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Vitrification (, via French ') is the full or partial transformation of a substance into a
glass Glass is an amorphous (non-crystalline solid, non-crystalline) solid. Because it is often transparency and translucency, transparent and chemically inert, glass has found widespread practical, technological, and decorative use in window pane ...
, 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. In the production of ceramics, vitrification is responsible for their impermeability to
water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...
. Vitrification is usually achieved by heating materials until they liquify, then cooling the liquid, often rapidly, so that it passes through the
glass transition The glass–liquid transition, or glass transition, is the gradual and Reversible reaction, reversible transition in amorphous solid, amorphous materials (or in amorphous regions within Crystallinity, semicrystalline materials) from a hard and rel ...
to form a glassy solid. Certain chemical reactions also result in glasses. In terms of
chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...
, vitrification is characteristic for amorphous materials or disordered systems and occurs when bonding between elementary particles (
atoms Atoms are the basic particles of the chemical elements. An atom consists of a nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished from each other ...
,
molecules A molecule is a group of two or more atoms that are held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemistry ...
, forming blocks) becomes higher than a certain threshold value. Thermal fluctuations break the bonds; therefore, the lower the
temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...
, the higher the degree of connectivity. Because of that, amorphous materials have a characteristic threshold temperature termed glass transition temperature (''T''g): below ''T''g amorphous materials are glassy whereas above ''T''g they are molten. The most common applications are in the making of
pottery Pottery is the process and the products of forming vessels and other objects with clay and other raw materials, which are fired at high temperatures to give them a hard and durable form. The place where such wares are made by a ''potter'' is al ...
, 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 that, during the
eruption of Mount Vesuvius in 79 AD In 79 AD, Mount Vesuvius, a stratovolcano located in the modern-day region of Campania, erupted, causing List of volcanic eruptions by death toll, one of the deadliest eruptions in history. Vesuvius violently ejected a Eruption column, cloud of ...
, a victim's
brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...
was vitrified by the extreme heat of the
volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to r ...
; however, this has been strenuously disputed.


Ceramics

Vitrification is the progressive partial fusion of a
clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...
, 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. 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. An example is by
ASTM ASTM International, formerly known as American Society for Testing and Materials, is a standards organization that develops and publishes voluntary consensus technical international standards for a wide range of materials, products, systems and s ...
, 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."
Pottery Pottery is the process and the products of forming vessels and other objects with clay and other raw materials, which are fired at high temperatures to give them a hard and durable form. The place where such wares are made by a ''potter'' is al ...
can be made impermeable to water by glazing or by vitrification.
Porcelain Porcelain (), also called china, is a ceramic material made by heating Industrial mineral, raw materials, generally including kaolinite, in a kiln to temperatures between . The greater strength and translucence of porcelain, relative to oth ...
, bone china, and sanitaryware are examples of vitrified pottery, and are impermeable even without glaze.
Stoneware Stoneware is a broad class of pottery fired at a relatively high temperature, to be impervious to water. A modern definition is a Vitrification#Ceramics, vitreous or semi-vitreous ceramic made primarily from stoneware clay or non-refractory fire ...
may be vitrified or semi-vitrified; the latter type would not be impermeable without glaze.


Applications

When sucrose is cooled slowly it results in crystal
sugar Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecul ...
(or rock candy), but when cooled rapidly it can form syrupy cotton candy (candy/fairy floss). 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 Ice is water that is frozen into a solid state, typically forming at or below temperatures of 0 ° C, 32 ° F, or 273.15 K. It occurs naturally on Earth, on other planets, in Oort cloud objects, and as interstellar ice. As a naturally oc ...
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. 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. 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 Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundan ...
. 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 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 Obsidian ( ) is a naturally occurring volcanic glass formed when lava extrusive rock, extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock. Produced from felsic lava, obsidian is rich in the lighter element ...
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 Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...
contamination Contamination is the presence of a constituent, impurity, or some other undesirable element that renders something unsuitable, unfit or harmful for the physical body, natural environment, workplace, etc. Types of contamination Within the scien ...
. Bulk vitrification uses
electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or a gas). In electrochemical cells, electrodes are essential parts that can consist of a varie ...
s 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."


Vitrification in cryopreservation

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 Liquid nitrogen (LN2) is nitrogen in a liquid state at cryogenics, low temperature. Liquid nitrogen has a boiling point of about . It is produced industrially by fractional distillation of liquid air. It is a colorless, mobile liquid whose vis ...
and liquid helium. 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. Additives used in cryobiology or produced naturally by organisms living in polar regions are called cryoprotectants.


See also

* Cryogenics * Crystallization * Supercooling * Vitrified fort


Literature

* *Stefan Lovgren
"Corpses Frozen for Future Rebirth by Arizona Company"
March 2005, '' National Geographic''


References

{{Reflist Glass Phase transitions Cryobiology it:Criopreservazione