Solvation Mechanisms of Nedocromil Sodium From Activation Energy and Reaction Enthalpy Measurements of Dehydration and Dealcoholation

2002 ◽  
Vol 91 (4) ◽  
pp. 1101-1116 ◽  
Author(s):  
Alison C. Richards ◽  
Ian J. McColm ◽  
J.Barrie Harness
Keyword(s):  
Activation Energy ◽  
Nedocromil Sodium ◽  
Reaction Enthalpy ◽  
Solvation Mechanisms

scholarly journals Thermoanalytische Untersuchungen zur Rückoxidation von Ba2YCu3O6+x

1988 ◽  
Vol 43 (11) ◽  
pp. 965-970 ◽  
Author(s):  
Chr. L. Teske ◽  
Hk. Müller-Buschbaum
Keyword(s):  
Activation Energy ◽  
Oxygen Uptake ◽  
Ceramic Material ◽  
Maximum Rate ◽  
Reaction Enthalpy ◽  
Super Conducting ◽  
Dta And Tg ◽  
Superconducting Ceramic

Abstract The reoxidation reaction of Ba2YCu3O6+ x forming the superconducting ceramic material Ba2YCu3O6 93 is studied by thermoanalytical methods (DTA and TG). The exothermal oxygen uptake in pure O2-atmosphere is at a maximum rate in the range of 230-330 °C (≈ 150min). The reoxidation temperature can be lowered by treatment of Ba2YCu3O6 0 in Ar : H2 = 1: 1 atmosphere but the uptake of greater amounts of hydrogen prevents the material from becoming super-conducting again at low reoxidation temperatures. The process has an activation energy Ea = 70.9 ± 2kJ Mol and a reaction enthalpy ΔH = - 86.7kJ/Mol Ba2YCu3O6.0 (normalized to a 1/2 O2 basis) which is estimated from DTA-data.

MINDO-FORCES Calculation of the Benzyl and Vinyl Radicals and the Reactions 1CH2 + H2 → CH4 and CH4.+ → CH3+ + H

1978 ◽  
Vol 33 (6) ◽  
pp. 722-730
Author(s):  
Salim M. Khalil ◽  
Muthana Shanshal
Keyword(s):  
Activation Energy ◽  
Transition State ◽  
Decomposition Reaction ◽  
Geometric Parameters ◽  
Reaction Enthalpy ◽  
Vinyl Radicals ◽  
Vinyl Radical ◽  
Calculated Activation Energy ◽  
Methylene Group ◽  
Calculated Activation

Abstract The MINDO/3-F0RCES method is applied for the calculation of the 1CH2+H2 → CH4 reaction. The variation of geometry is carried out in such a manner as to allow for the deviation from the C2v symmetry along the H7 -CH2 reaction coordinate. The changes in the geometric parameters of the system during the reaction are followed. It is found that the transition state of the reaction corresponds to R = 1.8 Å and has a geometry closer to the reactants than the products. The calculated activation energy is 13.57 kcal/mol and the calculated reaction enthalpy 106.36 kcal/mol (118.9 kcal/mol exp.). Similar calculations for the CH4.+ yield a D2d structure and a ⊿Hf value of 269.68 kcal/mol (274.0 kcal/mol exp.). The activation energy of the decomposition reaction CH4.+ → CH3+ + H· is 84.54 kcal/mol, the reaction enthalpy is 42.83 kcal/mol (38.10 kcal/mol exp.). Using both MINDO/2- and MINDO/3.FORCES a C2v geometry is calculated for the benzyl radical. The ⊿Hf values are 48.40 and 67.93 kcal/mol respectively. The latter calculation shows that the rotated perpendicular conformation of the methylene group is by 2 kcal/mol less stable than the planar one. The rotation transition state corresponds to the rotation angle 50°. The change in ithe geometric parameters during the rotation is followed. For he vinyl radical the MINDO/3-FORCES calculation yields a CCH angle of 151.1° and a Hf value of 69.8 kcal/mol (65 kcal/mol exp.).

scholarly journals Curing kinetics of two commercial urea-formaldehyde adhesives studied by isoconversional method

2011 ◽  
Vol 65 (6) ◽  
pp. 717-726 ◽  
Author(s):  
Mladjan Popovic ◽  
Jaroslava Budinski-Simendic ◽  
Mirjana Jovicic ◽  
Joszef Mursics ◽  
Milanka Djiporovic-Momcilovic ◽  
...  
Keyword(s):  
Activation Energy ◽  
Urea Formaldehyde ◽  
Curing Kinetics ◽  
Isoconversional Methods ◽  
Isoconversional Method ◽  
Reaction Enthalpy ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Dsc Measurements ◽  
Kinetics Of

Differential scanning calorimetry (DSC) was used to evaluate the curing kinetics of two commercial urea-formaldehyde (UF) adhesives having different formaldehyde to urea (F/U) ratio of 1.112 (UF1) and 1.086 (UF2). DSC measurements were done in dynamic scanning regime with heating rates of 5, 10, 15 and 20?C?min-1 in order to determine the activation energy for each adhesive. Obtained data were analyzed using isoconversional methods with application of Ozawa-Flynn-Wall and Kissinger-Akahira-Sunose kinetic models. In addition, different catalyst levels were tested at the heating rate of 10?C/min. Results showed that the adhesive with higher F/U ratio achieved higher activation energy, while having lower peak temperature of curing reaction. It was also noticed that the increase of catalyst level influenced the increase of reaction enthalpy of the adhesive with lower F/U ratio.

