Nafion® Membranes: Molecular Diffusion, Proton Conductivity and Proton Conduction Mechanism

1992 ◽  
Vol 293 ◽  
Author(s):  
Klaus-Dieter Kreuer ◽  
Thomas Dippel ◽  
Wolfgang Meyer ◽  
Joachim Maier
Keyword(s):  
Water Content ◽  
Proton Conductivity ◽  
Molecular Diffusion ◽  
Local Environment ◽  
Bulk Water ◽  
Exponential Factor ◽  
Nmr Diffusion ◽  
The One ◽  
Low Degrees ◽  
Pfg Nmr

AbstractH-PFG-NMR diffusion and proton conductivity data for NAFION® 117 is presented as a function of temperature and water content. From this, H2O diffusion on a molecular scale is concluded to be similar to the one in bulk water. But “geometrical” restrictions of diffusion lead to a decreasing pre-exponential factor, i.e. decreasing macroscopic diffusion coefficient with decreasing water content. It is shown that proton conductivity is correlated with water diffusion for low degrees of hydration (vehicle mechanism). With increasing hydration there is an increasing contribution from “structure diffusion” culminating in an amplification factor of A = 2.5 for fully hydrated protonic NAFION® 117 at room temperature. The bonding of water in NAFION® as well as the local environment (hydration) of the acidic proton are concluded to be similar as in acidic aqueous solutions.

STEM measurement of subcellular water distributions

1993 ◽  
Vol 51 ◽  
pp. 568-569
Author(s):  
R.D. Leapman ◽  
S.Q. Sun ◽  
S-L. Shi ◽  
R.A. Buchanan ◽  
S.B. Andrews
Keyword(s):  
Water Content ◽  
Internal Standard ◽  
Dry Weight ◽  
Dry Mass ◽  
Scanning Transmission Electron Microscope ◽  
Dark Field ◽  
Bulk Water ◽  
Inelastic Electron ◽  
Scanning Transmission ◽  
Annular Dark Field

Recent advances in rapid-freezing and cryosectioning techniques coupled with use of the quantitative signals available in the scanning transmission electron microscope (STEM) can provide us with new methods for determining the water distributions of subcellular compartments. The water content is an important physiological quantity that reflects how fluid and electrolytes are regulated in the cell; it is also required to convert dry weight concentrations of ions obtained from x-ray microanalysis into the more relevant molar ionic concentrations. Here we compare the information about water concentrations from both elastic (annular dark-field) and inelastic (electron energy loss) scattering measurements.In order to utilize the elastic signal it is first necessary to increase contrast by removing the water from the cryosection. After dehydration the tissue can be digitally imaged under low-dose conditions, in the same way that STEM mass mapping of macromolecules is performed. The resulting pixel intensities are then converted into dry mass fractions by using an internal standard, e.g., the mean intensity of the whole image may be taken as representative of the bulk water content of the tissue.

Numerical simulation of coupled liquid water, stress and heat for frozen soil in the thawing process

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Wei Xiao ◽  
Enlong Liu ◽  
Xiao Yin ◽  
Guike Zhang ◽  
Chong Zhang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Water Content ◽  
Coupled Model ◽  
Frozen Soil ◽  
Water Migration ◽  
Overburden Pressure ◽  
Content Type ◽  
Thawing Process ◽  
Sample Water ◽  
The One

PurposeThe purpose of this paper is to perform the thermo-hydro-mechanical (THM) numerical analysis in order to study the thawing process for frozen soil and to predict the thawing settlement.Design/methodology/approachA new one-dimensional multi-field physical coupled model was proposed here to describe the thawing process of saturated frozen soil, whereby the void ratio varied linearly with effective stress (Eq. 10) and hydraulic conductivity (Eq. 27b). The thawing process was simulated with different initial and boundary conditions in an open system with temperature variations. The mechanical behavior and water migration of the representative cases were also investigated.FindingsThe comparisons of representative cases with experimental data demonstrated that the model predicts thawing settlement well. It was found that the larger temperature gradient, higher overburden pressure and higher water content could lead to larger thawing settlement. The temperature was observed that to distribute height linearly in both frozen zone and unfrozen zone of the sample. Water migration forced to a decrease in the water content of the unfrozen zone and an increase in water content at the thawing front.Research limitations/implicationsIn this study, only the one-directional thawing processes along the frozen soil samples were investigated numerically and compared with test results, which can be extended to two-dimensional analysis of thawing process in frozen soil.Originality/valueThis study helps to understand the thawing process of frozen soil by coupled thermo-hydro-mechanical numerical simulation.

Importance of water content and motion in the one-dimensional conductorK2Pt(CN)4Cl0.3·nH2O

1974 ◽  
Vol 10 (5) ◽  
pp. 1778-1783 ◽  
Author(s):  
M. A. Butler ◽  
H. J. Guggenheim
Keyword(s):  
Water Content ◽  
One Dimensional ◽  
The One

Characterization of thin water layers in pulp by tritium exchange. Part 1: Methods development

Holzforschung ◽  
2007 ◽  
Vol 61 (2) ◽  
pp. 115-119 ◽  
Author(s):  
Frances L. Walsh ◽  
Sujit Banerjee
Keyword(s):  
Water Content ◽  
Surface Area ◽  
Tritiated Water ◽  
Bound Water ◽  
Free Water ◽  
Fiber Surface ◽  
Bulk Water ◽  
Methods Development ◽  
A Value ◽  
A New Technique

Abstract A new technique for measuring the monolayer water content of fiber is presented. Tritiated water is added to a pulp/water suspension, whereupon the tritium partitions between the bulk water and the pulp. In the pulp phase the tritium can exchange with free water, bound water, and with hydroxyl and other protons present in the pulp matrix. The free water in the pulp is then removed by displacement with acetone. The tritium remaining in the pulp is mostly associated with tightly bound water, with a small fraction being tied up with the exchangeable hydrogen in pulp. The procedure provides a value of 10% for the tightly bound water content of hardwood or softwood fiber, either bleached or unbleached. If this water is assumed to cover the fiber surface as a monolayer, then an estimate of the wet surface area of the fiber can be obtained. This estimate compares well with independent measurements of surface area.

Fire Behavior of Raw Earth Bricks: Influence of Water Content and Cement Stabilization

2022 ◽  
Author(s):  
Rafik Isaam Abdallah ◽  
Céline Perlot ◽  
Hélène Carré ◽  
Christian La Borderie ◽  
Haissam El Ghoche
Keyword(s):  
Water Content ◽  
Thermal Instability ◽  
Fire Behavior ◽  
Standard Fire ◽  
Influence Of Water ◽  
Cement Stabilization ◽  
The One ◽  
Raw Earth ◽  
Water Contents ◽  
Soil And Water

This study focus on the effects of both water content and cement stabilization on the fire behavior of earth bricks. To observe the effect of cement stabilization, two materials are formulated: raw earth with only soil and water, and stabilized bricks with soil, water and cement (3.5% by mass of soil). Since the material’s mechanical strength can strongly influence its fire behavior, the raw bricks were compacted at 50 MPa to reach a compressive strength similar to the one of stabilized bricks. Four different water contents were tested; dry state obtained with oven drying and three others achieved through equalization at 50%, 75% and 100% of relative humidities. Bricks are then subjected to an ISO 834-1 standard fire. Results show that water content has caused a thermal instability behavior on the raw earth bricks after equalization at 50% and 75% relative humidities. Thermally stable bricks displayed a noticeable diffusion of cracks on their heated face. Furthermore, cement stabilization helps to prevent from thermal instabilities.

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