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  • Articles: DFG German National Licenses  (4)
  • 1985-1989  (4)
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  • Articles: DFG German National Licenses  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    Optical dielectric functions for amorphous Al2O3 and γ-Al2O3 (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 3727-3730 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using the classical oscillator model, the optical dielectric functions for amorphous alumina (a-Al2O3) and gamma alumina (γ-Al2O3) thin films prepared by ion implantation and subsequent annealing of sapphire (α-Al2O3) substrates were determined for the first time from analysis of infrared reflection spectra. Two transverse optical modes at 422 and 721 cm−1 were obtained for the a-Al2O3 film while four modes at 357, 536, 744, and 807 cm−1 were identified for the γ-Al2O3 film. Also, the problems involving the analysis of modes with large damping are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341367
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Diffusion of hydrogen in Pb β‘ alumina (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 4587-4593 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hydrogen diffuses into Pb β‘ alumina during ion exchange of Na β‘ alumina in molten lead halide salts. The hydrogen resides in the lattice as OH− groups with the protons bound at several kinds of sites. The intrinsic diffusion coefficients of hydrogen and deuterium determined from analysis of infrared absorption profiles following isotope exchange are 9.1, 5.3, and 1.1.×10−7 cm2/s at 515, 455, and 350 °C, respectively. These data fit an Arrhenius equation with an activation energy of 0.54 eV and a preexponential factor of 2.67×10−3 cm2/s. Protons are transported through the conduction layers by hopping to adjacent O= ions. The principal contribution to the activation energy is the energy required to break the O–H bond.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336251
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Comparison of thermal conductivity data for partially stabilized zirconia with values derived from thermal diffusivity results (1988)
    Springer
    International journal of thermophysics 9 (1988), S. 587-598 
    Details
    ISSN: 1572-9567
    Keywords: thermal conductivity ; thermal diffusivity ; zirconia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The thermal conductivity of partially stabilized zirconia was measured over the temperature range 320–1273 K using the radial heat flow method. The data have an absolute uncertainty of about ±2% and repeat measurements showed no evidence of changes in the thermal conductivity at high temperatures. This also was true for the thermal diffusivity data, which were obtained in vacuum over the temperature range 300–1473 K. Both sets of thermal conductivity data pass through minima at high temperatures. Quantitative differences were observed in the temperatures and thermal conductivities of the two minima. The results were analyzed by assuming parallel conduction by phonons and photons, and the phonon component was identified by fitting lower-temperature data. Extrapolating this curve allowed identification of the photon contribution to the thermal conductivity at high temperatures. The photon contribution approached a T 3 function and was larger in the thermal conductivity specimens. The difference in the photon contributions correlates with changes in the optical properties of the samples produced during the high temperature measurments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00503157
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Reaction of polycrystalline Na β″ -alumina with CO2 and H2O and the formation of hydroxyl groups (1985)
    Springer
    Journal of materials science 20 (1985), S. 3219-3229 
    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 reactions of polycrystalline Na β″-alumina with CO2 and H2O were investigated using infrared reflectance methods. These reactions result in the replacement of Na+ ions with H3O+ ions and the formation of a scale of NaHCO3 or hydrated Na2CO3 on the surfaces of ceramic specimens. The composition of the scale formed depends on the pressures of CO2 and H2O: NaHCO3 forms at high CO2 pressure while Na2CO3 · XH2O forms at low CO2 pressures. The H3O+ ions dislocate by an endothermic process to produce OH− species in the conduction layers of the grains. The removal of these species by H2O evolution at high temperature implies that an irreversible change occurs in the composition of the surface region of the ceramic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00545188
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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