Layer Growth Model Research Articles

Evaluation of flow accelerated corrosion by coupled analysis of corrosion and flow dynamics. Relationship of oxide film thickness, hematite/magnetite ratio, ECP and wall thinning rate

Systematic approaches to evaluate flow accelerated corrosion (FAC) are desired before discussing application of countermeasures for FAC. First, future FAC occurrence should be evaluated to identify locations where a higher possibility of FAC occurrence exists, and then, wall thinning rate at the identified FAC occurrence zone is evaluated to obtain the preparation time for applying countermeasures. Wall thinning rates were calculated with two coupled models: 1. static electrochemical analysis and 2. dynamic oxide layer growth analysis. The anodic current density and the electrochemical corrosion potential (ECP) were calculated with the static electrochemistry model based on an Evans diagram. The ferrous ion release rate, determined by the anodic current density, was applied as input for the dynamic double oxide layer model. Some of the dissolved ferrous ion was removed to the bulk water and others precipitated on the surface as magnetite particles. The thickness of oxide layer was calculated with the dynamic oxide layer growth model and then its value was used as input in the electrochemistry model. It was confirmed that the calculated results (corrosion rate and ECP) based on the coupled models were in good agreement with the measured ones. Higher ECP was essential for preventing FAC rate. Moderated conditions due to lower mass transfer coefficients resulted in thicker oxide layer thickness and then higher ECP, while moderated corrosion conditions due to higher oxidant concentrations resulted in larger hematite/magnetite rate and then higher ECP.

Optical, structural, and chemical properties of flash evaporated In2S3 buffer layer for Cu(In,Ga)Se2 solar cells

In 2 S 3 layers were deposited by flash evaporation technique with varying flash rates. The optical constants of layers based on Tauc–Lorentz model dielectric function were extracted from spectroscopic ellipsometry measurements. X-ray photoelectron spectroscopic investigation revealed the presence of oxygen impurity in as-deposited and air-annealed layers with traces of Na inclusion in the layer grown at high flash rate. The enhancement in crystalline arrangement of as-deposited layer after air annealing was confirmed by Raman spectroscopy. Rutherford backscattering measurements revealed the growth of off-stoichiometric layers at all flash rates. An analytical layer growth model has been proposed supporting the results obtained by various layer characterization techniques. The solar cells were prepared with flash evaporated In2S3 buffer layers and their performances were compared with CdS reference solar cell. A significant gain in short-circuit current was obtained after air annealing of the complete device at 200 °C for 20 min. A maximum conversion efficiency of 12.6% was delivered by a high flash rate In2S3 buffered cell with open-circuit voltage close to that of CdS reference cell. The improvement in device performance after air annealing treatment is explained by thermally enhanced Cu and oxygen diffusion from Cu(In,Ga)Se2 and i-ZnO to In2S3 layer, respectively.

The Calculation of Kinetic Parameters in Manganese Nitriding

The present work confirmed and achieved the relevant parameters which belong to the manganese nitriding model via experiments. Based on the metallic iron nitriding model and the nitride layer growth model, metal manganese nitrding model was set up. The change laws between the kinetic parameters and temperature of the solid metal manganese nitriding model was studied by using the optimum method. The experimental results showed that the ratio of weight gain for samples relatively increased with the increasing of nitriding temperature, and the results obtained from the numerical model indicated that the kinetic parameters of manganese nitriding model increased with the increasing of nitriding temperature.

