scholarly journals Фотополимеризация в слоях фуллерена молекулярного донорно-акцепторного комплекса \Pt(nPr-=SUB=-2-=/SUB=-dtc)-=SUB=-2-=/SUB=-\·(C-=SUB=-60-=/SUB=-)-=SUB=-2-=/SUB=-

2018 ◽  
Vol 60 (10) ◽  
pp. 2057
Author(s):  
К.П. Мелетов
Keyword(s):  
Activation Energy ◽  
Raman Spectra ◽  
Room Temperature ◽  
Thermal Destruction ◽  
Arrhenius Equation ◽  
Fullerene Complexes ◽  
Donor Acceptor ◽  
Increasing Temperature ◽  
Kinetics Of ◽  
532 Nm

AbstractWe measured Raman spectra in crystals of molecular donor–acceptor fullerene complexes { Me ( n Pr_2 dtc )_2} · (C_60)_2 ( Me = Ni, Cu, Pt). In the spectra of the {Pt( n Pr_2 dtc )_2} · (C_60)_2 complex under prolonged irradiation with a laser with λ = 532 nm, characteristic changes in the photopolymerization of fullerene are observed, associated with the splitting of degenerate phonon Hg modes and softening of Ag modes of the C_60 molecule. The kinetics of photopolymerization under conditions of weak irradiation at room temperature is studied. It was found that thermal destruction of the photopolymer with increasing temperature leads to a decrease in its concentration in the final photopolymerization product. The kinetics of thermal destruction is described by the Arrhenius equation, with the activation energy E _A of (0.68 ± 0.03) eV; the dimers are destructed to a concentration of 1% within 15 min at ~114°C.

Decomposition kinetics of cobalt complexes of phenoxy radicals studied by EPR method

1980 ◽  
Vol 45 (2) ◽  
pp. 464-474 ◽  
Author(s):  
Ladislav Omelka ◽  
Alexander Tkáč
Keyword(s):  
Activation Energy ◽  
Room Temperature ◽  
Effective Activation Energy ◽  
Decomposition Kinetics ◽  
Peroxy Radicals ◽  
Substitution Reactions ◽  
Phenoxy Radicals ◽  
Increasing Temperature ◽  
Kinetics Of ◽  
Homolytic Substitution

In bimolecular homolytic substitution reactions type SH2 between coordinated peroxy radicals [Co(III)]RO2 and partially hindered bisphenol 4,4'-thiobis-(3-methyl-6-tert-butylphenol) (an antioxidant with commercial name Santonox R) in non-polar medium at room temperature an equilibrium is established between free and Co(III)-coordinated phenoxy radicals. Increasing temperature shifts the equilibrium in favour of the decomplexed free radicals. The complexation-decomplexation process of phenoxy radicals is practically reversible up to 90°C. Polar coordinating solvents (methanol, H2O, diethyl ether, tetrahydrofurane) displace irreversibly the radicals from the complexes. From their decomposition kinetics at various temperatures activation energy of decomplexation by methanol has been determined (110 ± 8 kJ mol-1). The displaced free partially hindered phenoxy radicals are not sufficiently stable and undergo subsequent radical transformations (dimerization, intramolecular and intermolecular H-transfer) with effective activation energy about 67 kJ mol-1.

On the use of Ozawa/Flynn/Wall method to determine aging activation energy for elastomers

2021 ◽  
pp. 009524432110203
Author(s):  
Sudhir Bafna
Keyword(s):  
Mechanical Properties ◽  
Activation Energy ◽  
Weight Loss ◽  
Oxygen Consumption ◽  
Dwell Time ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Degradation Mechanism ◽  
Kinetics Of ◽  
Wall Method

