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  • 1
    Electronic Resource
    Electronic Resource
    Ion beam controllable modification of YBa2Cu3O7−x superconducting thin films (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7915-7917 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The superconducting transport properties of high-quality epitaxial YBa2Cu3O7−x thin films have been controllably modified using Ar+ ion implantation. It was found that both the critical current density Jc and the superconducting transition temperature Tc significantly decreased with fluence. However, when Jc (at 77 K, H=0) decreased by six orders of magnitude, Tc only decreased from 89 to 77.5 K. A fluence of 5×1012 Ar/cm2 was sufficient to reduce Jc near zero, but Tc still remained above 77 K. We have observed the structure and the morphology of the sample using x-ray diffraction and high-resolution transmission electron microscopy. A film irradiated with Ar+ ions became semiconductor at a bombardment fluence of about 1.2×1013 Ar/cm2, while its superconducting state completely disappeared for an Ar+ dose of about 2.2×1013 Ar/cm2. An Ar+ fluence of 5×1014 Ar/cm2 made the sample amorphous with so high resistivity that it could be treated as insulator. The experimental results showed the possibility of fabricating Josephson junction devices from YBa2Cu3O7−x superconducting thin films and patterning this kind of films by ion implantation technique.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347481
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  • 2
    Electronic Resource
    Electronic Resource
    Wetting front instability in randomly stratified soils (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 8 (1996), S. 353-369 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A probabilistic criterion is derived for the onset of wetting front instability during surface water infiltration into a randomly stratified soil. It is based on the common assumption that the natural log hydraulic conductivity of the soil is a random, multivariate Gaussian function of space. Whereas the mean (expectation) of this function may exhibit a drift, its fluctuations about the mean are statistically homogeneous with constant variance and autocorrelation scale. The wetting front is taken to form a sharp boundary. Closed-form expressions for the probability of instability, and for the mean critical wave number, are obtained either directly or via a first-order reliability method. Monte Carlo simulations are used to verify these analytical solutions as well as to determine the mean maximum rate of incipient finger growth and corresponding mean wave number. The effects of applied pressure gradient, capillary pressure head at the wetting front, and statistical parameters of the hydraulic conductivity field on instability and incipient finger growth are investigated for a wide range of these variables. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868790
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  • 3
    Electronic Resource
    Electronic Resource
    Preparation of high J c YBa2Cu3O7−δ superconducting thin films by ion beam sputtering deposition (1991)
    Springer
    Applied physics 52 (1991), S. 203-205 
    Details
    ISSN: 1432-0630
    Keywords: 74.75.+t ; 81.15.Cd
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Preparation of high T c and high J c YBa2Cu3O7−δ superconducting thin films by ion beam sputtering deposition is reported. The main factors affecting the composition of the films and the orientation of the crystal grains have been examined. Experimental results show that the Y, Ba and Cu composition of as-deposited films can be conveniently and accurately adjusted by a combined sputtering target which consists of a large sintered target of YBa2Cu3O7−δ and a small one that is Ba and Cu rich (YBa2.5Cu3.3Ox). Fabrication conditions of highly oriented superconducting thin films are described. YBa2Cu3O7−δ superconducting films with zero resistance at 88–90.5K and critical current density J c (at 77K) of 1.5×105 A/cm2 are obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00324419
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  • 4
    Electronic Resource
    Electronic Resource
    The mechanism of copper oxide segregations in Y-Ba-Cu-O/YSZ thin films (1990)
    Springer
    Applied physics 50 (1990), S. 165-168 
    Details
    ISSN: 1432-0630
    Keywords: 66.30.−h ; 68.20.+t ; 68.48.+f ; 74.70Rv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Experimental results show that copper-oxide segregation occurs by chemical reaction at the interface between Y-Ba-Cu-O thin films and ZrO2 substrates, which results in a layer of BaZrO3 (thickness ∼0.8 μm). A “buffer layer” of silver inbetween the film and substrate as a barrier for the diffusion of Ba atoms into YSZ or the formation of silver-copper alloys during a high temperature annealing process prevents the copper oxide segregation. It is concluded that BaZrO3 is a prospective candidate substrate for the fabrication of high-T cthin films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00343413
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  • 5
    Electronic Resource
    Electronic Resource
    Superconducting characteristics and epitaxial-growth analyses of YBa2Cu3O7−x thin films by direct-current magnetron sputtering (1993)
    Springer
    Journal of materials science 28 (1993), S. 4846-4849 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Using direct-current magnetron sputtering deposition, we have successfully prepared highquality epitaxial YBa2Cu3O7−x thin films, on (1 0 0) and (1 1 0) ZrO2, SrTiO3 and LaAlO3 substrates. The films reached zero resistance at about 90 K and had a critical current density, J c (at 77 K, H=O), above 106 Acm−2. Electrical measurements showed that the films had a small microwave surface resistance. The epitaxial structure of the films was studied by X-ray diffraction (XRD), Rutherford backscattering (RBS) and channeling spectroscopy, X-ray double-crystalline diffraction and transmission electron microscopy (TEM). It was found that the c-axis of the film grown on the (1 0 0) substrates under optimum deposition conditions was perpendicular to the substrate surface. But on the (1 1 0) substrates, epitaxial growth was along the (1 1 0) or (1 0 3) direction. The experimental results indicate that the films had excellent superconducting properties and complete epitaxial structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00361145
