Calculations of Impurity Atom Diffusion Through a Narrow Diffusion Mask Opening

1966 ◽  
Vol 10 (1) ◽  
pp. 6-12 ◽  
Author(s):  
D. P. Kennedy ◽  
P. C. Murley
Keyword(s):  
Impurity Atom ◽  
Atom Diffusion

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.

Evidence for a shear mechanism for the precipitation of γ-zirconium hydride in zirconium

1978 ◽  
Vol 36 (1) ◽  
pp. 658-659
Author(s):  
G.J.C. Carpenter
Keyword(s):  
Elevated Temperature ◽  
Strain Field ◽  
Zirconium Hydride ◽  
Zirconium Atom ◽  
Atom Diffusion ◽  
Solvus Temperature ◽  
Hexagonal Close Packed ◽  
Partial Dislocations ◽  
The Face

In zirconium-hydrogen alloys, rapid cooling from an elevated temperature causes precipitation of the face-centred tetragonal (fct) phase, γZrH, in the form of needles, parallel to the close-packed <1120>zr directions (1). With low hydrogen concentrations, the hydride solvus is sufficiently low that zirconium atom diffusion cannot occur. For example, with 6 μg/g hydrogen, the solvus temperature is approximately 370 K (2), at which only the hydrogen diffuses readily. Shears are therefore necessary to produce the crystallographic transformation from hexagonal close-packed (hep) zirconium to fct hydride.The simplest mechanism for the transformation is the passage of Shockley partial dislocations having Burgers vectors (b) of the type 1/3<0110> on every second (0001)Zr plane. If the partial dislocations are in the form of loops with the same b, the crosssection of a hydride precipitate will be as shown in fig.1. A consequence of this type of transformation is that a cumulative shear, S, is produced that leads to a strain field in the surrounding zirconium matrix, as illustrated in fig.2a.

A comparative study of helium atom diffusion via an interstitial mechanism in nickel and palladium

2006 ◽  
Vol 243 (3) ◽  
pp. 579-583 ◽  
Author(s):  
Jixing Xia ◽  
Wangyu Hu ◽  
Jianyu Yang ◽  
Bingyun Ao ◽  
Xiaolin Wang
Keyword(s):  
Comparative Study ◽  
Helium Atom ◽  
Atom Diffusion

scholarly journals Impurity Diffusion in Lithium

1970 ◽  
Vol 25 (10) ◽  
pp. 1477-1483 ◽  
Author(s):  
Aadu Ott
Keyword(s):  
Thin Film ◽  
Impurity Atom ◽  
Thin Film Deposition ◽  
Film Deposition ◽  
Impurity Diffusion ◽  
Experimental Results ◽  
Vacancy Mechanism ◽  
Lithium Metal ◽  
Qualitative Explanation ◽  
Sectioning Method

Abstract The diffusion of 115mCd, 203Hg and 72Ga tracers in lithium metal has been studied, using a thin film deposition and sectioning method.The experimental results can be expressed by the following Arrhenius relations:These results, which do not agree with any established theory of impurity diffusion in a metallic lattice, are discussed together with data from previous experiments in terms of the systematics of the dependence of the diffusivity on the "ionizability" of an impurity atom in Li, and on the size of the impurity. In this way a qualitative explanation of the different diffusions rates can be obtained. The relatively large and electropositive impurities appear to diffuse mainly via a vacancy mechanism and the small and electronegative ones mainly as interstitials. The distinction substitutional-interstitial is less pronounced for very large impurities, which may also exhibit tendencies to be trapped at lattice defects.

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