Diffusion model for deposition of epitaxial GaAs layers prepared by the MOCVD method

1991 ◽  
Vol 56 (10) ◽  
pp. 2020-2029
Author(s):  
Jindřich Leitner ◽  
Petr Voňka ◽  
Josef Stejskal ◽  
Přemysl Klíma ◽  
Rudolf Hladina
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Kinetic Model ◽  
Gas Phase ◽  
Substrate Surface ◽  
Deposition Process ◽  
Hydrogen Atmosphere ◽  
Epitaxial Gaas ◽  
Kinetics Of ◽  
Good Agreement

The authors proposed and treated quantitatively a kinetic model for deposition of epitaxial GaAs layers prepared by reaction of trimethylgallium with arsine in hydrogen atmosphere. The transport of gallium to the surface of the substrate is considered as the controlling process. The influence of the rate of chemical reactions in the gas phase and on the substrate surface on the kinetics of the deposition process is neglected. The calculated dependence of the growth rate of the layers on the conditions of the deposition is in a good agreement with experimental data in the temperature range from 600 to 800°C.

scholarly journals Further study on kinetic modeling of sunflower oil methanolysis catalyzed by calcium-based catalysts

2016 ◽  
Vol 22 (2) ◽  
pp. 137-144 ◽  
Author(s):  
Marija Miladinovic ◽  
Marija Tasic ◽  
Olivera Stamenkovic ◽  
Vlada Veljkovic ◽  
Dejan Skala
Keyword(s):  
Experimental Data ◽  
Mass Transfer ◽  
Kinetic Model ◽  
Sunflower Oil ◽  
Coefficient Of Determination ◽  
Reaction Conditions ◽  
High Coefficient ◽  
Relative Percentage ◽  
Kinetics Of ◽  
Good Agreement

The kinetic model, which was originally developed for sunflower oil methanolysis catalyzed by CaO.ZnO, was examined for several other calcium-based catalysts like neat CaO, quicklime and Ca(OH)2. This model including triacylglycerols mass transfer- and chemically-controlled regimes demonstrated a good agreement with the experimental data in terms of a high coefficient of determination (0.971?0.022) and acceptable mean relative percentage deviation (?15.9%). Hence, this model is recommended for modeling the kinetics of sunflower oil methanolysis over calcium-based catalysts under widely ranging reaction conditions.

scholarly journals Kinetic Modelling of Lovastatin Biosynthesis by Aspergillus Terreus Cultivated on Lactose and Glycerol as Carbon Sources

2012 ◽  
Vol 33 (4) ◽  
pp. 651-665 ◽  
Author(s):  
Marta Pawlak ◽  
Marcin Bizukojć
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Kinetic Model ◽  
Organic Nitrogen ◽  
Aspergillus Terreus ◽  
Specific Growth ◽  
Kinetic Modelling ◽  
Carbon Sources ◽  
Batch Experiments ◽  
Kinetics Of

A kinetic model to describe lovastatin biosynthesis by Aspergillus terreus ATCC 20542 in a batch culture with the simultaneous use of lactose and glycerol as carbon sources was developed. In order to do this the kinetics of the process was first studied. Then, the model consisting of five ordinary differential equations to balance lactose, glycerol, organic nitrogen, lovastatin and biomass was proposed. A set of batch experiments with a varying lactose to glycerol ratio was used to finally establish the form of this model and find its parameters. The parameters were either directly determined from the experimental data (maximum biomass specific growth rate, yield coefficients) or identified with the use of the optimisation software. In the next step the model was verified with the use of the independent sets of data obtained from the bioreactor cultivations. In the end the parameters of the model were thoroughly discussed with regard to their biological sense. The fit of the model to the experimental data proved to be satisfactory and gave a new insight to develop various strategies of cultivation of A. terreus with the use of two substrates.

scholarly journals ANALYSIS OF THE CURRENT STATE OF RESEARCHES OF THE DEPOSITION OF ASPHALT-RESINOUS SUBSTANCES, PARAFFIN, AND MODELING METHODS. REVIEW PART II: WAX DEPOSITION

2021 ◽  
pp. 13-23
Author(s):  
M.R. Manafov ◽  
◽  
G.S. Aliyev ◽  
A.I. Rustamova ◽  
V.I. Kerimli ◽  
...  
Keyword(s):  
Experimental Data ◽  
Kinetic Model ◽  
Deposition Process ◽  
Real Field ◽  
Wax Deposition ◽  
Scaling Effect ◽  
Modeling Methods ◽  
Current State ◽  
Simulation Results ◽  
Reliable Interpretation

The mechanism of paraffin formation in transport pipes is briefly discussed. A kinetic model of the formation and wax deposition from oil is proposed. Comparison of the model with the available experimental data gave satisfactory results. The review considers software tools for modeling the wax deposition process. It is noted that the simulation results are not always applicable to real field cases. For a more reliable interpretation, the scaling effect must be taken into account. In the work various technologies for wax removal are considered

Simulation on Coal Devolatilization Combined a Multi-Step Kinetic Model with Chemkin Software

