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  • 1
    Electronic Resource
    Electronic Resource
    Microhardness measurements on dopant modified superconducting YBa2Cu3O7 ceramics (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1307-1311 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the microhardness of undoped and dopant modified YBa2Cu3O7 superconducting ceramics as a function of load and dopant concentration using the Vickers indentation technique. In the undoped composition, the hardness value increased monotonically with decreasing load. We concluded that the higher hardness values, measured at lower loads, represent the hardness of single-crystalline grains. The higher loads [∼100–200 gf (1–2 N)] usually resulted in complex crack patterns and extensive crack propagation along the grain boundaries. With Zn or Li as the substitutional dopant in the Cu site, the hardness increased linearly with the dopant concentration up to 10% of dopant to Cu ratio at a load of 25 gf (0.25 N). Our data can be modeled by a solute solution strengthening mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341851
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  • 2
    Electronic Resource
    Electronic Resource
    Antiplasticization and volumetric behavior in glassy polymers (1988)
    s.l. : American Chemical Society
    Macromolecules 21 (1988), S. 1470-1475 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00183a042
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  • 3
    Electronic Resource
    Electronic Resource
    Second phase development in Sr-doped TiO2 (1983)
    Springer
    Journal of materials science 18 (1983), S. 2688-2696 
    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 In the Ti-rich region of the SrO-TiO2 system, a temperature-composition range is found to exhibit limited solubility of strontium, the maximum limit being 0.5 mol % Sr. It is also found that a two-phase region exists between this solubility limit and SrTiO3, in agreement with existing phase diagrams. When the strontium concentration is small (⩽ 0.5 mol %), strontium segregates to the grain boundaries to form a second phase of SrTiO3 below the solubility limit. Above 1200
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00547585
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  • 4
    Electronic Resource
    Electronic Resource
    Lead zinc niobate pyrochlore: Structure and dielectric properties (1989)
    Springer
    Journal of materials science 24 (1989), S. 541-548 
    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 In Pb(B x ′B1−x ″)O3 ceramic compositions, it is customary to find a mixture of cubic pyrochlore and perovskite phases after calcination. Based on X-ray diffraction analysis, we concluded that both phases are made up of the same structural unit of BO6 octahedra. The B′ and B″ ions occupy the B sites randomly to the extent that local charge equilibrium is maintained. Thus a general formula for the pyrochlore phase can be expressed as Pb(B x ′B1−x )O3 · Op where O ⩽p ⩽ 0.5. An extensive study of the Pb(Zn x Nb1−x )O3.5−1.5x pyrochlore system was made by varying the zinc concentration. We interpret changes in the X-ray diffraction pattern and the lattice constant as indicative of the changing occupancy of the seventh oxygen sites in order to maintain local charge balance. The best combination of the dielectric properties, with a dielectric constant of130 and a σ factor greater than 1000 at10 MHz, is achieved at a composition of 0.3 ⩽x ⩽ 0.4 and a sintering temperature of 980° C. The temperature coefficient of the dielectric constant measures −0.75 × 10−3° C−1. It decreases to −0.54 × 10−3° C−1 when5 mol% of PbTiO3 was mixed with the nominal pyrochlore compositions and sintered. Thus, it may be possible to effect a larger change in the temperature coefficient by judiciously including selective amounts of a second phase which has the best compensating temperature coefficient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01107439
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  • 5
    Electronic Resource
    Electronic Resource
    Superconductivity and microstructures of fluorinated and chlorinated YBa2Cu3Oz (1989)
    Springer
    Journal of materials science 24 (1989), S. 703-707 
    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 Superconductivity and microstructures of fluorinated and chlorinated YBa2Cu3O z were investigated with BaF2 and BaCl2 as the fluorination and chlorination agents. The incomplete decomposition of BaF2 and BaCl2 led to inhomogeneous phase and elemental distributions as shown by energy dispersive analysis of X-rays (EDAX) and X-ray diffraction (XRD) analysis. A high (y ⩾ 2) chlorine concentration stabilized a tetragonal perovskite structure in the YBa2Cu3Cl y O z compositions while an orthorhombic structure was observed in samples with a lower chlorine concentration. The maximum superconductivity transition temperature,T c, was ⩽ 95 K in these fluorinated and chlorinated samples. Thus, our data are contradictory to the claims of high transition temperatures (155 K) recently reported for some of these compositions. The microstructural and phase composition data reported here could provide useful information in the search for possibly highT c phases in these fluorinated and chlorinated compositions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01107463
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  • 6