It is often necessary to assess the effect of aging at room temperature over years/decades for hardware containing elastomeric components such as oring seals or shock isolators. In order to determine this effect, accelerated oven aging at elevated temperatures is pursued. When doing so, it is vital that the degradation mechanism still be representative of that prevalent at room temperature. This places an upper limit on the elevated oven temperature, which in turn, increases the dwell time in the oven. As a result, the oven dwell time can run into months, if not years, something that is not realistically feasible due to resource/schedule constraints in industry. Measuring activation energy (Ea) of elastomer aging by test methods such as tensile strength or elongation, compression set, modulus, oxygen consumption, etc. is expensive and time consuming. Use of kinetics of weight loss by ThermoGravimetric Analysis (TGA) using the Ozawa/Flynn/Wall method per ASTM E1641 is an attractive option (especially due to the availability of commercial instrumentation with software to make the required measurements and calculations) and is widely used. There is no fundamental scientific reason why the kinetics of weight loss at elevated temperatures should correlate to the kinetics of loss of mechanical properties over years/decades at room temperature. Ea obtained by high temperature weight loss is almost always significantly higher than that obtained by measurements of mechanical properties or oxygen consumption over extended periods at much lower temperatures. In this paper, data on five different elastomer types (butyl, nitrile, EPDM, polychloroprene and fluorocarbon) are presented to prove that point. Thus, use of Ea determined by weight loss by TGA tends to give unrealistically high values, which in turn, will lead to incorrectly high predictions of storage life at room temperature.

scholarly journals Kinetics of carbothermic reduction of synthetic chromite

2014 ◽  
Vol 50 (1) ◽  
pp. 15-21 ◽  
Author(s):  
Y. Wang ◽  
L. Wang ◽  
J. Yu ◽  
K.C. Chou
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Reduction Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Chromite Ore ◽  
Current Reduction ◽  
Increasing Temperature ◽  
Isothermal Mode ◽  
Kinetics Of

In order to optimize the current reduction process of chromite, a good knowledge of reduction mechanism involved is required. The basic component in chromite ore is FeCr2O4, thus, kinetic investigation of synthetic FeCr2O4 with different amount of carbon were carried out in the temperature range of 1473K to 1673K under both isothermal and non-isothermal mode. The iron can be easily reduced compared with chromium. And higher reduction degree of chromite can be achieved by increasing temperature and carbon content. With the supporting of X-ray Diffraction and Scanning Electron Microscope methods, the formation of metallic products followed the sequence: Fe-C alloy, (Fe,Cr)7C3and Fe-Cr-C alloy. Kinetics analysis showed that the first stage was controlled by nucleation with an apparent activation energy of 120kJ/mol, while the chromium reduction was controlled by crystallochemical transformation with an apparent activation energy of 288kJ/mol.

scholarly journals The kinetics of mutarotation in solution

1940 ◽  
Vol 176 (966) ◽  
pp. 352-367 ◽  
Keyword(s):  
Aqueous Solution ◽  
Room Temperature ◽  
Reducing Sugars ◽  
Arrhenius Equation ◽  
Energy Of Activation ◽  
A Value ◽  
Temperature Ranges ◽  
Velocity Coefficient ◽  
Kinetics Of ◽  
True Energy

The kinetics of the mutarotation of representative reducing sugars from the pentose, hexose and disaccharide series have been investigated polarimetrically over wide temperature ranges in aqueous solution. The dependence of the velocity coefficient, k , upon temperature is fairly well reproduced by an equation of the form ln k = C + ( J/R ) ln T - E/RT . The true energy of activation, E , is found to be some 6000 calories greater than the apparent value afforded by the Arrhenius equation at room temperature. J/R has a value of — 10, which is identified as the number of oscillators contributing to the activation. The constants C, J and E of this equation are discussed, with reference to many reactions, in terms of a theory of unimolecular reactions in solution.

Kinetics and Thermodynamics Studies of Prodigiosin Dyeing on Polyester

2013 ◽  
Vol 779-780 ◽  
pp. 156-160 ◽  
Author(s):  
Jia Jia Shen ◽  
Ying Yang
Keyword(s):  
Activation Energy ◽  
Antimicrobial Activity ◽  
Arrhenius Equation ◽  
Disperse Dyes ◽  
Natural Pigment ◽  
Kinetics And Thermodynamics ◽  
Textile Dyeing ◽  
Exothermic Process ◽  
Enthalpy And Entropy ◽  
Increasing Temperature

Prodigiosin is a natural pigment which has antimicrobial activity and produced by a microorganism, but it is insoluble in water, thereby limiting their application in textile dyeing. With the study of the Prodigiosin’s kinetics and thermodynamics on PET, the feasibility of using Prodigiosin as disperse dyes was discussed. The thermodynamics results show that the up-take of Prodigiosin in PET fiber is linear to the dye bath concentration, with increasing temperature, the distribution coefficient decreases and the thermodynamic affinity of the dye has little gown up, the enthalpy and entropy of dyeing were -2.51[kJ/mol] and 5.05[J/(mol·K)] respectively, which show that PET dyeing with prodigiosin is a exothermic process and the diffusion coefficient increases with the temperature rise. The activation energy calculated with the Arrhenius equation is 6.09 [kcal /mol].

