Visualization of Freezing Process in situ upon Cooling and Warming of Aqueous Solutions
| Autor: | Anatoli Bogdan, Mario J. Molina, Heikki Tenhu, Erminald Bertel, Natalia Bogdan, Thomas Loerting |
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| Přispěvatelé: | Department of Chemistry, Laboratory of Polymer Chemistry (-2016), Department of Physics, Faculty of Medicine, Polymers |
| Jazyk: | angličtina |
| Rok vydání: | 2014 |
| Předmět: | |
| Zdroj: | Scientific reports, vol 4, iss 1 Scientific Reports |
| Popis: | The freezing of aqueous solutions and reciprocal distribution of ice and a freeze-concentrated solution (FCS) are poorly understood in spite of their importance in fields ranging from biotechnology and life sciences to geophysics and climate change. Using an optical cryo-miscroscope and differential scanning calorimetry, we demonstrate that upon cooling of citric acid and sucrose solutions a fast freezing process results in a continuous ice framework (IF) and two freeze-concentrated solution regions of different concentrations, FCS1 and FCS2. The FCS1 is maximally freeze-concentrated and interweaves with IF. The less concentrated FCS2 envelops the entire IF/FCS1. We find that upon further cooling, the FCS1 transforms to glass, whereas the slow freezing of FCS2 continues until it is terminated by a FCS2-glass transition. We observe the resumed slow freezing of FCS2 upon subsequent warming. The net thermal effect of the resumed freezing and a reverse glass-FCS1 transition produces the Ttr2-transition which before has only been observed upon warming of frozen hydrocarbon solutions and which nature has remained misunderstood for decades. |
| Databáze: | OpenAIRE |
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