Oxygen Self-Diffusion In Mgo Grain Boundaries

1994 ◽  
Vol 357 ◽  
Author(s):  
Michael Liberatore ◽  
Bernhardt J. Wuensch
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Experimental Error ◽  
Boundary Diffusion ◽  
High Energy ◽  
Activation Energies ◽  
Grain Boundary Diffusion ◽  
Low Energy ◽  
Enhanced Diffusion ◽  
Self Diffusion

AbstractOxygen grain boundary diffusion has been studied in low energy (∑5, ∑13) and high energy (asymmetric 16° tilt) MgO grain boundaries. Enhanced diffusion of oxygen was observed in all boundaries, but more so in the general, high energy boundary, by 1 - 2 orders of magnitude. This supports the theory that the better the atomic registry between the adjoining grains the lower the diffusivities in the grain boundary. Also the activation energies for bulk and grain boundary diffusion (in the ∑13 boundaries) were found to be equal to within experimental error. (≈ 3.9eV)

Structure and Properties of Polycrystalline Materials From Simulation: An Interfacial Perspective

1999 ◽  
Vol 586 ◽  
Author(s):  
S. R. Phillpot ◽  
P. Keblinski ◽  
D. Wolf ◽  
F. Cleri
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Diffusion ◽  
Simulation Method ◽  
High Energy ◽  
Grain Boundary Diffusion ◽  
Dynamics Simulation ◽  
Polycrystalline Materials ◽  
Diffusion Creep ◽  
Fcc Metals

ABSTRACTWe have recently developed a novel molecular-dynamics simulation method to grow polycrystals from a melt containing randomly oriented crystalline seeds. The resulting microstructures contain only randomly oriented (i.e., high-energy) grain boundaries. We find that these grain boundaries, which are highly constrained by their close proximity to grain junctions, are highly disordered in fcc metals and amorphous in silicon. From simulations of infinitely extended high-energy grain boundaries in bicrystals, we find that such highly disordered and amorphous grain boundaries are actually the thermodynamic ground state; by contrast, low-energy grain boundaries are crystalline. High-energy grain boundaries in diamond, however, are structurally ordered at the expense of a significant amount of graphite-like bonding. We show that these complex grain boundary structures have important effects on properties including grain boundary diffusion (fcc metals and silicon), grain boundary diffusion creep (silicon) and grain boundary electrical activity and strength (diamond). The implications for engineering materials with prescribed properties are discussed.

Grain Boundary Diffusion and Segregation in the Solid State Phase Transformations

1998 ◽  
Vol 527 ◽  
Author(s):  
E. Rabkin ◽  
W. Gust
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Solute Diffusion ◽  
Apparent Difference ◽  
Impurity Drag ◽  
The Difference ◽  
Boundary Width ◽  
Dynamic Segregation

ABSTRACTWe consider the problem of solute diffusion and segregation in the grain boundaries moving during a phase transformation in the framework of Cahn's impurity drag model. The concept of a dynamic segregation factor for the diffusion along moving grain boundaries is introduced. The difference between static and dynamic segregation factors may cause the apparent difference of the triple product of the segregation factor, grain boundary width and grain boundary diffusion coefficient for stationary and moving grain boundaries. The difference between static and dynamic segregation is experimentally verified for the Cu(In)-Bi system, for which the parameters of static segregation are well-known. It is shown that the complications associated with the dynamic segregation may be avoided during the study of the discontinuous ordering reaction. From the kinetics of this reaction, the activation energy of the grain boundary self-diffusion can be determined.

SELF-DIFFUSION IN POLYCRYSTALLINE NICKEL

1959 ◽  
Vol 37 (10) ◽  
pp. 1623-1628 ◽  
Author(s):  
J. R. MacEwan ◽  
J. U. MacEwan ◽  
L. Yaffe
Keyword(s):  
Grain Boundary ◽  
Boundary Diffusion ◽  
Volume Diffusion ◽  
Grain Boundary Diffusion ◽  
The Self ◽  
Polycrystalline Nickel ◽  
Self Diffusion ◽  
Diffusion Studies

The self-diffusion of nickel has been studied in polycrystalline samples by a sectioning technique. There is evidence of grain boundary diffusion below temperatures of 1150 °C. The results obtained between 1150° and 1400 °C are representative of volume diffusion and are represented by the expression[Formula: see text]A comparison is made with the results of other self-diffusion studies using Zener's hypothesis.

Grain boundary Diffusion of Ni through Pd2Si

1983 ◽  
Vol 25 ◽  
Author(s):  
E. C. Zingu ◽  
J. W. Mayer
Keyword(s):  
Thin Film ◽  
Activation Energy ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Diffusion ◽  
Rutherford Backscattering Spectrometry ◽  
High Mobility ◽  
Grain Boundary Diffusion ◽  
Rutherford Backscattering

ABSTRACTInterdiffusion in the Si<100>/Pd2Si/Ni and Si<111>/Pd2Si/Ni thin film systems has been investigated using Rutherford backscattering spectrometry. Nickel is found to diffuse along the grain boundaries of polycrystalline Pd2Si upon which it accumulates at the Si<100>Pd2Si interface. The high mobility of Ni compared to that of si suggests that Pd diffuses faster than Si along the Pd2Si grain boundaries. An activation energy of 1.2 eV is determined for Ni grain boundary diffusion in Pd2Si.

