Research Center for Advanced Measurement and Characterization, National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan.
J Chem Phys. 2020 Apr 14;152(14):144501. doi: 10.1063/5.0003787.
When a dilute aqueous solution freezes at 1 atm, it is segregated into water-rich ice Ih and solute-rich freeze-concentrated glassy solution. A similar segregation is observed at the crystallization of homogeneous glassy aqueous solutions by heating. The influence of solutes on the nucleation of solvent water and the solute discharge process from the crystalline ice are not clear. In this study, I made a homogeneous dilute glassy glycerol aqueous solution (0.07 mol fraction) using pressure liquid cooling vitrification (PLCV), measured the specific volume and the sample temperature during the compression and decompression processes, and examined the polyamorphic and crystallization behaviors. It is found that the sample crystallized slightly above the crystallization temperature is amorphized homogeneously under pressure, and that the amorphized sample is equivalent to the homogeneous glassy sample made by PLCV. This indicates that glycerol solutes in the crystalline sample are dispersed homogeneously and the crystalline sample does not segregate. These experimental results suggest that nucleation does not involve segregation and that crystal growth induces segregation. The discovery of the non-segregated crystalline state has an implication in not only the understanding of crystallization of glassy ice in meteorology and planetary physics but also the application to cell thawing techniques in cryobiology and food engineering.
当稀水溶液在 1 大气压下冷冻时，它会分离成富含水的冰 Ih 和溶质丰富的冷冻浓缩玻璃态溶液。在通过加热使均相玻璃态水溶液结晶时，也会观察到类似的分离。溶质对溶剂水成核和结晶冰中溶质排出过程的影响尚不清楚。在这项研究中，我使用压力液体冷却玻璃化（PLCV）制备了均相稀甘油水溶液（0.07 摩尔分数），在压缩和解压过程中测量了比容和样品温度，并研究了多晶型和结晶行为。结果发现，在结晶温度以上稍微结晶的样品在压力下均匀地非晶化，并且非晶化样品与通过 PLCV 制备的均相玻璃态样品等效。这表明结晶样品中的甘油溶质均匀分散，结晶样品没有分离。这些实验结果表明，成核不涉及分离，而晶体生长诱导分离。非分离晶态的发现不仅对气象学和行星物理学中玻璃冰结晶的理解具有意义，而且对细胞解冻技术在低温生物学和食品工程中的应用也具有意义。
