The Role of Grain Boundary Diffusion in Initial Selective Oxidation Kinetics of a Manganese-Aluminum TRIP Steel

2005 ◽  
Vol 26 (5) ◽  
pp. 539-546 ◽  
Author(s):  
Casper Thorning ◽  
Seetharaman Sridhar
Keyword(s):  
Grain Boundary ◽  
Selective Oxidation ◽  
Oxidation Kinetics ◽  
Trip Steel ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Manganese Aluminum ◽  
Kinetics Of

scholarly journals The oxidation kinetics of thin nickel films between 250 and 500 °C

2017 ◽  
Vol 19 (13) ◽  
pp. 9045-9052 ◽  
Author(s):  
Y. Unutulmazsoy ◽  
R. Merkle ◽  
D. Fischer ◽  
J. Mannhart ◽  
J. Maier
Keyword(s):  
Grain Boundary ◽  
Oxidation Kinetics ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion ◽  
Diffusion Controlled ◽  
Ni Oxidation ◽  
Thin Nickel ◽  
P Diffusion ◽  
Kinetics Of ◽  
Nio Films

Diffusion controlled Ni oxidation is enhanced by fast grain boundary diffusion in growing nanocrystalline NiO films.

Diffusion Mechanisms in Nanocrystalline and Nanolaminated Au-Cu

2007 ◽  
Vol 266 ◽  
pp. 13-28 ◽  
Author(s):  
Alan F. Jankowski
Keyword(s):  
Low Temperature ◽  
Grain Boundary ◽  
Grain Growth ◽  
Boundary Diffusion ◽  
Bulk Diffusion ◽  
Grain Boundary Diffusion ◽  
Dominant Mechanism ◽  
Temperature Range ◽  
Diffusion Mechanisms ◽  
Kinetics Of

Thermal anneal treatments are used to identify the temperature range of the two dominant diffusion mechanisms – bulk and grain boundary. To assess the transition between mechanisms, the low temperature range for bulk diffusion is established utilizing the decay of static concentration waves in composition-modulated nanolaminates. These multilayered structures are synthesized using vapor deposition methods as thermal evaporation and magnetron sputtering. However, at low temperature the kinetics of grain-boundary diffusion are much faster than bulk diffusion. The synthesis of Au-Cu alloys (0-20 wt.% Cu) with grain sizes as small as 5 nm is accomplished using pulsed electro-deposition. Since the nanocrystalline grain structure is thermally unstable, these structures are ideal for measuring the kinetics of grain boundary diffusion as measured by coarsening of grain size with low temperature anneal treatments. A transition in the dominant mechanism for grain growth from grain boundary to bulk diffusion is found with an increase in temperature. The activation energy for bulk diffusion is found to be 1.8 eV·atom-1 whereas that for grain growth at low temperatures is only 0.2 eV·atom-1. The temperature for transitioning from the dominant mechanism of grain boundary to bulk diffusion is found to be 57% of the alloy melt temperature and is dependent on composition.

The role of solute segregation in grain boundary diffusion

1982 ◽  
Vol 379 (1776) ◽  
pp. 159-178 ◽  
Keyword(s):  
Grain Boundary ◽  
Boundary Diffusion ◽  
Boundary Energy ◽  
Grain Boundary Diffusion ◽  
Enrichment Ratio ◽  
Tin Alloys ◽  
Bulk Diffusivity ◽  
Tin Content ◽  
Grain Boundary Transport

In measurements of grain boundary transport it is the product of the grain boundary enrichment ratio and the grain boundary diffusivity that is usually obtained. This work presents the first study in which these two terms are separated and in which the role of the grain boundary composi­tion in grain boundary diffusion is analysed in detail. This leads to the general prediction that the grain boundary diffusion of solute and solvent will be reduced by strongly segregating solutes if they do not simultaneously enhance the bulk diffusivities. The converse occurs if the solute weakly segregates but strongly enhances the bulk diffusivities. The diffusion measurements are made in iron–tin alloys in the tempera­ture range 563–750 °C by using radiotracers, and the segregation measure­ments, similarly, by Auger electron spectroscopy. The measured bulk diffusivities are similar to those found previously. The grain boundary diffusivities, determined via Suzuoka’s (1964) analysis, for iron and tin in pure iron have pre-exponential coefficients of 225 x 10 -4 and 9.2 x 10 -4 m 2 s -1 and activation energies of 165770 and 166600 J mol -1 respectively. Contrary to the increase in the bulk diffusivity produced by the ‘fast’ diffuser, tin, both grain boundary diffusivities are sharply reduced as the tin content rises. These and earlier results are interpreted through the effect of tin segregation on the grain boundary energy described by the theory of Borisov et al . (1964).

Role of segregating impurities in grain-boundary diffusion

2007 ◽  
Vol 126 (9) ◽  
pp. 094707 ◽  
Author(s):  
P. Kansuwan ◽  
J. M. Rickman
Keyword(s):  
Grain Boundary ◽  
Boundary Diffusion ◽  
Grain Boundary Diffusion

scholarly journals Role of grain boundary diffusion in H-D exchange in mantle xenoliths

2020 ◽  
Author(s):  
Konstantinos Thomaidis ◽  
Jannick Ingrin
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Hydrogen Exchange ◽  
Boundary Diffusion ◽  
Water Concentration ◽  
Grain Boundary Diffusion ◽  
Mantle Xenoliths ◽  
Host Magma ◽  
Oxidation Reduction

<p>Water concentration in pyroxenes from mantle xenoliths is frequently used to trace water content in the lithospheric mantle. We do not understand yet how these pyroxenes can preserve a memory of their deep equilibrium during their transport to the surface. In an attempt to evaluate the role of grain boundaries in the exchange of hydrogen between the pyroxenes of the xenoliths and the host magma, we have launched a program of experiments of H exchange in blocks of mantle xenoliths of centimetre size. The blocks, all from the same xenolith, contain clinopyroxenes, orthopyroxenes and olivine of mm to sub-millimetre size. We present here the results of a series of H-D exchange performed at 600, 700 and 900 <sup>o</sup>C at room pressure in a deuterium enriched gas. OH-OD profiles recorded by micro-infrared spectroscopy in pyroxenes at the edge of the block are only slightly different from the ones recorded in pyroxenes at the centre of the block. These results show that the diffusion/solubility of hydrogen in grain boundaries is fast enough to equilibrate rapidly the grains at the center of the xenoliths. It proves that in nature the δD signature of xenoliths is very likely controlled by the equilibrium with the host magma even in the case of xenoliths with large grain size.</p><p>We will also present preliminary results on the role of grain boundary diffusion in the control of hydrogen exchange involving reactions activated at a higher temperature such as the oxidation-reduction of iron (1/2H<sub>2</sub> + Fe<sup>3+</sup>  =  H<sub>i</sub><sup>+</sup> + Fe<sup>2+</sup>) and the formation/destruction of cation vacancies.</p>

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