Heats of transfer and activation energy for bound water diffusion in wood

1991 ◽  
Vol 25 (3) ◽  
pp. 193-202 ◽  
Author(s):  
Ralph M. Nelson
Keyword(s):  
Activation Energy ◽  
Bound Water ◽  
Water Diffusion ◽  
Heats Of Transfer

Inverse analysis of the transient bound water diffusion in wood

Holzforschung ◽  
2005 ◽  
Vol 59 (1) ◽  
pp. 38-45 ◽  
Author(s):  
Wiesław Olek ◽  
Patrick Perré ◽  
Jerzy Weres
Keyword(s):  
Experimental Data ◽  
Diffusion Coefficients ◽  
Inverse Analysis ◽  
Bound Water ◽  
Water Diffusion ◽  
European Species ◽  
Alternative Approach ◽  
Transfer Problems ◽  
Bound Water Content ◽  
Water Diffusion Coefficient

Abstract The methods so far applied to determine the bound water diffusion coefficient in wood do not provide credible results on this coefficient as well as on the boundary condition. An alternative approach based on the concept of solving the inverse transfer problems was recently applied. Two European species were investigated in the present study. A series of sorption experiments was performed and followed by the numerical identification of the coefficients. Several case studies were carried out for the constant and bound water content dependent diffusion coefficients. The obtained results were validated by comparison to a set of experimental data.

scholarly journals Activation energy for water diffusion across the toad bladder: evidence against the pore enlargement hypothesis

1971 ◽  
Vol 50 (5) ◽  
pp. 1016-1018 ◽  
Author(s):  
Richard M. Hays ◽  
Nicholas Franki ◽  
Roy Soberman
Keyword(s):  
Activation Energy ◽  
Water Diffusion ◽  
Toad Bladder ◽  
Pore Enlargement

Diffusion of water in crystalline and glassy oxides: Diffusion–reaction model

1999 ◽  
Vol 14 (9) ◽  
pp. 3754-3758 ◽  
Author(s):  
R. H. Doremus
Keyword(s):  
Activation Energy ◽  
Oxygen Isotopes ◽  
Reaction Model ◽  
Water Diffusion ◽  
Diffusion Reaction ◽  
Molecular Water ◽  
Oh Groups ◽  
Hydrogen And Oxygen Isotopes ◽  
Activation Energy For Diffusion ◽  
And Diffusion

Diffusion of water in oxides is modeled as resulting from the solution and diffusion of molecular water in the oxide. This dissolved water can react and exchange with the oxide network to form immobile OH groups and different hydrogen and oxygen isotopes in the oxide. The model agrees with many experiments on water diffusion in oxides. The activation energy for diffusion of water in oxides correlates with the structural openness of the oxide, suggesting that molecular water is the diffusing species.

scholarly journals The State of Water in Human and Dog Red Cell Membranes

1970 ◽  
Vol 55 (4) ◽  
pp. 451-466 ◽  
Author(s):  
F. L. Vieira ◽  
R. I. Sha'afi ◽  
A. K. Solomon
Keyword(s):  
Activation Energy ◽  
Cell Membrane ◽  
Apparent Activation Energy ◽  
Water Diffusion ◽  
Red Cells ◽  
Red Cell ◽  
Kcal Mole ◽  
Red Cell Membrane ◽  
Temperature Range ◽  
Human Red Cells

The apparent activation energy for the water diffusion permeability coefficient, Pd, across the red cell membrane has been found to be 4.9 ± 0.3 kcal/mole in the dog and 6.0 ± 0.2 kcal/mole in the human being over the temperature range, 7° to 37°C. The apparent activation energy for the hydraulic conductivity, Lp, in dog red cells has been found to be 3.7 ± 0.4 kcal/mole and in human red cells, 3.3 ± 0.4 kcal/mole over the same temperature range. The product of Lp and the bulk viscosity of water, η, was independent of temperature for both dog and man which indicates that the geometry of the red cell membrane is not temperature-sensitive over our experimental temperature range in either species. In the case of the dog, the apparent activation energy for diffusion is the same as that for self-diffusion of water, 4.6–4.8 kcal/mole, which indicates that the process of water diffusion across the dog red cell membrane is the same as that in free solution. The slightly, but significantly, higher activation energy for water diffusion in human red cells is consonant with water-membrane interaction in the narrower equivalent pores characteristic of these cells. The observation that the apparent activation energy for hydraulic conductivity is less than that for water diffusion across the red cell membrane is characteristic of viscous flow and suggests that the flow of water across the membranes of these red cells under an osmotic pressure gradient is a viscous process.

