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102-403: Glass is an amorphous ( non-crystalline ) solid. Because it is often transparent and chemically inert, glass has found widespread practical, technological, and decorative use in window panes, tableware , and optics . Some common objects made of glass are named after the material, e.g. "glass" , " glasses ", " magnifying glass ". Glass is most often formed by rapid cooling ( quenching ) of

204-399: A glass (or vitreous solid) is a non-crystalline solid formed by rapid melt quenching . However, the term "glass" is often defined in a broader sense, to describe any non-crystalline ( amorphous ) solid that exhibits a glass transition when heated towards the liquid state. Glass is an amorphous solid . Although the atomic-scale structure of glass shares characteristics of the structure of

306-432: A supercooled liquid , glass exhibits all the mechanical properties of a solid. As in other amorphous solids , the atomic structure of a glass lacks the long-range periodicity observed in crystalline solids . Due to chemical bonding constraints, glasses do possess a high degree of short-range order with respect to local atomic polyhedra . The notion that glass flows to an appreciable extent over extended periods well below

408-807: A turquoise colour in glass, in contrast to copper(I) oxide (Cu 2 O) which gives a dull red-brown colour. Soda–lime sheet glass is typically used as a transparent glazing material, typically as windows in external walls of buildings. Float or rolled sheet glass products are cut to size either by scoring and snapping the material, laser cutting , water jets , or diamond-bladed saw. The glass may be thermally or chemically tempered (strengthened) for safety and bent or curved during heating. Surface coatings may be added for specific functions such as scratch resistance, blocking specific wavelengths of light (e.g. infrared or ultraviolet ), dirt-repellence (e.g. self-cleaning glass ), or switchable electrochromic coatings. Structural glazing systems represent one of

510-452: A 3D image. After image acquisition, a significant amount of processing must be done to correct for issues such as drift, noise, and scan distortion. High quality analysis and processing using atomic electron tomography results in a 3D reconstruction of an amorphous material detailing the atomic positions of the different species that are present. Fluctuation electron microscopy is another transmission electron microscopy based technique that

612-484: A clear "ring" sound when struck. However, lead glass cannot withstand high temperatures well. Lead oxide also facilitates the solubility of other metal oxides and is used in coloured glass. The viscosity decrease of lead glass melt is very significant (roughly 100 times in comparison with soda glass); this allows easier removal of bubbles and working at lower temperatures, hence its frequent use as an additive in vitreous enamels and glass solders . The high ionic radius of

714-399: A few nanometres to tens of micrometres thickness that are deposited onto a substrate. So-called structure zone models were developed to describe the microstructure of thin films as a function of the homologous temperature ( T h ), which is the ratio of deposition temperature to melting temperature. According to these models, a necessary condition for the occurrence of amorphous phases

816-440: A function of temperature, and thermal conductivity has nearly quadratic temperature dependence. These properties are conventionally called anomalous being very different from properties of crystalline solids . On the phenomenological level, many of these properties were described by a collection of tunneling two-level systems. Nevertheless, the microscopic theory of these properties is still missing after more than 50 years of

918-438: A green tint in thick sections. Manganese dioxide (MnO 2 ), which gives glass a purple colour, may be added to remove the green tint given by FeO. FeO and chromium(III) oxide (Cr 2 O 3 ) additives are used in the production of green bottles. Iron (III) oxide , on the other-hand, produces yellow or yellow-brown glass. Low concentrations (0.025 to 0.1%) of cobalt oxide (CoO) produce rich, deep blue cobalt glass . Chromium

1020-405: A human timescale. Silicon dioxide (SiO 2 ) is a common fundamental constituent of glass. Fused quartz is a glass made from chemically pure silica. It has very low thermal expansion and excellent resistance to thermal shock , being able to survive immersion in water while red hot, resists high temperatures (1000–1500 °C) and chemical weathering, and is very hard. It is also transparent to

1122-404: A lighter alternative to traditional glass. Molecular liquids, electrolytes , molten salts , and aqueous solutions are mixtures of different molecules or ions that do not form a covalent network but interact only through weak van der Waals forces or transient hydrogen bonds . In a mixture of three or more ionic species of dissimilar size and shape, crystallization can be so difficult that