Effect of Initial Value on Non-homogeneous Frost Layer Growth Model and Prediction of Frost Surface Temperature under Natural Convection

Effect of Initial Value on Non-homogeneous Frost Layer Growth Model and Prediction of Frost Surface Temperature under Natural Convection

A Lagrangian model for boundary layer growth and bed shear stress in the swash zone

A new model for the boundary layer development and associated skin friction coefficients and shear stress within the swash zone is presented. The model is developed within a Lagrangian reference frame, following fluid trajectories, and can be applied to both laminar flow and smooth turbulent flow. The model is based on the momentum integral approach for steady, flat-plate boundary layers, with appropriate modifications to account for the unsteady flow regime and flow history. The model results are consistent with previous measurements of bed shear stress and skin friction coefficients within the swash zone. These indicate strong temporal and spatial variation throughout the swash cycle, and a clear distinction between the uprush and backwash phase. This variation has been previously attributed the unsteady flow regime and flow history effects, both of which are accounted for in the new model. Fluid particle trajectories and velocity are computed using the non-linear shallow water wave equations and the boundary layer growth across the entire swash zone is estimated. Predictions of the bed shear stress and skin friction coefficients agree reasonably well with direct bed shear stress measurements reported by Barnes et al. (Barnes, M.P., O’Donaghue, T., Alsina, J.M., Baldock, T.E., 2009. Direct bed shear stress measurements in bore-driven swash. Coastal Engineering 56 (8), 853–867) and, for a given flow velocity, give stresses which are consistent with the bias toward uprush sediment transport which has consistently been observed in measurements. The data and modelling suggest that the backwash boundary layer is initially laminar, which results in the late development of significant bed shear during the backwash, with a transition to a turbulent boundary layer later in the backwash. A new conceptual model for the boundary layer structure at the leading edge of the swash is proposed, which accounts for both the no-slip condition at the bed and the moving wet–dry interface. However, further development of the Lagrangian Boundary Layer Model is required in order to include bore-generated turbulence and to account for variable roughness and mobile beds.

Preparation of BiFeO 3 thin film by the liquid phase deposition (LPD) method on functionalized organic self-assembled monolayers (SAMs)

BiFeO 3 thin films were prepared for the first time on the functionalized self-assembled monolayers (SAMs) by the liquid phase deposition (LPD) method. The measurement of contact angle showed that after the substrate was immersed into octadecyl trichlorosilane (OTS) solution for 30 min, the surface of the substrate was covered with a layer of hydrophobe. The hydrophobe on the substrate was changed into hydrophile after UV irradiation. It was found that the octadecyl trichlorosilane self-assembled monolayers (OTS-SAMs) as chemical templates played an active role in controlling nucleation and growth of BiFeO 3 thin film. The study on the effect of different soaking times showed that the BiFeO 3 thin film was a layer growth model and the optimum deposition time was 12 h.

Limiting flux prediction during tubular ultrafiltration

Ultrafiltration of polyethylene glycol aqueous solutions was analyzed using concentration polarization-gel layer model. The model is based on coupling concentration polarization layer and gel layer growth. The concentration polarization layer development is given by the convective-diffusion equation. However, the gel layer growth model is obtained by using the experimental observations. The limiting flux was found to be proportional to the square root of the axial velocity. Beyond the critical concentration, both concentration polarization and gel formation are the main factors controlling the limiting flux in the tubular UF system. The developed semi-empirical model, which contains a single empirical constant to be evaluated from experiments, predicted satisfactorily the limiting flux data over the range of experimental variables examined in this study.

425 自然対流下における着霜現象(省エネルギー(1))

In this paper, we investigated experimentally the growth of frost layer under natural convection to obtain effects of conditions related to air and cooling surface. We compared the results with numerical calculations, which are based on a non-homogeneous frost layer growth model and a homogeneous frost layer growth model used in the study of the forced convection. The comparison showed that the trend of the numerical results for a non-homogeneous frost layer growth model is in good agreement with the experimental results. The growth of the frost layer is markedly influenced by the thermal conductivity of the frost layer. The present numerical calculations suggest a thermal conductivity for the frost layer that is twice the value predicted by Yonko-Sepsy relationship. An accurate evaluation of the thermal conductivity of the frost layer is necessary to be able to match the frost layer thicknesses with those of the experiments. The present numerical model has the potential as a tool for the systematic investigation of influences of various factors affecting the frost phenomenon.

