Dynamic Vitrification and the Activation Energy of Rubbery Polymers

1961 ◽  
Vol 34 (4) ◽  
pp. 1201-1211 ◽  
Author(s):  
G. M. Bartenev ◽  
V. D. Zaĭtseva
Keyword(s):  
Activation Energy ◽  
Mechanical Action ◽  
Equilibrium Structure ◽  
Glass Temperature ◽  
High Activation ◽  
Molecular Rearrangement ◽  
Small Temperature ◽  
Rate Of Development ◽  
Exponential Law ◽  
Brittle State

Abstract 1. The resistance to brittleness of a wide variety of rubbers was studied by the method of periodic deformation. 2. Dynamic glassing, during which transition from the highly elastic into the brittle state is observed, always occurs in the liquid state of aggregation of a polymer, where the activation energy of molecular rearrangement changes with temperature according to an exponential law. 3. In a small temperature interval the change of the activation energy can be approximated by a linear law; consequently, Equations (1) and (4) expressing the dependence of the temperature of transition of the rubber into the brittle state on the frequency of deformations are satisfied approximately. The constants entering into these equations and their relationship to the activation energy are determined. 4. The activation energy of dynamic glassing is directly proportional to the glass temperature of the polymer and is greater than the activation energy of static glassing by approximately 5–10%, consequently the rate of establishment of the equilibrium structure is greater than the rate of stress relaxation or the rate of development of elastomeric deformation. 5. The relatively high activation energy of dynamic in comparison with static glassing is caused, apparently, by the larger size of the segments of the polymer chain during mechanical action compared to the size during free thermal motion.

Dielectric Relaxation Studies of Silver Nanoparticles dispersed Liquid Crystal

2015 ◽  
Vol 8 (3) ◽  
pp. 2176-2188 ◽  
Author(s):  
Keisham Nanao Singh
Keyword(s):  
Activation Energy ◽  
Silver Nanoparticles ◽  
Liquid Crystal ◽  
Dielectric Relaxation ◽  
Relaxation Process ◽  
Relaxation Times ◽  
Low Frequency ◽  
Bulk Liquid ◽  
Molecular Rearrangement ◽  
Relaxation Studies

This article reports on the Dielectric Relaxation Studies of two Liquid Crystalline compounds - 7O.4 and 7O.6 - doped with dodecanethiol capped Silver Nanoparticles. The liquid crystal molecules are aligned homeotropically using CTAB. The low frequency relaxation process occurring above 1 MHz is fitted to Cole-Cole formula using the software Dielectric Spectra fit. The effect of the Silver Nanoparticles on the molecular dipole dynamics are discussed in terms of the fitted relaxation times, Cole-Cole distribution parameter and activation energy. The study indicate a local molecular rearrangement of the liquid crystal molecules without affecting the order of the bulk liquid crystal molecules but these local molecules surrounding the Silver Nanoparticles do not contribute to the relaxation process in the studied frequency range. The observed effect on activation energy suggests a change in interaction between the nanoparticles/liquid crystal molecules.

Front instability in a condensed phase combustion model

2015 ◽  
Vol 4 (3) ◽  
pp. 153-176 ◽  
Author(s):  
Alexis Bonnet ◽  
Fathi Dkhil ◽  
Elisabeth Logak
Keyword(s):  
Activation Energy ◽  
Condensed Phase ◽  
Linear Instability ◽  
Combustion Model ◽  
Energy Limit ◽  
High Activation ◽  
Front Solution ◽  
High Activation Energy ◽  
Linearized Problem ◽  
Existence Of Zeros

AbstractWe consider a condensed phase (or solid) combustion model and its linearization around the travelling front solution. We construct an Evans function to characterize the eigenvalues of the linearized problem. We estimate this functional in the high activation energy limit. We deduce the existence of zeros with nonnegative real part for high activation energy, which proves the linear instability of the travelling front solution.

Observation of Rheed Intensity Oscillations During PbSe/CaF2/Si(111) MBE

1996 ◽  
Vol 441 ◽  
Author(s):  
W. K. Liu ◽  
X. M. Fang ◽  
P. J. McCann ◽  
M. B. Santos
Keyword(s):  
Activation Energy ◽  
Melting Point ◽  
Substrate Temperature ◽  
High Melting ◽  
Arrhenius Behavior ◽  
High Activation ◽  
High Melting Point ◽  
Mbe Growth ◽  
Sublimation Energy ◽  
Initial Nucleation