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1224-558: A long period at a temperature just insufficient to cause fusion. In this way, the crystalline, devitrified material, known as Réaumur's glass porcelain is produced. Although generally transparent to visible light, glasses may be opaque to other wavelengths of light . While silicate glasses are generally opaque to infrared wavelengths with a transmission cut-off at 4 μm, heavy-metal fluoride and chalcogenide glasses are transparent to infrared wavelengths of 7 to 18 μm. The addition of metallic oxides results in different coloured glasses as

1326-481: A mass of hot semi-molten glass, inflating it into a bubble using a hollow blowpipe, and forming it into the required shape by blowing, swinging, rolling, or moulding. While hot, the glass can be worked using hand tools, cut with shears, and additional parts such as handles or feet attached by welding. Flat glass for windows and similar applications is formed by the float glass process, developed between 1953 and 1957 by Sir Alastair Pilkington and Kenneth Bickerstaff of

1428-412: A mechanical truss is isostatic when the number of constraints equals the number of degrees of freedom of the nodes. In this case, the truss is optimally constrained, being rigid but free of stress . This criterion has been applied by Phillips to molecular networks, which are called flexible, stressed-rigid or isostatic when the number of constraints per atoms is respectively lower, higher or equal to 3,

1530-648: A microscopic theory of elasticity that provides G {\displaystyle G} as a function of the internal coordination number of nodes and of the number of degrees of freedom. The problem has been solved by Alessio Zaccone and E. Scossa-Romano in 2011, who derived the analytical formula for the shear modulus of a 3D network of central-force springs (bond-stretching constraints): G = ( 1 / 30 ) κ R 0 2 ( z − 2 d ) {\displaystyle G=(1/30)\kappa R_{0}^{2}(z-2d)} . Here, κ {\displaystyle \kappa }

1632-452: A non-crystalline intergranular phase of grain boundaries . Glass-ceramics exhibit advantageous thermal, chemical, biological, and dielectric properties as compared to metals or organic polymers. The most commercially important property of glass-ceramics is their imperviousness to thermal shock. Thus, glass-ceramics have become extremely useful for countertop cooking and industrial processes. The negative thermal expansion coefficient (CTE) of

1734-421: A plastic resin with glass fibres . It is made by melting glass and stretching the glass into fibres. These fibres are woven together into a cloth and left to set in a plastic resin. Fibreglass has the properties of being lightweight and corrosion resistant and is a good insulator enabling its use as building insulation material and for electronic housing for consumer products. Fibreglass was originally used in

1836-460: A priori , the theory is often employed in conjunction with computational methods in materials science such as molecular dynamics (MD). Notably, the theory played a major role in the development of Gorilla Glass 3 . Extended to glasses at finite temperature and finite pressure, rigidity theory has been used to predict glass transition temperature, viscosity and mechanical properties. It was also applied to granular materials and proteins . In

1938-459: A refractive index of 1.4 to 2.4, and an Abbe number (which characterises dispersion) of 15 to 100. The refractive index may be modified by high-density (refractive index increases) or low-density (refractive index decreases) additives. Glass transparency results from the absence of grain boundaries which diffusely scatter light in polycrystalline materials. Semi-opacity due to crystallization may be induced in many glasses by maintaining them for

2040-409: A spinning metal disk. Several alloys have been produced in layers with thicknesses exceeding 1 millimetre. These are known as bulk metallic glasses (BMG). Liquidmetal Technologies sells several zirconium -based BMGs. Batches of amorphous steel have also been produced that demonstrate mechanical properties far exceeding those found in conventional steel alloys. Experimental evidence indicates that

2142-433: A structural analogue of silica, fluoride , aluminate , phosphate , borate , and chalcogenide glasses) have physicochemical properties useful for their application in fibre-optic waveguides in communication networks and other specialised technological applications. Silica-free glasses may often have poor glass-forming tendencies. Novel techniques, including containerless processing by aerodynamic levitation (cooling

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2244-410: A structurally metastable state with respect to its crystalline form, although in certain circumstances, for example in atactic polymers, there is no crystalline analogue of the amorphous phase. Glass is sometimes considered to be a liquid due to its lack of a first-order phase transition where certain thermodynamic variables such as volume , entropy and enthalpy are discontinuous through

