Diffusion coefficients of metals in inert gases: Comparison of calculations with experimental data

1980 ◽  
Vol 30 (12) ◽  
pp. 1293-1306 ◽  
Author(s):  
T. P. Reďko ◽  
I. Košinár
Keyword(s):  
Experimental Data ◽  
Diffusion Coefficients ◽  
Inert Gases

Diffusion Coefficients of Interest for the Simulation of Heat Treatment in Rare-Earth Transition Metal Magnets

2012 ◽  
Vol 727-728 ◽  
pp. 163-168 ◽  
Author(s):  
Marcos Flavio de Campos
Keyword(s):  
Experimental Data ◽  
Heat Treatment ◽  
Activation Energy ◽  
Rare Earth ◽  
Transition Metal ◽  
Impurity Atom ◽  
Diffusion Coefficients ◽  
Arrhenius Equation ◽  
Atom Diffusion ◽  
Essential Input

In the case of the modeling of sintering and heat treatments, the diffusion coefficients are an essential input. However, experimental data in the literature about diffusion coefficients for rare-earth transition metal intermetallics is scarce. In this study, the available data concerning diffusion coefficients relevant for rare-earth transition metal magnets are reviewed and commented. Some empirical rules are discussed, for example the activation energy is affected by the size of the diffusing impurity atom. Diffusion coefficients for Dy, Nd and Fe into Nd2Fe14B are given according an Arrhenius equation D=D0exp (-Q/RT). For Dy diffusion into Nd2Fe14B, Q 315 kJ/mol and D08 . 10-4m2/s.

scholarly journals Anisotropic Diffusion and the Townsend?Huxley Experiment

1973 ◽  
Vol 26 (4) ◽  
pp. 469 ◽  
Author(s):  
JJ Lowke
Keyword(s):  
Experimental Data ◽  
Electric Field ◽  
Electron Mobility ◽  
Diffusion Coefficients ◽  
Applied Electric Field ◽  
Anisotropic Diffusion ◽  
Diffusion Tubes ◽  
New Formula ◽  
The Relationship ◽  
Diffusion Tube

The relationship between current ratios and electron diffusion coefficients for the Townsend-Huxley experiment is reanalysed with the assumption that diffusion can be represented by two coefficients DT and DL for diffusion transverse and parallel respectively to the applied electric field. When the new formula is used to interpret previous experimental data obtained with a diffusion tube of length 2 cm, the derived values of DT/fl become independent of pressure (fl being the electron mobility). For longer diffusion tubes (~ 6 cm), current ratios are insensitive to DL and the results differ insignificantly from those obtained using the formula previously derived on the assumption that diffusion is isotropic.

APPLICATION OF THE EAM POTENTIALS TO THE STUDY OF DIFFUSION COEFFICIENTS OF LIQUID NOBLE AND TRANSITION METALS

2002 ◽  
Vol 16 (25) ◽  
pp. 3837-3846 ◽  
Author(s):  
A. Z. ZIAUDDIN AHMED ◽  
G. M. BHUIYAN
Keyword(s):  
Experimental Data ◽  
Solid State ◽  
Diffusion Coefficients ◽  
Noble Metals ◽  
Packing Fraction ◽  
Embedded Atom Method ◽  
Embedded Atom ◽  
Atomic Transport ◽  
Liquid Transition ◽  
Variational Calculations

The embedded atom method (EAM) potentials, originally proposed for solid state calculations, have been applied to investigate the atomic transport property namely the diffusion coefficients of liquid Ni, Cu, Ag and Au. Two different liquid state theories, specifically the linearized Weeks–Chandler–Andersen (LWCA) theory and the Gibbs–Boguliubov variational method (GB) are used to evaluate the packing fraction near melting temperature. Calculated values for the diffusion coefficients are compared with the available experimental data. Results of variational calculations are found to be better in agreement. Results of calculations also allow us to conclude that the concerning EAM potentials are transferable to the study of atomic transport properties of liquid transition and noble metals.

