Activation energy for diffusion and welding of PLA films

RésuméObservations have been made of the modification produced by a temperature gradient in the shape of air bubbles in natural snow crystals, and also of the shrinkage of the bubbles with time. The rate of shrinkage is governed by a constant which is strongly temperature dependent with an activation energy of about 15.1 kcal./mole, a value sufficiently similar to the activation energy for diffusion of tritium, dielectric relaxation and mechanical relaxation to suggest that atomic diffusion processes may be responsible for all of these phenomena.

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The Influence of Nitrogen on Dislocation Locking in Float-Zone Silicon

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.108-109.139 ◽

2005 ◽

Vol 108-109 ◽

pp. 139-144 ◽

Cited By ~ 6

Author(s):

John D. Murphy ◽

A. Giannattasio ◽

Charles R. Alpass ◽

Semih Senkader ◽

Robert J. Falster ◽

...

Keyword(s):

Activation Energy ◽

Annealing Time ◽

Nitrogen Concentration ◽

Dislocation Core ◽

Float Zone ◽

A Value ◽

Rate Of Increase ◽

Activation Energy For Diffusion ◽

Nitrogen Concentrations ◽

Locking Effect

Dislocation locking by nitrogen impurities has been investigated in float-zone silicon with nitrogen concentrations of 2.2 x 1015cm-3 and 3 x 1014cm-3. The stress required to unlock dislocations pinned by nitrogen impurities was measured as a function of annealing time (0 to 2500 hours) and temperature (550 to 830°C). For all conditions investigated the locking effect was found to increase linearly with annealing time before saturating. It is assumed that the rate of increase of unlocking stress with annealing time is a measure of transport of nitrogen to the dislocation core. This rate of increase was found to depend linearly on nitrogen concentration, which is consistent with transport by a dimeric species, whose activation energy for diffusion is approximately 1.4eV. The saturation unlocking stress has been found to be dependent on the nitrogen concentration. Additionally, the temperature dependence of the stress required to move dislocations immobilised by nitrogen impurities has been studied. By assuming a value for the binding energy of the nitrogen to the dislocation, the density of the locking species at the dislocation core has been calculated.

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The State of Water in the Isolated Toad Bladder in the Presence and Absence of Vasopressin

The Journal of General Physiology ◽

10.1085/jgp.45.5.933 ◽

1962 ◽

Vol 45 (5) ◽

pp. 933-948 ◽

Cited By ~ 52

Author(s):

Richard M. Hays ◽

Alexander Leaf

Keyword(s):

Activation Energy ◽

Activation Energies ◽

Bulk Water ◽

Permeability Barrier ◽

High Activation ◽

State Of Water ◽

Activation Energy For Diffusion ◽

Presence And Absence ◽

Rate Limiting ◽

Resistance To Penetration

An attempt has been made to assess the validity of applying the frictional and viscous coefficients of bulk water to the movement of water and solutes through the urinary bladder of the toad. The temperature dependence of diffusion of THO, C14-urea, C14-thiourea, and net water transfer across the bladder was determined in the presence and absence of vasopressin. The activation energy for diffusion of THO was 9.8 kcal per mole in the absence of vasopressin and 4.1 kcal per mole with the hormone present. Activation energies simultaneously determined following vasopressin for diffusion and net transfers of water were similar, and in the same range as known activation energies for diffusion and viscous flow in water. Urea had activation energies for diffusion of 4.1 and 3.9 kcal per mole in the absence and presence of vasopressin, respectively. Thiourea had a high activation energy for diffusion of 6.3 kcal per mole, which was unchanged, 6.6 kcal per mole, following hormone. These findings suggest that in its rate-limiting permeability barrier, water is present in a structured state, offering a high resistance to penetration by water. Vasopressin enlarges the aqueous channels so that the core of water they contain possesses the physical properties of ordinary bulk water. Urea penetrates the tissue via these aqueous channels while thiourea is limited by some other permeability barrier.