2346-520: A wider spectral range than ordinary glass, extending from the visible further into both the UV and IR ranges, and is sometimes used where transparency to these wavelengths is necessary. Fused quartz is used for high-temperature applications such as furnace tubes, lighting tubes, melting crucibles, etc. However, its high melting temperature (1723 °C) and viscosity make it difficult to work with. Therefore, normally, other substances (fluxes) are added to lower

2448-413: Is 3.25 × 10/°C as compared to about 9 × 10/°C for a typical soda–lime glass). They are, therefore, less subject to stress caused by thermal expansion and thus less vulnerable to cracking from thermal shock . They are commonly used for e.g. labware , household cookware , and sealed beam car head lamps . The addition of lead(II) oxide into silicate glass lowers the melting point and viscosity of

2550-549: Is a common volcanic glass with high silica (SiO 2 ) content formed when felsic lava extruded from a volcano cools rapidly. Impactite is a form of glass formed by the impact of a meteorite , where Moldavite (found in central and eastern Europe), and Libyan desert glass (found in areas in the eastern Sahara , the deserts of eastern Libya and western Egypt ) are notable examples. Vitrification of quartz can also occur when lightning strikes sand , forming hollow, branching rootlike structures called fulgurites . Trinitite

2652-887: Is a form of pottery using lead glazes. Due to its ease of formability into any shape, glass has been traditionally used for vessels, such as bowls , vases , bottles , jars and drinking glasses. Soda–lime glass , containing around 70% silica , accounts for around 90% of modern manufactured glass. Glass can be coloured by adding metal salts or painted and printed with vitreous enamels , leading to its use in stained glass windows and other glass art objects. The refractive , reflective and transmission properties of glass make glass suitable for manufacturing optical lenses , prisms , and optoelectronics materials. Extruded glass fibres have applications as optical fibres in communications networks, thermal insulating material when matted as glass wool to trap air, or in glass-fibre reinforced plastic ( fibreglass ). The standard definition of

2754-709: Is a glassy residue formed from the desert floor sand at the Trinity nuclear bomb test site. Edeowie glass , found in South Australia , is proposed to originate from Pleistocene grassland fires, lightning strikes, or hypervelocity impact by one or several asteroids or comets . Naturally occurring obsidian glass was used by Stone Age societies as it fractures along very sharp edges, making it ideal for cutting tools and weapons. Glassmaking dates back at least 6000 years, long before humans had discovered how to smelt iron. Archaeological evidence suggests that

2856-645: Is a tool for predicting properties of complex networks (such as glasses ) based on their composition. It was introduced by James Charles Phillips in 1979 and 1981, and refined by Michael Thorpe in 1983. Inspired by the study of the stability of mechanical trusses as pioneered by James Clerk Maxwell , and by the seminal work on glass structure done by William Houlder Zachariasen , this theory reduces complex molecular networks to nodes (atoms, molecules, proteins, etc.) constrained by rods (chemical constraints), thus filtering out microscopic details that ultimately don't affect macroscopic properties. An equivalent theory

2958-413: Is a very powerful colouring agent, yielding dark green. Sulphur combined with carbon and iron salts produces amber glass ranging from yellowish to almost black. A glass melt can also acquire an amber colour from a reducing combustion atmosphere. Cadmium sulfide produces imperial red , and combined with selenium can produce shades of yellow, orange, and red. Addition of copper(II) oxide (CuO) produces

3060-515: Is able to describe the many orders of magnitude drop of the shear modulus upon approaching the glass transition from below. In 2001, Boolchand and coworkers found that the isostatic compositions in glassy alloys—predicted by rigidity theory—exist not just at a single threshold composition; rather, in many systems it spans a small, well-defined range of compositions intermediate to the flexible (under-constrained) and stressed-rigid (over-constrained) domains. This window of optimally constrained glasses

3162-447: Is achieved by homogenizing the raw materials mixture ( glass batch ), stirring the melt, and crushing and re-melting the first melt. The obtained glass is usually annealed to prevent breakage during processing. Colour in glass may be obtained by addition of homogenously distributed electrically charged ions (or colour centres ). While ordinary soda–lime glass appears colourless in thin section, iron(II) oxide (FeO) impurities produce