scholarly journals ON MATHEMATICAL MODELLING OF METALS DISTRIBUTION IN PEAT LAYERS

2014 ◽  
Vol 19 (4) ◽  
pp. 568-588
Author(s):  
Ilmars Kangro ◽  
Harijs Kalis ◽  
Aigars Gedroics ◽  
Erika Teirumnieka ◽  
Edmunds Teirumnieks
Keyword(s):  
Experimental Data ◽  
Mathematical Model ◽  
Finite Difference ◽  
Diffusion Coefficients ◽  
Boundary Value ◽  
Finite Difference Methods ◽  
Circulant Matrix ◽  
Elliptic Type ◽  
Difference Methods ◽  
The Mathematical Model

In this paper we consider averaging and finite difference methods for solving the 3-D boundary-value problem in multilayered domain. We consider the metals Fe and Ca concentration in the layered peat blocks. Using experimental data the mathematical model for calculation of concentration of metals in different points in peat layers is developed. A specific feature of these problems is that it is necessary to solve the 3-D boundary-value problems for elliptic type partial differential equations (PDEs) of second order with piece-wise diffusion coefficients in the layered domain. We develop here a finite-difference method for solving of a problem of one, two and three peat blocks with periodical boundary condition in x direction. This procedure allows to reduce the 3-D problem to a system of 2-D problems by using circulant matrix.

Transport of Neutral Solute Across Articular Cartilage: The Role of Zonal Diffusivities

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
V. Arbabi ◽  
B. Pouran ◽  
H. Weinans ◽  
A. A. Zadpoor
Keyword(s):  
Experimental Data ◽  
Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Equilibrium Concentration ◽  
Cartilage Tissue ◽  
Zone Model ◽  
Superficial Zone ◽  
Time Curve ◽  
Order Of Magnitude ◽  
Multizone Model

Transport of solutes through diffusion is an important metabolic mechanism for the avascular cartilage tissue. Three types of interconnected physical phenomena, namely mechanical, electrical, and chemical, are all involved in the physics of transport in cartilage. In this study, we use a carefully designed experimental-computational setup to separate the effects of mechanical and chemical factors from those of electrical charges. Axial diffusion of a neutral solute (Iodixanol) into cartilage was monitored using calibrated microcomputed tomography (micro-CT) images for up to 48 hr. A biphasic-solute computational model was fitted to the experimental data to determine the diffusion coefficients of cartilage. Cartilage was modeled either using one single diffusion coefficient (single-zone model) or using three diffusion coefficients corresponding to superficial, middle, and deep cartilage zones (multizone model). It was observed that the single-zone model cannot capture the entire concentration-time curve and under-predicts the near-equilibrium concentration values, whereas the multizone model could very well match the experimental data. The diffusion coefficient of the superficial zone was found to be at least one order of magnitude larger than that of the middle zone. Since neutral solutes were used, glycosaminoglycan (GAG) content cannot be the primary reason behind such large differences between the diffusion coefficients of the different cartilage zones. It is therefore concluded that other features of the different cartilage zones such as water content and the organization (orientation) of collagen fibers may be enough to cause large differences in diffusion coefficients through the cartilage thickness.

On the concentration dependence of surface diffusion coefficients in capillary porous materials

1991 ◽  
Vol 434 (1891) ◽  
pp. 317-340 ◽  
Keyword(s):  
Experimental Data ◽  
Carbon Dioxide ◽  
Pore Size ◽  
Surface Diffusion ◽  
Diffusion Coefficients ◽  
Physical Adsorption ◽  
Structural Heterogeneity ◽  
Size Dependent ◽  
Chemical Potentials ◽  
Uniform Pore Size

The influence of structural heterogeneity, in the form of a non-uniform pore size distribution, on the isotherms and surface diffusion coefficients for monolayer physical adsorption is studied. A pore size dependent langmuirian isotherm is used along with consideration of equality of chemical potentials at the pore mouths at an intersection. The diffusion is modelled by a recently developed random walk formulation. It is found that the surface diffusion coefficients are strongly influenced by the heterogeneity and have a stronger increase with overall coverage than that predicted by the Darken equation. The results are found to match the experimental data of P. C. Carman and F. A. Raal on the diffusion of carbon dioxide in carbon black without the use of a fitting parameter.

