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Atomic diffusion in polycrystalline materials is therefore often modeled using an effective diffusion coefficient, which is a combination of lattice, and grain boundary diffusion coefficients. In general, surface diffusion occurs much faster than grain boundary diffusion , and grain boundary diffusion occurs much faster than lattice diffusion .
Surface diffusion, also referred to as atomic diffusion, describes the process along the surface interface, when atoms move from surface to surface to free energy. The grain boundary diffusion terms the free migration of atoms in free atomic lattice spaces. This is based on polycrystalline layers and its boundaries of incomplete matching of the ...
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A diffusionless transformation, commonly known as displacive transformation, denotes solid-state alterations in crystal structures that do not hinge on the diffusion of atoms across extensive distances. Rather, these transformations manifest as a result of synchronized shifts in atomic positions, wherein atoms undergo displacements of distances ...
The Kirkendall effect is the motion of the interface between two metals that occurs due to the difference in diffusion rates of the metal atoms. The effect can be observed, for example, by placing insoluble markers at the interface between a pure metal and an alloy containing that metal, and heating to a temperature where atomic diffusion is reasonable for the given timescale; the boundary ...
Each atomic species can be given its own intrinsic diffusion coefficient ~ and ~, expressing the diffusion of a certain species in the whole system. The interdiffusion coefficient D ~ {\displaystyle {\tilde {D}}} is defined by the Darken's equation as:
This splitting is called fine structure. The splitting is larger for atoms with higher atomic number. The splitting decreases towards the series limit. Another splitting occurs on the redder line of the doublet. This is because of splitting in the D level and . Splitting in the D level has a lesser amount than the P level, and it reduces as the ...
In crystals, atomic diffusion typically consists of jumps between vacant lattice sites. On time and length scales that average over many single jumps, the net motion of the jumping atoms can be described as regular diffusion. Jump diffusion can be studied on a microscopic scale by inelastic neutron scattering and by Mößbauer spectroscopy.