Molecular relaxation in Chitosan films in GHz frequency range

2014 ◽  
Vol 1613 ◽  
pp. 83-88
Author(s):  
Siva Kumar-Krishnan ◽  
Evgen Prokhorov ◽  
Gabriel Luna-Barcenas
Keyword(s):  
Activation Energy ◽  
Low Frequency ◽  
Bound Water ◽  
Wide Frequency Range ◽  
Frequency Range ◽  
Temperature Range ◽  
A Value ◽  
Chitosan Films ◽  
First Time

ABSTRACTThe molecular relaxations behavior of chitosan (CS) films in the wide frequency range of 0.1-3x109 Hz (by using three different impedance analyzers) have been investigated in the temperature range of -100C to 120°C using Dielectric Spectroscopy (DS). Additionally to the low frequency molecular relaxations such as α and β relaxations, for the first time, high frequency (1-3 GHz) relaxation process has been observed in the chitosan films. This relaxation exhibits Arrhenius-type dependence in the temperature range of -100 C to 54°C with negative activation energy -2.7 kJ/mol. At temperatures above 54°C, the activation energy changes from -2.7 kJ/mol to +4.4 kJ/mol. Upon cooling, the activation energy becomes negative again with a value of -1.2 kJ/mol. The bound water between chitosan molecules strongly modifies molecular motion and the relaxation spectrum, giving rise to a new relaxation at the frequency at ca. 1 GHz. In situ FTIR analysis has shown that this relaxation related to the changes in vibration of the –OH, NH and –CO functional groups.

scholarly journals Erratum to: Quantitative determination of bound water diffusion in multilayer boards by means of neutron imaging

2010 ◽  
Vol 68 (3) ◽  
pp. 351-352
Author(s):  
Walter Sonderegger ◽  
Stefan Hering ◽  
David Mannes ◽  
Peter Vontobel ◽  
Eberhard Lehmann ◽  
...  
Keyword(s):  
Quantitative Determination ◽  
Bound Water ◽  
Water Diffusion ◽  
Neutron Imaging

scholarly journals Cellulose Non Freezing Bound Water and Activation Energy of Desorption by Thermogravimetric Analysis

2021 ◽  
Author(s):  
Ricardo Klaus Kramer ◽  
Antonio José Felix Carvalho
Keyword(s):  
Activation Energy ◽  
Thermogravimetric Analysis ◽  
Cellulose Degradation ◽  
Bound Water ◽  
Free Water ◽  
Advanced Materials ◽  
Water Desorption ◽  
Processing Strategies ◽  
Key Factor ◽  
Activation Energy Of Desorption

Abstract Understand water-cellulose interaction isa key factor in cellulose processing strategies and to achieve the best propertiesfor each application. The emergence of new advanced materials based on nanocelluloses calls for more precise methods to study these systems. In this work, we described the study of water-cellulose interaction by thermogravimetric analysis (TGA), comparing dynamic and auto stepwise methods. The auto stepwise method was able to identify with precision the different species of water: i) the free water or freezing water, ii) the freezing bound water and iii) the non-freezing bound water. The Ozawa-Flynn-Wall method was used to estimate the activation energy of bound water desorption, Ea average = 50.45 kJ.mol-1 and the cellulose degradation energy, Ea average = 143.18 kJ.mol-1. The results obtained given a new knowledge on the interaction between water and cellulose since other techniques such as DSC are not sensitive to non-freezing bound water increasing the range of water content that can be studied.

Epoxidized natural rubber toughened poly(lactic acid)/halloysite nanocomposites with high activation energy of water diffusion

2015 ◽  
Vol 133 (3) ◽  
pp. n/a-n/a ◽  
Author(s):  
Wei Ling Tham ◽  
Beng Teik Poh ◽  
Zainal Arifin Mohd Ishak ◽  
Wen Shyang Chow
Keyword(s):  
Activation Energy ◽  
Lactic Acid ◽  
Natural Rubber ◽  
Water Diffusion ◽  
Epoxidized Natural Rubber ◽  
Poly Lactic Acid ◽  
High Activation ◽  
High Activation Energy ◽  
Rubber Toughened
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