Activation energy requirements in hydrogen abstractions. Quantitative description of the causes in terms of bond energies and infrared frequencies

1972 ◽  
Vol 94 (8) ◽  
pp. 2779-2789 ◽  
Author(s):  
Andreas A. Zavitsas
Keyword(s):  
Activation Energy ◽  
Quantitative Description ◽  
Energy Requirements ◽  
Bond Energies ◽  
Infrared Frequencies

Molecular-beam study of the activation energy requirements for the dioxetane reaction

1978 ◽  
Vol 100 (11) ◽  
pp. 3274-3278 ◽  
Author(s):  
K. T. Alben ◽  
A. Auerbach ◽  
W. M. Ollison ◽  
J. Weiner ◽  
R. J. Cross
Keyword(s):  
Activation Energy ◽  
Molecular Beam ◽  
Energy Requirements

Wet And Dry Oxidation of Polycrystalline SixGe1-x Films

1998 ◽  
Vol 533 ◽  
Author(s):  
P.-E. Hellberg ◽  
S.-L. Zhang ◽  
F. M. d'Heurle ◽  
C. S. Petersson
Keyword(s):  
Activation Energy ◽  
Reaction Rate ◽  
Quantitative Description ◽  
Reaction Rate Constant ◽  
Enhancement Effect ◽  
Wet Oxidation ◽  
Simultaneous Oxidation ◽  
Dry Oxidation ◽  
Different Temperatures ◽  
Si Films

AbstractWet and dry oxidations of polycrystalline SixGe1-x, with various compositions have been studied at different temperatures. The growth rate of SiO2 is found to be enhanced by Ge, and the enhancement effect is more pronounced in H2O than in O2. A mathematical model, which assumes simultaneous oxidation of Si and Ge and reduction of GeO2 by free Si available at the growing-oxide/SixGe1-x interface, is found to give a quantitative description of the SiO2 growth during thermal oxidation of SixGe1-x. Kinetic parameters are extracted by comparing the model with experiments. The linear and parabolic rate constants for Si oxidation are determined on control Si (100) wafers and polycrystalline Si films. Simple expressions are used for the interdiffusion of Si and Ge in SixGe1-x. For wet oxidation, the activation energy for the reaction rate constant of Ge oxidation is found to be smaller than that of Si oxidation.

Energy Requirements of Mechanical Shear Degradation in Concentrated Polymer Solutions

1960 ◽  
Vol 33 (4) ◽  
pp. 909-920
Author(s):  
A. B. Bestul
Keyword(s):  
Activation Energy ◽  
Degradation Process ◽  
Energy Requirements ◽  
Shear Load ◽  
Molecular Weights ◽  
Shear Degradation ◽  
Carbon Carbon Bonds ◽  
Shearing Energy ◽  
Weight Decrease ◽  
Mechanical Shearing

Abstract Molecular weight decrease by mechanical shearing results when solutions of around 10% of polyisobutene having average molecular weights above 500,000 are forced through a capillary at nominal rates of shear above 10,000 sec−1. Comparison of observed plots of shear load vs. duration of shearing at fixed rates of shear during this degradation process with the corresponding estimated plots which would be expected to obtain if degradation did not occur provide a means of evaluating the amount of applied shearing energy which is dissipated by the degradation process. The result is several hundred thousand kilo-calories per mole of broken bonds, which is several thousand times the bond energy of carbon-carbon bonds. This finding is consistent with the hypothesis that whenever a bond breaks the system loses much of the free energy temporarily stored in bonds and macromolecular chains located in a comparatively large volume surrounding the broken bond, these bonds and chains having been involved in concentrating the required activation energy into the ruptured bond.

Comparison of H2 Desorption Kinetics from Si(111)7×7 and Si(100)2×l

1990 ◽  
Vol 204 ◽  
Author(s):  
M. L. Wise ◽  
B. G. Koehler ◽  
P. Gupta ◽  
P. A. Coon ◽  
S. M. George
Keyword(s):  
Activation Energy ◽  
Preexponential Factor ◽  
Desorption Kinetics ◽  
Bond Energies ◽  
First Order ◽  
First Order Kinetics ◽  
Upper Limits ◽  
Desorption Activation Energy ◽  
Temperature Programmed ◽  
Kinetics Of