Constrained Grain Boundary Diffusion In Thin Copper Films

2004 ◽  
Vol 821 ◽  
Author(s):  
Markus J. Buehler ◽  
Alexander Hartmaier ◽  
Huajian Gao
Keyword(s):  
Thin Films ◽  
Theoretical Analysis ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Atomic Scale ◽  
Diffusional Creep ◽  
Copper Films ◽  
And Diffusion

AbstractIn a recent study of diffusional creep in polycrystalline thin films deposited on substrates, we have discovered a new class of defects called the grain boundary diffusion wedges (Gao et al., Acta Mat. 47, pp. 2865-2878, 1999). These diffusion wedges are formed by stress driven mass transport between the free surface of the film and the grain boundaries during the process of substrate-constrained grain boundary diffusion. The mathematical modeling involves solution of integro-differential equations representing a strong coupling between elasticity and diffusion. The solution can be decomposed into diffusional eigenmodes reminiscent of crack-like opening displacement along the grain boundary which leads to a singular stress field at the root of the grain boundary. We find that the theoretical analysis successfully explains the difference between the mechanical behaviors of passivated and unpassivated copper films during thermal cycling on a silicon substrate. An important implication of our theoretical analysis is that dislocations with Burgers vector parallel to the interface can be nucleated at the root of the grain boundary. This is a new dislocation mechanism in thin films which contrasts to the well known Mathews-Freund-Nix mechanism of threading dislocation propagation. Recent TEM experiments at the Max Planck Institute for Metals Research have shown that, while threading dislocations dominate in passivated metal films, parallel glide dislocations begin to dominate in unpassivated copper films with thickness below 400 nm. This is consistent with our theoretical predictions. We have developed large scale molecular dynamics simulations of grain boundary diffusion wedges to clarify the nucleation mechanisms of parallel glide in thin films. Such atomic scale simulations of thin film diffusion not only show results which are consistent with both continuum theoretical and experimental studies, but also revealed the atomic processes of dislocation nucleation, climb, glide and storage in grain boundaries. The study should have far reaching implications for modeling deformation and diffusion in micro- and nanostructured materials.

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.

Oxygen Diffusion along Symmetric [0001] Tilt Grain Boundaries in α-Alumina

2006 ◽  
Vol 317-318 ◽  
pp. 415-418 ◽  
Author(s):  
Tsubasa Nakagawa ◽  
Isao Sakaguchi ◽  
Katsuyuki Matsunaga ◽  
Takahisa Yamamoto ◽  
Hajime Haneda ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Oxygen Diffusion ◽  
Isotopic Exchange ◽  
Boundary Diffusion ◽  
Depth Profiling ◽  
Grain Boundary Diffusion ◽  
Symmetric Tilt ◽  
And Diffusion ◽  
Diffusion Properties

Grain boundary diffusion coefficients of oxygen (δDgb) at 1793K in high purity α-alumina bicrystals with Σ7{2 _ ,310}/[0001] and Σ31{7 _ ,1140}/[0001] symmetric tilt grain boundaries were measured by means of the isotopic exchange and diffusion depth profiling using SIMS. δDgb of both grain boundaries were determined to be 7.1x10-24 [m3/sec] for Σ7 grain boundary and 5.3 x10-24 [m3/sec] for Σ31 grain boundary, respectively. These results indicate that Σ values do not directly relate to grain boundary diffusion properties.

The State of Grain Boundaries and Grain-Boundary Diffusion in Ultrafine-Grained Mo Obtained by Severe Plastic Deformation

2016 ◽  
Vol 367 ◽  
pp. 130-139 ◽  
Author(s):  
Vladimir V. Popov ◽  
A.V. Sergeev
Keyword(s):  
Plastic Deformation ◽  
High Pressure ◽  
Grain Boundary ◽  
Severe Plastic Deformation ◽  
Grain Boundaries ◽  
Boundary Diffusion ◽  
High Pressure Torsion ◽  
Grain Boundary Diffusion ◽  
Fast Diffusion ◽  
Non Equilibrium

The grain-boundary diffusion of Co in ultra-fine grained Mo processed by high-pressure torsion has been studied by emission Mössbauer spectroscopy and radio-tracer analysis. It is demonstrated that under the severe plastic deformation by high-pressure torsion the non-equilibrium grain boundaries are formed which are the ultra-fast diffusion paths. At annealing in the temperature range of 623-823 K the relaxation of the non-equilibrium boundaries proceeds and their properties approach to those of equilibrium boundaries of recrystallization origin.

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