Self-Diffusion in Single Crystals of Ice
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概要
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There are only two published works on the selfdiffusion in ice. Kuhn and Thurkauf measured self-diffusion in polycrystalline ice at -2℃ only. Riehl and Dengel measured self-diffusion in synthetic single crystals of ice between -10 and -35℃ and obtained 13.5Kcal/mole for the activation energy but they did not pay any attention to the anisotropy of the coefficient of selfdiffusion. The single crystals of ice used in the present study are natural crystals brought from the Mendenhall Glacier, Alaska. The impurity concentrations of the crystals are (4 ± 1)×10^<-8> grams of ionic chlorine per 1 gram of melted water and 2.1±0.15 cc of dissolved O_2 per one gram of solid ice. The ionic impurity content is very low, but the gaseous oxygen concentration is rather high. Specimen was cut into a disc with the end plane parallel to (0001) or (1O10). Tritiated water (specific activity 30 mc/ml) was evaporated on the end surface. Since tritium emits β-rays of only 18KeV, surface activity measured with a gas flow counter indicates the concentration of tritium in a surface layer of only 6μ thick. Surface layers where removed with a microtome and the thickness of the removed layers was measured with a dial gauge. Surface activity was measured at 1Oμ intervals. Penetration curves thus obtained were quite linear. The duration of diffusion annealing in these experiments varied from one to one hundred days. As sbown in Fig. 1 (-10℃), the diffusion constant varies with the diffusion time. The same tendency was also found at -20℃ but it could not be observed at -30℃, because the short diffusion time prevented accurate measurement. The diffusion constant reaches a stable value with an error of ±15% for the diffusion time more than 3 days. The accivation energy and D_0 for self-diffusion derived from the Arrhenius plot for a diffusion time of 7 days in Fig. 2 are 15.7±2Kcal/mole (0.6=0.08eV) and 2.8x1O^2 cm^2/sec respectively.
- 社団法人日本物理学会の論文
- 1964-06-05