AbstractRHEED intensity oscillations observed during MBE growth of CaF2 on Si(111) and PbSe on CaF2/Si(111) are presented. The effects of substrate temperature and initial nucleation procedure are investigated. Strong temporal oscillations of the specular beam intensity are found to be most readily observed at temperatures below 200°C for both CaF2 and PbSe. Growth rates measured as a function of cell temperatures exhibit Arrhenius behavior with activation energies of 5.0 eV and 1.93 eV for CaF2 and PbSe, respectively. The relatively high activation energy obtained for CaF2 is consistent with the high melting point and sublimation energy of ionic fluorides.

scholarly journals Gas-phase detonation propagation in mixture composition gradients

2012 ◽  
Vol 370 (1960) ◽  
pp. 567-596 ◽  
Author(s):  
D. A. Kessler ◽  
V. N. Gamezo ◽  
E. S. Oran
Keyword(s):  
Activation Energy ◽  
Reaction Model ◽  
Single Step ◽  
Mixture Composition ◽  
Composition Gradient ◽  
Detonation Properties ◽  
High Activation ◽  
Zone Structure ◽  
Detonation Cell ◽  
High Activation Energy

The propagation of detonations through several fuel–air mixtures with spatially varying fuel concentrations is examined numerically. The detonations propagate through two-dimensional channels, inside of which the gradient of mixture composition is oriented normal to the direction of propagation. The simulations are performed using a two-component, single-step reaction model calibrated so that one-dimensional detonation properties of model low- and high-activation-energy mixtures are similar to those observed in a typical hydrocarbon–air mixture. In the low-activation-energy mixture, the reaction zone structure is complex, consisting of curved fuel-lean and fuel-rich detonations near the line of stoichiometry that transition to decoupled shocks and turbulent deflagrations near the channel walls where the mixture is extremely fuel-lean or fuel-rich. Reactants that are not consumed by the leading detonation combine downstream and burn in a diffusion flame. Detonation cells produced by the unstable reaction front vary in size across the channel, growing larger away from the line of stoichiometry. As the size of the channel decreases relative to the size of a detonation cell, the effect of the mixture composition gradient is lessened and cells of similar sizes form. In the high-activation-energy mixture, detonations propagate more slowly as the magnitude of the mixture composition gradient is increased and can be quenched in a large enough gradient.

scholarly journals Crystallization behavior of ion beam sputtered HfO2 thin films and its effect on the laser-induced damage threshold

2021 ◽  
Vol 17 (1) ◽  
Author(s):  
Zoltán Balogh-Michels ◽  
Igor Stevanovic ◽  
Aurelio Borzi ◽  
Andreas Bächli ◽  
Daniel Schachtler ◽  
...  
Keyword(s):  
Activation Energy ◽  
Crystallization Process ◽  
Ion Beam ◽  
Damage Threshold ◽  
High Activation ◽  
Quarter Wave ◽  
Dimensional Growth ◽  
Laser Induced Damage ◽  
Significant Increment

AbstractIn this work, we present our results about the thermal crystallization of ion beam sputtered hafnia on 0001 SiO2 substrates and its effect on the laser-induced damage threshold (LIDT). The crystallization process was studied using in-situ X-ray diffractometry. We determined an activation energy for crystallization of 2.6 ± 0.5 eV. It was found that the growth of the crystallites follows a two-dimensional growth mode. This, in combination with the high activation energy, leads to an apparent layer thickness-dependent crystallization temperature. LIDT measurements @355 nm on thermally treated 3 quarter-wave thick hafnia layers show a decrement of the 0% LIDT for 1 h @773 K treatment. Thermal treatment for 5 h leads to a significant increment of the LIDT values.

Anomalous high activation energy for creep in nanostructured 3YTZP/Ni cermets

2007 ◽  
Vol 27 (11) ◽  
pp. 3295-3299 ◽  
Author(s):  
A. Morales-Rodríguez ◽  
D. Gómez-García ◽  
T. Rodriguez-Suarez ◽  
S. Lopez-Esteban ◽  
C. Pecharroman ◽  
...  
Keyword(s):  
Activation Energy ◽  
High Activation ◽  
High Activation Energy

Cu-based metal-organic frameworks for highly sensitive X‑ray detector

2021 ◽  
Author(s):  
Zheng Li ◽  
Shuquan Chang ◽  
Haiqian Zhang ◽  
Yong Hu ◽  
Yulong Huang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Metal Organic Frameworks ◽  
High Activation ◽  
X Ray ◽  
High Activation Energy ◽  
Highly Sensitive ◽  
Metal Organic

Here, we constructed Pb-free Cu-DABDT-MOFs-based (DABDT = 2,5-diamino-1,4-benzenedithiol dihydrochloride) X-ray detectors. Combined with the advantage of high activation energy, Cu-DABDT-MOFs-based detector can effectively generate and capture electron under X-ray exposure...

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

1962 ◽  
Vol 45 (5) ◽  
pp. 933-948 ◽  
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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