Prediction of Frost Growth under Natural Convection using Non-homogeneous Frost Layer Growth Model

Prediction of Frost Growth under Natural Convection using Non-homogeneous Frost Layer Growth Model

Theoretical calculations of the AES intensity–film thickness functions for different growth models

The surface spectroscopic methods, e.g. AES and XPS, are widely used in studies of thin film growth. In experiments spectroscopic data are recorded as intensity–film thickness curves. Much theoretical effort had been devoted to calculation AES intensity–thickness functions for different growth modes. A key element of such calculations is finding coverage in each layer. Recently, we developed two models of thin film growth that allow exact determining of coverage in all layers of a growing film. In island growth model the lateral islands growth occurs via capture of migrating adatoms whereas their vertical growth-owing to direct impingement of deposited atoms. Analysis of arising film morphology yields coverage in each layer in analytic form. In layer growth model based on rate equation approach combined with a feeding zone accounting for interlayer mass transport coverage in successive layers are calculated in a straightforward manner. Thus the AES intensity–film thickness functions were derived analytically for island growth and computed numerically for layer growth in various growth regimes (complete/incomplete condensation) and modes (smooth/rough), enabling experimental data to be examined quantitatively and in greater detail than has previously been reported.

Kinetic Roughening and Energetics of Tetragonal Lysozyme Crystal Growth

Lysozyme crystal growth rates over 5 orders of magnitude in range can be described using a layer-by-layer model where growth occurs by 2D nucleation on the crystal surface. Based upon the 2D nucleation model of layer growth, the effective barrier for growth was determined to be gamma = 1.3 plus or minus 0.3 x 10(exp -13) erg/molecule, corresponding to a barrier of 3.2 plus or minus 0.7 k(sub B)T, at 22 C. For solution supersaturation, In c/c(sub eq) greater than or equal to 1.9 plus or minus 0.2, the nucleation model would not predict or consistently estimate the highest observable crystal growth rates. As such, a kinetic roughening hypothesis where crystal growth occurs by a continuous mode was implemented for all growth rate data obtained above In c(sub r)/c(sub eq) greater than or equal to 2. That is, independent of the solution conditions that vary with either buffer pH, temperature or precipitant concentration, crystal growth occurs by the continuous addition of molecules anywhere on the crystal surface, above a roughening solution supersaturation. The energy barrier, E(sub c), for the continuous growth process is determined as 6.1 plus or minus 0.4 x 10(exp -13) erg/molecule or 15 plus or minus 1 k(sub B)T at 22 C.

Transmission Electron Microscopy and X-ray Diffraction Investigation of the Microstructure of Nanoscale Multilayer TiAlN/VN Grown by Unbalanced Magnetron Deposition

Cubic NaCl-B1 structured multilayer TiAlN/VN with a bi-layer thickness of approximately 3 nm and atomic ratios of (Ti+Al)/V = 0.98 to 1.15 and Ti/V = 0.55 to 0.61 were deposited by unbalanced magnetron sputtering at substrate bias voltages between -75 and -150 V. In this paper, detailed transmission electron microscopy and x-ray diffraction revealed pronounced microstructure changes depending on the bias. At the bias -75 V, TiAlN/VN followed a layer growth model led by a strong (110) texture to form a T-type structure in the Thornton structure model of thin films, which resulted in a rough growth front, dense columnar structure with inter-column voids, and low compressive stress of -3.8 GPa. At higher biases, the coatings showed a typical Type-II structure following the strain energy growth model, characterized by the columnar structure, void-free column boundaries, smooth surface, a predominant (111) texture, and high residual stresses between -8 and -11.5 GPa.