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3264-467: Is carried out into thin amorphous films as a gas separating membrane layer. The technologically most important thin amorphous film is probably represented by a few nm thin SiO 2 layers serving as isolator above the conducting channel of a metal-oxide semiconductor field-effect transistor (MOSFET). Also, hydrogenated amorphous silicon (Si:H) is of technical significance for thin-film solar cells . In

3366-671: Is extensively used for fibreglass , used for making glass-reinforced plastics (boats, fishing rods, etc.), top-of-stove cookware, and halogen bulb glass. The addition of barium also increases the refractive index. Thorium oxide gives glass a high refractive index and low dispersion and was formerly used in producing high-quality lenses, but due to its radioactivity has been replaced by lanthanum oxide in modern eyeglasses. Iron can be incorporated into glass to absorb infrared radiation, for example in heat-absorbing filters for movie projectors, while cerium(IV) oxide can be used for glass that absorbs ultraviolet wavelengths. Fluorine lowers

3468-453: Is in widespread use in optical systems due to its ability to refract, reflect, and transmit light following geometrical optics . The most common and oldest applications of glass in optics are as lenses , windows , mirrors , and prisms . The key optical properties refractive index , dispersion , and transmission , of glass are strongly dependent on chemical composition and, to a lesser degree, its thermal history. Optical glass typically has

3570-488: Is incorrect, as once solidified, glass stops flowing. The sags and ripples observed in old glass were already there the day it was made; manufacturing processes used in the past produced sheets with imperfect surfaces and non-uniform thickness (the near-perfect float glass used today only became widespread in the 1960s). A 2017 study computed the rate of flow of the medieval glass used in Westminster Abbey from

3672-899: Is produced by forcing molten glass through a fine mesh by centripetal force and breaking the extruded glass fibres into short lengths using a stream of high-velocity air. The fibres are bonded with an adhesive spray and the resulting wool mat is cut and packed in rolls or panels. Besides common silica-based glasses many other inorganic and organic materials may also form glasses, including metals , aluminates , phosphates , borates , chalcogenides , fluorides , germanates (glasses based on GeO 2 ), tellurites (glasses based on TeO 2 ), antimonates (glasses based on Sb 2 O 3 ), arsenates (glasses based on As 2 O 3 ), titanates (glasses based on TiO 2 ), tantalates (glasses based on Ta 2 O 5 ), nitrates , carbonates , plastics , acrylic , and many other substances. Some of these glasses (e.g. Germanium dioxide (GeO 2 , Germania), in many respects

3774-439: Is proportional to the density of scattering TLSs. The theoretical significance of this important and unsolved problem was highlighted by Anthony Leggett . Amorphous materials will have some degree of short-range order at the atomic-length scale due to the nature of intermolecular chemical bonding . Furthermore, in very small crystals , short-range order encompasses a large fraction of the atoms ; nevertheless, relaxation at

3876-434: Is radial distribution function analysis, which measures the number of atoms found at varying radial distances away from an arbitrary reference atom. From these techniques, the local order of an amorphous material can be elucidated. X-ray absorption fine-structure spectroscopy is an atomic scale probe making it useful for studying materials lacking in long range order. Spectra obtained using this method provide information on

3978-651: Is sensitive to the medium range order of amorphous materials. Structural fluctuations arising from different forms of medium range order can be detected with this method. Fluctuation electron microscopy experiments can be done in conventional or scanning transmission electron microscope mode. Simulation and modeling techniques are often combined with experimental methods to characterize structures of amorphous materials. Commonly used computational techniques include density functional theory , molecular dynamics , and reverse Monte Carlo . Amorphous phases are important constituents of thin films . Thin films are solid layers of

4080-460: Is stronger than most metals, with a theoretical tensile strength for pure, flawless glass estimated at 14 to 35 gigapascals (2,000,000 to 5,100,000 psi) due to its ability to undergo reversible compression without fracture. However, the presence of scratches, bubbles, and other microscopic flaws lead to a typical range of 14 to 175 megapascals (2,000 to 25,400 psi) in most commercial glasses. Several processes such as toughening can increase

4182-407: Is sufficiently rapid (relative to the characteristic crystallization time) then crystallization is prevented and instead, the disordered atomic configuration of the supercooled liquid is frozen into the solid state at T g . The tendency for a material to form a glass while quenched is called glass-forming ability. This ability can be predicted by the rigidity theory . Generally, a glass exists in

