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  • 1995-1999  (4)
  • 1985-1989  (11)
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  • 1
    Electronic Resource
    Electronic Resource
    Properties and chemical stability of hot-rolled Ag(7 at. % Cu)-sheathed Bi2Sr2Ca0.64Cu1.64Ox powder-in-tube tapes (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4596-4607 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Bi2Sr2Ca0.64Cu1.64Ox (nominally Bi2212) powders were fabricated into powder-in-tube Ag- and Ag(7 at. % Cu)-sheathed tapes by cold and hot rolling to investigate the effects of sheath composition and rolling conditions on their microstructural development and superconducting properties. Bi2212 tapes with Ag(Cu) sheaths exhibited improved grain alignment and interfacial uniformity, as well as enhanced formation of the Bi-free phase (≈Sr7.5Ca6.5Cu14Ox), relative to the Ag-sheathed specimens. The hot-rolled Ag(Cu)-sheathed tapes displayed superior critical current densities (Jc), where magnetization Jcm=1.5×106 (H(parallel)c) and 4.6×105 A/cm2 (H⊥c) at T=5 K, H=1 T. Correspondingly, these specimens had transport critical current densities (Jct) of 6.7×104 A/cm2 (H(parallel)c) and 5.4×104 A/cm2 (H⊥c) at T=4.2 K, H=0 T and 2.2×104 A/cm2 (H(parallel)c) and 3.0×104 A/cm2 (H⊥c) at T=4.2 K, H=14 T. The chemical stability of the Ag(Cu) sheath regions during the partial melting process was also studied. Rapid oxidation of copper produced Cu2O precipitates in the sheath at 885 °C, and subsequently a Cu2O-free zone developed near the core/sheath interface. A theoretical analysis of Cu2O precipitate formation and decomposition during thermal processing is presented. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359805
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Reactivity and passivation for Bi adatoms on YBa2Cu3O6.9 and Bi2Ca1+xSr2−xCu2O8+y (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 1004-1006 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: X-ray photoemission spectroscopy was used to examine the reactivity of clean YBa2Cu3O6.9 and Bi2Ca1+xSr2−xCu2O8+y surfaces with adatoms of vapor-deposited bismuth. For YBa2Cu3O6.9, depositions ≤8 A(ring) of Bi induce O 1s, Cu 2p3/2, and Bi 4f line-shape changes due to BiO bonding, limited oxygen loss from the substrate, partial conversion of Cu2+ to Cu1+, and growth of Bi metal. For coverages greater than 8 A(ring), there is no reaction and only Bi metal growth is observed. For Bi deposition onto Bi1Ca1+xSr2−xCu2O8+y, there is minimal reaction with only subtle O 1s and Cu 2p3/2 line-shape changes and the nucleation and growth of Bi metal starting at low coverages (≥2 A(ring)). Comparison shows that Bi is less reactive than other metals, except Ag and Au, and that Bi2Ca1+xSr2−xCu2O8+y is more stable toward Bi deposition than YBa2Cu3O6.9.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100650
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  • 3
    Electronic Resource
    Electronic Resource
    rf properties of an oxide-superconductor half-wave resonant line (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 52 (1988), S. 930-932 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Cylindrical rods of YBa2Cu3O7−δ from 0.6 to 1.9 mm in diameter and up to 565 mm long have been used as the center conductor of a half-wave resonant coaxial line. The resonant line can be immersed in liquid nitrogen, which provides excellent cooling of the current-carrying superconducting surface, even in the presence of substantial rf losses. Such superconducting resonant lines have been operated at frequencies of a few hundred MHz and at rf surface magnetic fields up to 150 G at 77 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.99277
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  • 4
    Electronic Resource
    Electronic Resource
    Single-crystal YBa2Cu3O7−x and Bi2Ca1+xSr2−xCu2O8+y surfaces and Ag adatom-induced modification (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 3130-3135 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Comparison of x-ray photoemission results for single crystal and polycrystalline YBa2Cu3O7−x allows us to identify oxygen vacancies in the Cu-O chains and determine their effects on the Cu, Ba, and Y core level line shapes. The deposition of adatoms of Ag onto single crystals of YBa2Cu3O7−x and Bi2Ca1+xSr2−xCu2O8+y leads to changes in the Cu 2p3/2 emission indicative of slight Cu2+ to Cu1+ surface reduction, with greater modification for the 1-2-3's than the 2-1-2-2's. O 1s core level results show Ag-induced broadening because of these surface effects. The Ba 3d and Y 3d structures showed minimal changes for the 1-2-3 surface. Ag deposition onto the 2-1-2-2 samples also leads to Bi dissociation and subsequent surface segregation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342709
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  • 5
    Electronic Resource
    Electronic Resource
    A time-temperature-transformation diagram for the orthorhombic to tetragonal phase transition in YBa2Cu3O7−∂ (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 5411-5414 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An isothermal transformation curve marking the orthorhombic (O) to tetragonal (T) phase transition boundary has been established over a wide temperature range. There exists within the time-temperature-transformation diagram two distinct and separate regions containing superconducting samples with narrow 90- and 60-K transition temperatures, respectively. An oxygen diffusion coefficient at 300 °C in these materials is estimated based on isothermal data. The kinetic process of the T-O transformation is studied. It is found, at all temperatures investigated, that extended annealing reduces the normal-state conductivity of the material and that the best samples are produced for intermediate annealing times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340360