An Approximation of the Improved Rouse Equation

2012 ◽  
Vol 256-259 ◽  
pp. 2480-2485
Author(s):  
Chen Cheng ◽  
Zhi Yao Song ◽  
Yi Gang Wang ◽  
Jin Shan Zhang
Keyword(s):  
Experimental Data ◽  
Diffusion Coefficients ◽  
Diffusion Theory ◽  
Suspended Sediment Transport ◽  
Linear Diffusion ◽  
General Weight ◽  
Equilibrium Profiles ◽  
Erodible Beds ◽  
Whole Water ◽  
Better Than

Rouse equation, which was derived from the diffusion theory, is well known in the study of steady state suspended sediment transport over erodible beds. Although this equation being regarded as Rouse law could be applied effectively, it is unrealistic that the concentration at the free surface is always zero. In addition, for deriving the depth-averaged concentration, the numerical integration or the table lookup has to be performed. Bose and Dey[1] improved the Rouse equation using a modified sediment diffusivity in order to overcome the zero value concentration, but this equation can not be integrated analytically yet. In this paper, according to two equilibrium profiles respect to constant and linear diffusion coefficients, an approximate solution of the improved Rouse equation is given using a general weight-averaged method in order to be integrated analytically. Through verification with experimental data, the results show that the approximation of the improved Rouse equation behave generally better than itself, as well as the Rouse equation and van Rijn equation over the whole water depth. It is revealed that, nevertheless some empirical, this approximation is reasonable, and has higher accuracy. Moreover it can be integrated analytically.

The refractive indices and Verdet constants of the inert gases

1960 ◽  
Vol 259 (1298) ◽  
pp. 424-431 ◽  
Keyword(s):  
Experimental Data ◽  
Refractive Index ◽  
Atomic Hydrogen ◽  
Experimental Error ◽  
Atomic System ◽  
Inert Gases ◽  
Refractive Indices ◽  
Verdet Constant

A method is suggested by which the refractive index and Verdet constant of an atomic system may be derived theoretically. It is applied to atomic hydrogen and to the inert gases and a comparison is made with experimental data. The Verdet constant of neon is not anomalous. The origin of the suggestion appears to be an underestimate of the experimental error. The analysis yields values of th e polarizabilities of th e inert gases which are respectively He, 1-384; Ne, 2-663; Ar, 11-080; K r, 16-734; X e, 27-292 in units of α 3 0

Inverse analysis of the transient bound water diffusion in wood

Holzforschung ◽  
2005 ◽  
Vol 59 (1) ◽  
pp. 38-45 ◽  
Author(s):  
Wiesław Olek ◽  
Patrick Perré ◽  
Jerzy Weres
Keyword(s):  
Experimental Data ◽  
Diffusion Coefficients ◽  
Inverse Analysis ◽  
Bound Water ◽  
Water Diffusion ◽  
European Species ◽  
Alternative Approach ◽  
Transfer Problems ◽  
Bound Water Content ◽  
Water Diffusion Coefficient

Abstract The methods so far applied to determine the bound water diffusion coefficient in wood do not provide credible results on this coefficient as well as on the boundary condition. An alternative approach based on the concept of solving the inverse transfer problems was recently applied. Two European species were investigated in the present study. A series of sorption experiments was performed and followed by the numerical identification of the coefficients. Several case studies were carried out for the constant and bound water content dependent diffusion coefficients. The obtained results were validated by comparison to a set of experimental data.

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