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  • Articles  (162)
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  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (162)
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  • Articles  (162)
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  • 1
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The purpose of the present investigation is to describe the influence of the processing parameters on the dielectric behavior of manganese-doped Ba(Ti1−xZrx)O3ceramics, particularly variations in the small-signal aging rate, temperature characteristic, and hysteresis. In this paper, the aging behavior of base-metal electrode materials above the temperature of the permittivity maximum (TM), including the influence of the zirconium content and annealing conditions, is described for the first time. The aging rate at temperatures greater than TM decreases as the oxygen partial pressure increases during annealing and the zirconium content increases, whereas the aging rate exhibits a maximum at temperatures much less than TM. The behavior is explained in terms of a diffuse phase transition. Hysteresis-loop deformation is observed during aging.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 36 (1985), S. 1-13 
    ISSN: 1432-0630
    Keywords: 78.55.-m ; 78.55.Ds ; 71.55.Fr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Photoluminescence is studied in silicon, deformed in a well-defined and reproducible way. Usual deformation conditions (high temperature, low stress) result in sharp spectra of the D1 through D4 lines as recently described in the literature. New lines D5 and D6 emerge for predeformation as above and subsequent low-temperature, high-stress deformation. Another new sharp line, D12, is observed when both the familiar and the novel lines appear simultaneously. Annealing for 1 h atT A≳ 300 °C causes all new lines to disappear and the D1–D4 spectra to reappear. Quantitative annealing and TEM micrographs suggest that D5 is related to straight dislocations and D6 to stacking faults, whereas D1–D4 are due to relaxed dislocations. Photoluminescence under uniaxial stress shows that D1/D2 originate in tetragonal defects with random orientation relative to 〈100〉 directions, whereas D6 stems from triclinic centers, preferentially oriented — as are the D3/D4 centers. We conclude that the D3/D4 and the D5 and D6 defects are closely related, whereas the independent D1/D2 centers might be deformation-produced point defects in the strain region of dislocations.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We report formation of single- and two-phase glasses from rare-earth oxide–alumina materials. Liquids with the Y3Al5O12 and Er3Al5O12 compositions underwent a liquid–liquid phase transition which resulted in glasses with a cloudy appearance due to spheroids of one glass in a matrix of a second glass. The two glasses were isocompositional within the limits of experimental error. Clear, brilliant, single-phase glasses were obtained from La3Al5O12, ErLaYAl5O12, and compositions containing ≥5 mol% La2O3 substituted for the other rare-earth oxides. Formation of two glasses is attributed to nucleation and growth of the second liquid at a temperature below the equilibrium liquid–liquid transition temperature. Addition of lanthanum depresses the phase transition temperature below the glass transition temperature and the liquid–liquid phase transition is not observed. The results are discussed in the context of first-order liquid–liquid phase transitions (polyamorphism) and formation of single-phase glass from liquids that contain a high proportion of 4-coordinate aluminum ions.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 83 (2000), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We report the first measurements of the structure factor, S(Q), and the pair distribution function, G(r), of Al6Si2O13 (3:2 mullite) in the normal and supercooled liquid states in the temperature range 1776–2203 K. Measurements are obtained by synchrotron X-ray scattering on levitated, laser-heated liquid specimens. The S(Q) shows a prepeak at 2.0 Å−1 followed by a main peak at 4.5 Å−1 and a weak feature at 8 Å−1. The G(r) shows a strong (Si,Al)–O correlation at 1.80 Å at high temperature that moves to 1.72 Å as the liquid is supercooled. The second and third nearest neighbor peaks at 3.0 and 4.25 Å sharpen with supercooling. The short-range structure of the high-temperature liquid is similar to the corresponding glasses produced by rapid quenching. Supercooling causes an increase in the concentration of tetrahedral Si4+ ions, which is manifested by the large shift in the first peak to lower ionic distance, r, values in G(r). The increase in tetrahedrally coordinated Si4+ ions is offset by an increase in octahedral Al3+ ions. The clustering of the SiO44− tetrahedral units results in increased viscosity of the liquid at temperatures below the melting point, which is consistent with Al6Si2O13 being a fragile liquid.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 80 (1997), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Aspects of calibration of intensities of SIMS secondary ions vs concentration as well as sputtering time vs depth are considered for Cr-doped CoO. Advantages and limitations of the SIMS method in quantitative analysis of segregation-induced concentration profiles in oxide crystals are discussed. The studies indicate a substantial effect due to charging the surface during sputtering. The depth calibration was performed by using the Ta2O5/Ta system as a standard. Good depth resolution was revealed. The calibration dependence of Cr intensities on concentration is characterized by a wide scatter of data caused by charging the surface. Very good shape reproducibility of the intensity ratio vs depth profiles was revealed. Therefore, normalized intensity ratios can be used for calibration.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 80 (1997), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Surface segregation-induced depth profiles of Cr were determined for Cr-doped CoO single crystals equilibrated at different temperatures (1373–1673 K) and oxygen partial pressures (102–105 Pa). It was shown that the shape of the depth profiles depends on both conditions of annealing and subsequent cooling procedure. It has been observed that during slow cooling of specimens from the condition of segregation equilibrium at elevated temperatures to the temperature of the experiment (room temperature), there is substantial change of the concentration profile involving desegregation of Cr (Cr diffusion from the surface to the bulk) resulting in its depletion. It has also been shown that the rate of the desegregation process (the process which results in a decrease of surface concentration) is slower than the lattice transport kinetics of Cr in CoO. It is concluded that the desegregation is rate-controlled by the decomposition of a spinel-type bidimensional surface structure which is formed at elevated temperatures as a result of Cr segregation.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1520-5002
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1520-5002
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Chemistry of materials 4 (1992), S. 922-928 
    ISSN: 1520-5002
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Single-phase glasses containing 37.5 mol% Y2O3, 7 mol% La2O3, and 1 mol% Pr, Ho, Nd, Er, Sm, Tm, Eu, or Yb oxide substituted for part of the Y2O3 were synthesized by containerless melting. The spectral transmission and absorption cross sections of the glasses were determined at wavelengths from 360 to 3300 nm. The electronic transitions were broadened compared with results obtained in a crystalline yttrium aluminum garnet (YAG) host. The infrared transmission of the host glass extended to 6000 nm. The optical and physicochemical properties of these glasses are well suited for optical device applications.
    Type of Medium: Electronic Resource
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