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.

The influence of Au film thickness and annealing conditions on the VLS-assisted growth of ZnO nanostructures

2014 ◽  
Vol 25 (21) ◽  
pp. 215601 ◽  
Author(s):  
K Govatsi ◽  
A Chrissanthopoulos ◽  
V Dracopoulos ◽  
S N Yannopoulos
Keyword(s):  
Film Thickness ◽  
Zno Nanostructures ◽  
Au Film ◽  
Annealing Conditions

Kinetic Study on Phosphate Enrichment Behavior in CaO–SiO2–FeO–Fe2O3–P2O5 Steelmaking Slags

2018 ◽  
Vol 37 (5) ◽  
pp. 477-486
Author(s):  
Jin-yan Li ◽  
Mei Zhang ◽  
Min Guo ◽  
Xue-min Yang
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Crystallization Behavior ◽  
Crystallization Rate ◽  
Avrami Equation ◽  
One Dimensional ◽  
Thermal Crystallization ◽  
Steelmaking Slags ◽  
Cooling Schedules ◽  
Kinetics Of

AbstractThe iso-thermal crystallization behavior of phosphate-enriched phase has been experimentally investigated in the rapidly quenched CaO–SiO2–FeO–Fe2O3–P2O5 steelmaking slags under different cooling schedules. The experimental results indicate that increasing endpoint temperature from 1453 to 1533 K and prolonging holding time from 2 to 60 min can result in an increasing tendency of the size of phosphate-enriched phase in the shape of one-dimensional rod. The crystallization kinetics of phosphate-enriched phase in steelmaking slags has been described by Avrami equation. The Avrami constant $$n$$ was obtained to be 0.472, while the crystallization rate constant $$k$$ was recommended as $$\ln k{\rm{= 57}}{\rm{. 40 + 12,273}}{\rm{. 96}}/T - {\rm{8}}{\rm{. 25}}\,\ln T - {\rm{5}}{\rm{. 5}\times{\rm 10}^{- 3}}T$$. Thus, the apparent activation energy $$E$$ of crystallization is recommended as $$E{\rm{= 537}}{\rm{. 60}} - {\rm{206}}{\rm{. 015}}T$$ kJ/mol.

scholarly journals Isothermal and Non-Isothermal Crystallization Kinetics of PVDF and PVDF/PMMA Blends

2020 ◽  
Vol 2 (2) ◽  
Author(s):  
Jianbin SONG ◽  
Yuan CAI ◽  
Bin ZHANG ◽  
Lixin TANG ◽  
Rongrong SHI ◽  
...  
Keyword(s):  
Activation Energy ◽  
Crystallization Kinetics ◽  
Crystallization Rate ◽  
Crystallization Activation Energy ◽  
Nonisothermal Crystallization ◽  
Ozawa Equation ◽  
Nonisothermal Crystallization Kinetics ◽  
Kinetics Of ◽  
Pmma Blends ◽  
Pure Pvdf

Background: poly(vinylidene fluoride) PVDF and PVDF/PMMA blends have been investigated with a focus on the crystal structure, immiscibility and mechanical properties. However, few reports were found on the crystallization behaviors of PVDF and PVDF/PMMA blends, especially on crystallization kinetics. The article is to report the research on isothermal and nonisothermal crystallization kinetics for PVDF and PVDF/PMMA blends using differential scanning calorimetry (DSC). Results: Besides crystallization temperature and isothermal crystallization activation energy, the Avrami equation exponent of PVDF in blends decreased compared with pure PVDF. The nonisothermal crystallization kinetics of PVDF and PVDF/PMMA (70:30) blends were investigated by Ozawa equation, Jeziorny method and crystallization rate constant (CRC) in detail. The nonisothermal crystallization energy of pure PVDF and its blends were determined by the Kissinger and Vyazovkin’s method. Conclusion: The nucleation and growth mechanism of PVDF in blends changed compared with pure PVDF. The Ozawa equation is not applicable in nonisothermal crystallization kinetics of PVDF and PVDF/PMMA blends. The decreasing of crystallization ability of PVDF in blends were found and confirmed by CRC and the decline of crystallization rate constant in Jeziorny method. Such is opposite to the results of Kissinger’s and Vyazovkin’s method, chances are that these two methods were not used to calculate the nonisothermal crystallization activation energy where the nucleation process was influenced.

