Selective two-component self-diffusion measurement of adsorbed molecules by pulsed field gradient Fourier transform NMR

1991 ◽  
Vol 113 (13) ◽  
pp. 4812-4815 ◽  
Author(s):  
Uwe Hong ◽  
Joerg Kaerger ◽  
Harry Pfeifer
Keyword(s):  
Fourier Transform ◽  
Field Gradient ◽  
Diffusion Measurement ◽  
Adsorbed Molecules ◽  
Pulsed Field ◽  
Self Diffusion ◽  
Two Component

Pulsed Field Gradient NMR Investigation of Molecular Mobility of Trimethoxymethane in Nafion Membranes

1997 ◽  
Vol 496 ◽  
Author(s):  
Y. Wu ◽  
T. A. Za Wodzinski ◽  
M. C. Smart ◽  
S. G. Greenbaum ◽  
G.K.S. Prakash ◽  
...  
Keyword(s):  
Field Gradient ◽  
Molecular Mobility ◽  
Alternative Fuels ◽  
Direct Oxidation ◽  
Effective Distance ◽  
Pulsed Field ◽  
Self Diffusion ◽  
Lower Extent ◽  
The Difference ◽  
Nmr Signals

ABSTRACTMolecular mobility of water and trimethoxymethane (TMM) in NAFION membranes of two different equivalent weights (EW), 1100 and 1500, were investigated. Self-diffusion coefficients were determined by the NMR pulsed field gradient method, using the water and methyl protons NMR signals, in saturated NAFION samples containing concentrations of TMM in water varying between 0.5 and 14 M, and at temperatures varying from 30°C to 80°C. Diffusion of molecular species containing methyl protons is more than a factor of two slower in the 1500 EW membrane than in the 1100 EW membrane at 30°C and 1 M concentration. The difference rises to about a factor of four at 80°C and 14 M concentration. These differences are attributed to the lower extent of plasticization of the higher EW material as well as the greater effective distance between acid functional groups. NAFION samples containing methanol/water mixtures were also investigated. Comparison with the methanol results and the permeation behavior, as characterized by gas Chromatographie methods, show that more than half of the TMM is hydrolyzed to methanol as it passes through the acidic membrane. The implications of these findings for alternative fuels in direct oxidation fuel cells are discussed.

c , T-Dependence of the Self Diffusion in Concentrated Aqueous Sucrose Solutions

1994 ◽  
Vol 49 (3-4) ◽  
pp. 258-264 ◽  
Author(s):  
D. Girlich ◽  
H.-D. Lüdemann ◽  
C. Buttersack ◽  
K. Buchholz
Keyword(s):  
Field Gradient ◽  
Concentration Dependence ◽  
Diffusion Coefficients ◽  
The Self ◽  
Water Molecules ◽  
Pulsed Field Gradient Nmr ◽  
Pulsed Field ◽  
Self Diffusion ◽  
Sucrose Solutions ◽  
Wide Range

The self diffusion coefficients D of the water molecules and of sucrose have been determined by the pulsed field gradient NMR technique over a wide range of temperatures and concentrations (cmax: 70% w/w suc.). 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

On the limits of the application of the n.m.r. pulsed-field gradient technique for self-diffusion measurements in zeolites

Zeolites ◽  
1989 ◽  
Vol 9 (4) ◽  
pp. 299-302 ◽  
Author(s):  
Chr. Förste ◽  
W. Heink ◽  
J. Kärger ◽  
H. Pfeifer ◽  
N.N. Feokistova ◽  
...  
Keyword(s):  
Field Gradient ◽  
Pulsed Field ◽  
Self Diffusion ◽  
Gradient Technique
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