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of gas production induced volumetric strain on permeability of coal (1997)
    Springer
    Geotechnical and geological engineering 15 (1997), S. 303-325 
    Details
    ISSN: 1573-1529
    Keywords: coalbed methane ; matrix shrinkage ; permability ; coal ; volume strain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Summary The gas permeability of a coalbed, unlike that of conventional gas reservoirs, is influenced during gas production not only by the simultaneous changes in effective stress and gas slippage, but also by the volumetric strain of the coal matrix that is associated with gas desorption. A technique for conducting laboratory experiments to separate these effects and estimate their individual contribution is presented in this paper. The results show that for a pressure decrease from 6.2 to 0.7 MPa, the total permeability of the coal sample increased by more than 17 times. A factor of 12 is due to the volumetric strain effect, and a factor of 5 due to the gas slippage effect. Changes in permeability and porosity with gas depletion were also estimated using the measured volumetric strain and the matchstick reservoir model geometry for flow of gas in coalbeds. The resulting variations were compared with results obtained experimentally. Furthermore, the results show that when gas pressure is above 1.7 MPa, the effect of volumetric strain due to matrix shrinkage dominates. As gas pressure falls below 1.7 MPa, both the gas slippage and matrix shrinkage effects play important roles in influencing the permeability. Finally, the change in permeability associated with matrix shrinkage was found to be linearly proportional to the volumetric strain. Since volumetric strain is linearly proportional to the amount of gas desorbed, the change in permeability is a linear function of the amount of desorbing gas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00880711
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  • 7
    Electronic Resource
    Electronic Resource
    Influence of gas production induced volumetric strain on permeability of coal (1997)
    Springer
    Geotechnical and geological engineering 15 (1997), S. 303-325 
    Details
    ISSN: 1573-1529
    Keywords: coalbed methane ; matrix shrinkage ; permability ; coal ; volume strain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The gas permeability of a coalbed, unlike that of conventional gas reservoirs, is influenced during gas production not only by the simultaneous changes in effective stress and gas slippage, but also by the volumetric strain of the coal matrix that is associated with gas desorption. A technique for conducting laboratory experiments to separate these effects and estimate their individual contribution is presented in this paper. The results show that for a pressure decrease from 6.2 to 0.7 MPa, the total permeability of the coal sample increased by more than 17 times. A factor of 12 is due to the volumetric strain effect, and a factor of 5 due to the gas slippage effect. Changes in permeability and porosity with gas depletion were also estimated using the measured volumetric strain and the matchstick reservoir model geometry for flow of gas in coalbeds. The resulting variations were compared with results obtained experimentally. Furthermore, the results show that when gas pressure is above 1.7 MPa, the effect of volumetric strain due to matrix shrinkage dominates. As gas pressure falls below 1.7 MPa, both the gas slippage and matrix shrinkage effects play important roles in influencing the permeability. Finally, the change in permeability associated with matrix shrinkage was found to be linearly proportional to the volumetric strain. Since volumetric strain is linearly proportional to the amount of gas desorbed, the change in permeability is a linear function of the amount of desorbing gas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018419927038
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  • 8
    Electronic Resource
    Electronic Resource
    Study on the α2/γ interfacial structures in a two-phase (α2 + γ) alloy deformed at elevated temperature (2000)
    Springer
    Journal of materials science 35 (2000), S. 399-409 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The details of structure modification on α2/γ interface induced by deformation in a hot-deformed Ti-45Al-10Nb alloy were investigated by conventional and high-resolution transmission electron microscopy. A new type of dislocation ledge containing 1/3[111] partials was identified. The Burgers vectors of these dislocation ledges were determined to be 1/2[110] or 1/2〈101]. The formation mechanism of this new type of dislocation ledge is discussed. Also, two types of hot deformation induced α2/γ interfaces, coherent interfaces with high density of ledges and misoriented semi-coherent α2/γ interfacial boundaries were observed. For the misoriented semi-coherent α2γ interfaces, the density of dislocation ledges in these interfaces increases with the misoriented angle between the (111) $$_\gamma $$ and (0001) $$_{\alpha 2} $$ planes, and 1/3[111] partial dislocations were involved in all the dislocation ledges. The formation mechanism of these deformation-induced α2/γ interfaces were discussed related to the role of α2/γ interfaces adjusting the deformation as a dislocation sink absorbing the slipping dislocations in the γ phase. Moreover, misoriented semi-coherent α2γ interface related deformation twinning and structure transformation induced by deformation were analyzed and discussed related to the role of α2/γ interfaces as a dislocation source during deformation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004711216371
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  • 9
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    Characteristics and mechanisms of cadmium adsorption from aqueous solution using lotus seedpod-derived biochar at two pyrolytic temperatures (2018)
    Springer
    Details
    Publication Date: 2018-02-14
    Print ISSN: 0944-1344
    Electronic ISSN: 1614-7499
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Springer
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  • 10
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    Copper and l-(−)-quebrachitol catalyzed hydroxylation and amination of aryl halides under air (2020)
    Elsevier
    Details
    Publication Date: 2020-08-01
    Print ISSN: 0040-4039
    Electronic ISSN: 1873-3581
    Topics: Chemistry and Pharmacology
    Published by Elsevier
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