation of the potential of silica-bonded macrocyclic ligands for separation of metal ions from nuclear waste

Description: This report describes the testing of some novel separations materials known as SuperLig{trademark} materials for their ability to separate efficiently and selectively certain metal ions from a synthetic, nonradioactive nuclear waste solution. The materials, developed and patented by IBC Advanced Technologies, are highly selective macrocyclic ligands that have been covalently bonded to silica gel. The SuperLig{trademark} materials that were tested are: (1) SuperLig{trademark} 601 for barium (Ba{sup 2+}) and strontium (Sr{sup 2+}) separation, (2) SuperLig{trademark} 602 for cesium (Cs{sup +}) and rubidium (Rb{sup +}) separation, (3) SuperLig{trademark} 27 for palladium (Pd{sup 2+}) separation, and (4) SuperLig{trademark} II for silver (Ag{sup +}) and ruthenium (Ru{sup 3+}) separation. Our observations show that the technology for separating metal ions using silica-bonded macrocycles is essentially sound and workable to varying degrees of success that mainly depend on the affinity of the macrocycle for the metal ion of interest. It is expected that ligands will be discovered or synthesized that are amenable to separating metal ions of interest using this technology. Certainly more development, testing, and evaluation is warranted. 3 figs., 11 tabs.
Date: January 1, 1992
Creator: Camaioni, D. M.; Colton, N. G. & Bruening, R. L.
Partner: UNT Libraries Government Documents Department

The oxidation state and magnetic behaviour of Tb in high-{Tc} related materials

Description: L{sub 3}-X-ray absorption spectroscopy is used together with inelastic neutron scattering and magnetic susceptibility measurements to characterize the Tb oxidation state and bonding in the high-{Tc} related materials Y{sub 1-x}Tb{sub x}Ba{sub 2}Cu{sub 3}O{sub 7} and Pb{sub 2}Sr{sub 2}TbCu{sub 3}O{sub 8}. The Tb is found to be essentially trivalent in both compounds with no indications of significant hybridization. However, there is evidence of significant Tb-Tb magnetic interactions in Pb{sub 2}Sr{sub 2}TbCu{sub 3}O{sub 8} that persist to temperatures much higher than the Tb long-range ordering temperature.
Date: February 1, 1995
Creator: Soderholm, L.; Staub, U.; Skanthakumar, S. & Antonio, M. R.
Partner: UNT Libraries Government Documents Department

Practical superconductor development for electrical power applications. Annual report for FY 1992

Description: Development of useful high-critical-temperature (high-{Tc}) superconductors requires synthesis of superconducting compounds; fabrication of wires, tapes, and films from these compounds; production of composite structures that incorporate stabilizers or insulators; and design and testing of efficient components. This report describes the technical progress of research and development efforts aimed at producing superconducting components that are based on the Y-Ba-Cu, Bi-Sr-Ca-Cu, Bi-Pb-Sr-Ca-Cu, and (TI,Pb)-(Ba,Sr)-Ca-Cu oxide systems. Topics discussed are synthesis and heat treatment of high-{Tc} superconductors, formation of monolithic and composite wires and tapes, superconductor/metal connectors, characterization of structures and superconducting and mechanical properties, fabrication and properties of thin films, and development of prototype components. Collaborations with industry and academia are documented.
Date: October 1, 1992
Creator: Goretta, K. C.
Partner: UNT Libraries Government Documents Department

HTS current lead using a composite heat pipe

Description: This paper discusses the design and fabrication of HTS current leads being built by Los Alamos to supply power to a demonstration HTS coil which will operate in a vacuum cooled by a cryocooler. Because vapor cooling is not an option for this application the leads must be entirely conductively cooled. In the design of HTS current leads for this type of application, it is desirable to intercept part of the heat load at an intermediate temperature. This thermal intercept or connection must be electrically insulating but thermally conductive, two mutually exclusive properties of most candidate solid materials. To achieve this end we incorporate a composite nitrogen heat pipe, constructed of conducting and non-conducting materials, to provide efficient thermal communication and simultaneously, electrical isolation between the lead and the intermediate temperature heat sink. Another important feature of the current lead design is the use of high Jc thick film superconductors deposited on a non-conducting substrate to reduce the conductive heat leak through the lower portion of the lead. Two flexible electrical conductors are incorporated to accommodate handling, assembly and the dissimilar expansion coefficients of the various materials.
Date: December 31, 1995
Creator: Daugherty, M. A.; Prenger, F. C.; Hill, D. D.; Daney, D. E. & Woloshun, K. A.
Partner: UNT Libraries Government Documents Department

