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'Diffusion' in keywords Facet   Publication Year 1994  [X]
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1Author    D. Girlich, H.-D Lüdemann, C. Buttersack, K. BuchholzRequires cookie*
 Title    c , T-Dependence of the Self Diffusion in Concentrated Aqueous Sucrose Solutions  
 Abstract    The self diffusion coefficients D of the water molecules and of sucrose have been deter­ mined by the pulsed field gradient NMR technique over a wide range of temperatures and concentrations (cmax: 70% w/w sue.). All temperature dependencies can be fitted to a Vogel-Tammann-Fulcher equation. The isothermic concentration dependence of D for the sucrose is given by a simple exponential concentration dependence. 
  Reference    Z. Naturforsch. 49c, 258—264 (1994); received December 21993 
  Published    1994 
  Keywords    Diffusion, Sucrose, Water, Aqueous Solution 
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 TEI-XML for    default:Reihe_C/49/ZNC-1994-49c-0258.pdf 
 Identifier    ZNC-1994-49c-0258 
 Volume    49 
2Author    O. Wegener3, R. K. Üchler3, A. W. AtterichbRequires cookie*
 Abstract    12STe nuclear spin relaxation (NSR) and electrical conductivity measurements were performed on ultrapure single-crystalline paratellurite (a -T e0 2) between about 50 K and the melting point (1007 K) at various oxygen partial pressures (1 b a r -10"4 bar). At elevated temperatures the NSR rate l / 7 \ and conductivity a are caused by the diffusive motion o f point defects. From the observed p02-dependence of 1/Ti and a a defect model is developed which is shown to be consistent with the experimental data. The m odel involves ionic oxygen interstitials (O"), doubly charged oxygen vacancies (Vo') and charge-com pensating electron holes (h'). The observed pressure dependence suggests that the N SR rate is induced by the m otion of \ q while the conductivity is due to the m obility o f h*. Evaluation o f the data leads to 3.3 eV for the incorporation enthalpy o f oxygen on interstitial sites and to 4.5 eV for the formation enthalpy of oxygen Frenkel pairs (O "-V q'). Further, the chemical diffusion coefficient Dc is found to be caused by the ambipolar diffusion o f OS' and h \ At 950 K we obtained from both the NSR and conductivity experiments D c = (1 ± 0.3) • 10" 5 cm 2/s. 
  Reference    Z. Naturforsch. 49a, 1151 (1994); received August 22 1994 
  Published    1994 
  Keywords    Oxides, Point defects, Diffusion, N M R, Conductivity 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-1151.pdf 
 Identifier    ZNA-1994-49a-1151 
 Volume    49