Impeding effect of air bubbles on normal grain growth of ice

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• 作者：Nobuhiko Azuma ; Tutomu Miyakoshi ; Syuhei Yokoyama ; Morimasa Takata
• 关键词：Ice ; Normal grain growth ; Grain boundary migration ; Grain boundary diffusion ; Polar ice ; Zener pinning
• 刊名：Journal of Structural Geology
• 出版年：2012
• 出版时间：September, 2012
• 年：2012
• 卷：42
• 期：Complete
• 页码：184-193
• 全文大小：975 K

文摘

Normal grain growth experiments were performed using polycrystalline ice samples with and without air bubbles. The bubble-free polycrystalline ice was prepared by a special sample preparation technique that employed a phase change method. The ice samples with air bubbles were prepared from a mixture of ice powder and pure distilled water using conventional methods. The temperature dependencies of the rate of grain growth were measured in artificial polycrystalline ice samples with and without air bubbles. The average grain growth exponent n of the ice with bubbles was much greater than the theoretical value of 2, while that of bubble-free ice was close to 2. The activation energy for the grain boundary migration of bubble-free ice was 110-120?kJ?mol^?1, whereas that of the ice with bubbles was between 40 and 70?kJ?mol^?1. The observation of the microscopic images of samples and analyses of the evolution of bubble size distribution and location during grain growth revealed that small air bubbles are caught and swept by moving grain boundaries and a coalescence of bubbles occurs. This indicates that the slow grain boundary migration of ice with bubbles is controlled by the migration of air bubbles dragged by grain boundary migration.