几种碘化银焰剂成冰性能检测

Examination and Analysis of Ice Nucleating Properties of Several AgI Pyrotechnic Nucleants

碘化银焰剂是人工影响天气作业中重要的冷云催化剂,目前国内使用的碘化银焰剂有多种配方,有必要对它们的成冰性能进行统一评估。本研究采用1m^3等温云室,对我国人影作业中使用的7种碘化银焰剂(编号为1~7号)进行了统一检测。结果表明:7种焰剂成核率的量级按每克催化剂计算在10^(10)~10^(13)g^(-1)(-8^-18℃)之间,用指数函数拟合能较好地反映成核率随温度的变化;在低温段(≤-16℃),各焰剂成核率较高,不同焰剂之间的成核率差异相对于高温段(>-16℃)要小;在高温段,3、4、7号焰剂也具有较高的成核率,成冰性能要好于其他焰剂;7种焰剂的核化速率不同,-8℃时90%的冰核完成核化的时间在7.8~18min之间,推断该温度下的成核机制以接触核化等慢过程为主。

AgI pyrotechnic nucleants are important seeding agents used in cold cloud seeding operation of weather modification.Currently,several kinds of AgI pyrotechnic nucleants are being used in weather modification operation in China,and their differences in ice nucleating properties need to be evaluated through the uniform test method.In this study,seven kinds of AgI pyrotechnic nucleants,numbered from1 to 7,were tested in an 1-m^3 isothermal cloud chamber,and their ice nucleating properties including ice nucleation effectiveness and nucleation rate are compared.The results show that the orders of the ice nuclei numbers calculated by the pyrotechnic nucleant per a gram are in the range of 10^10（-8 ℃）to 10^13（-18 ℃）,and the variation of ice nucleation effectiveness versus temperature can be expressed reasonably by the exponential function.In the low temperature section（≤-16 ℃）,high ice nucleation effectiveness can be achieved by various AgI pyrotechnic nucleants.The differences in nucleation effectiveness among those AgI pyrotechnic nucleants in low temperature section are smaller than those in high temperature section（-16 ℃）.In the high temperature section,No.3,No.4 and No.7 samples of pyrotechnic nucleants show higher ice nucleation effectiveness than other four pyrotechnic nucleants.The nucleation rates of all pyrotechnic nucleants are also not the same.The time of 90% AgI ice nuclei grown into ice crystals are in the range of 7.8 to 18 minutes for various pyrotechnic nucleants when the temperature is at-8 ℃,and the slow nucleation processes such as contact-freezing nucleation may be the main nucleation mechanism of AgI ice nuclei produced by all AgI pyrotechnic nucleants at this temperature.