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Activation Energy for Diffusion of 133 Xe Through MgO-Ni Cermet Compacts

Journal of the American Ceramic Society ◽

10.1111/j.1151-2916.1960.tb13632.x ◽

1960 ◽

Vol 43 (12) ◽

pp. 634-640

Author(s):

W. E. MOODY ◽

W. D. WHITEHEAD ◽

W. W. KRIEGEL

Keyword(s):

Activation Energy ◽

Activation Energy For Diffusion

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Activation energy for diffusion in AuGe thin film couples

phys stat sol (a) ◽

10.1002/pssa.2210530148 ◽

1979 ◽

Vol 53 (1) ◽

pp. 397-401 ◽

Cited By ~ 3

Author(s):

E. N. Mgbenu

Keyword(s):

Thin Film ◽

Activation Energy ◽

Activation Energy For Diffusion

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Effect of Initial Microstructure on Soft Annealing of a Low-Carbon Bainitic Steel

Materials Proceedings ◽

10.3390/iec2m-09246 ◽

2021 ◽

Vol 3 (1) ◽

pp. 6

Author(s):

Lei Zhu ◽

Ying Yang ◽

Yuyang Li ◽

Huanhuan Xuan ◽

Hongtao Chen ◽

...

Keyword(s):

Activation Energy ◽

Annealing Temperature ◽

High Hardness ◽

Air Cooling ◽

Low Carbon ◽

Initial Microstructure ◽

Annealing Step ◽

Activation Energy For Diffusion ◽

Bainitic Structure ◽

Carbide Content

A low-carbon bainitic tool steel exhibiting high hardness after hot rolling typically has poor machinability. To soften this type of steel and to accelerate the soft annealing process, an austenitizing step was designed based on thermodynamic calculations of phase stability and introduced prior to the annealing step. Different initial microstructures were prepared by three austenitizing temperatures (680 °C, 850 °C, 1000 °C) and three cooling methods (water quenching, oil quenching, and air cooling). The effect of initial microstructure on microstructures and hardness was studied. Softening equations, a function of annealing temperature and time, were established for different initial microstructures, and the relationships between annealing temperature, annealing time, activation energy, and hardness were explored. The predicted hardness was consistent with the measured values. Martensitic structure has a low activation energy for diffusion and a higher softening rate compared to that of the bainitic structure. In addition, the higher the carbide content in the bainitic structure, the smaller the activation energy tended to be.

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

Journal of Materials Research ◽

10.1557/jmr.1999.0508 ◽

1999 ◽

Vol 14 (9) ◽

pp. 3754-3758 ◽

Cited By ~ 23

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.

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Air Drying Kinetics of Pomegranate Seeds

International Journal of Food Engineering ◽

10.2202/1556-3758.1691 ◽

2011 ◽

Vol 7 (2) ◽

Cited By ~ 4

Author(s):

Sajeev Rattan Sharma ◽

Sadhna Arora ◽

Tarsem Chand

Keyword(s):

Activation Energy ◽

Moisture Content ◽

Effective Diffusivity ◽

Air Drying ◽

Air Temperatures ◽

Thin Layer Drying ◽

Activation Energy For Diffusion ◽

Drying Behavior ◽

Pomegranate Seeds ◽

Kinetics Of

The thin layer drying of pretreated wild pomegranate seeds was conducted in a laboratory mechanical dryer at air temperatures of 55, 60 and 65°C. Six different mathematical models were used to predict the drying behavior. Thompson model was adjudged as the best model. The coefficients of this model were found to be correlated best with drying temperatures by using two degree polynomials. The effective diffusivity was determined to be 3.18 x 10-10 to 4.36 x 10-10 m2/s. The activation energy for diffusion was found to be 29.07 kJ /mol. The variation in shrinkage exhibited a linear relationship with moisture content. The rate constants for a and b parameters of colour were determined and their value was 0.0128 and 0.0136 min-1, respectively.

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