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of oxygen concentration on processing YBa2Cu3O7−x (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 2485-2488 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The sintering kinetics of YBa2Cu3O7−x have been studied from 870 to 930 °C in oxygen/argon mixtures ranging from 0.2% to 100% oxygen. For sintering at temperatures below that required for formation of any liquid phase, densification rates increased with decreasing oxygen concentration, and transport critical current densities increased with increasing density. The activation energy for sintering was 190±30 kJ/mol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344260
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  • 7
    Electronic Resource
    Electronic Resource
    High-temperature deformation of YBa2Cu3O7−δ (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 2079-2082 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Steady-state flow stress of dense (99% of theoretical) polycrystalline YBa2Cu3O7−δ has been measured in direct compression at temperatures between 870 and 980 °C in oxygen partial pressures of 0.03, 0.18, and 1.0×105 Pa for strain rates between 5×10−6 and 4×10−5 s−1. The stress exponent was close to one, indicating that diffusional flow was the dominant deformation mechanism. The flow stress decreased with decreasing oxygen partial pressure, obeying a power law with an exponent of approximately 1/2 . The activation energy was about 800 kJ/mol at an oxygen partial pressure 1×105 Pa, but decreased to 600 kJ/mol at a pressure of 3×103 Pa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344300
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  • 8
    Electronic Resource
    Electronic Resource
    Influence of experimental conditions on the electric field effect in the ceramic (BiPb)2Sr2Ca2Cu3Ox (1997)
    Springer
    Physics of the solid state 39 (1997), S. 1759-1761 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An experimental study is reported of the influence of temperature (T), electric field polarity (±E), as well as of changes in the electrode/insulator/superconductor (E/I/S) measuring system on the field effect in the ceramic (BiPb)2Sr2Ca2Cu3Ox. It has been established that at 77 K and for E⩾60 MV/m the critical current I c and conductivity of the sample increase for I〉I c, irrespective of the field polarity. For lower fields and a negative electrode potential the conductivity in an electric field may decrease. The field effect decreases with increasing temperature, to practically vanish near T c where the sample is still in superconducting state. Experiments carried out with more complex systems E/I/M/I/S and E/I/M/S (M stands for a metallic foil) support the conclusion that it is the external electric field that is responsible for the observed effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1130166
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  • 9
    Electronic Resource
    Electronic Resource
    Some physical properties of an Al2O3-SiC-TiC composite (1997)
    Springer
    Technical physics letters 23 (1997), S. 923-926 
    Details
    ISSN: 1090-6533
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Ceramic samples obtained by hot pressing from a mixture of Al2O3 with admixtures of 23 vol.% TiC powder and 30.9 vol.% SiC whisker crystals are investigated experimentally. The resistivity of the material is measured at temperatures of 4.2–300 K, the infrared reflection spectra are recorded in the region 400–4200 cm–1, and the temperature dependence of the Young’s modulus is investigated at temperatures up to 1300 K. As a result it is it is shown that the conductivity and optical reflection of the high-strength composite have a semimetallic character, which is due to the titanium carbide particles contained in it.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1261934
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of Y2O3 additions on the plasticity of sintered Cr2O3 (1988)
    Springer
    Oxidation of metals 29 (1988), S. 217-223 
    Details
    ISSN: 1573-4889
    Keywords: Oxide plasticity ; Cr2O3 ; Y2O3 additions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract We have carried our constant strain-rate compression tests on polycrystalline Cr2O3 and Cr2O3 doped with 0.09 wt. % Y2O3 to establish whether there exists an effect of Y2O3 on the plasticity of Cr2O3. This study is motivated by previous work on the oxidation of alloys containing reactive-element additions. In that work, it has been observed that the addition of oxygen-active elements, such as Y to alloys that form Cr2O3 or Al2O3 oxide layers upon exposure at high temperature, strongly enhances the adhesion of the oxide layer to the base alloy as compared with alloys without reactive-element additions. We have found that at 1200°C (1) chromia exhibits limited plasticity at high temperatures, and (2) the presence of Y in the oxides does not enhance plasticity compared with addition-free oxides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00751796
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