Superconducting submillimeter and millimeter wave detectors

Description: The series of projects described in this dissertation was stimulated by the discovery of high temperature superconductivity. Our goal was to develop useful applications which would be competitive with the current state of technology. The high-[Tc] microbolometer was developed into the most sensitive direct detector of millimeter waves, when operated at liquid nitrogen temperatures. The thermal boundary resistance of thin YBa[sub 2]Cu[sub 3]0[sub 7-[delta]] films was subsequently measured and provided direct evidence for the bolometric response of high-[Tc] films to fast (ns) laser pulses. The low-[Tc] microbolometer was developed and used to make the first direct measurements of the frequency dependent optical efficiency of planar lithographed antennas. The hot-electron microbolometer was invented less than a year prior to the writing of this dissertation. Our analysis, presented here, indicates that it should be possible to attain up to two orders of magnitude higher sensitivity than that of the best available direct detectors when operated at the same temperature. The temperature readout scheme for this device could also be used to measure the intrinsic interaction between electrons and phonons in a metal with a sensitivity that is five orders of magnitude better than in previous measurements. Preliminary measurements of quasiparticle trapping effects at the interface between a metal and a superconductor are also presented.
Date: October 20, 1992
Creator: Nahum, M.
Partner: UNT Libraries Government Documents Department

Structural phase transitions in BaMo/sub 6/S/sub 8/: Evidence for an incommensurate phase

Description: The structure of BaMo/sub 6/S/sub 8/ has been studied over the temperature range 19 K to 573 K by time-of-flight neutron powder diffraction. Below 175 K the data can be suitably refined in a triclinic, P1, cell with volume equal to the rhombohedral, R3, cell common to most Chevrel-phase structures. At temperatures immediately above 175 K, the rhombohedral, R3, Bragg peaks are broadened by satellite reflections which appear to be identical to those recently observed at low temperature in PbMo/sub 6/S/sub 8/ and SnMo/sub 6/S/sub 8/. An abrupt change in the sign of the temperature dependence of the hexagonal c axis (par. deltac/par. deltaT) signals the transition to an undistorted rhombohedral, R3, structure at temperatures above about 350 K. An extended Landau theory determines both continuous and discontinuous transitions from R3 induced by a single order parameter. Analysis of the order parameters inducing commensurate transitions imposes symmetry restrictions on the atomic displacements in the lower symmetry phases. The assumption of an R3 commensurate phase is not consistent with the bond lengths obtained for the distortions to the P1 (or P1) phase for any of the possible cells preserving order parameters. Thus the phase immediately above 175 K cannot be a commensurate R3 structure. This is consistent with experimental evidence. 25 refs., 11 figs., 8 tabs.
Date: January 1, 1986
Creator: Jorgensen, J.D.; Hinks, D.G.; Hatch, D.M. & Putnam, R.M.
Partner: UNT Libraries Government Documents Department

Neutron diffraction study of the magnetic ordering of the Cu{sup ++} spins in Nd{sub 1.5}Ba{sub 1.5}Cu{sub 3}O{sub 6+x}

Description: Elastic neutron scattering experiments performed on single crystals of Nd{sub 1.5}Ba{sub 1.5}Cu{sub 3}O{sub 6+y} reveal successive antiferromagnetic (AF) ordering of the Cu{sup ++} spins. The as grown single crystals show an AF structure characterized by a Neel temperature T{sub N1} {approximately} 390K and a magnetic wave vector (1/2 1/2 0) referring to the tetragonal structure of NdBa{sub 2}Cu{sub 3}O{sub 6}. As the temperature is lowered below T{sub N2} {approximately} 150K, a spin reorientation develops and a second AF ordering with (1/2 1/2 1/2) wave vector is stabilized. When the samples are oxygenated the tetragonal symmetry and the Neel temperature T{sub N1} remain unchanged, whereas the spin reorientation at T{sub N2} is suppressed. The results indicate that the Nd/Ba substitution increases the stability of the tetragonal structure upon the oxygen content. This may induce new possibilities of local oxygen ordering that favour the presence of holes in the deficient layer.
Date: December 31, 1991
Creator: Moudden, A. H.; Hennion, B.; Schweiss, P.; Gehring, P. M.; Shirane, G. & Hidaka, Y.
Partner: UNT Libraries Government Documents Department

Microstructural factors influencing critical-current densities of high-temperature superconductors

Description: Microstructural defects are the primary determining factors for the values of critical current densities in superconductors. A review is made to assess, (1) what would be the maximum achievable critical-current density in the oxide superconductors if nearly ideal pinning sites were introduced? and (2) what types of pinning defects are currently introduced in these superconductors and how effective are these in pinning the vortices? Only the case where the applied field is parallel to the c-axis is considered here.
Date: December 31, 1992
Creator: Suenaga, M.
Partner: UNT Libraries Government Documents Department

Studies of structural damage in high-{Tc} superconductors by high-energy heavy-ion irradiation

Description: The results of studies of structural damage by high-energy (MeV) Si{sup +13}, Cu{sup +18}, Ag{sup +21}, and Au{sup +24} ions, using transmission electron microscopy techniques, revealed that the size of the damaged area (amorphous) is strongly dependent on: (1) the stopping power [dE/dx (keV/nm)] of the irradiating ions, (2) the thermal diffusivity of the crystal, (3) the degree of oxygenation, in the case of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}, and (4) the direction of the ion beam with respect to the crystallographic axis.
Date: December 31, 1992
Creator: Zhu, Yimei; Cai, Z. X.; Budhani, R. C.; Welch, D. O. & Suenaga, M.
Partner: UNT Libraries Government Documents Department