Evaluation of an empirical representation of ternary diffusion paths in a system with constant diffusion coefficients

1983 ◽  
Vol 14 (12) ◽  
pp. 2479-2485 ◽  
Author(s):  
Guojing Wo ◽  
Louis S. Castleman
Keyword(s):  
Diffusion Coefficients ◽  
Ternary Diffusion ◽  
Constant Diffusion ◽  
Diffusion Paths

The Sequence of the Phase Growth during Diffusion in Ti-Based Systems

2019 ◽  
Vol 38 (2019) ◽  
pp. 151-157 ◽  
Author(s):  
Bartek Wierzba ◽  
Wojciech J. Nowak ◽  
Daria Serafin
Keyword(s):  
Theoretical Analysis ◽  
Entropy Production ◽  
Diffusion Coefficients ◽  
Intermetallic Phase ◽  
Intermetallic Phases ◽  
Diffusion Couples ◽  
Intrinsic Diffusion ◽  
Phase Growth ◽  
Diffusion Paths

AbstractThe interdiffusion in Ti-based alloys was studied. It was shown that during diffusion at 1,123 K formation of four intermetallic phases occurs. The diffusion paths for six different diffusion couples were determined. Moreover, the entropy production was calculated – the approximation used for determination of the sequence of intermetallic phase formation. In theoretical analysis, the intrinsic diffusion coefficients were determined from the modified Wagner method.

Concentration Oscillations During Diffusion With Slow First-Order Chemical Reaction in Aqueous Solutions of trans-Dichloro-bis(ethane-1,2-diamine)cobalt(III) Chloride, trans-[Co(en)2Cl2]Cl

1988 ◽  
Vol 41 (4) ◽  
pp. 469 ◽  
Author(s):  
DG Leaist
Keyword(s):  
Aqueous Solutions ◽  
Chemical Reaction ◽  
Diffusion Coefficients ◽  
Potassium Acetate ◽  
Potassium Sulfate ◽  
Rate Equations ◽  
Ternary Diffusion ◽  
Mixed Electrolyte ◽  
First Order ◽  
First Order Chemical Reaction

The rate equations for diffusion and chemical reaction have been solved for isothermal diffusion with the first-order reactionA → Bin stirred diaphragm cells. Provided pseudo-steady-state conditions are established in the diaphragms, the concentration differences across the diaphragm for the reactant and product are predicted to show damped oscillations in time for certain values of the solute diffusivities. Diffusion coefficients have been determined for aqueous solutions of trans-dichlorobis (ethane-1,2-diamine)cobalt(III) chloride in which the 1 : 1 salt slowly converts into a 1:2 salt through the reaction [Co(en)2Cl2]+ + Cl - → [Co(en)2Cl]2+ +2Cl- with k = 3.6×10-5 s-1 at 25°C. Supplementary ternary diffusion coefficients have been determined for aqueous solutions of potassium acetate + potassium sulfate, a ternary mixed electrolyte with ionic mobilities similar to those of the aqueous cobalt salts.

Refinement in the Mathematical and Numerical Treatment of the Internal Oxidation of Alloys

2005 ◽  
Vol 237-240 ◽  
pp. 1157-1162 ◽  
Author(s):  
Wiktor Miszuris ◽  
Andreas Öchsner
Keyword(s):  
Boundary Conditions ◽  
Internal Oxidation ◽  
Diffusion Coefficients ◽  
Finite Dimension ◽  
Time Dependent ◽  
Diffusion Equations ◽  
Numerical Treatment ◽  
Constant Diffusion ◽  
Finite Difference Solution ◽  
Oxide Particles

When oxygen dissolves from atmosphere and diffuses into an alloy during oxidation, the less noble alloy components may react to form oxide particles within the metal. This process is termed internal oxidation. Classical approaches to describe this phenomenon were derived under many strong simplifications such as constant diffusion coefficients, certain boundary conditions and semi-infinite sample. The presented general approach is based on the finite difference solution of the general diffusion equations coupled through the stoichiometry of reaction between oxygen and the considered element. The main enhancement is the consideration of concentration dependent diffusion coefficients, concentration dependent source terms and arbitrary time-dependent boundary conditions formulated as a concentration, a flux or mixed conditions. Furthermore, finite dimension of the specimen is incorporated. This general treatment also allows for the incorporation of the energy balance.

scholarly journals Thermal Annealing of InGaN/GaN Strained-Layer Quantum Well

1999 ◽  
Vol 4 (S1) ◽  
pp. 642-647
Author(s):  
Michael C.Y. Chan ◽  
Kwok-On Tsang ◽  
E. Herbert Li ◽  
Steven P. Denbaars
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Quantum Well ◽  
Thermal Annealing ◽  
Diffusion Coefficients ◽  
Green Light ◽  
Optical Gain ◽  
Quantum Well Structures ◽  
Strained Layer ◽  
Constant Diffusion

Quantum well (QW) material engineering has attracted a considerable amount of interest from many people because of its ability to produce a number of optoelectronic devices. QW composition intermixing is a thermal induced interdiffusion of the constituent atoms through the hetero-interface. The intermixing process is an attractive way to achieve the modification of the QW band structure. It is known that the band structure is a fundamental determinant for such electronic and optical properties of materials as the optical gain, the refractive index and the absorption. During the process, the as-grown square-QW compositional profile is modified to a graded profile, thereby altering the confinement profile and the subband structure in the QW. The blue-shifting of the wavelength in the intermixed QW structure is found in this process.In recent years, III-nitride semiconductors have attracted much attention. This is mainly due to their large bandgap range from 1.89eV (wurtzite InN) to 3.44eV (wurtzite GaN). InGaN/GaN quantum well structures have been used to achieve high lumens blue and green light emitting diodes. Such structures also facilitate the production of full colour LED displays by complementing the colour spectrum of available LEDs.In this paper, the effects of thermal annealing on the strained-layer InGaN/GaN QW will be presented. The effects of intermixing on the confinement potential of InGaN/GaN QWs have been theoretically analysed, with sublattices interdiffusion as the basis. This process is described by Fick’s law, with constant diffusion coefficients in both the well and the barrier layers. The diffusion coefficients depend on the annealing temperature, time and the activation energy of constituent atoms. The optical properties of intermixed InGaN/GaN QW structure of different interdiffusion rates have been theoretically analyzed for applications of novel optical devices. The photoluminescence studies and the intermixed QW modeling have been used to understand the effects of intermixing.

QUASI-REGULAR DIRICHLET FORMS ON FREE RIEMANNIAN PATH SPACES

2009 ◽  
Vol 12 (02) ◽  
pp. 251-267 ◽  
Author(s):  
FENG-YU WANG ◽  
BO WU
Keyword(s):  
Large Class ◽  
Free Path ◽  
Riemannian Manifolds ◽  
Diffusion Coefficients ◽  
Dirichlet Forms ◽  
Integration By Parts ◽  
Constant Diffusion ◽  
Integration By Parts Formula ◽  
Noncompact Riemannian Manifolds ◽  
Initial Distributions

The integration by parts formula on free path spaces over noncompact Riemannian manifolds is established for initial distributions with densities in [Formula: see text]. As an application, a large class of Dirichlet forms with (unbounded and non-constant) diffusion coefficients are constructed on free Riemannian path spaces, which are quasi-regular under mild curvature conditions.

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