海氷の亜結晶粒の結晶軸方位差

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書誌事項

タイトル別名
  • Misalignment of crystal axes of subgrains in Antarctic sea ice
  • カイヒョウ ノ アケッショウリュウ ノ ケッショウジク ホウイサ

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説明

Crystal axes of minute subgrains in sea ice grown near Syowa Station, Antarctica were examined by X-ray Laue photographs. Subgrains which usually can not be distinguished by polarized light are bounded by subboundaries accompanied with brine pockets in a crystal grain of the polycrystals of sea ice. The misalignment angles of the crystal axes between adjacent subgrains were deduced from X-ray Laue photographs. Samples from 0.10 m and 0.17 m depths from the surface had the misalignment angles ranged from 0 to 10 degree or more. Those from 1.1 m and 1.5 m depths had the angles less than 7 degrees, and most of them were 0 degree. The average values of the misalignment angles were 7 and 3 degrees with the samples from 0.10 m and 0.17 m depths respectively, and 1 and 1.7 degrees with those from 1.1 m and 1.5 m depths respectively.<BR>Subgrains are formed from cellular growth of ice into the constitutionally supercooled sea water. The misalignment between the adjacent subgrains could be caused by some disturbances associated with the growth of subgrains; intrinsically the thermal expansion force and extrinsically the effects of wave and underwater current.<BR>The misalignment angle decreases with increase of the depth of sea ice partly because of the decrease of disturbances with increasing depth. Essential reason is to reduce the grain boundary energy in ice so that large misalignment angles disappear first, and misalignment angles are almost 0 degree near the bottom of sea ice although there occurs cellular growth.

収録刊行物

  • 雪氷

    雪氷 45 (4), 169-176, 1983

    公益社団法人 日本雪氷学会

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