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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 pr… more
Date: October 20, 1992
Creator: Nahum, M.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department
open access

Aspects of the SrO-CuO-TiO2 Ternary System Related to the Deposition of SrTiO3 and Copper-Doped SrTiO3 Thin-Film Buffer Layers

Description: YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) coated conductors are promising materials for large-scale superconductivity applications. One version of a YBCO coated conductor is based on ion beam assisted deposition (IBAD) of magnesium oxide (MgO) onto polycrystalline metal substrates. SrTiO{sub 3} (STO) is often deposited by physical vapor deposition (PVD) methods as a buffer layer between the YBCO and IBAD MgO due to its chemical stability and lattice mismatch of only {approx}1.5% with YBCO. In … more
Date: December 20, 2004
Creator: Ayala, A.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department
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Fabrication and characterization of Ag-clad Bi-2223 tapes.

Description: The powder-in-tube (PIT) technique was used to fabricate multifilament (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} (Bi-2223) superconducting tapes. Transport current properties of these tapes were enhanced by increasing the packing density of the precursor powder and improving the mechanical deformation condition. A critical current (I{sub c}) of > 35 A in long lengths (> 200 m) tapes has been achieved. In measuring the dependence of critical current density on magnetic field and te… more
Date: April 20, 1999
Creator: Balachandran, U.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Influence of pulse width and target density on pulsed laser deposition of thin YBaCuO film.

Description: We have studied the effects of temporal pulse width and target density on the deposition of thin films of YBaCuO. A 248nm excimer laser and an 825nm Ti-sapphire laser were used to conduct the experiments with pulse widths of 27 ns, 16 ns, and 150 fs, and target densities of 80% and 90%. Scanning electron microscope photomicrographs and profilometer traces show a striking difference between nanosecond and femtosecond laser irradiation. Shortening the pulse width reduced particulate formation, pr… more
Date: January 20, 1999
Creator: Vikram, S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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The use of cubic Nd-Ba-Cu-O seeds to create {theta}[100], 90{degree}-{theta}[100], and {theta}[001] tilt Y-Ba-Cu-O grain boundaries.

Description: Using seeding techniques to control the orientation of grains, we have been able to create a wide variety of YBa{sub 2}Cu{sub 3}O{sub 6+x}, grain boundaries. In addition to five domain samples with 90{degree}[100] twist and tilt grain boundaries, we have now developed a method to produce grain boundaries in the same sample that have the misorientations {theta}[001] tilt, {theta}[100] tilt, and 90{degree} {approximately} {theta}[100], where the disorientation angle {theta} is fully controllable.… more
Date: October 20, 1998
Creator: Field, M. B.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Atomic Capture of $mu$$sup -$ Mesons in Chemical Compounds and The "Fermiteller Z Law"

Description: Experimental studies of the relative atomic mu --meson capture probabilities in the constituents of chemical compounds are described. Fermi and Teller had predicted that the atomic-capture probability is proportional to the nuclear charge of the atomic species weighted by its atomic concentration. This is sometimes referred to as the Fermi-Teller Z law.'' Previous experiments indicated no clear systematics to this capture process, and there are conflicts between the results of several measureme… more
Date: August 20, 1962
Creator: Baijal, J. S.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries Government Documents Department
open access

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 pr… more
Date: October 20, 1992
Creator: Nahum, M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Magnetic excitations in the S = {1/2} quasi-one-dimensional magnet Sr{sub 14{minus}x}Ca{sub x}Cu{sub 24}O{sub 41}

Description: Neutron scattering experiments have been performed on Sr{sub 14{minus}x}Ca{sub x}Cu{sub 24}O{sub 41} (x = 3 and 6), which consists of CuO{sub 2} chains and CuO{sub 2}O{sub 3} ladders, in order to study the effect of Ca substitution on the dimerized state in the chains. The Ca substitution broadens the excitation peak although the excitation energy is almost unchanged. The effects of Ca and Y substitution on the dimerized state are compared.
Date: August 20, 1998
Creator: Matsuda, M.; Katsumata, K.; Shapiro, S.M. & Shirane, G.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Coal conversion wastewater treatment by catalytic oxidation in supercritical water

Description: Wastewaters from coal-conversion processes contain phenolic compounds in appreciable concentrations. These compounds need to be removed so that the water can be discharged or re-used. Catalytic oxidation in supercritical water is one potential means of treating coal-conversion wastewaters, and this project examined the reactions of phenol over different heterogeneous oxidation catalysts in supercritical water. More specifically, the authors examined the oxidation of phenol over a commercial cat… more
Date: October 20, 1999
Creator: Savage, Phillip E.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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Solution Deposition Approaches To Coated Conductor Fabrication on Biaxially Textured Ni-W Alloy Substrates

Description: Sol-gel processing of La{sub 2}Zr{sub 2}O{sub 7} (LZO) was used to process buffer layers on biaxially textured Ni-3 at.%W substrates. A reel-to-reel continuous dip-coating unit was used to deposit the solution buffers. Epitaxial LZO films have been obtained through continuous processing on Ni-3 at.%W substrates with strong texture and uniform microstructure. The carbon content in these films were analyzed using proton resonance Rutherford Backscattering (RBS). The process parameters have been m… more
Date: June 20, 2001
Creator: Sathyamurthy, S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+delta} c-axis twist Josephson junctions : a new phase-sensitive test of order parameter symmetry.

Description: Li et al. found that the critical current density J{sub c}{sup J} across atomically clean c-axis twist junctions of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} is the same as that of the constituent single crystal, J{sub c}{sup S}, independent of the twist angle {phi}{sub 0}, even at and below T{sub c}. They investigated theoretically if a d{sub x{sup 2}{minus}y{sup 2}} wave order parameter might twist by mixing in d{sub xy}-wave components, but found that such mixing cannot possibly explain … more
Date: September 20, 1999
Creator: Klemm, R. A.; Arnold, G.; Bille, A.; Rieck, C. T. & Scharnberg, K.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Studies of grain boundaries in melt textured YBa{sub 2}Cu{sub 3}O{sub x}.

Description: [001] tilt grain boundaries were studied in bi-crystal samples of melt textured YBa{sub 2}Cu{sub 3}O{sub x}. Grain boundary critical current densities J{sub CB} were obtained from SQUID magnetization measurements on ring samples that contain the grain boundary. The dependence of J{sub CB} on oxygen stoichiometry and oxygen ordering were investigated and preliminary studies of grain boundary doping with selected cations, including Ca, Sr, and Bi were undertaken.
Date: May 20, 2002
Creator: Veal, B. W.; Claus, H.; Chen, L. & Paulikas, A. P.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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