High Temperature n- and p-type Doped Microcrystalline Silicon Layers Grown by VHF PECVD Layer-by-Layer Deposition

2003 ◽  
Vol 762 ◽  
Author(s):  
A. Gordijn ◽  
J.K. Rath ◽  
R.E.I. Schropp
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
High Temperatures ◽  
Continuous Wave ◽  
Hydrogen Plasma ◽  
Silicon Layer ◽  
Dark Conductivity ◽  
High Deposition Rate ◽  
Layer By Layer ◽  
Microcrystalline Silicon

AbstractDue to the high temperatures used for high deposition rate microcrystalline (μc-Si:H) and polycrystalline silicon, there is a need for compact and temperature-stable doped layers. In this study we report on films grown by the layer-by-layer method (LbL) using VHF PECVD. Growth of an amorphous silicon layer is alternated by a hydrogen plasma treatment. In LbL, the surface reactions are separated time-wise from the nucleation in the bulk. We observed that it is possible to incorporate dopant atoms in the layer, without disturbing the nucleation. Even at high substrate temperatures (up to 400°C) doped layers can be made microcrystalline. At these temperatures, in the continuous wave case, crystallinity is hindered, which is generally attributed to the out-diffusion of hydrogen from the surface and the presence of impurities (dopants).We observe that the parameter window for the treatment time for p-layers is smaller compared to n-layers. Moreover we observe that for high temperatures, the nucleation of p-layers is more adversely affected than for n-layers. Thin, doped layers have been structurally, optically and electrically characterized. The best n-layer made at 400°C, with a thickness of only 31 nm, had an activation energy of 0.056 eV and a dark conductivity of 2.7 S/cm, while the best p-layer made at 350°C, with a thickness of 29 nm, had an activation energy of 0.11 V and a dark conductivity of 0.1 S/cm. The suitability of these high temperature n-layers has been demonstrated in an n-i-p microcrystalline silicon solar cell with an unoptimized μc-Si:H i-layer deposited at 250°C and without buffer. The Voc of the cell is 0.48 V and the fill factor is 70 %.

White- and Brown-Rice Supplementation Improves Insulin Tolerance, Brown Fat Activation, Energy Expenditure, and Changes the Gut Microflora in Diet-Induced Obesity

Diabetes ◽  
2018 ◽  
Vol 67 (Supplement 1) ◽  
pp. 1897-P
Author(s):  
HISASHI YOKOMIZO ◽  
ATSUSHI ISHIKADO ◽  
TAKANORI SHINJO ◽  
KYOUNGMIN PARK ◽  
YASUTAKA MAEDA ◽  
...  
Keyword(s):  
Activation Energy ◽  
Energy Expenditure ◽  
Brown Rice ◽  
Brown Fat ◽  
Gut Microflora ◽  
Diet Induced Obesity ◽  
Insulin Tolerance

Activation energy of relaxation processes in chalcogenide glasses

2013 ◽  
Vol 34 (0) ◽  
pp. 59-63
Author(s):  
А. А. Горват ◽  
В. М. Кришеник ◽  
А. Е. Кріштофорій ◽  
В. В. Мінькович ◽  
О. А. Молнар
Keyword(s):  
Activation Energy ◽  
Chalcogenide Glasses ◽  
Relaxation Processes

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.

Pt-Pd Nanoalloy for the Unprecedented Activation of Carbon-Fluorine Bond at Low Temperature

2019 ◽  
Author(s):  
Raghu Nath Dhital ◽  
keigo nomura ◽  
Yoshinori Sato ◽  
Setsiri Haesuwannakij ◽  
Masahiro Ehara ◽  
...  
Keyword(s):  
Activation Energy ◽  
Low Temperature ◽  
Dft Calculations ◽  
Bond Activation ◽  
Mild Conditions ◽  
Selective Transformation ◽  
Rate Determining Step ◽  
Highly Active ◽  
Harsh Conditions ◽  
Reaction Profile

Carbon-Fluorine (C-F) bonds are considered the most inert organic functionality and their selective transformation under mild conditions remains challenging. Herein, we report a highly active Pt-Pd nanoalloy as a robust catalyst for the transformation of C-F bonds into C-H bonds at low temperature, a reaction that often required harsh conditions. The alloying of Pt with Pd is crucial to activate C-F bond. The reaction profile kinetics revealed that the major source of hydrogen in the defluorinated product is the alcoholic proton of 2-propanol, and the rate-determining step is the reduction of the metal upon transfer of the <i>beta</i>-H from 2-propanol. DFT calculations elucidated that the key step is the selective oxidative addition of the O-H bond of 2-propanol to a Pd center prior to C-F bond activation at a Pt site, which crucially reduces the activation energy of the C-F bond. Therefore, both Pt and Pd work independently but synergistically to promote the overall reaction

Sign in / Sign up

Export Citation Format

Share Document