抄録
In order to clarify the effect of bubble nuclei on freezing of supercooled water, various kinds of experiments were carried out with invisible sizes of bubbles in supercooled water. Each sample waters was kept in a test tube and cooled down at a constant cooling rate until the water solidified. Then, the degree of supercooling at freezing was measured. Two kinds of water surfaces were applied. One is the surface exposed to the atmosphere, and the other is covered with silicone oil. Three kinds of pressure condition were applied. The first type is the one kept at the atmospheric pressure. The second type is compressed up to 6.0 atm. And the third type is vacuumed down to 0.02 atm. Two kinds of holding time periods before starting the experiments were applied. One is zero and the other is 24 hours. It was found that degree of supercooling at freezing is high in the case of free surface compared to the one with oil-water surface. The reason was suggested that the bubbles in the water can be released from the surface in the case of free surface and trapped at the oil-water interface in the case of water covered with oil. It was also found that the degree of supercooling at freezing becomes high even in the case f water covered with oil, if the sample is under compression. The reason was suggested that the bubble nuclei at the oil-water interface were dissolved due to compression if the holding time exceeds a certain time period. Hence, it was clarified that the bubble nuclei has an effect on the freezing of supercooled water, and controlling the existence of bubble nuclei nuclei leads to control the freezing of supercooled water.
