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  • 2000-2004  (7)
  • 1970-1974
  • 2001  (7)
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  • 2000-2004  (7)
  • 1970-1974
Year
  • 1
    Electronic Resource
    Electronic Resource
    Maxwell–Wagner piezoelectric relaxation in ferroelectric heterostructures (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 5708-5712 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using a serial bilayer model we show that heterogeneous ferroelectric systems may exhibit substantial Maxwell–Wagner piezoelectric relaxation. The relaxation has its origin in the coupling of the dielectric and piezoelectric properties. The model predicts both retardation (positive phase angle and counterclockwise charge–pressure hysteresis) and relaxation (negative phase angle and clockwise charge–pressure hysteresis) of the longitudinal direct piezoelectric coefficient. The theoretical results are confirmed experimentally in ferroelectric ceramic–ceramic bilayers and in a single-phase ferroelectric Aurivillius compound ceramic in which neighboring grains with strongly anisotropic properties may behave as basic Maxwell–Wagner units. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1412272
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    High-power AlGaInN flip-chip light-emitting diodes (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3379-3381 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Data are presented on high-power AlGaInN flip-chip light-emitting diodes (FCLEDs). The FCLED is "flipped-over" or inverted compared to conventional AlGaInN light-emitting diodes (LEDs), and light is extracted through the transparent sapphire substrate. This avoids light absorption from the semitransparent metal contact in conventional epitaxial-up designs. The power FCLED has a large emitting area (∼0.70 mm2) and an optimized contacting scheme allowing high current (200–1000 mA, J∼30–143 A/cm2) operation with low forward voltages (∼2.8 V at 200 mA), and therefore higher power conversion ("wall-plug") efficiencies. The improved extraction efficiency of the FCLED provides 1.6 times more light compared to top-emitting power LEDs and ten times more light than conventional small-area (∼0.07 mm2) LEDs. FCLEDs in the blue wavelength regime (∼435 nm peak) exhibit ∼21% external quantum efficiency and ∼20% wall-plug efficiency at 200 mA and with record light output powers of 400 mW at 1.0 A. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1374499
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Suspected toxicity of atracurium in the neonate (2001)
    Oxford UK : Blackwell Science Ltd
    Pediatric anesthesia 11 (2001), S. 0 
    Details
    ISSN: 1460-9592
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9592.2001.0750d.x
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Micromechanics of Deformation in Porous Liquid-Phase-Sintered Alumina under Hertzian Contact (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    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: A series of fine-grained porous alumina samples, with and without a liquid phase, were fabricated in compositions matched closely to commercially available alumina used as microelectronic substrates. Hertzian indentation on monolithic specimens of the glass-containing samples produced a greater quasi-ductile stress–strain response compared with that observed in the pure alumina. Maximum residual indentation depths, determined from surface profilometry, correlated with the stress–strain results. Moreover, microstructural observations from bonded interface specimens revealed significantly more damage in the form of microcracking and under extreme loading, pore collapse, in the glass-containing specimens. The absence of the typical twin faulting mechanism observed for larger-grained alumina suggests that the damage mechanism for quasi-ductility in these fine-grained porous aluminas was derived from the pores acting as a stress concentrator and the grain boundary glass phase providing a weak path for short crack propagation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00925.x
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of Dopant Concentration on Creep Properties of Nd2O3-Doped Alumina (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    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 microstructural features and tensile creep behavior of Al2O3 doped with Nd2O3 at levels ranging from 100 to 1000 ppm (Nd:Al atomic ratio) were systematically investigated. Compositional mapping, using both high-resolution scanning transmission electron microscopy and secondary ion mass spectroscopy revealed that, for all of the compositions studied, the Nd3+ ions were strongly segregated to the Al2O3 grain boundaries. Microstructural observations revealed that the solubility of Nd2O3 was between 100 and 350 ppm. Tensile creep tests were conducted over a range of temperatures (1200°–1350°C) and stresses (20–75 MPa). Both the stress and grain-size exponents were analyzed. In selected experiments, controlled grain-growth anneals were used to enable creep testing of samples of the same average grain size but different neodymium concentrations. Independent of dopant level, the neodymium additions decreased the creep rate by 2–3 orders of magnitude, compared with that of undoped Al2O3. The value of the apparent creep activation energy increased with increased dopant concentration and then saturated at dopant levels exceeding the solubility limit. Overall, the results of the present study were consistent with a creep-inhibition mechanism whereby oversized segregant ions reduce grain-boundary diffusivity by a site-blocking mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00783.x
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of Liquid Volume Fraction on Grain Growth of Magnesium Oxide Grains in Molten Calcium Magnesium Silicate Matrix (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    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 grain-growth kinetics of fully dense MgO compacts containing various amounts of CaMgSiO4 from 1 to 20 wt% was investigated. The relationship between grain size, volume fraction of liquid phase, and annealing time was determined. The exponent of grain growth (n) was 3, independent of the volume fraction of the liquid phase, and the rate constant (k) was inversely proportional to the volume of liquid. The overall grain-growth kinetics was governed by mass transport through liquid pockets at grain corners, which provided the longest diffusion paths between the grains. This result was modeled after a solid-state system containing isolated pores in which the pores move by vapor-phase diffusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb01131.x
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of Zirconium Oxide on the Reaction Bonding of Aluminum Oxide (2001)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 84 (2001), S. 0 
    Details
    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: In the reaction-bonded aluminum oxide (RBAO) process, attrition-milled Al/Al2O3 powder compacts are reacted in air to form Al2O3-based ceramics. Typically, ZrO2 powder is added to control the final microstructure and properties, resulting in fine-grained, high-strength materials. In this study, the effects of ZrO2 on the reactivity of RBAO samples were examined using thermogravimetric analysis, X-ray diffractometry, and other techniques. Previously, it was shown that a self-propagating reaction could occur during firing of RBAO in air. This reaction was attributed solely to the fast and highly exothermic oxidation of the aluminum on the surface of the sample, but the results of the current study show that it is related to a reaction between aluminum and ZrO2, forming Al2O3 and Al3Zr. As a consequence, a new reaction sequence for RBAO consistent with these observations has been proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2001.tb00779.x
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