Influence of dislocations on diffusion kinetics in solids with particular reference to the alkali halides

Abstract

Preferential diffusion along dislocations may give rise to several limiting types of behaviour, in some of which the kinetics of diffusion remain, on a macroscopic scale, in apparent agreement with Fick's law. The various possible types of behaviour are classified, and the conditions required for each type are discussed in detail, with complete derivations where necessary. The features of each type of diffusion which will appear in different experimental techniques are discussed.Self-diffusion in the alkali halides is discussed in the light of this classification. It is concluded that, for the anions, no simple model of enhanced mobility in a dislocation network (or grain boundaries) is in complete accord with all the known facts. It is suggested that the only reported autoradiographic experiment gives some evidence for a rather long-range effect of large-angle boundaries. By analogy, the external surface may cause abnormal distribution of vacancies throughout the region in which diffusion is usually studied.

Silicon self‐diffusion in wadsleyite: Implications for rheology of the mantle transition zone and subducting plates

“…We always measured the diffusion profiles in areas including a grain boundary. Two segments were recognized in the diffusion profiles, indicating that the diffusion occurred within a type B kinetic regime described by Harrison [1961]. In the region near the sample surface, volume diffusion is the dominant diffusion mechanism, whereas in the deeper region, grain-boundary diffusion is dominant.…”

Study of Grain Boundary Oxidation of High Alloyed Carbon Steels at Coiling Temperature

“…As far as we consider the lateral resolution of SIMS is sufficient to detect silicon concentration gradient around the grain boundary oxidation zones, the SIMS results lead to consider that there is no silicon diffusion from the grains. In the frame of this hypothesis, for Fe-0.2%Si and Fe-0.5%Si the results can be interpreted by Harrisons classification in type C regime diffusion [8] and also through Wagner's model [5] of the diffusion within the grain boundary. According to Wagner's theory, grain boundary oxidation length square (ξ²) is proportional to time, as expressed by Eq.…”

Interdiffusion at Room Temperature in Cu-Ni(Fe) Nanolaminates

“…The present room-temperature Cu-Ni(Fe) result is the data point marked by the largest (solid red) circle in Figure 6. The diffusion coefficient computed at 23 • C rests just below the guideline for grain-boundary diffusion mechanism, and may well represents an extension of the grain-boundary diffusion data [38][39][40][41][42][43] for both Ni and Fe in Cu as well as Ni self-diffusion. The lack of grain growth, i.e., recrystallization, implies that the role of grain-boundary motion induced diffusion [48] is not a significant factor for the nanolaminates of this study whereas the use of grain boundaries and dislocation pipes provide paths for accelerated atomic transport between layers.…”

“…The effect of dislocations on diffusion kinetics in solids can be categorized as well by three basic types [41] of length scale where type-A refers to long diffusion distances, type-B refers to higher temperatures and longer anneal times with a diffusion distance on the order of the scale of the dislocation network, and type-C to lower temperature and shorter times where it can be considered that the diffusion is taking place only in the dislocation network itself. Type-C is considered that for grain boundary diffusion.…”