For the first time, Chinese scientists have confirmed the existence of “critical ice cores” in the process of water icing, and have given the relationship between the size of the “critical ice core” and the temperature of the overcooling, thus confirming the prediction of the “classic nuclear theory”. The results of the research were published online in the internationally renowned academic journal Nature on the 19th.
The phenomenon of cold water freezing can not be more common, but the micro-level “water ice” the specific process is not known. Nearly a hundred years ago, based on the principle of thermodynamics, scientistgibbs and others put forward the “classic nuclear theory” of phase change, that such as water ice change needs to go through a nuclear process, water too cold to form a xiaobing core, only when the formation of the ice core accidentally exceeds the critical size (i.e., “critical ice core”) can occur spontaneously.
However, due to the chance, momentary (nanosecond level) and microscopic (nanolevel) of the “critical ice core”, microscopic detection is extremely difficult. Over the decades, the development of micro-detection technology has confirmed many inferences about “classic nuclear theory”, but researchers have been unable to give direct experimental evidence about the existence of the core concept of nuclear theory, “critical nuclei”.
This time, Wang Jianjun of the Institute of Chemistry of the Chinese Academy of Sciences and Zhou Wei of the University of The Chinese Academy of Sciences creatively used a series of fixed-size nanoparticles to detect “critical ice cores”, and the experimental combination of theoretical calculations, concisely and clearly obtained the size of the “critical ice core”.
“This experiment can be understood as using the size of nanoparticles as a ruler to measure the ‘critical ice core’: continuously lowering the temperature to achieve the critical size of the ice core, when this size is exactly the same as the size of the nanoparticle, the ‘critical ice core’ is easy to form and causes the macro ice crystaltobes to occur rapidly and thus be detected.” Wang Jianjun said.
According to the introduction, the research of this topic deepens the understanding of the micro-mechanism of the important phase change phenomenon of water ice, and also provides important theoretical guidance for the realization of artificial ice control application, such as regulating the formation and growth of ice crystals, improving the recovery efficiency of cryopreservation such as cell tissue, improving the preservation of food production and refrigeration, etc., will be in the chemical industry, cryogenic biology, Materials science plays a vital role in other fields.
Further research shows that the conclusion of the research is universal and can be used as a universal method to study other phases into nuclear problems.