Numerical Determination of Intrinsic Diffusion Coefficient of Aluminide Coatings on Metals

2009 ◽  
Vol 289-292 ◽  
pp. 269-276 ◽  
Author(s):  
Bartłomiej Wierzba ◽  
Sébastien Chevalier ◽  
Olivier Politano ◽  
Marek Danielewski
Keyword(s):  
Diffusion Coefficient ◽  
Concentration Profile ◽  
Diffusion Coefficients ◽  
Reactive Diffusion ◽  
Intrinsic Diffusion Coefficient ◽  
Numerical Determination ◽  
Intrinsic Diffusion ◽  
Aluminide Coatings ◽  
Interdiffusion Process

This paper presents a numerical method to determine the composition dependent diffusivities and to predict the concentration profile during the interdiffusion process. The intrinsic diffusion coefficients in diffusion aluminide coatings (Fe-Al) were determined at 1000oC. The obtained diffusion coefficient for iron in Fe3Al or FeAl is in the range 10-10 to 10-9 cm2.s-1. The aluminum diffusion coefficient varies from 10-11 to 10-7 cm2.s-1 in the same phases.The present approach also permits to model the reactive diffusion in the Fe-Al systems.

Numerical Determination of Intrinsic Diffusion in Fe-Cr-Al Systems

2010 ◽  
Vol 297-301 ◽  
pp. 948-953
Author(s):  
Bartłomiej Wierzba ◽  
Olivier Politano ◽  
Sébastien Chevalier ◽  
Marek Danielewski
Keyword(s):  
Concentration Profile ◽  
Diffusion Coefficients ◽  
Numerical Results ◽  
Multicomponent Systems ◽  
Numerical Determination ◽  
Intrinsic Diffusion ◽  
Aluminide Coatings ◽  
Interdiffusion Process

The intrinsic diffusion coefficients in diffusion aluminide coatings based on Fe-30Cr were determined at 1000oC. The diffusion fluxes were given by the Nernst Planck formulae and the Darken method for multicomponent systems was applied. This paper summarizes some numerical results to determine the composition dependent diffusivities in Fe-Cr-Al systems. The method presented in this study to obtain average intrinsic diffusion coefficients is as an alternative to the Dayananda method. Our method based on empirical parameters allowed us to predict the concentration profile during the interdiffusion process.

Self-Diffusion in Intrinsic and Extrinsic Silicon Using Isotopically Pure 30Silicon Layer

2001 ◽  
Vol 669 ◽  
Author(s):  
Yukio Nakabayashi ◽  
Hirman I. Osman ◽  
Toru Segawa ◽  
Kazunari Toyonaga ◽  
Satoru Matsumoto ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Diffusion Coefficient ◽  
Temperature Dependence ◽  
Diffusion Coefficients ◽  
Secondary Ion Mass Spectrometry ◽  
Intrinsic Diffusion Coefficient ◽  
Intrinsic Diffusion ◽  
Self Diffusion ◽  
Secondary Ion ◽  
Diffusion Profiles

ABSTRACTSilicon self–diffusion coefficients were measured in intrinsic and extrinsic silicon from870 to 1070°C using isotopically pure 30Si layer. 30Si diffusion profiles are determined by secondary ion mass spectrometry. The temperature dependence of intrinsic diffusion coefficient in bulk Si isobtained. Comparing it in heavily As-doped or B-doped Si, it is found that Si self-diffusion is entirely mediated by interstitialcy mechanism at lower temperatures below 870°C.

scholarly journals Diffusion coefficients in multiphase Ni80Cr20-Ti system

2021 ◽  
Vol 57 (1) ◽  
pp. 137-144
Author(s):  
B. Wierzba ◽  
D. Serafin ◽  
W.J. Nowak ◽  
P. Wierzba ◽  
A. Ciecko ◽  
...  
Keyword(s):  
Ternary System ◽  
Diffusion Couple ◽  
Diffusion Coefficients ◽  
Effective Diffusion ◽  
Intermetallic Phases ◽  
Reactive Diffusion ◽  
Intrinsic Diffusion ◽  
Two Phase ◽  
Effective Diffusion Coefficients

In this paper, the reactive diffusion in Ni80C20r?Ti ternary system is discussed at 1173K. The diffusion couple was prepared and annealed for 100 h. The two intermetallic phases and two two-phase zones occurred, namely: Ti2Ni, TiNi, TiNi+Cr, and TiNi3+Cr. Based on the experimental results (molar fractions, thicknesses of the intermetallic phases), the intrinsic diffusion coefficients of all components in each phase were numerically approximated. The Wagner method was used in the pure intermetallic phases. In the two phase zones the approximation was based on the generalized Darken and Wagner methods. The presented methods allowed for determination of the effective diffusion coefficients in each presented phase.

