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Divergence vacancies

Above 570°C, a distinct break occurs in the Arrhenius plot for iron, corresponding to the appearance of FeO in the scale. The Arrhenius plot is then non-linear at higher temperatures. This curvature is due to the wide stoichiometry limits of FeO limits which diverge progressively with increasing temperature. Diffraction studies have shown that complex clusters of vacancies exist in Fe, , 0 Such defect clustering is more prevalent in oxides... [Pg.968]

The flux is increased by a factor of 2 due to the freedom of the vacancy diffusion flux to diverge initially, thereby providing additional available area. [Pg.496]

The simplest and classical treatment of the Kirkendall effect in binary homogeneous systems assumes that the differences between the intrinsic diffusion fluxes of the two substitutional constituents are compensated by the action of local vacancy sinks and sources that maintains the system in local equilibrium, i.e. in states that can be completely defined by the knowledge of appropriate state variables to permit the calculation of pertinent state functions such as, for example, the chemical potential of system constituents. The drift of lattice planes is one important characteristic of the Kirkendall effect in stress-free homogeneous systems and is a consequence of the action of these vacancy sources and/or sinks distributed along the diffusion zone. As the system remains in local equilibrium by the action of vacancy sinks and sources, the vacancy concentration or molar fraction remains constant and equal to its equilibrium value within the entire diffusion couple. Therefore, no effective gradient of vacancy concentration is established in the diffusion zone. However, the local action of vacancy sinks or sources along the diffusion direction is formally equivalent to a vacancy flux Jy related to the required local density of vacancy sources or sinks ps equal to the flux divergence,... [Pg.11]


See other pages where Divergence vacancies is mentioned: [Pg.181]    [Pg.522]    [Pg.270]    [Pg.234]    [Pg.358]    [Pg.128]    [Pg.221]    [Pg.342]    [Pg.197]    [Pg.8]    [Pg.174]    [Pg.175]    [Pg.178]    [Pg.189]    [Pg.59]    [Pg.7]    [Pg.107]    [Pg.269]   
See also in sourсe #XX -- [ Pg.20 ]




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