    Electronic Resource
    Electronic Resource
    In situ observation of electrode melting in multilayer ceramic capacitors (1989)
    Springer
    Journal of materials science 24 (1989), S. 4128-4137 
    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 In the usage of multilayer ceramic capacitors, we are concerned with the intrinsic dielectric properties of the ceramic and its long-term stability/reliability under external stresses in service conditions. Of equal importance to long-term reliability is the short-term survivability under current (power)-surge conditions. It differs from the ability to withstand voltage surge, which is determined by the dielectric strength of the ceramic. In this paper, we present some observations on sectioned and polished multilayer ceramic capacitors, which were subjected to “controlled” current-surge test conditions. Capacitors from several vendors were examined. The samples were examinedin situ under an optical microscope while current pulses of varying magnitude were applied at a constant voltage. Subsequently some samples were further examined by scanning electron microscopy. The failure mechanism appeared to be the heat-induced local melting of internal electrodes, which might then lead to a blow-out or charring of the capacitor. In less severe cases, we observed local melting and crack formation in the surrounding ceramic as well. The primary change in capacitor properties was in the degradation of the insulation resistance. In severe cases, this also led to an increase in the dissipation factor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01168985
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  • 7
    Electronic Resource
    Electronic Resource
    Enhancement of impurity removal from polymer films (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 30 (1985), S. 4499-4516 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The problem of the enhancement of the removal of a volatile impurity in a polymer film by the addition of a second solvent is analyzed. The introduction of a second solvent that diffuses faster than the impurity can increase the free volume of the system and can thus facilitate removal of the volatile impurity. Solution of the ternary diffusion problem indicates the role of the properties of the second solvent and of processing conditions on the devolatilization effectiveness. It is shown that more than a 10-fold decrease in the devolatilization time can be achieved using a second solvent and appropriate processing conditions.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1985.070301201
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  • 8
    Electronic Resource
    Electronic Resource
    Influence of the glass transition on solvent self-diffusion in amorphous polymers (1988)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 26 (1988), S. 1059-1065 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The free-volume theory of diffusion is used to analyze the temperature dependence of solvent self-diffusion coefficients both above and below the glass transition temperature at concentrations removed from the pure polymer limit. The glass transition can have a pronounced effect on the temperature dependence of solvent self-diffusion coefficients at small solvent concentrations, but the theory predicts a decreased effect of the transition on the diffusion process with increasing solvent concentration.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1988.090260510
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  • 9
    Electronic Resource
    Electronic Resource
    Self-diffusion in polymer-solvent-solvent systems (1984)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 22 (1984), S. 459-469 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The ternary self-diffusion data of Ferguson and von Meerwall are analyzed using a generalized form of the free-volume theory of diffusion proposed by Vrentas and Duda. It is shown that the predicative capabilities of this form of the theory are satisfactory and comparable to those of the Fujita version. The lack of significant differences in the predictive capabilities of the two theories for the two ternary systems studied is explained in terms of the properties of the materials utilized. The data of Ferguson and von Meerwall are consistent with the hypothesis that the size of a polymer jumping unit is a fixed property of the polymer and that the jumping units for sufficiently large n-paraffins are smaller than the entire solvent molecule.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1984.180220308
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  • 10
    Electronic Resource
    Electronic Resource
    Free-volume theories for self-diffusion in polymer-solvent systems. I. Conceptual differences in theories (1985)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 23 (1985), S. 275-288 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Conceptual differences in two recent versions of the free-volume theory for self-diffusion in polymer-solvent systems are identified and discussed. The validity of the assumptions of these two theories is tested using experimental data. In all cases, the experimental evidence favors the Vrentas-Duda free-volume theory over the Paul version of this theory.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1985.180230204
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