Self-Diffusion


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self-diffusion

[¦self di¦fyü·zhən]
(solid-state physics)
The spontaneous movement of an atom to a new site in a crystal of its own species.

Self-Diffusion

 

the special case of diffusion in a pure substance or a solution of constant composition where the substance’s own particles undergo diffusion. In self-diffusion, the atoms that participate in the diffusion movement have the same chemical properties but can differ in their physical characteristics—in the composition of their nuclei (see ISOTOPES). In the case of a difference in the isotopic composition of the substance, self-diffusion can be observed through the use of radioactive isotopes (see ISOTOPE TRACERS) or through analysis of the isotopic composition by means of mass spectrometers.

The change over time in the concentration of a given isotope in the volume of the substance under consideration is described by the usual equations for diffusion, and the rate of the process is characterized by the coefficient of self-diffusion (see DIFFUSION). When such forces as surface tension, gravity, elastic forces, or electrical forces act on a solid specimen for a long time, the diffusion displacements of the solid’s particles can result in a change in its shape or in other effects. These diffusion processes are evidenced in the joining together of two polished specimens of the same substance placed next to each other, in the sintering of powders, and in the stretching of a body under the action of a load suspended from it (diffusion creep). The study of the kinetics of these processes permits determination of the coefficient of self-diffusion of a substance.

References in periodicals archive ?
In the absence of a chemical gradient, we call it self-diffusion coefficient.
Then he examines defects in group IV semiconductors, self-diffusion experiments and their theoretical modeling as practical tools to deduce the nature and presence of native defects in group IV semiconductors, and defects in group IV carbides.
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Increased water self-diffusion in chronic plaques and in apparently normal white matter in patients with multiple sclerosis.
Reimschussel, Self-Diffusion and Conductance Studies of Acetonitrile"Water Solutions of Tetraethylammonium Iodide, Berichte der Bunsengesalschaft fir Physikalischechemie.
Eccles CD, Callaghan PT, Jenner CF (1988) Measurement of the self-diffusion coefficient of water as a function of position in wheat grain using nuclear magnetic resonance imaging.
Gradient methods enable also a study of flow and self-diffusion, allowing inferring a distribution of the droplet size or the rheological properties.
The common and simplistic mechanism for latex film formation is dominated by three main phases: (1) evaporation of primary solvent, resulting in a close-packing formation of the particles, (2) particle deformation and filling in the voids, and (3) polymer self-diffusion across boundaries to yield a continuous film where the original particle shape and locations are no longer distinguishable.
The relation between self-diffusion and bulk diffusion.
Mariette, "NMR study of tomato pericarp tissue by spin-spin relaxation and water self-diffusion," Appl.
The self-evident multiplicity of intelligible forms testifies to the self-diffusion of the Good, which, in turn, is the only possible answer to the Ultimate Why Question.