Topic

# Atomic diffusion

About: Atomic diffusion is a research topic. Over the lifetime, 1733 publications have been published within this topic receiving 35358 citations.

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TL;DR: It is shown that fully dense cubic Y2O3 with a grain size of 60 nm can be prepared by a simple two-step sintering method, at temperatures of about 1,000 °C without applied pressure, and the suppression of the final-stage grain growth is achieved by exploiting the difference in kinetics between grain- boundary diffusion and grain-boundary migration.

Abstract: Sintering is the process whereby interparticle pores in a granular material are eliminated by atomic diffusion driven by capillary forces. It is the preferred manufacturing method for industrial ceramics. The observation of Burke and Coble that certain crystalline granular solids could gain full density and translucency by solid-state sintering was an important milestone for modern technical ceramics. But these final-stage sintering processes are always accompanied by rapid grain growth, because the capillary driving forces for sintering (involving surfaces) and grain growth (involving grain boundaries) are comparable in magnitude, both being proportional to the reciprocal grain size. This has greatly hampered efforts to produce dense materials with nanometre-scale structure (grain size less than 100 nm), leading many researchers to resort to the 'brute force' approach of high-pressure consolidation at elevated temperatures. Here we show that fully dense cubic Y2O3 (melting point, 2,439 degrees C) with a grain size of 60 nm can be prepared by a simple two-step sintering method, at temperatures of about 1,000 degrees C without applied pressure. The suppression of the final-stage grain growth is achieved by exploiting the difference in kinetics between grain-boundary diffusion and grain-boundary migration. Such a process should facilitate the cost-effective preparation of other nanocrystalline materials for practical applications.

1,328 citations

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TL;DR: In this paper, a mathematical analysis of grain boundary and surface diffusion is completed, assuming that grain boundary diffusion is analogous to the diffusion of heat along a thin copper foil imbedded in cork.

Abstract: Diffusion in solids is known to occur along grain boundaries and over free surfaces more rapidly than through the interiors of crystals. In order to facilitate quantitative investigation of grain boundary and surface diffusion, a mathematical analysis of the problem has been completed, assuming that grain boundary diffusion is analogous to the diffusion of heat along a thin copper foil imbedded in cork. The calculated diffusion‐penetration relationship for grain boundary diffusion is shown to agree with the experimentally determined grain boundary self‐diffusion of silver.

1,130 citations

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TL;DR: In this paper, the radius of a spherical precipitate particle growing in a solid solution of initially uniform composition was shown to be equal to α(Dt)½, where D is the atomic diffusion coefficient, t the time of growth, and α, the growth coefficient, is a dimensionless function of the pertinent compositions.

Abstract: The radius of a spherical precipitate particle growing in a solid solution of initially uniform composition may be shown to be equal to α(Dt)½, where D is the atomic diffusion coefficient, t the time of growth, and α, the growth coefficient, is a dimensionless function of the pertinent compositions. In this paper the precise dependence is found of this function upon the pertinent concentrations. A similar computation is made for the growth coefficient corresponding to the one‐dimensional growth of a plate.

961 citations

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Union Carbide

^{1}TL;DR: In this paper, a spinel-type material LiMn2O4 with aqueous acid was found to result in conversion of the spinel to nearly pure MnO2.

846 citations

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TL;DR: In this paper, the kinetics of reaction between CO2 and lime are investigated in the range of 673 to 998 K with a view to examining the effects of product layer deposition and variations in the limestone calcination atmosphere.

Abstract: The kinetics of reaction between CO2 and lime is investigated in the range of 673 to 998 K with a view to examining the effects of product layer deposition and variations in the limestone calcination atmosphere. The reaction is initially rapid and chemically controlled and goes through a sudden transition to a much slower regime controlled by diffusion in the product CaCO3 layer. The magnitude of the estimated product layer diffusivity is in the range of 10−18 to 10−21 m2/s, the corresponding activation energy is 88.9 ± 3.7 kJ/mol below 688 K and 179.2 ± 7.0 kJ/mol above that temperature, suggestive of solid state diffusion. Plausible mechanisms are discussed.

603 citations