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.

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Equation 7 has three terms: the first bracket is the estimation of the self-diffusion coefficient; the second term is the thermodynamic terms using the Flory-Huggins thermodynamic model to relate the mutual binary diffusion coefficient to the self-diffusion coefficient, and the last term accounts for the tortuosity.
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 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.
Among the topics there are the comparative Mossbauer analysis of the superfine structure of Hadfield steel under different kinds of severe deformation, the isochronal and isothermal annealing of wrought aluminum alloy, the quantitative analysis of fiber fracture in powder injection molded metal composites, the characterization and properties of copper-silica sand nanoparticle composites, modeling three-dimensional moving heat sources in a semi-infinite medium and applications to submerged arc welding, and self-diffusion in nano zinc sulphide.
Among specific topics are domain wall engineering in lead-free piezoelectric materials, fabricating dielectric/conductive hybrid artificial superlattices using the molecular beam epitaxy method, zinc self-diffusion in isotopic heterostructures zinc oxide thin films, electrical properties of conductive paste with silver nanoparticles and its application to flexible substrates, piezoelectric ceramics for high-temperature applications, the mixed conduction of proton and electron in tungsten phosphate glass and its hydrogen transport, and thermophysical behavior in crystalline halides with temperature.
Barriers such as myelin sheaths, membranes, or white matter tracts result in greater self-diffusion along the axis of the barrier and reduced diffusion out of the tract.
However, all the variations of this approach operate in term of self-diffusion coefficients.
The self-diffusion coefficient for glycerol in the liquid state at 30[degrees]C (12) is approximately three orders of magnitude larger than the D value for TPG/glycerol diffusion in Region III (Table 2).
Estimation of the effective self-diffusion tensor from the NMR spin echo.
35]CI NMR Studies of the Interactions of Sodium and Chloride Ions with Meat Products; NMR Studies of Complex Foods in Off-line and Online Situations; Determination of Water Self-Diffusion Behaviour in Microorganisms by using PFG-NMR.
Laloe, Resonance magnetique en champ de radiofrequence inhomogene, II: Verifications experimetales; mesure du coefficient de self-diffusion de [He.