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4284-509: Is that ( T h ) has to be smaller than 0.3. The deposition temperature must be below 30% of the melting temperature. Regarding their applications, amorphous metallic layers played an important role in the discovery of superconductivity in amorphous metals made by Buckel and Hilsch. The superconductivity of amorphous metals, including amorphous metallic thin films, is now understood to be due to phonon -mediated Cooper pairing . The role of structural disorder can be rationalized based on

4386-601: Is the spring constant, R 0 {\displaystyle R_{0}} is the distance between two nearest-neighbor nodes, z {\displaystyle z} the average coordination number of the network (note that here z N / 2 ≡ N c {\displaystyle zN/2\equiv N_{c}} and z / 2 ≡ n c {\displaystyle z/2\equiv n_{c}} ), and 2 d = 6 {\displaystyle 2d=6} in 3D. A similar formula has been derived for 2D networks where

4488-432: Is transparent, easily formed, and most suitable for window glass and tableware. However, it has a high thermal expansion and poor resistance to heat. Soda–lime glass is typically used for windows , bottles , light bulbs , and jars . Borosilicate glasses (e.g. Pyrex , Duran ) typically contain 5–13% boron trioxide (B 2 O 3 ). Borosilicate glasses have fairly low coefficients of thermal expansion (7740 Pyrex CTE

4590-520: The Late Bronze Age , there was a rapid growth in glassmaking technology in Egypt and Western Asia . Archaeological finds from this period include coloured glass ingots , vessels, and beads. Much early glass production relied on grinding techniques borrowed from stoneworking , such as grinding and carving glass in a cold state. The term glass has its origins in the late Roman Empire , in

4692-532: The Renaissance period in Europe, the use of large stained glass windows became much less prevalent, although stained glass had a major revival with Gothic Revival architecture in the 19th century. During the 13th century, the island of Murano , Venice , became a centre for glass making, building on medieval techniques to produce colourful ornamental pieces in large quantities. Murano glass makers developed

4794-531: The Roman glass making centre at Trier (located in current-day Germany) where the late-Latin term glesum originated, likely from a Germanic word for a transparent , lustrous substance. Glass objects have been recovered across the Roman Empire in domestic, funerary , and industrial contexts, as well as trade items in marketplaces in distant provinces. Examples of Roman glass have been found outside of

4896-463: The dielectric constant of glass. Fluorine is highly electronegative and lowers the polarizability of the material. Fluoride silicate glasses are used in the manufacture of integrated circuits as an insulator. Glass-ceramic materials contain both non-crystalline glass and crystalline ceramic phases. They are formed by controlled nucleation and partial crystallisation of a base glass by heat treatment. Crystalline grains are often embedded within

4998-421: The fundamental physics level. Amorphous solids is an important area of condensed matter physics aiming to understand these substances at high temperatures of glass transition and at low temperatures towards absolute zero . From 1970s, low-temperature properties of amorphous solids were studied experimentally in great detail. For all of these substances, specific heat has a (nearly) linear dependence as

5100-435: The glass batch preparation and mixing, the raw materials are transported to the furnace. Soda–lime glass for mass production is melted in glass-melting furnaces . Smaller-scale furnaces for speciality glasses include electric melters, pot furnaces, and day tanks. After melting, homogenization and refining (removal of bubbles), the glass is formed . This may be achieved manually by glassblowing , which involves gathering

5202-529: The molten form. Some glasses such as volcanic glass are naturally occurring, and obsidian has been used to make arrowheads and knives since the Stone Age . Archaeological evidence suggests glassmaking dates back to at least 3600 BC in Mesopotamia , Egypt , or Syria . The earliest known glass objects were beads , perhaps created accidentally during metalworking or the production of faience , which

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5304-417: The oxidation state , coordination number , and species surrounding the atom in question as well as the distances at which they are found. The atomic electron tomography technique is performed in transmission electron microscopes capable of reaching sub-Angstrom resolution. A collection of 2D images taken at numerous different tilt angles is acquired from the sample in question, and then used to reconstruct