2012 ◽  
Vol 608-609 ◽  
pp. 1375-1382
Author(s):  
Rui Zhang ◽  
Qin Hui Wang ◽  
Zhong Yang Luo ◽  
Meng Xiang Fang
Keyword(s):  
Experimental Data ◽  
Kinetic Model ◽  
Intermediate Product ◽  
Coal Combustion ◽  
Model Complexity ◽  
Coal Pyrolysis ◽  
Simple Application ◽  
Calculation Results ◽  
Simulation Results ◽  
Good Agreement

As the first step in coal combustion and gasification, coal devolatilization has significant effect on reaction process. Previous coal devolatilization models have some disadvantages, such as poor flexibility, model complexity, and requirement of characterization parameters. Recently, Sommariva et al. have proposed a multi-step kinetic model of coal devolatilization. This model avoids the disadvantages mentioned above and can predict elemental composition of tar and char. In this paper, the mechanism of this model has been revised for simple application to Chemkin. Revision method is that some reactions are split into more reactions by using one pseudo-intermediate-product to replace several final products. Simulation results show that calculation results from revised mechanism compare quite well with that from original mechanism and have good agreement with experimental data. The revised mechanism is accurate and can be applied to Chemkin very easily, which gives it wide application to simulation of coal pyrolysis, gasification and combustion.

The Effect of Hydrogen on the Kinetics of Solid Phase Epitaxy in Amorphous Silicon

1990 ◽  
Vol 205 ◽  
Author(s):  
J. A. Roth ◽  
G. L. Olson ◽  
D. C. Jacobson ◽  
J. M. Poate ◽  
C. Kirschbaum
Keyword(s):  
Growth Rate ◽  
Solid Phase ◽  
Intrinsic Value ◽  
Amorphous Layer ◽  
Inert Gas ◽  
Solid Phase Epitaxy ◽  
Depth Profiles ◽  
Kinetics Of ◽  
Crystal Interface ◽  
Good Agreement

AbstractThis paper discusses the intrusion of H into a-Si layers during solid phase epitaxy and the effect of this H on the growth kinetics. We show that during annealing in the presence of water vapor, H is continuously generated at the oxidizing a-Si surface and diffuses into the amorphous layer, where it causes a reduction in the epitaxial growth rate. The measured variation of growth rate with the depth of the amorphous/crystal interface is correlated with the concentration of H at the interface. The diffusion coefficient for H in a-Si is determined by comparing measured depth profiles with calculated values. Hydrogen intrusion is observed even in layers annealed in vacuum and in inert gas ambients. Thin (<;5000 Åthick) a-Si layers are especially susceptible to this effect, but we show that in spite of the presence of H the activation energy for SPE derived earlier from thin-layer data is in good agreement with the intrinsic value obtained from thick, hydrogen-free layers.

Coalesced oriented diamond films on nickel

1998 ◽  
Vol 13 (5) ◽  
pp. 1120-1123 ◽  
Author(s):  
P. C. Yang ◽  
C. A. Wolden ◽  
W. Liu ◽  
R. Schlesser ◽  
R. F. Davis ◽  
...  
Keyword(s):  
Gas Phase ◽  
Profile Analysis ◽  
Substrate Surface ◽  
Diamond Films ◽  
Diamond Powder ◽  
Hydrogen Atmosphere ◽  
Nucleation Density ◽  
Annealing Stage ◽  
Multistep Process ◽  
Degree Of Orientation

The growth of coalesced, highly oriented diamond films has been achieved on nickel substrates using a multistep process that consisted of (i) seeding the Ni surface with 0.5 μm diamond powder, (ii) annealing at 1100 °C in a hydrogen atmosphere, and (iii) growth at 900 °C in a mixture of hydrogen and 0.5% methane. Auger depth profile analysis of a sample quenched after the annealing stage showed the presence of significant amounts of carbon (6 at. %) close to the substrate surface and about 3 at.% deeper in the substrate. The loss of carbon into the substrate resulted in relatively low nucleation density. The addition of methane into the gas phase during the annealing stage proved very effective in compensating for the diffusion. An addition of 0.5% methane in the gas phase produced optimum results, as the nucleation density, orientation of diamond particles, and uniformity were substantially improved. Substrates nucleated under these conditions were grown out into coalesced, 30 μm thick films. Both (100) and (111) oriented films showed a high degree of orientation and Raman spectra obtained from these orientations showed intense and narrow diamond signature peaks with FWHM's of 5 and 8 cm-1, respectively.

scholarly journals Kinetics of Transesterification of Safflower Oil to Obtain Biodiesel Using Heterogeneous Catalysis

2016 ◽  
Vol 14 (4) ◽  
pp. 929-938 ◽  
Author(s):  
Gabriel E. Galván Muciño ◽  
Rubi Romero ◽  
Armando Ramírez ◽  
María Jesús Ramos ◽  
Ramiro Baeza-Jiménez ◽  
...  
Keyword(s):  
Experimental Data ◽  
Statistical Analysis ◽  
Heterogeneous Catalysis ◽  
Kinetic Model ◽  
Methyl Esters ◽  
Molar Ratio ◽  
Safflower Oil ◽  
Estimated Parameters ◽  
Kinetics Of ◽  
Best Fit

