Water Self-Diffusion within Nematic Dispersions of Nanocomposites:  A Multiscale Analysis of1H Pulsed Gradient Spin−Echo NMR Measurements

2003 ◽  
Vol 107 (17) ◽  
pp. 4012-4023 ◽  
Author(s):  
P. Porion ◽  
M. Al Mukhtar ◽  
A. M. Faugère ◽  
R. J. M. Pellenq ◽  
S. Meyer ◽  
...  
Keyword(s):  
Multiscale Analysis ◽  
Spin Echo ◽  
Self Diffusion

Self- diffusion of H2O in stevensite gel: effects of temperature and clay fraction

Clay Minerals ◽  
2002 ◽  
Vol 37 (1) ◽  
pp. 83-91 ◽  
Author(s):  
Y. Nakashima
Keyword(s):  
Spin Echo ◽  
Polymer Network ◽  
Clay Fraction ◽  
Weight Fraction ◽  
Bulk Water ◽  
Proton Nuclear Magnetic Resonance ◽  
Exponential Dependence ◽  
Self Diffusion ◽  
Effects Of Temperature ◽  
Characteristic Interval

AbstractSelf-diffusion coefficients of water molecules (1H2O) in Na-stevensite gel were measured by pulsed-gradient spin-echo (PGSE) proton nuclear magnetic resonance (NMR). The effects of clay fraction (0.00 37.7 wt.%) and temperature (20.0 60.3°C) were studied. The results show: (1) phenomenologically, the H2O self-diffusivity in the clay gel, D, is expressed by D/D0 = exp( 0.0198w) where D0 is the H2O self-diffusivity in bulk water of the temperature and wis the clay weight fraction (wt.%). (2) The activation energy of the diffusivity in the stevensite gel is nearly equal to that in bulk water. Thus, the normalized diffusivity, D/D0, obeys a temperature-independent master curve. (3) The exponential dependence of D/D0 on wfor w <25 wt.% (≈ 12 vol.%) can be explained by a random walk model, in which unbound H2O molecules diffuse in the geometrically tortuous pore structure of randomly scattered clay mineral grains. (4) The measured diffusivity can also be explained by a model of unbound H2O diffusing in a polymer network with a specific meshsize or characteristic interval of the crosslinkage.

Self-Diffusion in Molten Lithium Nitrate

1992 ◽  
Vol 47 (10) ◽  
pp. 1047-1050 ◽  
Author(s):  
C. Herdlicka ◽  
J. Richter ◽  
M. D. Zeidler
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Spin Echo ◽  
The Self ◽  
Lithium Nitrate ◽  
Equimolar Ratio ◽  
Self Diffusion ◽  
Field Gradients ◽  
Molten Lithium ◽  
Self Diffusion Coefficient

AbstractSelf-diffusion coefficients of 7Li+ ions have been measured in molten LiNO3 with several compositions of 6Li+ and 7Li+ over a temperature range from 537 to 615 K. The NMR spin-echo method with pulsed field gradients was applied. It was found that the self-diffusion coefficient depends on the isotopic composition and shows a maximum at equimolar ratio. At temperatures above 600 K this behaviour disappears.

Time-dependent self-diffusion by NMR spin-echo

1993 ◽  
Vol 183 (4) ◽  
pp. 343-350 ◽  
Author(s):  
Janez Stepišnik
Keyword(s):  
Spin Echo ◽  
Time Dependent ◽  
Self Diffusion

PGSE-NMR & Sans from TPB Based Microemulsions

1989 ◽  
Vol 177 ◽  
Author(s):  
Paul M. Lindemuth ◽  
Boualem Hammouda ◽  
Joseph R. Duke ◽  
Frank D. Blum ◽  
Raymond L. Venable
Keyword(s):  
Diffusion Coefficients ◽  
Small Angle Neutron Scattering ◽  
Spin Echo ◽  
Water Concentration ◽  
Conductivity Measurements ◽  
Self Diffusion ◽  
Nmr Data ◽  
Pgse Nmr ◽  
Isotropic Region ◽  
Complete Inversion

ABSTRACTSelf-diffusion coefficients from pulsed-gradient spin-echo NMR are reported for four components of the tetradecylpyridinium bromide - 85% heptane/15% pentanol - water pseudoternary system. Measurements were taken throughout the inverted microemulsion region and also in a small isotropic region beyond the domain of lamellar liquid crystals. Observations of the self-diffusion coefficients for water relative to those of the surfactant, oil and alchohol show several distinct structural transitions within the water-in-oil region of the phase diagram. The smaller isotropic region exhibits a complete inversion of phase relative to the water-in-oil region. Conductivity measurements were used to further clarify the NMR data. Subsequent small angle neutron scattering (SANS) measurements on the same system show the transition from the single particle (heavy water + Stern layer droplet) scattering regime at low water concentration to the mixed single/interdroplet scattering regime when the intermicellar distance becomes comparable to the size of the micelles.

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