Accumulation and diffusion of charges in kinetics of polymer electric breakdown

2021 ◽  
Author(s):  
I. K. Aliyeva ◽  
T. M. Veliyev
Keyword(s):  
Activation Energy ◽  
Low Temperatures ◽  
Opposite Sign ◽  
Constant Electric Field ◽  
Strength Properties ◽  
Mean Value ◽  
Time Interval ◽  
Kinetics Of ◽  
And Diffusion ◽  
Mean Value Formula

In this paper, the distribution in electric durability [Formula: see text] of polymers in constant electric field at low temperatures has been measured. The results of continuous experiments and experiments of field discontinuous effect on polymer samples being remained not disruptive after exposure for time equal to mean value [Formula: see text] have been compared. During the interval, we have varied the time interval, temperature [Formula: see text] and electric intensity of opposite sign [Formula: see text] according to which various degree of regeneration of polymer electric strength properties has been observed. By the degree of regeneration, relaxation time [Formula: see text] of the accumulated charges in polymers causing breakdown has been found. It is established that the process of charge diffusion, which accumulation leads to breakdown has a thermofluctuation behavior and the activation energy of given process depends on the counter field intensity magnitude.

Effect of Hyperbranched Polymer on Crystallization Kinetics of Isotactic Polypropylene

2012 ◽  
Vol 535-537 ◽  
pp. 1142-1145
Author(s):  
Guang Tian Liu ◽  
Jing Lei
Keyword(s):  
Activation Energy ◽  
Crystallization Kinetics ◽  
Isotactic Polypropylene ◽  
Isothermal Crystallization ◽  
Hyperbranched Polymer ◽  
Crystallization Rate ◽  
Crystallization Activation Energy ◽  
Scanning Calorimetry ◽  
Isothermal Crystallization Kinetics ◽  
Kinetics Of

In this paper, the isothermal crystallization kinetics of isotactic polypropylene (iPP) and iPP with 5% hyperbranched polymer (HBP) added had been investigated by differential scanning calorimetry (DSC). The results show that a small addition of HBP affects the crystallization behavior of iPP. During isothermal crystallization, the crystallization rate of the blend is higher than those of iPP remarkably. An increase in the Avrami exponent may be attributed to the fractal structure of hyperbranched polymer. The crystallization activation energy is estimated by the Friedman equation, the results show that the activation energy decreases remarkably by addition of HBP and the crystallization rate of the blend is more sensitive to temperature than that of iPP.

Light Induced Defects in a-Si:H, Temperature Dependence of their Creation and Anneal and their effect on Photocarrier Lifetime

1994 ◽  
Vol 336 ◽  
Author(s):  
Paul Stradins ◽  
Hellmut Fritzsche ◽  
Minh Q. Tran
Keyword(s):  
Glow Discharge ◽  
Temperature Dependence ◽  
Low Temperatures ◽  
Plasma Discharge ◽  
Hot Wire ◽  
Defect Creation ◽  
Normal Glow Discharge ◽  
Induced Defects ◽  
Kinetics Of ◽  
Effect Of Light

ABSTRACTWe compared the effect of light soaking on the photoresponse and defect concentration ND of samples prepared by normal glow discharge, by remote plasma discharge, by the heated mesh and by the hot wire deposition methods. After exposure to 4×1027 cm−3 absorbed photons all samples have the nearly the same Np and photoresponse. At low temperatures additional defects with small anneal energies are created. Defects created at low temperatures were found to relax between 100K and 300K before they anneal. These new results cannot be explained by present models of defect creation. The kinetics of defect creation at low temperatures is discussed.

KINETICS OF THE DECOMPOSITIONS OF ETHANE AND PROPANE SENSITIZED BY AZOMETHANE: THE DECOMPOSITION OF THE NORMAL PROPYL RADICAL

1966 ◽  
Vol 44 (24) ◽  
pp. 2927-2940 ◽  
Author(s):  
M. C. Lin ◽  
K. J. Laidler
Keyword(s):  
Activation Energy ◽  
Satisfactory Agreement ◽  
Rate Constant ◽  
Dissociation Energy ◽  
Low Temperatures ◽  
Heats Of Formation ◽  
Kcal Mole ◽  
Energy Diagram ◽  
A Value ◽  
Kinetics Of