Abstract The kinetics of the transesterification of safflower oil and methanol catalyzed by K2O/NaX was studied and modeled. The influence of the oil-methanol initial molar ratio and amount of catalyst were investigated to achieve a maximum triglycerides conversion (99 %) and a final methyl esters content of 94 % ±1. A kinetic model based on an Eley–Rideal mechanism was found to best fit the experimental data when assuming methanol adsorption as determining step. Other models derived from Langmuir – Hinshelwood – Hougen –Watson (LHHW) mechanisms were rejected based on statistical analysis, mechanistic considerations and physicochemical interpretation of the estimated parameters.

Relationship between growth rate and undercooling in Pt-added Y1Ba2Cu3O7−x

1996 ◽  
Vol 11 (5) ◽  
pp. 1114-1119 ◽  
Author(s):  
A. Endo ◽  
H. S. Chauhan ◽  
Y. Nakamura ◽  
Y. Shiohara
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Parabolic Equation ◽  
Growth Rates ◽  
Crystal Size ◽  
Experimental Conditions ◽  
Seed Crystals ◽  
Cooling Method ◽  
Increasing Trend ◽  
Good Agreement

Y1Ba2Cu307−x (Y123) crystals were grown by two different methods, the constant undercooling solidification and the continual cooling method, with top seeding by Sm123 seed crystals in order to investigate a relationship between undercooling (ΔT) and a growth rate (R). The crystals of Y123 with a sharp faceted interface, which consisted of {100} and {001} faces, grew epitaxially from the seed. It was found that the growth rates of {100} face (Ra) and that of {001} face (Rc) showed an increasing trend with increasing ΔT, and Rc was faster than Ra within these experimental conditions, ΔT < 20 K. The relation between R and ΔT follows the parabolic equation, viz. Ra ∝ ΔT1.9 and Rc ∝ ΔT1.3 for {100} and {001} faces, respectively. The simulated crystal size using the R and ΔT relations obtained from the constant undercooling method showed good agreement with experimental data by the continual cooling.

Realization of Detailed Kinetic Models for the Growth of II-VI Compounds: Adopting DFT Calculations and Experimental Evidences

1999 ◽  
Vol 584 ◽  
Author(s):  
Carlo Cavallotti ◽  
Valeria Bertani ◽  
Maurizio Masi ◽  
Sergio Carrà
Keyword(s):  
Experimental Data ◽  
Kinetic Theory ◽  
Gas Phase ◽  
Quantum Chemical ◽  
Kinetic Scheme ◽  
Kinetic Constants ◽  
Surface Processes ◽  
Gas Phase Reactions ◽  
Elementary Reactions ◽  
Kinetics Of

AbstractThe kinetics of deposition of CdTe, ZnS and ZnSe films was studied. An overall microkinetically reversible kinetic scheme consisting of elementary reactions, comprehensive of gas phase and surface processes was developed. Kinetic constants of gas phase reactions were either found in the literature or determined through quantum chemistry methods. Kinetic constants of surface reactions were first guessed combining kinetic theory with quantum chemical calculations and then their values were refined to reproduce experimental data. The kinetics schemes so developed were tested through the simulation of deposition reactors. Measured growth rates and gas phase compositions were thus compared with those calculated. The major finding of this studies is that the growth of CdTe, ZnS and ZnSe can be represented adopting a surface kinetic scheme constituted essentially by the same fundamental steps.

Pyrolysis of Sugarcane Bagasse: A Consecutive Reactions Kinetic Model from TGA Experiments

2010 ◽  
Vol 660-661 ◽  
pp. 593-598 ◽  
Author(s):  
Kássia Graciele dos Santos ◽  
Taisa S. Lira ◽  
Valéria V. Murata ◽  
Marco Gianesella ◽  
Marcos A.S. Barrozo
Keyword(s):  
Kinetic Model ◽  
Sugarcane Bagasse ◽  
Room Temperature ◽  
Linear Method ◽  
Pyrolysis Kinetics ◽  
Heating Rates ◽  
Exponential Factor ◽  
Consecutive Reactions ◽  
Kinetics Of ◽  
Good Agreement

The pyrolysis kinetics of sugarcane bagasse in nitrogen flow was studied by thermogravimetric analysis from room temperature to 1173 K at different heating rates (1.5, 3, 5, 10, 15, 20, 30 and 50 K/min). As there are three distinct devolatilization peaks in the DTG curve, each peak was associated to thermal decomposition of an individual biomass subcomponent (hemicellulose, cellulose and lignin). The kinetic model adopted was a consecutive reactions model. The kinetic parameters of the pyrolysis process, such as activation energy and pre-exponential factor, were calculated by least squares non-linear method and Scilab are used as the simulation tool. The simulated results showed a good agreement with the experimental data and the parameters found are similar to reported by the literature.

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