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  • 1985-1989  (5)
  • 1980-1984  (2)
  • Chemical Engineering  (6)
  • 68.55Jh  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Transmission electron microscopy study of defects in Sn-doped GaAs films grown by molecular beam epitaxy (1987)
    Springer
    Applied physics 44 (1987), S. 143-151 
    Details
    ISSN: 1432-0630
    Keywords: 68.55Jh ; 81.30Fb ; 68.35
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Films of GaAs, heavily doped with Sn, which have been grown by molecular-beam epitaxy are found to contain single-crystal Sn particles situated in the nearsurface region of the epilayer GaAs. The morphology and chemical composition of the particles have been examined by using cross-section transmission electron microscopy combined with energy-dispersive x-ray spectroscopy. Different growth conditions were used to study the Sn-particle formation and high-resolution transmission electron microscopy was used to investigate microstructures. The observations are discussed in terms of several models previously proposed for these phenomena.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00626415
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Fickian diffusion of alkanes through glassy polymers: Effects of temperature, diffusant size, and polymer structure (1980)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 20 (1980), S. 40-50 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Diffusivities D ranging over six orders of magnitude with values as low as 2 × 10-13 cm2/s have been obtained by a recently developed permeation apparatus, employing a gas-flow method and a flame ionization detector; Log D for hydrocarbons in bisphenol-A polycarbonate (PC) at 120°C is proportional to the square of the molecular diameter (d2) as given by the Lennard-Jones 6-12 potential. This correlation holds even for the nonspherical n-hexane molecule. The activation energy for diffusion is also linearly related to d2, with values of 9.5 and 23 kcal/mol for methane and neopentane in PC, respectively. Comparison of PC with two similar polymers of higher glass-transition temperatures (Tg) indicates that our diffusion data do not correlate with the Tg of these polymers. The presence of subsidiary transitions, however, appears to enhance segmental mobilities, increasing the rate of diffusion of the hydrocarbons. The thermodynamic solubility of alkanes in glassy PC can be directly related to their boiling points, and in addition, their enthalpy of solution is linearly related to the heat of condensation of these permeants.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760200108
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Tracer diffusion in dense ethanol: A generalized correlation for nonpolar and hydrogen-bonded solvents (1986)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 32 (1986), S. 1367-1371 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Tracer diffusion coefficients were measured for benzene, toluene, mesitylene, naphthalene, and phenanthrene in dense ethanol at 0.56 ≤ TR ≤ 1.07 and ρR ≥ 1.44. The results were used to examine the temperature dependence of the degree of association between ethanol molecules across the entire range of temperature. The hard-sphere tracer diffusion equation and the Stokes-Einstein equation were used to develop two engineering correlations. The former approach was found to be adequate for solvents of relatively compact molecules, and the latter to be more general in its applications. The absolute deviation of prediction from observed values of tracer diffusivities is 4%, with a maximum error of 13%.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690320814
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  • 4
    Electronic Resource
    Electronic Resource
    An evaluation of the lamellar stretch description of mixing with diffusion and chemical reaction (1986)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 32 (1986), S. 1043-1048 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690320616
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Diffusion of benzene, toluene, naphthalene, and phenanthrene in supercritical dense 2,3-dimethylbutane (1985)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 1904-1910 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The conditions under which the Taylor-Aris dispersion phenomenon can be employed to generate accurate tracer diffusion data in supercritical dense fluids are established. The technique is used to determine the diffusivities of benzene, toluene, naphthalene, and phenanthrene in supercritical dense 2,3-dimethylbutane as a function of temperature and pressure. A molecular theory incorporating the Sung-Stell formulation of molecular dynamic correlations in smooth-hardsphere fluids and the Baleiko-Davis molecular roughness for polyatomics with the Enskog-Thorne dense gas diffusivity relationship is found to represent our experimental data to within ±4%. The values of the effective hard-sphere diameters involved in the present theory can be predicted fairly accurately from the critical volumes of the solutes and solvent considered here.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690311115
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Tracer diffusion in methanol, 1-butanol and 1-octanol from 298 to 433 K (1983)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 29 (1983), S. 640-645 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Diffusion coefficients of argon, krypton, xenon, methane, carbon tetrachloride and the tetraalkyltins (methyl through butyl) were measured in methanol, 1-butanol and 1-octanol over the temperature range 298 to 433 K. With temperature-dependent solvent diameters fitted from the tracer diffusivity of one of the solutes, a rough-hard-sphere theory predicts well the observed tracer diffusivity over the solvent density range in which hard-sphere computer simulations are available. The Wilke-Chang correlation predicts diffusion coefficients in the higher alcohols with an average error of 80% and a maximum error of 200%. A correlation of the form Dμp/T = A where p and A depend on solute and solvent size is more successful giving an average error of 7% and a maximum error of 24%.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690290418
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Tracer diffusion of aromatic hydrocarbons in liquid cyclohexane up to its critical temperature (1985)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 1510-1515 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Tracer diffusion coefficients in liquid cyclohexane of benzene, toluene, p-xylene, mesitylene, naphthalene, and phenanthrene have been determined from 298.2 to 523.2 K (TR = 0.54 ∼ 0.95) using the Taylor dispersion method. Positive deviations from the Arrhenius relationship are observed as the critical temperature is approached, but a rough-hard-sphere theory is found to be adequate for describing the data across the entire temperature range. On the basis of the computer simulation results for hard-sphere fluids, correlations involving solute and solvent critical volumes and their molecular weights have also been developed for practical applications. Tracer diffusivities in supercritical carbon dioxide are also adequately represented by the proposed correlation, as the fluid density is not far removed from that of liquid carbon dioxide.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690310914
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    Paper (German National Licenses)
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