Intergranular Coupling and Grain Isolation of Thin Co Films

AbstractThe effects of rapid oxidation and overcoat diffusion processes on the intergranular coupling and grain isolation in thin Co films were studied. The oxidation process was found to be strongly temperature dependent. The optimal coercivities can only be achieved within a narrow range of temperatures, while further increasing the temperature incurs significant thermal instability. CrMn underlayers were confirmed to be more effective in enhancing the grain isolation by the grain boundary diffusion during the oxidation process. The oxidation process does not change the Co anisotropy, and hence the coercivity increase is appears to be a result of better grain isolation. The in-situ diffusion of Ag and Cr overcoats were also found to have siginificant effects on the grain isolation in Co and CoCr films.

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Influence of Al/Cu content on grain boundary diffusion in Nd-Fe-B magnet via in-situ observation

Journal of Rare Earths ◽

10.1016/j.jre.2018.07.010 ◽

2019 ◽

Vol 37 (4) ◽

pp. 398-403 ◽

Cited By ~ 3

Author(s):

Xinghua Cheng ◽

Jian Li ◽

Lei Zhou ◽

Tao Liu ◽

Xiaojun Yu ◽

...

Keyword(s):

Grain Boundary ◽

Boundary Diffusion ◽

Grain Boundary Diffusion ◽

In Situ Observation ◽

Cu Content

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Mechanistic Two Stage Fission Gas Release Model

10th International Conference on Nuclear Engineering, Volume 4 ◽

10.1115/icone10-22635 ◽

2002 ◽

Author(s):

Yong-Soo Kim ◽

Chan-Bok Lee

Keyword(s):

Grain Boundary ◽

Diffusion Coefficients ◽

Boundary Diffusion ◽

Diffusion Processes ◽

Lattice Diffusion ◽

Grain Boundary Diffusion ◽

Factor Α ◽

Two Stages ◽

Grain Surface ◽

Release Model

In this study, a mechanistic two stages model is developed which analytically simulates the two-step diffusion processes, grain lattice diffusion and grain boundary diffusion, coupled with the bubbles trap/resolution. Mathematical manipulation reveals that the release at high burn-up depend on the ratio of the diffusivities in the both processes, i.e., α ≅ Dveff/Dgbeff where Dveff and Dgbeff are effective volume and grain boundary diffusion coefficients, respectively. Thus, the ratio α is incorporated in the time-dependent third kind boundary condition at the equivalent grain surface. This model brings forth analytical solutions of the fractional release which are identical to that of either ANS5.4 or modified ANS5.4 model when α goes to the infinity. It turns out that this model describes the release behavior well in the high burn-up fuel and puts out a comparable prediction to the solution of FRAPCON-3 model under the same condition. It is also demonstrated that the new factor α not only ease the computational treatment for the high burn-up fuel performance evaluation, but also enables us to possibly separate the burn-up enhancement from the diffusion coefficients and to easily simulate the bubble-related phenomena in the grain boundary.

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The effect of grain boundary diffusion processes on the formation of Cu2S layers on polycrystalline CdS films

Journal of Physics Condensed Matter ◽

10.1088/0953-8984/3/s/041 ◽

1991 ◽

Vol 3 (S) ◽

pp. S265-S270 ◽

Cited By ~ 3

Author(s):

M Al-Achkar ◽

C G Scott

Keyword(s):

Grain Boundary ◽

Boundary Diffusion ◽

Diffusion Processes ◽

Grain Boundary Diffusion ◽

Cds Films

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Low-Temperature Grain Boundary Diffusion Data Measured from Historical Artifacts

MRS Proceedings ◽

10.1557/proc-852-oo1.5 ◽

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.

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Grain Boundary Diffusion-Controlled Processes and Properties of Bulk Nanostructured Alloys and Steels

Materials Science Forum ◽

10.4028/www.scientific.net/msf.503-504.141 ◽

2006 ◽

Vol 503-504 ◽

pp. 141-148 ◽

Cited By ~ 4

Author(s):

Yu.R. Kolobov ◽

Konstantin Ivanov

Keyword(s):

Plastic Deformation ◽

Grain Boundary ◽

Severe Plastic Deformation ◽

Boundary Diffusion ◽

Diffusion Processes ◽

Grain Boundary Diffusion ◽

Controlled Processes ◽

Bioactive Coating ◽

Diffusion Controlled ◽

Theoretical Investigations

The experimental and theoretical investigations of grain boundary diffusion processes have been performed using metals and alloys in nanostructured state produced by severe plastic deformation and the respective polycrystalline counterparts. The main features of diffusioncontrolled mechanisms of plastic deformation observed by the creep of nanostructured metals are considered. The use of severe plastic deformation treatment and of the effect of activation of diffusion-controlled processes for enhancing the properties of nanostructured steels and alloys designed for engineering and medical applications (nanostructured titanium-bioactive coating composite included) is described and examples are offered.

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Lattice and Grain-Boundary Diffusion Processes Involved in the High-Temperature Oxidation and Sulfidation of Metals and Alloys

Selected Topics in High Temperature Chemistry - Defect Chemistry of Solids - Studies in Inorganic Chemistry ◽

10.1016/b978-0-444-88534-0.50013-8 ◽

1989 ◽

pp. 185-225 ◽

Cited By ~ 2

Author(s):

D.L. Douglass

Keyword(s):

High Temperature ◽

Grain Boundary ◽

High Temperature Oxidation ◽

Boundary Diffusion ◽

Diffusion Processes ◽

Grain Boundary Diffusion ◽

Metals And Alloys ◽

Temperature Oxidation

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Kinetic Modeling of Grain Boundary Diffusion: The Influence of Grain Size and Surface Processes

Materials ◽

10.3390/ma13051051 ◽

2020 ◽

Vol 13 (5) ◽

pp. 1051 ◽

Cited By ~ 3

Author(s):

Justina Jaseliunaite ◽

Arvaidas Galdikas

Keyword(s):

Grain Size ◽

Grain Boundary ◽

Diffusion Coefficients ◽

Boundary Diffusion ◽

Diffusion Processes ◽

Error Function ◽

Grain Boundary Diffusion ◽

Surface Processes ◽

Rate Equations ◽

The Impact

Based on rate equations, the kinetics of atom adsorption, desorption, and diffusion in polycrystalline materials is analyzed in order to understand the influence of grain boundaries and grain size. The boundary conditions of the proposed model correspond with the real situation in the electrolytes of solid oxide hydrogen fuel cells (SOFC). The role of the ratio of grain boundary and grain diffusion coefficients in perpendicular and parallel (to the surface) concentration profiles is investigated. In order to show the influence of absolute values of grain and grain boundary diffusion coefficients, we select four different cases in which one of the diffusion coefficients is kept constant while the others vary. The influence of grain size on diffusion processes is investigated using different geometrical models. The impact of kinetic processes taking place on the surface is analyzed by comparing results obtained assuming the first layer as a constant source and then involving in the model the processes of adsorption and desorption. It is shown that surface processes have a significant influence on the depth distribution of diffusing atoms and cannot be ignored. The analytical function of overall concentration dependence on grain and grain boundary volume ratio (Vg/Vgb) is found. The solution suggests that the concentration increases as a complementary error function while Vg/Vgb decreases.

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