Vitrification is a process of converting a material into a
glass-like amorphous solidthat is free from any crystalline structure, either by the quick removal or addition of heat, or by mixing with an additive. Solidification of a vitreoussolid occurs at the glass transition temperature(which is lower than melting temperature, "T"m, due to supercooling).
When the starting material is solid, vitrification usually involves heating the substances to very high
temperatures. Many ceramics are produced in such a manner. Vitrification may also occur naturally when lightningstrikes sand, where the extreme and immediate heat can create hollow, branching rootlike structures of glass, called fulgurite. When applied to whiteware ceramics, vitreous means the material has an extremely low permeability to liquids, often but not always water, when determined by a specified test regime. The microstructure of whiteware ceramics frequently contain both amorphousand crystalline phases.
sucroseis cooled slowly, the result is crystal sugar(or rock candy), but, when cooled rapidly, the result can be in the form of syrupy cotton candy(candyfloss). Vitrification can also occur when starting with a liquid such as water, usually through very rapid cooling or the introduction of agents that suppress the formation of icecrystals. Additives used in cryobiologyor produced naturally by organisms living in polar regions are called cryoprotectants. Arctic frogs and some other ectotherms naturally produce glycerolor glucosein their livers to reduce ice formation. When glucose is used as a cryoprotectant by Arctic frogs, massive amounts of glucose are released at low temperature [cite journal | author=Jack R. Layne, Jr., Richard E. Lee, Jr. | title=Adaptations of frogs to survive freezing | journal=Climate Research | volume=5 | year=1995 | pages=53–59 |url=http://www.int-res.com/articles/cr/5/c005p053.pdf | doi=10.3354/cr005053] , and a special form of insulinallows for this extra glucose to enter the cells. When the frog rewarms during spring, the extra glucose must be rapidly removed from the cells and recycled via renal excretion and storage in the bladder. Arctic insects also use sugars as cryoprotectants. Arctic fish use antifreeze proteins, sometimes appended with sugars, as cryoprotectants.
glass, used in windows and tableware, is created by the addition of sodium carbonateand lime ( calcium oxide) to silicon dioxide. Without these additives, silicon dioxide will (with slow cooling) form sandor quartzcrystal, not glass.
Vitrification is a proven technique in the disposal and long-term storage of
nuclear wasteor other hazardous wastes [M. I. Ojovan, W.E. Lee. "An Introduction to Nuclear Waste Immobilisation", Elsevier, Amsterdam, 315pp. (2005) ] . Waste is mixed with glass-forming chemicals to form molten glass that then solidifies, immobilizing the waste. The final waste form resembles obsidianand is a non- leaching, durable material that effectively traps the waste inside. The waste can be stored for relatively long periods in this form without concern for air or groundwatercontamination. Bulk vitrification uses electrodes to melt soil and wastes where they lie buried. The hardened waste may then be disinterred with less danger of widespread contamination. According to the Pacific Northwest National Labs, "Vitrification locks dangerous materials into a stable glass form that will last for thousands of years."cite web | title = Waste Form Release Calculations for the 2005 Integrated Disposal Facility Performance Assessment | work = PNNL-15198 | publisher = Pacific Northwest National Laboratory | date = July, 2005 | format =
accessdate = 2006-11-08 ]
Ethylene glycolis used as automotive antifreezeand propylene glycolhas been used to reduce ice crystals in ice cream, making it smoother.
glycerolhas been used in cryobiologyas a cryoprotectant for blood cells and bull sperm, allowing storage at liquid nitrogentemperatures. However, glycerol cannot be used to protect whole organs from damage. Instead, many biotechnology companies are currently researching the development of other cryoprotectants more suitable for such uses. A successful discovery may eventually make possible the bulk cryogenic storage (or "banking") of transplantable human and xenobioticorgans. A substantial step in that direction has already occurred. At the July 2005 annual conference of the Society for Cryobiologycite web | title = Plenary Session: Fundamentals of Biopreservation | work = CRYO 2005 Scientific Program | publisher = Society for Cryobiology | date = Sunday, July 24, 2005 | url=http://www.me.umn.edu/events/cryo2005/program.html
accessdate = 2006-11-08 ] ,
Twenty-First Century Medicineannounced the vitrification of a rabbit kidneyto -135°C with their proprietary vitrification cocktail. Upon rewarming, the kidney was successfully transplanted into a rabbit, with complete functionality and viability.
In the context of
cryonics, especially in preservation of the human brain, vitrification of tissue is thought to be necessary to prevent destruction of the tissue or information encoded in the brain. At present, vitrification techniques have only been applied to brains ( neurovitrification) by Alcor and to the upper body by the Cryonics Institute, but research is in progress by both organizations to apply vitrification to the whole body.
*Steven Ashle, "Divide and Vitrify," June 2002, Scientific American
*Stefan Lovgren, "Corpses Frozen for Future Rebirth by Arizona Company," March 2005, National Geographic
*Vitrification: Putting the Heat on Waste
List of emerging technologies
*Radioactive waste vitrification
* [http://www.benbest.com/cryonics/vitrify.html Vitrification in Cryonics]
* [http://www.21cm.com/abstract.jsp?AID=62&SPub=&STitle=&SAuthor=&SDateStart=mm%2Fyyyy&SDateStop=mm%2Fyyyy&STopic=&SKeywords=&Page=1 CRYOBIOLOGY 48(1):22-35 (2004)]
* [http://regionalaffairs.pnl.gov/seminars/speakers/sundaram.stm Vitrification: Putting the Heat on Waste]
* [http://eprints.iisc.ernet.in/archive/00000257/01/kjrao.pdf Fragility thy name is glass]
* [http://www.public.asu.edu/~caangell/Abstracts/395.pdf Liquid fragility and the glass transition in water and aqueous solutions]
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