5406-653: The pharmaceutical industry , some amorphous drugs have been shown to offer higher bioavailability than their crystalline counterparts as a result of the higher solubility of the amorphous phase. However, certain compounds can undergo precipitation in their amorphous form in vivo , and can then decrease mutual bioavailability if administered together. Amorphous materials in soil strongly influence bulk density , aggregate stability , plasticity , and water holding capacity of soils. The low bulk density and high void ratios are mostly due to glass shards and other porous minerals not becoming compacted . Andisol soils contain

5508-510: The 10th century onwards, glass was employed in stained glass windows of churches and cathedrals , with famous examples at Chartres Cathedral and the Basilica of Saint-Denis . By the 14th century, architects were designing buildings with walls of stained glass such as Sainte-Chapelle , Paris, (1203–1248) and the East end of Gloucester Cathedral . With the change in architectural style during

5610-457: The 1930s, which later became known as Depression glass . In the 1950s, Pilkington Bros. , England , developed the float glass process, producing high-quality distortion-free flat sheets of glass by floating on molten tin . Modern multi-story buildings are frequently constructed with curtain walls made almost entirely of glass. Laminated glass has been widely applied to vehicles for windscreens. Optical glass for spectacles has been used since

5712-463: The Maxwell isostatic condition. A similar analysis can be done for 3D networks with bond-bending interactions (on top of bond-stretching), which leads to the isostatic condition z = 2.4 {\displaystyle z=2.4} , with a lower threshold due to the angular constraints imposed by bond-bending. Rigidity theory allows the prediction of optimal isostatic compositions, as well as

5814-680: The Middle Ages. The production of lenses has become increasingly proficient, aiding astronomers as well as having other applications in medicine and science. Glass is also employed as the aperture cover in many solar energy collectors. In the 21st century, glass manufacturers have developed different brands of chemically strengthened glass for widespread application in touchscreens for smartphones , tablet computers , and many other types of information appliances . These include Gorilla Glass , developed and manufactured by Corning , AGC Inc. 's Dragontrail and Schott AG 's Xensation. Glass

5916-538: The Pb ion renders it highly immobile and hinders the movement of other ions; lead glasses therefore have high electrical resistance, about two orders of magnitude higher than soda–lime glass (10 vs 10 Ω⋅cm, DC at 250 °C). Aluminosilicate glass typically contains 5–10% alumina (Al 2 O 3 ). Aluminosilicate glass tends to be more difficult to melt and shape compared to borosilicate compositions but has excellent thermal resistance and durability. Aluminosilicate glass

6018-530: The UK's Pilkington Brothers, who created a continuous ribbon of glass using a molten tin bath on which the molten glass flows unhindered under the influence of gravity. The top surface of the glass is subjected to nitrogen under pressure to obtain a polished finish. Container glass for common bottles and jars is formed by blowing and pressing methods. This glass is often slightly modified chemically (with more alumina and calcium oxide) for greater water resistance. Once

6120-490: The United Kingdom and United States during World War II to manufacture radomes . Uses of fibreglass include building and construction materials, boat hulls, car body parts, and aerospace composite materials. Glass-fibre wool is an excellent thermal and sound insulation material, commonly used in buildings (e.g. attic and cavity wall insulation ), and plumbing (e.g. pipe insulation ), and soundproofing . It

6222-709: The action of water, making it an ideal material for the manufacture of containers for foodstuffs and most chemicals. Nevertheless, although usually highly resistant to chemical attack, glass will corrode or dissolve under some conditions. The materials that make up a particular glass composition affect how quickly the glass corrodes. Glasses containing a high proportion of alkali or alkaline earth elements are more susceptible to corrosion than other glass compositions. The density of glass varies with chemical composition with values ranging from 2.2 grams per cubic centimetre (2,200 kg/m) for fused silica to 7.2 grams per cubic centimetre (7,200 kg/m) for dense flint glass. Glass

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6324-486: The amorphous phase only after the latter has exceeded a certain thickness, the precise value of which depends on deposition temperature, background pressure, and various other process parameters. The phenomenon has been interpreted in the framework of Ostwald's rule of stages that predicts the formation of phases to proceed with increasing condensation time towards increasing stability. Rigidity theory (physics) Rigidity theory , or topological constraint theory,