ABSTRACTThe desorption kinetics of hydrogen from the β1 H2 -TPD state on Si(111)7×7 and Si(100)2×l were studied using laser-induced thermal desorption (LITD) and temperature programmed desorption (TPD) techniques. Isothermal LITD studies of H2 desorption from Si(111)7×7 revealed second-order kinetics with a desorption activation energy of Ed = 62 ±4 kcal/mol and a preexponential factor of Vd = 92 ±10 cm2 /s. In contrast, H2 desorption from Si(100)2×l revealed first-order kinetics with an activation energy of Ed = 58 ±2 kcal/mol and a preexponential factor of Vd = 5.5 ±0.5 × 1015 s−1. The desorption kinetics yield similar upper limits for the Si-H bond energies but different desorption mechanisms on Si(lll)7×7 and Si(100)2×l.

scholarly journals Kinetics of pearlite spheroidization

2017 ◽  
Vol 62 (1) ◽  
pp. 231-234 ◽  
Author(s):  
P. Matusiewicz ◽  
J. Augustyn-Nadzieja ◽  
A. Czarski ◽  
T. Skowronek
Keyword(s):  
Activation Energy ◽  
High Purity ◽  
Surface Density ◽  
Quantitative Description ◽  
Carbon Diffusion ◽  
Interface Diffusion ◽  
Interface Surface ◽  
Kinetics Of ◽  
Good Agreement

Abstract The pearlite spheroidization in Fe-0.76%C high purity steel was investigated. The samples of a coarse pearlite microstructure were isothermal annealed at 700, 680, 660, 640 and 620°C for various times, up to 800 hours. For quantitative description of the spheroidization process stereological parameter, SV (ferrite/cementite interface surface density) was used. The activation energy 104.8±11.4 kJ/mol was found for the spheroidization process. This value shows good agreement with the activation energy for iron and carbon diffusion along a ferrite/cementite interface, so the coupled interface diffusion is the rule-controlling process.

ChemInform Abstract: MOLECULAR-BEAM STUDY OF THE ACTIVATION ENERGY REQUIREMENTS FOR THE DIOXETANE REACTION

1978 ◽  
Vol 9 (35) ◽  
Author(s):  
K. T. ALBEN ◽  
A. AUERBACH ◽  
W. M. OLLISON ◽  
J. WEINER ◽  
R. J. JUN. CROSS
Keyword(s):  
Activation Energy ◽  
Molecular Beam ◽  
Energy Requirements

High-resolution observations of metastable γ’ precipitation in Al-15at.%Ag

1996 ◽  
Vol 54 ◽  
pp. 1004-1005
Author(s):  
N. V. Larcher ◽  
I. G. Solorzano
Keyword(s):  
Discontinuous Precipitation ◽  
Equilibrium Phase ◽  
Quantitative Description ◽  
Present Contribution ◽  
Α Phase ◽  
The Matrix ◽  
Aging Sequence ◽  
Matrix Precipitation ◽  
Considerable Detail ◽  
Kinetics Of

It is currently well established that, for an Al-Ag alloy quenched from the α phase and aged within the metastable solvus, the aging sequence is: supersaturated α → GP zones → γ’ → γ (Ag2Al). While GP zones and plate-shaped γ’ are metastable phases, continuously distributed in the matrix, formation of the equilibrium phase γ takes place at grain boundaries by discontinuous precipitation (DP). The crystal structure of both γ’ and γ is hep with the following orientation relationship with respect to the fee α matrix: {0001}γ′,γ // {111}α, <1120>γ′,γ, // <110>α.The mechanisms and kinetics of continuous matrix precipitation (CMP) in dilute Al-Ag alloys have been studied in considerable detail. The quantitative description of DP kinetics, however, has received less attention. The present contribution reports the microstructural evolution resulting from aging an Al-Ag alloy with Ag content higher than those previously reported in the literature, focusing the observations of γ' plate-shaped metastable precipitates.

Respiratory energy requirements and rate of protein turnover in vivo determined by the use of an inhibitor of protein synthesis and a probe to assess its effect

1994 ◽  
Vol 92 (4) ◽  
pp. 585-594 ◽  
Author(s):  
T. J. Bouma ◽  
R. De Visser ◽  
J. H. J. A. Janssen ◽  
M. J. De Kock ◽  
P H. Van Leeuwen ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Protein Turnover ◽  
Energy Requirements ◽  
Inhibitor Of Protein Synthesis
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