Modeling of solid layer growth from melt for Taylor bubbles rising in a vertical crystallization tube

This paper presents a mathematical model for the prediction of solid layer growth from melt contained in a crystallization tube of a bubble column crystallizer. The model was solved by using the integral formulation approach together with the assumption of a second-degree polynomial approximation of temperature profile within the solid layer. In the model, the convective heat transfer coefficient at solid layer–melt interface was calculated by analogy between heat and mass transfer from the models developed for mass transfer in the case of Taylor bubbles rising in a vertical liquid column. The predicted growth rates of solid layer were compared with experiments of caprolactam melt solidification which were carried out in a 19 mm inner diameter crystallization tube at superficial gas velocities of 0.04 and 0.08 m s −1 . A good agreement was obtained between experimental and predicted data. Different characteristics of layer growth for slug units passing through different growing stages were also described and discussed.

Microstructure and growth kinetics of the Mo 5Si 3 and Mo 3Si layers in MoSi 2/Mo diffusion couple

The microstructures and growth kinetics of the Mo 5Si 3 and Mo 3Si layers in the MoSi 2/Mo diffusion couple was investigated using optical microscopy, field-emission scanning electron microscopy, electron probe microanalyzer, and cross-sectional transmission electron microscopy. The MoSi 2/Mo diffusion couple was made by chemical vapor deposition CVD of Si on a Mo substrate at 1100 °C and annealed at temperatures between 1250 and 1600 °C in an Ar atmosphere. Simultaneous parabolic growth of the Mo 5Si 3 and Mo 3Si layers was observed at the early annealing stage of the MoSi 2/Mo diffusion couple. From the marker experiments using ZrO 2 particles, the growth mechanism of the Mo 5Si 3 and Mo 3Si layers and the dominant diffusion element in each phase were revealed. The difference in the growth rates of Mo 3Si layer between the MoSi 2/Mo diffusion couple and the Mo 5Si 3/Mo diffusion couple was explained by a multiple layer growth model.

Modeling of frost growth and frost properties with airflow over a flat plate

A physical model of frost layer growth and frost properties with airflow over a flat plate at subfreezing temperature was developed. Frost roughness was measured, and an empirical correlation for the average frost roughness was suggested. Heat and mass transfer coefficients were calculated using the modified Prandtl mixing-length scheme containing the effects of both frost roughness and turbulent boundary layer thickness. Frost thermal conductivity was theoretically analyzed by solving the combined equations of air equivalent conductivity and thermal conductivity of the frost inner layer. Based on the present model, heat and mass transfer coefficient, frost thermal conductivity, frost thickness, frost mass concentration and frost density with time and space were estimated. The model showed good agreement with the basic trends of the test data taken from other literature. Spatial and temporal changes of heat flux and frost surface temperature were also investigated.

Growth kinetics of three Mo-silicide layers formed by chemical vapor deposition of Si on Mo substrate

The growth kinetics of three Mo-silicide layers formed by chemical vapor deposition (CVD) of Si on a Mo substrate using SiCl 4-H 2 gas mixtures were investigated at temperatures between 950 and 1200 °C. Three Mo-silicide layers (Mo 3Si, Mo 5Si 3, and MoSi 2) grew simultaneously with a parabolic rate law after an initial nucleation period, indicating the diffusion-controlled growth. The activation energy (130 kJ/mol) for the MoSi 2 layer were in a good agreement with the previous results having low activation energy (130±20∼157 kJ/mol), but its growth rate was higher than the previous results with high activation energy (209∼241±25 kJ/mol). A possible explanation about this difference may be the detrimental effect of impurities such as oxygen on the growth rate of the MoSi 2 layer. The activation energy (350 kJ/mol) for growth of the Mo 5Si 3 layer was consistent with the prior values (297∼360 kJ/mol) obtained by annealing of the MoSi 2/Mo diffusion couples, but its growth rate was an order of magnitude lower than the rate measured in the MoSi 2/Mo diffusion couples. The activation energy (223 kJ/mol) for the growth of the Mo 3Si layer was similar with the value (199 kJ/mol) obtained from annealed Mo 5Si 3/Mo diffusion couple at temperatures between 1250 and 1350 °C. This value was lower than the value (326 kJ/mol) reported at higher temperatures from 1500–1715 °C. This suggests that the rate-limiting step for growth of the Mo 3Si layer is the grain boundary diffusion-controlled process at low temperatures but volume diffusion-controlled process at high temperatures. The growth rates of the Mo 3Si layer measured at condition of the simultaneous parabolic growth of three Mo-silicide layers were approximately two orders of magnitude lower than the rates measured in the Mo 5Si 3/Mo diffusion couples. The differences in the growth rates of the Mo 5Si 3 and Mo 3Si layers depending on the type of diffusion couples were well explained by the multiple layer growth model.