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.

scholarly journals Determination of Diffusion Coefficients Using Thermogravimetric Measurements during High Temperature Oxidation

2012 ◽  
Vol 323-325 ◽  
pp. 289-294
Author(s):  
Patrice Berthod ◽  
Lionel Aranda
Keyword(s):  
Diffusion Coefficient ◽  
High Temperature ◽  
Diffusion Coefficients ◽  
High Temperature Oxidation ◽  
Concentration Profiles ◽  
Metallic Elements ◽  
Chromium Diffusion ◽  
Temperature Oxidation ◽  
Iron Based

Thermogravimetry measurements associated to concentration profiles allow determining a diffusion coefficient at high temperature of the most oxidable one among the metallic elements belonging to the chemical composition of an alloy. In this work the employed method is described and applied to chromia-forming alloys essentially based on nickel but also to selected cobalt-based and iron-based alloys. More precisely DCrvalues were estimated for chromium diffusing through the carbide-free zones developed during high temperature oxidation. The effects of the base element, of the chromium carbides density and of the dendritic orientations on the chromium diffusion were evidenced.

scholarly journals The diffusion coefficients of dye solutions and their interpretation

1935 ◽  
Vol 148 (865) ◽  
pp. 681-695 ◽  
Keyword(s):  
Particle Size ◽  
Diffusion Coefficient ◽  
Einstein Equation ◽  
Diffusion Coefficients ◽  
Complex Ions ◽  
Nernst Equation ◽  
Theoretical Paper ◽  
Qualitative Measure ◽  
Dye Solutions

In a previous theoretical paper Hartley and Robinson have pointed out what very misleading results are obtained in calculating the particle size of a dye from the diffusion coefficient if the Stokes-Einstein equation is used and the electrical forces are neglected. The complicating effect of the electrical forces on the diffusion coefficient has, of course, been realized in researches on other colloidal electrolytes. Thus Svedberg, Tizelius, Northrop, McBain and others have taken them into account in the case of proteins, while McBain and Liu pointed out that the diffusion coefficient of soaps is given by an extension of the Nernst equation. But in experiments with dyes, although many diffusion measurements were reported, this aspect of the matter had been entirely overlooked. An investigation of the diffusion coefficients of dyes is, therefore, of particular interest and also because of the light it throws on the more general problem of determination of the particle size of a colloidal electrolyte, where the particle (unlike that of the protein, which appears to be a simple molecule) consists of a number of ions in association. Many dyes are colloidal electrolytes containing multivalent complex ions. Their diffusion coefficient is consequently largely determined by the mobilities of the ions. It was shown that a minimum value for the diffusion coefficient can be calculated from the conductivity. It follows that all dyes that have high conductivities—this seems to include most, if not all, substantive dyes—must have high diffusion coefficients. Consequently, as was shown, it is not possible to obtain even a qualitative measure of the particle size from the diffusion coefficient and the Stokes-Einstein equation.

On Concentration-Dependent Solid State Diffusion

1991 ◽  
Vol 230 ◽  
Author(s):  
Yang-Tse Cheng
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
The Self ◽  
Solid State Diffusion ◽  
Equation Approach ◽  
Intrinsic Diffusion ◽  
Self Diffusion ◽  
State Diffusion ◽  
Master Equation Approach ◽  
Semi Empirical

AbstractUsing a master equation approach, we derive a general expression for the diffusion coefficient as a function of concentration-dependent jump rates. When this approach is applied to diffusion in a binary solid, Darken's equation for intrinsic diffusion coefficients is derived together with an expression for self diffusion coefficients which satisfies the semi-empirical Ugaste relationship. This analysis suggests that the Darken term and the self diffusion coefficients are in general related.

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