FUNDAMENTAL RESEARCH ON FREEZING OF SUPERCOOLED WATER WITH HETEROGENEOUS NUCLEATING SUBSTANCE

对非均相成核物质冻结过冷水的基础研究进行了实验和分析研究，得到了以下结果：(1)研究了固体颗粒对过冷水冻结的影响。选择碘化银作为固体颗粒，制备了几种类型的污染物。颗粒大小和表面润湿性分别为三种和两种。颗粒的数量也不同。将样品水放入试管中，以恒定的冷却速度冷却，直至水凝固。研究了冷冻过冷度与各变量之间的关系。然后介绍了预测结果的解析方法。结果与实验结果吻合较好。因此，可以得出结论，冻结温度与固体颗粒的大小和数量无关，而是由暴露在水中的总面积决定的。(2)用分子动力学方法研究了水的非均相成核。将具有fcc（111）表面的固体放置在由864个水分子组成的细胞底部。采用ST2模型。水与固体的相互作用基于Spohr提出的方程。结果表明，在平面情况下，只有一层水分子被吸附，而将表面改为三点表面时，则发生了冰核。改变施波尔相互作用，使水的偶极矩变为非铁电态，进一步促进了冰的生长。研究了固体晶格常数对成核的影响。

Fundamental research on freezing of supercooed water with heterogeneous nucleating substance was investigated experimentally and analytically, and the following results were obtained.(1) The effect of solid particles on the freezing of the supercooled water was investigated. Silver iodide was selected as the solid particle, and several types of contaminants were prepared. The size of the particle and wet-ability of the surface were varied to three, and to two types, respectively. The amount of the particle was also varied. The sample water was put into a test tube and cooled at a constant cooling rate until the water solidified. The relationship between the degree of supercooling at freezing and various variables were investigated. Then, analytical method to predict the results was introduced. It was found that the results agreed quite well with the experiments. Hence, it was concluded that the freezing temperature does not depend upon the size of the solid particle nor its amount, but is decided by the total area exposed to the water.(2) Heterogeneous nucleation of water was investigated using Molecular Dynamics method. Solid with fcc (111) surface was placed at the bottom of a cell consisting of 864 water molecules. ST2 model was used. The interaction between water and the solid were based on the equations proposed by Spohr. It was found that the only one layer of water molecules was adsorbed in a case of flat surface, whereas ice nucleation occurred by changing the surface to 3-point surface. Modifying the Spohr interaction so that the dipole moment of water becomes unti-ferroelectric increased the ice growth further. The effect of lattice constant of solid on nucleation was also investigated.