The azomethane-sensitized pyrolysis of ethane was studied at low temperatures from 280 to 350 °C. Measurements were made of initial rates of formation of methane, nitrogen, and butane. From the rate of nitrogen production the rate constant for the azomethane decomposition into 2CH3 + N2 was[Formula: see text]A similar study of the propane decomposition, at temperatures from 260 to 300 °C, led to the value[Formula: see text]in satisfactory agreement. The rate of decomposition of the n-propyl radical into CH3 and C2H4 was obtained by comparing the rates of formation of C2H4 and n-C6H14; the rate constant was[Formula: see text]The activation energy of 31.4 kcal/mole, together with that of 8.9 kcal/mole for the reverse reaction obtained by Brinton, leads to a value of 20.3 kcal/mole for the dissociation energy of n-CH3—CH CH2 at 0 °K, and to a value of 22.8 at 25 °C. The corresponding values for the heats of formation 2of the n-propyl radical are 28.4 kcal/mole at 0 °K, and 23.1 kcal/mole at 25 °C. The dissociation energy of n-CH3CH2CH2—H is deduced to be 99.4 kcal/mole at 0 °K and 99.9 kcal/mole at 25 °C. An energy diagram is constructed for the various reactions of n-C3H7 and i-C3H7.

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.

Oxidation kinetics of nanocrystalline Al thin films

2019 ◽  
Vol 66 (5) ◽  
pp. 638-643
Author(s):  
Jinsong Luo ◽  
Ligong Zhang ◽  
Haigui Yang ◽  
Nan Zhang ◽  
Yongfu Zhu ◽  
...  
Keyword(s):  
Thin Films ◽  
Activation Energy ◽  
Grain Boundary ◽  
Film Thickness ◽  
Silicon Substrate ◽  
Oxidation Kinetics ◽  
Oxidation Rate ◽  
Boundary Diffusion ◽  
Content Type ◽  
Kinetics Of

Purpose This paper aims to study the oxidation kinetics of the nanocrystalline Al ultrathin films. The influence of structure and composition evolution during thermal oxidation will be observed. The reason for the change in the oxidation activation energy on increasing the oxidation temperature will be discussed. Design/methodology/approach Al thin films are deposited on the silicon wafers as substrates by vacuumed thermal evaporation under the base pressure of 2 × 10−4 Pa, where the substrates are not heated. A crystalline quartz sensor is used to monitor the film thickness. The film thickness varies in the range from 30 to 100 nm. To keep the silicon substrate from oxidation during thermal oxidation of the Al film, a 50-nm gold film was deposited on the back side of silicon substrate. Isothermal oxidation studies of the Al film were carried out in air to assess the oxidation kinetics at 400-600°C. Findings The activation energy is positive and low for the low temperature oxidation, but it becomes apparently negative at higher temperatures. The oxide grains are nano-sized, and γ-Al2O3 crystals are formed at above 500°C. In light of the model by Davies, the grain boundary diffusion is believed to be the reason for the logarithmic oxidation rate rule. The negative activation energy at higher temperatures is apparent, which comes from the decline of diffusion paths due to the formation of the γ-Al2O3 crystals. Originality/value It is found that the oxidation kinetics of nanocrystalline Al thin films in air at 400-600°C follows the logarithmic law, and this logarithmic oxidation rate law is related to the grain boundary diffusion. The negative activation energies in the higher temperature range can be attributed to the formation of γ-Al2O3 crystal.

Effect of ionizing radiation on the kinetics of hydrogenation on the Ni-MgO mixed catalyst

1982 ◽  
Vol 47 (7) ◽  
pp. 1780-1786 ◽  
Author(s):  
Rostislav Kudláček ◽  
Jan Lokoč
Keyword(s):  
Experimental Data ◽  
Activation Energy ◽  
Liquid Phase ◽  
Ionizing Radiation ◽  
Oxide Catalyst ◽  
Absorbed Dose ◽  
Hydrogenation Rate ◽  
Solution Composition ◽  
Mixed Catalyst ◽  
Kinetics Of

The effect of gamma pre-irradiation of the mixed nickel-magnesium oxide catalyst on the kinetics of hydrogenation of maleic acid in the liquid phase has been studied. The changes of the hydrogenation rate are compared with the changes of the adsorbed amount of the acid and with the changes of the solution composition, activation energy, and absorbed dose of the ionizing radiation. From this comparison and from the interpretation of the experimental data it can be deduced that two types of centers can be distinguished on the surface of the catalyst under study, namely the sorption centres for the acid and hydrogen and the reaction centres.

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