Vitrification (Template:Etymology, via French Template:Wikt-lang) is the full or partial transformation of a substance into a glass,<ref>Template:Cite book</ref> that is to say, a non-crystalline or amorphous solid. Glasses differ from liquids structurally and glasses possess a higher degree of connectivity with the same Hausdorff dimensionality of bonds as crystals: dimH = 3.<ref>Template:Cite book</ref> In the production of ceramics, vitrification is responsible for their impermeability to water.<ref name = doddmurfin>Template:Cite book</ref>
Vitrification is usually achieved by heating materials until they liquify, then cooling the liquid, often rapidly, so that it passes through the glass transition to form a glassy solid. Certain chemical reactions also result in glasses.
In terms of chemistry, vitrification is characteristic for amorphous materials or disordered systems and occurs when bonding between elementary particles (atoms, molecules, forming blocks) becomes higher than a certain threshold value.<ref>Template:Cite journal</ref> Thermal fluctuations break the bonds; therefore, the lower the temperature, the higher the degree of connectivity. Because of that, amorphous materials have a characteristic threshold temperature termed glass transition temperature (Tg): below Tg amorphous materials are glassy whereas above Tg they are molten.
The most common applications are in the making of pottery, glass, and some types of food, but there are many others, such as the vitrification of an antifreeze-like liquid in cryopreservation.
In a different sense of the word, the embedding of material inside a glassy matrix is also called vitrification. An important application is the vitrification of radioactive waste to obtain a substance that is thought to be safer and more stable for disposal.
One study suggests<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> that, during the eruption of Mount Vesuvius in 79 AD, a victim's brain was vitrified by the extreme heat of the volcanic ash; however, this has been strenuously disputed.<ref>Template:Cite journal</ref>
CeramicsEdit
Vitrification is the progressive partial fusion of a clay, or of a body, as a result of a firing process. As vitrification proceeds, the proportion of glassy bond increases and the apparent porosity of the fired product becomes progressively lower.<ref name = doddmurfin/><ref>'Role Of Accessory Minerals On The Vitrification Of Whiteware Compositions.' N.M.Ghoneim; E.H.Sallam; D.M. Ebrahim. Ceram.Int. 16. No.1. 1990.</ref> Vitreous bodies have open porosity, and may be either opaque or translucent. In this context, "zero porosity" may be defined as less than 1% water absorption. However, various standard procedures define the conditions of water absorption.<ref>Whitewares: Production, Testing and Quality Control. William Ryan & Charles Radford. Institute of Materials, 1997</ref><ref>'Methods Of Extending The Narrow Vitrification Range Of Clays.' E.V. Glass & Ceramics 36, (8), 450, 1979.</ref><ref>'Control Of Optimum Vitrification In Vitreous And Porcelain Bodies.' E.Signorini. Ceram.Inf. 26. No.301. 1991</ref> An example is by ASTM, who state "The term vitreous generally signifies less than 0.5% absorption, except for floor and wall tile and low-voltage electrical insulators, which are considered vitreous up to 3% water absorption."<ref>ASTM C242-01. 'Standard Terminology Of Ceramic Whitewares and Related Products'.</ref>
Pottery can be made impermeable to water by glazing or by vitrification. Porcelain, bone china, and sanitaryware are examples of vitrified pottery, and are impermeable even without glaze. Stoneware may be vitrified or semi-vitrified; the latter type would not be impermeable without glaze.<ref>'Body Builders.' J.Ahmed. Asian Ceramics. June 2014 Template:Full citation needed</ref><ref name = doddmurfin/><ref>'An Introduction To The Technology Of Pottery.' Paul Rado, Institute of Ceramics. 1988.</ref>
ApplicationsEdit
When sucrose is cooled slowly it results in crystal sugar (or rock candy), but when cooled rapidly it can form syrupy cotton candy (candyfloss).
Vitrification can also occur in a liquid such as water, usually through very rapid cooling or the introduction of agents that suppress the formation of ice crystals. This is in contrast to ordinary freezing which results in ice crystal formation. Vitrification is used in cryo-electron microscopy to cool samples so quickly that they can be imaged with an electron microscope without damage.<ref name="Vitrification of pure water for electron microscopy">Template:Cite journal</ref><ref name="Cryo-EM-the first thirty years">Template:Cite journal</ref> In 2017, the Nobel prize for chemistry was awarded for the development of this technology, which can be used to image objects such as proteins or virus particles.<ref name="NewYorkTimes 2017 Nobel">Template:Cite news</ref>
Ordinary soda-lime glass, used in windows and drinking containers, is created by the addition of sodium carbonate and lime (calcium oxide) to silicon dioxide. Without these additives, silicon dioxide would require very high temperature to obtain a melt, and subsequently (with slow cooling) a glass.
Vitrification is used in disposal and long-term storage of nuclear waste or other hazardous wastes<ref>Template:Cite journal</ref> in a method called geomelting. Waste is mixed with glass-forming chemicals in a furnace to form molten glass that then solidifies in canisters, thereby immobilizing the waste. The final waste form resembles obsidian and is a non-leaching, durable material that effectively traps the waste inside. It is widely assumed that such waste can be stored for relatively long periods in this form without concern for air or groundwater contamination. 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."<ref name="Waste">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Vitrification in cryopreservationEdit
Vitrification in cryopreservation is used to preserve, for example, human egg cells (oocytes) (in oocyte cryopreservation) and embryos (in embryo cryopreservation). It prevents ice crystal formation and is a very fast process: -23,000 °C/min.
Currently, 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.
Many woody plants living in polar regions naturally vitrify their cells to survive the cold. Some can survive immersion in liquid nitrogen and liquid helium.<ref>Template:Cite journal</ref> Vitrification can also be used to preserve endangered plant species and their seeds. For example, recalcitrant seeds are considered hard to preserve. Plant vitrification solution (PVS), one of application of vitrification, has successfully preserved Nymphaea caerulea seeds.<ref name=":0">Template:Cite book</ref>
Additives used in cryobiology or produced naturally by organisms living in polar regions are called cryoprotectants.
| Formula | Tg (Mid, °C) |
| 1M sucrose | -30.9 |
| 1M glucose | -41.3 |
| 1M trehalose | -68.0 |
| 50% sucrose + 50% glycerol (PVS3) | -90.7 |
| 50% sucrose + 50% EG | -101.1 |
| 50% sucrose + 50% PG | -89.1 |
| 75% sucrose + 25% glycerol | -81.2 |
| 75% sucrose + 25% EG | -80.7 |
| 75% sucrose + 25% PG | -63.6 |
| 25% sucrose + 75% glycerol | -91.3 |
| 25% sucrose + 75% EG | -108.9 |
| 25% sucrose + 75% PG | -98.0 |
See alsoEdit
LiteratureEdit
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- Stefan Lovgren, "Corpses Frozen for Future Rebirth by Arizona Company", March 2005, National Geographic