6426-404: The composition dependence of glass properties, by a simple enumeration of constraints. These glass properties include, but are not limited to, elastic modulus , shear modulus , bulk modulus , density, Poisson's ratio , coefficient of thermal expansion, hardness, and toughness . In some systems, due to the difficulty of directly enumerating constraints by hand and knowing all system information

6528-492: The context of soft glasses, rigidity theory has been used by Alessio Zaccone and Eugene Terentjev to predict the glass transition temperature of polymers and to provide a molecular-level derivation and interpretation of the Flory–Fox equation . The Zaccone–Terentjev theory also provides an expression for the shear modulus of glassy polymers as a function of temperature which is in quantitative agreement with experimental data, and

6630-410: The cost factor has a low priority. In the laboratory mostly pure chemicals are used. Care must be taken that the raw materials have not reacted with moisture or other chemicals in the environment (such as alkali or alkaline earth metal oxides and hydroxides, or boron oxide ), or that the impurities are quantified (loss on ignition). Evaporation losses during glass melting should be considered during

6732-425: The crystalline ceramic phase can be balanced with the positive CTE of the glassy phase. At a certain point (~70% crystalline) the glass-ceramic has a net CTE near zero. This type of glass-ceramic exhibits excellent mechanical properties and can sustain repeated and quick temperature changes up to 1000 °C. Fibreglass (also called glass fibre reinforced plastic, GRP) is a composite material made by reinforcing

6834-680: The desired form is obtained, glass is usually annealed for the removal of stresses and to increase the glass's hardness and durability. Surface treatments, coatings or lamination may follow to improve the chemical durability ( glass container coatings , glass container internal treatment ), strength ( toughened glass , bulletproof glass , windshields ), or optical properties ( insulated glazing , anti-reflective coating ). New chemical glass compositions or new treatment techniques can be initially investigated in small-scale laboratory experiments. The raw materials for laboratory-scale glass melts are often different from those used in mass production because

6936-450: The diffraction patterns of amorphous materials. It is useful to obtain diffraction data from both X-ray and neutron sources as they have different scattering properties and provide complementary data. Pair distribution function analysis can be performed on diffraction data to determine the probability of finding a pair of atoms separated by a certain distance. Another type of analysis that is done with diffraction data of amorphous materials

7038-464: The exceptionally clear colourless glass cristallo , so called for its resemblance to natural crystal, which was extensively used for windows, mirrors, ships' lanterns, and lenses. In the 13th, 14th, and 15th centuries, enamelling and gilding on glass vessels were perfected in Egypt and Syria. Towards the end of the 17th century, Bohemia became an important region for glass production, remaining so until

7140-456: The first true synthetic glass was made in Lebanon and the coastal north Syria , Mesopotamia or ancient Egypt . The earliest known glass objects, of the mid-third millennium BC, were beads , perhaps initially created as accidental by-products of metalworking ( slags ) or during the production of faience , a pre-glass vitreous material made by a process similar to glazing . Early glass

7242-749: The former Roman Empire in China , the Baltics , the Middle East , and India . The Romans perfected cameo glass , produced by etching and carving through fused layers of different colours to produce a design in relief on the glass object. In post-classical West Africa, Benin was a manufacturer of glass and glass beads. Glass was used extensively in Europe during the Middle Ages . Anglo-Saxon glass has been found across England during archaeological excavations of both settlement and cemetery sites. From

7344-552: The glass and melt phases. Important polymer glasses include amorphous and glassy pharmaceutical compounds. These are useful because the solubility of the compound is greatly increased when it is amorphous compared to the same crystalline composition. Many emerging pharmaceuticals are practically insoluble in their crystalline forms. Many polymer thermoplastics familiar to everyday use are glasses. For many applications, like glass bottles or eyewear , polymer glasses ( acrylic glass , polycarbonate or polyethylene terephthalate ) are

7446-490: The glass transition range. The glass transition may be described as analogous to a second-order phase transition where the intensive thermodynamic variables such as the thermal expansivity and heat capacity are discontinuous. However, the equilibrium theory of phase transformations does not hold for glass, and hence the glass transition cannot be classed as one of the classical equilibrium phase transformations in solids. Glass can form naturally from volcanic magma. Obsidian

7548-401: The glass transition temperature is not supported by empirical research or theoretical analysis (see viscosity in solids ). Though atomic motion at glass surfaces can be observed, and viscosity on the order of 10–10 Pa s can be measured in glass, such a high value reinforces the fact that glass would not change shape appreciably over even large periods of time. For melt quenching, if the cooling

