氷単結晶中の自己拡散に対する転位密度の影響

概要

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The self-diffusion in deformed single crystals of Mendenhall ice was investigated by the tritium tracer sectioning method. Since the penetration curves bent concave upward (Fig. 5), it was concluded that the normal method of deriving diffusion coefficient D from the curves was not adequate for deformed specimens. A new method of successive approximation for calculating D from the residual surface activity of each specimen was developed (Fig. 7). This method gave successful results which indicated approximately 5 times enhancement of self-diffusion when the dislocation density increased from 105cm-2 to 6 × 106cm-2. Invariability of activation energy of D for both deformed and undeformed specimens indicates that the enhancement occurs only in pre-exponential term Do. Mechanism of enhancement is interpreted by the lowering of elastic energy required for the lattice around a saddle point when free interstitials diffuse through screw dislocatilons on the basal plane of ice crystal. This lowering causes the increase of entropy S of activated complexes involved and eventually the increase of Do. This interpretation is also favorable for the existence of anisotropy of D in ice crystal.
社団法人日本雪氷学会の論文