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From Wikipedia, the free encyclopedia

A vitrification experiment, using molten glass.
A vitrification experiment, using molten glass.

Vitrification (from Latin vitreum, "glass" via French vitrifier) is the transformation of a substance into a glass,[1] that is to say, a non-crystalline amorphous solid. In the production of ceramics, vitrification is responsible for its impermeability to water.[2]

Vitrification is usually achieved by heating materials until they liquidize, 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.[3] 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 hopefully safer and more stable for disposal.

During the eruption of Mount Vesuvius in 79 C.E. a victim's brain was vitrified by the extreme heat of the volcanic ash.[4][5][6][7]

Ceramics

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.[2][8] 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.[9][10][11] 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."[12]

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.[13][2][14]

Applications

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.[15][16] 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.[17]

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 will 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[18] 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."[19]

Vitrification in cryopreservation

Vitrification in cryopreservation is used to preserve, for example, human egg cells (oocytes) (in oocyte cryopreservation) and embryos (in embryo cryopreservation).

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.[20]

Additives used in cryobiology or produced naturally by organisms living in polar regions are called cryoprotectants.

See also

Literature

  • Steven Ashle (June 2002). "Divide and Vitrify" (PDF). Scientific American. 286 (6): 17–19. Bibcode:2002SciAm.286f..17A. doi:10.1038/scientificamerican0602-17. Retrieved May 10, 2015.
  • Stefan Lovgren, "Corpses Frozen for Future Rebirth by Arizona Company", March 2005, National Geographic

References

  1. ^ Varshneya, A. K. (2006). Fundamentals of Inorganic Glasses. Sheffield: Society of Glass Technology.
  2. ^ a b c Dodd, Arthur; Murfin, David (1994). Dictionary of Ceramics (3rd ed.). London: The Institute of Minerals. ISBN 0901716561.
  3. ^ Ojovan, M. I.; Lee, W. E. (2010). "Connectivity and glass transition in disordered oxide systems". Journal of Non-Crystalline Solids. 356 (44–49): 2534–2540. Bibcode:2010JNCS..356.2534O. doi:10.1016/j.jnoncrysol.2010.05.012.
  4. ^ Pucci, Piero; Niola, Massimo; Baxter, Peter J.; Fontanarosa, Carolina; Giordano, Guido; Graziano, Vincenzo; et al. (2020). "Heat-Induced Brain Vitrification from the Vesuvius Eruption in C.E. 79". The New England Journal of Medicine. 382 (4): 383–384. doi:10.1056/NEJMc1909867. PMID 31971686.
  5. ^ Pucci, Piero; Niola, Massimo; Baxter, Peter J.; Fontanarosa, Carolina; Giordano, Guido; Graziano, Vincenzo; et al. (23 January 2020). "Supplementary Appendix to: Petrone P, Pucci P, Niola M, et al. Heat-induced brain vitrification from the Vesuvius eruption in c.e. 79" (PDF). The New England Journal of Medicine. 382 (4): 383–384. doi:10.1056/NEJMc1909867. PMID 31971686. Retrieved 13 September 2020.
  6. ^ Pinkowski, Jennifer (23 January 2020). "Brains Turned to Glass? Suffocated in Boathouses? Vesuvius Victims Get New Look". The New York Times. Retrieved 13 September 2020.
  7. ^ "Mount Vesuvius eruption: Extreme heat 'turned man's brain to glass'". BBC. BBC News Services. 23 January 2020. Retrieved 24 January 2020.
  8. ^ '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.
  9. ^ Whitewares: Production, Testing and Quality Control. William Ryan & Charles Radford. Institute of Materials, 1997
  10. ^ 'Methods Of Extending The Narrow Vitrification Range Of Clays.' E.V. Glass & Ceramics 36, (8), 450, 1979.
  11. ^ 'Control Of Optimum Vitrification In Vitreous And Porcelain Bodies.' E.Signorini. Ceram.Inf. 26. No.301. 1991
  12. ^ ASTM C242-01. 'Standard Terminology Of Ceramic Whitewares and Related Products'.
  13. ^ 'Body Builders.' J.Ahmed. Asian Ceramics. June 2014[full citation needed]
  14. ^ 'An Introduction To The Technology Of Pottery.' Paul Rado, Institute of Ceramics. 1988.
  15. ^ Dubochet, J.; McDowall, A.W. (December 1981). "Vitrification of pure water for electron microscopy". Journal of Microscopy. 124 (3): 3–4. doi:10.1111/j.1365-2818.1981.tb02483.x.
  16. ^ Dubochet, J. (March 2012). "Cryo-EM-the first thirty years". Journal of Microscopy. 245 (3): 221–224. doi:10.1111/j.1365-2818.2011.03569.x. PMID 22457877. S2CID 30869924.
  17. ^ "Nobel Prize in Chemistry Awarded for Cryo-Electron Microscopy". The New York Times. October 4, 2017. Retrieved 4 October 2017.
  18. ^ Ojovan, Michael I.; Lee, William E. (2011). "Glassy wasteforms for nuclear waste immobilization". Metallurgical and Materials Transactions A. 42 (4): 837–851. Bibcode:2011MMTA...42..837O. doi:10.1007/s11661-010-0525-7.
  19. ^ "Waste Form Release Calculations for the 2005 Integrated Disposal Facility Performance Assessment" (PDF). PNNL-15198. Pacific Northwest National Laboratory. July 2005. Retrieved 2006-11-08.
  20. ^ Strimbeck, GR; Schaberg, PG; Fossdal, CG; Schröder, WP; Kjellsen, TD (2015). "Extreme low temperature tolerance in woody plants". Frontiers in Plant Science. 6: 884. doi:10.3389/fpls.2015.00884. PMC 4609829. PMID 26539202.
This page was last edited on 5 February 2021, at 06:12
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