Metasomatic coronas around hornblendite xenoliths in granulite facies marble, Ivrea zone, N Italy, I: constraints on component mobility

Centimeter- to decimeter-thick reaction bands occur at hornblendite/marble interfaces in Val Fiorina in the granulite facies metamorphic Ivrea zone. From hornblendite to marble the reaction bands show a consistent succession of sharply bounded mineral layers comprising a monomineralic clinopyroxene layer, a garnet–clinopyroxene layer and a scapolite–clinopyroxene layer. Reaction band formation occurred as a response to gradients in the chemical potentials of calcium and magnesium as defined by the hornblendite assemblage and the marble matrix. The metasomatic corona primarily replaced the hornblendite, and only minor amounts of marble were consumed. The reaction band behaved as an open system with net transfer of calcium from the marble into the reaction band, and a net transfer of iron and magnesium in the opposite direction. Mass balance considerations allow us to constrain a range of feasible mass balance scenarios for which major element fluxes across the boundaries of the reaction band may be quantified. Modeling of layer growth as a steady diffusion process yields ratios of the phenomenological diffusion coefficients for Si, Al, Mg, and Ca of \({{L_{SiSi} } \over {L_{CaCa} }}> 2.5,{\kern 1pt} {\rm }{{L_{AlAl} } \over {L_{CaCa} }} 1.\) . The relative diffusivities are primarily constrained by the sequence of mineral layers of the reaction band and by the relative thickness of the layers. The results of steady-state diffusion modeling are relatively insensitive with respect to variations in the major element boundary fluxes.

CISCuT absorber layers — the present model of thin film growth

Experimental results and numeric calculations that have been contributed to a better understanding of how layer growth proceeds in the CISCuT process are given in this work. The heat transfer resistance between the heater and copper tape has been found to mainly determine the temperature of the copper tape during the CISCuT process. From this, more insight into the strongly temperature-dependent precursor formation has been gathered. The initial layer growth model of CISCuT absorber layer growth will be described and the partial solubility of CuInS 2 in CuIn-melts has been taken into account. Tape-like CISCuT-based solar cells, with a best efficiency of 5.4% achieved so far on an area of 4 cm 2, are presented.

Modelling of growth of thin solid films obtained by pulsed laser deposition

Pulsed laser deposition (PLD) method of thin films fabrication requires appropriate choice of technological parameters. These are: substrate temperature, the energy density of the laser radiation, its wavelength, the pulse duration, the distance target–substrate, etc. Exact analysis of the influence of these parameters on the layer growth is too difficult to be performed. Therefore, the computer simulation of the layer growth is very promising method for determining the growth parameters. In the paper, the growth of Si and CdTe films on the (001) substrate surface was simulated by the Monte Carlo method. The model for layer growth included: surface diffusion, adsorption and desorption of adatoms, kinetic energy distribution of atoms or ions in the plasma plume and its space and time structure. Results obtained have been compared with some experimental data.

Modelling of InAs thin layer growth from the liquid phase

InAs quantum wells have been grown using the rapid slider liquid phase epitaxial growth technique. Analysis of the layer thickness data as a function of supercooling and contact time revealed the presence of two different growth mechanisms. A mathematical model of the epitaxial growth based around simple assumptions relating to melt rolling has been shown to give a good explanation of the experimental findings and also provides an integrated mathematical description of the growth phenomena.