Temperature Dependence of the Band-Edge Injection Electroluminescence of 3C-SiC pn Structure

2007 ◽  
Vol 556-557 ◽  
pp. 427-430 ◽  
Author(s):  
Anatoly M. Strel'chuk ◽  
Alexander A. Lebedev ◽  
N.S. Savkina ◽  
Alexey N. Kuznetsov
Keyword(s):  
Activation Energy ◽  
Emission Band ◽  
Room Temperature ◽  
Free Exciton ◽  
Charge Carriers ◽  
Full Width ◽  
Half Maximum ◽  
Exciton Annihilation ◽  
Increasing Temperature ◽  
Injection Electroluminescence

We present the injection electroluminescence spectra in the temperature range 290-760 K of 3C-SiC pn structure, which was fabricated by sublimation epitaxy in vacuum on 6H-SiC substrate. The dominant emission band of injection electroluminescence (IEL) spectrum was observed in the green region; at room temperature the IEL intensity outside the region of hν ≈ 2.0- 2.5 eV was less than 3% of that of the green peak. The peak parameters at room temperature are: hνmax ≈ 2.32 eV, full width at half maximum w ≈ 100 meV. The green peak shifted in the longwave direction with increasing temperature; the hνmax (T) dependence was linear with the slope of - 1.3x10-4 eV/K. Both the IEL intensity of the green peak at hνmax and band width w increased upon heating. The w(T) dependence was linear with the slope of 4.6x10-4 eV/K; intensity increased with the activation energy of 70 meV. The green IEL band can be considered to be due to the free exciton annihilation or to the band-band recombination and edge IEL increasing with rising temperature can be explained by the nonequilibrium charge carriers lifetime increasing.

Formation and Effects of Secondary Defects in Ion implanted Silicon

1980 ◽  
Vol 2 ◽  
Author(s):  
Jack Washburn
Keyword(s):  
Activation Energy ◽  
Electron Microscope ◽  
Low Temperature ◽  
Ion Implantation ◽  
Room Temperature ◽  
Laser Annealing ◽  
Subsequent Annealing ◽  
Interface Migration ◽  
Kinetics Of ◽  
Ion Implanted

ABSTRACTThe clustering of isolated interstitial silicon, implanted atoms, and vacant lattice sites produced by low temperature and room temperature ion implantation during subsequent annealing is reviewed. An electron microscope method for studying the kinetics of the amorphous to crystalline transformation in silicon is described. The technique is applied to measurement of the activation energy for interface migration and the formation of microtwins for different growth directions. A very brief review of the effects of laser annealing after ion implantation is included.

Investigations in the Field of Rubber Vulcanization. VII. Influence of Organic Accelerators on the Kinetics of Vulcanization and the Properties of Natural-Rubber Vulcanizates

1950 ◽  
Vol 23 (3) ◽  
pp. 563-575
Author(s):  
B. Dogadkin ◽  
B. Karmin ◽  
A. Dobromyslova ◽  
L. Sapozhkova
Keyword(s):  
Activation Energy ◽  
Natural Rubber ◽  
Oxidative Destruction ◽  
Tetramethylthiuram Disulfide ◽  
Vulcanization Kinetics ◽  
Strength Curve ◽  
Increasing Temperature ◽  
Low Sulfur ◽  
Natural Rubber Vulcanizates ◽  
Kinetics Of

