Competing descriptions of diffusion profiles with two features: Surface space-charge layer versus fast grain-boundary diffusion

2016 ◽  
Vol 119 (6) ◽  
pp. 064903 ◽  
Author(s):  
H. Schraknepper ◽  
R. A. De Souza
Keyword(s):  
Grain Boundary ◽  
Space Charge ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Space Charge Layer ◽  
Layer Versus ◽  
Charge Layer ◽  
Diffusion Profiles

Numerical Study of Grain Boundary Diffusion in Nanocrystalline Materials

2005 ◽  
Vol 237-240 ◽  
pp. 1043-1048 ◽  
Author(s):  
D. Gryaznov ◽  
J. Fleig ◽  
Joachim Maier
Keyword(s):  
Grain Boundary ◽  
Nanocrystalline Materials ◽  
Boundary Diffusion ◽  
Nanocrystalline Material ◽  
Numerical Study ◽  
Average Length ◽  
Type A ◽  
Grain Boundary Diffusion ◽  
Conventional Models ◽  
Diffusion Profiles

Diffusion in nanocrystalline materials is becoming an increasingly important topic. The analysis of diffusion profiles obtained in nanocrystalline materials with enhanced grain boundary diffusion, however, is not straightforward since assumptions made in the deviation of the conventional models are often not fulfilled. In this contribution numerical diffusion studies are performed in order to investigate effects caused by the high density of interfaces in nanocrystalline material. A continuum model based on the 2D 2-nd Fick’s law was solved by means of the finite element method. This allows us to analyze diffusion profiles for different geometrical situations such as a single boundary, square grains with the grain size of 80 nm and 25 nm and geometries comprising differently oriented boundaries of the average length of 30 nm . The analysis was carried out for different diffusion lengths corresponding to Harrison type A and type B kinetic regimes. For the isolated boundary a very good agreement was achieved in comparison with the classical Whipple’s solution. For nanocrystalline material, however, considerable errors can occur when analyzing the averaged diffusion profiles in the conventional Harrison type A and B kinetics.

Zinc Self-Diffusion in ZnO

2005 ◽  
Vol 237-240 ◽  
pp. 163-168 ◽  
Author(s):  
M.A.N. Nogueira ◽  
Antônio Claret Soares Sabioni ◽  
Wilmar Barbosa Ferraz
Keyword(s):  
Diffusion Coefficient ◽  
Grain Boundary ◽  
Diffusion Coefficients ◽  
Boundary Diffusion ◽  
Volume Diffusion ◽  
Grain Boundary Diffusion ◽  
Polished Surface ◽  
Self Diffusion ◽  
Zinc Diffusion ◽  
Diffusion Profiles

This work deals with the study of zinc self-diffusion in ZnO polycrystal of high density and of high purity. The diffusion experiments were performed using the 65Zn radioactive isotope as zinc tracer. A thin film of the tracer was deposited on the polished surface of the samples, and then the diffusion annealings were performed from 1006 to 1377oC, in oxygen atmosphere. After the diffusion treatment, the 65Zn diffusion profiles were established by means of the Residual Activity Method. From the zinc diffusion profiles were deduced the volume diffusion coefficient and the product dDgb for the grain-boundary diffusion, where d is the grain-boundary width and Dgb is the grain-boundary diffusion coefficient. The results obtained for the volume diffusion coefficient show good agreement with the most recent results obtained in ZnO single crystals using stable tracer and depth profiling by secondary ion mass spectrometry, while for the grain-boundary diffusion there is no data published by other authors for comparison with our results. The zinc grain-boundary diffusion coefficients are ca. 4 orders of magnitude greater than the volume diffusion coefficients, in the same experimental conditions, which means that grain-boundary is a fast path for zinc diffusion in polycrystalline ZnO.

Low-Temperature Grain Boundary Diffusion Data Measured from Historical Artifacts

2004 ◽  
Vol 852 ◽  
Author(s):  
R.J. Kremer ◽  
M.A. Dayananda ◽  
A.H. King
Keyword(s):  
Low Temperature ◽  
Grain Boundary ◽  
Room Temperature ◽  
Boundary Diffusion ◽  
Diffusion Processes ◽  
Grain Boundary Diffusion ◽  
Accelerated Tests ◽  
Temperature Diffusion ◽  
Diffusion Profiles

ABSTRACTDiffusion processes in typical metals are slow at room temperature but there are many applications for which very long-term use is envisaged and stability needs to be assured over a timescale of 10, 000 years, where even slow processes can be important. It is common to perform accelerated tests at higher temperatures and extrapolate the necessary information from the measurements so obtained. We have tested the validity of this type of extrapolation for room-temperature, grain boundary diffusion in the copper-silver system, by measuring low-temperature diffusion profiles in antique samples of Sheffield plate.

Space-Charge Contribution to Grain-Boundary Diffusion

1977 ◽  
Vol 60 (3-4) ◽  
pp. 120-127 ◽  
Author(s):  
M. F. VAN ◽  
R. M. CANNON ◽  
H. K. BOWEN ◽  
R. L. COBLE
Keyword(s):  
Grain Boundary ◽  
Space Charge ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion

Mössbauer Investigations of Grain-Boundary Diffusion and Segregation

2006 ◽  
Vol 258-260 ◽  
pp. 497-508 ◽  
Author(s):  
Vladimir V. Popov
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Diffusion ◽  
Diffusion Mechanism ◽  
Boundary Segregation ◽  
Grain Boundary Diffusion ◽  
Grain Boundary Segregation ◽  
Emission Mössbauer Spectroscopy ◽  
Diffusion Profiles ◽  
Boundary Core

Possibilities of grain-boundary diffusion and segregation studies using nuclear gammaresonance spectroscopy (NGR) are considered. It is shown that the results of the Mössbauer investigations testify the necessity to specify the classical Fisher’s model of grain-boundary diffusion, and a possible way of such specification is suggested. It is demonstrated that investigation of grain boundaries using emission Mössbauer spectroscopy appreciably supplement the information obtained from the diffusion profiles analysis. In particular, Mössbauer investigations make it possible to evaluate directly the grain-boundary segregation factor, to determine the grain-boundary diffusion mechanism, to estimate the rate of the diffusant pumping from a grain boundary core into the bulk, etc.

GRAIN BOUNDARY DIFFUSION OF BULK INTERSTITIALS IN ALPHA-ZIRCONIUM

1990 ◽  
Vol 51 (C1) ◽  
pp. C1-691-C1-696 ◽  
Author(s):  
K. VIEREGGE ◽  
R. WILLECKE ◽  
Chr. HERZIG
Keyword(s):  
Grain Boundary ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion
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