Supercooling
Supercooling,
Explanation
A liquid crossing its standard freezing point will
Homogeneous nucleation can occur above the
Water normally freezes at 273.15 K (0.0 °C; 32 °F), but it can be "supercooled" at
Droplets of supercooled water often exist in stratus and cumulus clouds. An aircraft flying through such a cloud sees an abrupt crystallization of these droplets, which can result in the formation of ice on the aircraft's wings or blockage of its instruments and probes, unless the aircraft is equipped with an appropriate ice protection system. Freezing rain is also caused by supercooled droplets.
The process opposite to supercooling, the melting of a solid above the freezing point, is much more difficult, and a solid will almost always melt at the same temperature for a given
Supercooling should not be confused with
Constitutional supercooling
Constitutional supercooling, which occurs during solidification, is due to compositional solid changes, and results in cooling a liquid below the freezing point ahead of the solid–liquid interface. When solidifying a liquid, the interface is often unstable, and the velocity of the solid–liquid interface must be small in order to avoid constitutional supercooling.
Constitutional supercooling is observed when the
The liquidus slope from the binary phase diagram is given by , so the constitutional supercooling criterion for a binary alloy can be written in terms of the concentration gradient at the interface:
The concentration gradient ahead of a planar interface is given by
where is the interface velocity, the
For the steady-state growth of a planar interface, the composition of the solid is equal to the nominal alloy composition, , and the partition coefficient, , can be assumed constant. Therefore, the minimum thermal gradient necessary to create a stable solid front is given by
For more information, see Chapter 3 of[9]
In animals
In order to survive extreme low temperatures in certain environments, some animals use the phenomenon of supercooling that allow them to remain unfrozen and avoid cell damage and death. There are many techniques that aid in maintaining a liquid state, such as the production of antifreeze proteins, or AFPs, which bind to ice crystals to prevent water molecules from binding and spreading the growth of ice.[10] The winter flounder is one such fish that utilizes these proteins to survive in its frigid environment. The liver secretes noncolligative proteins into the bloodstream.[11] Other animals use colligative antifreezes, which increases the concentration of solutes in their bodily fluids, thus lowering their freezing point. Fish that rely on supercooling for survival must also live well below the water surface, because if they came into contact with ice nuclei they would freeze immediately. Animals that undergo supercooling to survive must also remove ice-nucleating agents from their bodies because they act as a starting point for freezing. Supercooling is also a common feature in some insect, reptile, and other ectotherm species. The potato cyst nematode larva (Globodera rostochiensis) could survive inside their cysts in a supercooled state to temperatures as low as −38 °C (−36 °F), even with the cyst encased in ice.
As an animal gets farther and farther below its melting point the chance of spontaneous freezing increases dramatically for its internal fluids, as this is a thermodynamically unstable state. The fluids eventually reach the supercooling point, which is the temperature at which the supercooled solution freezes spontaneously due to being so far below its normal freezing point.[12] Animals unintentionally undergo supercooling and are only able to decrease the odds of freezing once supercooled. Even though supercooling is essential for survival, there are many risks associated with it.
In plants
Plants can also survive extreme cold conditions brought forth during the winter months. Many plant species located in northern climates can acclimate under these cold conditions by supercooling, thus these plants survive temperatures as low as −40 °C (−40 °F).
Supercooling inhibits the formation of ice within the tissue by ice nucleation and allows the cells to maintain water in a liquid state and further allows the water within the cell to stay separate from extracellular ice.
In seawater
The presence of salt in seawater affects the freezing point. For that reason, it is possible for seawater to remain in the liquid state at temperatures below melting point. This is "pseudo-supercooling" because the phenomenon is the result of freezing point lowering caused by the presence of salt, not supercooling. This condition is most commonly observed in the oceans around
Applications
One commercial application of supercooling is in
Supercooling was successfully applied to organ preservation at Massachusetts General Hospital/Harvard Medical School. Livers that were later transplanted into recipient animals were preserved by supercooling for up to 4 days, quadrupling the limits of what could be achieved by conventional liver preservation methods. The livers were supercooled to a temperature of −6 °C (21 °F) in a specialized solution that protected against freezing and injury from the cold temperature.[25]
Another potential application is drug delivery. In 2015, researchers crystallized membranes at a specific time. Liquid-encapsulated drugs could be delivered to the site and, with a slight environmental change, the liquid rapidly changes into a crystalline form that releases the drug.[26]
In 2016, a team at Iowa State University proposed a method for "soldering without heat" by using encapsulated droplets of supercooled liquid metal to repair heat sensitive electronic devices.[27][28] In 2019, the same team demonstrated the use of undercooled metal to print solid metallic interconnects on surfaces ranging from polar (paper and Jello) to superhydrophobic (rose petals), with all the surfaces being lower modulus than the metal.[29][30]
Eftekhari et al. proposed an empirical theory explaining that supercooling of ionic liquid crystals can build ordered channels for diffusion for energy storage applications. In this case, the electrolyte has a rigid structure comparable to a solid electrolyte, but the diffusion coefficient can be as large as in liquid electrolytes. Supercooling increases the medium viscosity but keeps the directional channels open for diffusion.[31]
See also
References
- PMID 31427698.
- ^ Rathz, Tom. "Undercooling". NASA. Archived from the original on 2009-12-02. Retrieved 2010-01-12.
- ^ Science Mission Directorate (April 23, 2001). "Look Ma — No Hands!: What is "Undercooling"?". NASA Science. Retrieved 13 April 2023.
- ^ "Water freezing almost instantaneously when shaking a bottle that spend the night outside during a frosty night". 2021-04-07. Retrieved 2021-04-08.
- S2CID 1784703.
- ^ .
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- ^ . Retrieved 11 December 2016.
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- ^ PMID 25520725.
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- ^ Chill Chamber Archived March 1, 2009, at the Wayback Machine
- ^ Slush-It! Archived 2010-01-23 at the Wayback Machine
- ^ Charlie Sorrel (2007-09-21). "Coca Cola Plans High Tech, Super Cool Sprite". Wired. Condé Nast. Retrieved 2013-12-05.
- PMID 24973919.
- ^ Hunka, George (2015-05-06). "A "super cool" way to deliver drugs". R&D.
- ^ Mitch Jacoby (2016-03-14). "Soldering without heat". Chemical and Engineering News. Retrieved 2016-03-14.
- PMID 26902483.
- ^ Mitch Jacoby (2019-07-23). "Heat-free method yields printed metallic circuit connections". Chemical and Engineering News. Retrieved 2019-07-24.
- S2CID 199076266.
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Further reading
- Giovambattista, N.; Angell, C. A.; Sciortino, F.; Stanley, H. E. (July 2004). "Glass-Transition Temperature of Water: A Simulation Study" (PDF). Physical Review Letters. 93 (4): 047801. S2CID 8311857.
- Rogerson, M. A.; Cardoso, S. S. S. (April 2004). "Solidification in heat packs: III. Metallic trigger". AIChE Journal. 49 (2): 522–529. doi:10.1002/aic.690490222. Archived from the originalon 2012-12-09.
External links
- Supercooled water and coke on YouTube
- Supercooled water on YouTube
- Super Cooled Water #2 on YouTube
- Supercooled Water Nucleation Experiments on YouTube
- Supercooled liquids on arxiv.org
- Radiolab podcast on supercooling