Abstract 1. Vulcanization accelerators change all parameters of the kinetic strength curve during the vulcanization of natural-rubber mixtures with low sulfur contents. 2. Calculation of the kinetic constants of the fundamental vulcanization equation proposed by Dogadkin, Karmin, and Gol'berg shows that vulcanization accelerators affect both the kinetics of the interaction of rubber with sulfur and the kinetics of the interaction of rubber with oxygen. 3. Direct experiments on the oxidation of rubber have shown that tetramethylthiuram disulfide and diphenylguanidine retard the process of addition of oxygen to rubber, while mercaptobenzothiazole accelerates this process. 4. Data on the rate of plasticization and change in viscosity of rubber solutions during oxidation indicate that tetramethylthiuram disulfide and diphenylguanidine promote the disintegration of molecular chains of rubber during the oxidative destruction of the latter. 5. The activation energy of the process of oxidation of rubber in the presence of mercaptobenzothiazole corresponds to the activation energy calculated from the fundamental vulcanization reaction for the process of oxidative destruction. This provides additional proof of the participation of oxygen in the vulcanization process. 6. It has been established with the aid of the methyl iodide reaction that accelerators increase the bridge-sulfur content of the vulcanizate, which is present in the form of monosulfides, with one sulfur atom connected to an allyl type radical. 7. With increasing temperature, the tensile strength at the vulcanization optimum increases in mixtures containing tetramethylthiuram disulfide, decreases in mixtures containing mercaptobenzothiazole, and remains unchanged in mixtures containing diphenylguanidine. The limiting strength decreases in all cases with increasing temperature. This phenomenon is explained on the basis of the proposed concepts of the character of vulcanization kinetics and of the nature of the vulcanization optimum.

Kinetics of a-Si:H Crystallization Induced by Gold at Low Temperatures

1992 ◽  
Vol 258 ◽  
Author(s):  
A.A. Pasa ◽  
M.B. Schubert ◽  
C.-D. Abel ◽  
W. Beyer ◽  
W. Losch ◽  
...  
Keyword(s):  
Activation Energy ◽  
Glow Discharge ◽  
Film Thickness ◽  
Raman Spectra ◽  
Low Temperatures ◽  
Crystallization Rate ◽  
Au Film ◽  
Annealing Conditions ◽  
Kinetics Of ◽  
Induced Crystallization

ABSTRACTThe Au-induced crystallization of a-Si:H has been studied by evaporating Au films of different thicknesses onto intrinsic glow discharge deposited a-Si:H layers. The presence of a sharp peak in the Raman spectra (FWHM≈9 cm-1, ω516 cm-1) of samples with a Au thickness larger than 2 nm, which have been annealed in vacuum at 400K≤T≤600K, indicate that the crystallites have approximately the same size (6nm) regardless of the annealing conditions. An investigation of crystallization versus Au-film thickness revealed, that the total crystallized volume is increasing with Au thickness, and furthermore a saturation of the crystallized volume takes place, most probably due to an exhaustion of the Au reservoir. The increase of crystallization rate with temperature follows an Arrhenius-like dependence with an activation energy of 1.1 eV. Changes in hydrogen content as a consequence of the crystallization have been monitored by H-effusion measurements: Au-coated a-Si:H samples show a strong H2 evolution at temperatures substantially lower than uncoated ones.

Deep Donor-Acceptor Pair Luminescence in Codoped GaN

2002 ◽  
Vol 743 ◽  
Author(s):  
Bing Han ◽  
Joel M. Gregie ◽  
Melville P. Ulmer ◽  
Bruce W. Wessels
Keyword(s):  
Luminescence Band ◽  
Room Temperature ◽  
Deep Level ◽  
Excitation Density ◽  
Acceptor Pair ◽  
Deep Donor ◽  
Donor Acceptor ◽  
Donor Acceptor Pair ◽  
Increasing Temperature ◽  
Luminescent Behavior

ABSTRACTDeep level defects formed in p-type GaN:Mg codoped with shallow donors have been investigated by photoluminescence (PL) spectroscopy. A donor-acceptor pair (DAP) luminescence band peaked at 2.45 eV dominates the room temperature PL spectrum in heavily codoped epilayers. A superlinear dependence of PL intensity on excitation density is observed for this band, with an exponent of 1.4∼1.7. The intensity of this band increases with increasing temperature with a maximum at 264K. To explain the luminescent behavior a DAP model was developed whereby the recombination involves a deep donor and shallow Mg acceptor. The deep donor is tentatively attributed to a DX center.

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