7650-457: The high number of constraints and tend to crystallize instead of forming glass during a quick quenching. The conditions for isostaticity can be derived by looking at the internal degrees of freedom of a general 3D network. For N {\displaystyle N} nodes, N c {\displaystyle N_{c}} constraints, and M e q {\displaystyle M_{eq}} equations of equilibrium,

7752-528: The highest amounts of amorphous materials. The occurrence of amorphous phases turned out to be a phenomenon of particular interest for the studying of thin-film growth. The growth of polycrystalline films is often used and preceded by an initial amorphous layer, the thickness of which may amount to only a few nm. The most investigated example is represented by the unoriented molecules of thin polycrystalline silicon films. Wedge-shaped polycrystals were identified by transmission electron microscopy to grow out of

7854-452: The liquid can easily be supercooled into a glass. Examples include LiCl: R H 2 O (a solution of lithium chloride salt and water molecules) in the composition range 4< R <8. sugar glass , or Ca 0.4 K 0.6 (NO 3 ) 1.4 . Glass electrolytes in the form of Ba-doped Li-glass and Ba-doped Na-glass have been proposed as solutions to problems identified with organic liquid electrolytes used in modern lithium-ion battery cells. Following

7956-478: The melt whilst it floats on a gas stream) or splat quenching (pressing the melt between two metal anvils or rollers), may be used to increase the cooling rate or to reduce crystal nucleation triggers. In the past, small batches of amorphous metals with high surface area configurations (ribbons, wires, films, etc.) have been produced through the implementation of extremely rapid rates of cooling. Amorphous metal wires have been produced by sputtering molten metal onto

8058-430: The melt. The high density of lead glass (silica + lead oxide (PbO) + potassium oxide (K 2 O) + soda (Na 2 O) + zinc oxide (ZnO) + alumina) results in a high electron density, and hence high refractive index, making the look of glassware more brilliant and causing noticeably more specular reflection and increased optical dispersion . Lead glass has a high elasticity, making the glassware more workable and giving rise to

8160-616: The melting temperature and simplify glass processing. Sodium carbonate (Na 2 CO 3 , "soda") is a common additive and acts to lower the glass-transition temperature. However, sodium silicate is water-soluble , so lime (CaO, calcium oxide , generally obtained from limestone ), along with magnesium oxide (MgO), and aluminium oxide (Al 2 O 3 ), are commonly added to improve chemical durability. Soda–lime glasses (Na 2 O) + lime (CaO) + magnesia (MgO) + alumina (Al 2 O 3 ) account for over 75% of manufactured glass, containing about 70 to 74% silica by weight. Soda–lime–silicate glass

8262-406: The metallic ions will absorb wavelengths of light corresponding to specific colours. In the manufacturing process, glasses can be poured, formed, extruded and moulded into forms ranging from flat sheets to highly intricate shapes. The finished product is brittle but can be laminated or tempered to enhance durability. Glass is typically inert, resistant to chemical attack, and can mostly withstand

8364-407: The most significant architectural innovations of modern times, where glass buildings now often dominate the skylines of many modern cities . These systems use stainless steel fittings countersunk into recesses in the corners of the glass panels allowing strengthened panes to appear unsupported creating a flush exterior. Structural glazing systems have their roots in iron and glass conservatories of

8466-476: The nineteenth century Amorphous The term comes from the Greek a ("without"), and morphé ("shape, form"). Amorphous materials have an internal structure of molecular-scale structural blocks that can be similar to the basic structural units in the crystalline phase of the same compound. Unlike in crystalline materials, however, no long-range regularity exists: amorphous materials cannot be described by

8568-457: The number of constraints per atom in the isostatic condition of n c = 3 {\displaystyle n_{c}=3} . An alternative derivation is based on analyzing the shear modulus G {\displaystyle G} of the 3D network or solid structure. The isostatic condition, which represents the limit of mechanical stability, is equivalent to setting G = 0 {\displaystyle G=0} in

8670-421: The number of degrees of freedom is The node term picks up a factor of 3 due to there being translational degrees of freedom in the x , y , and z directions. By similar reasoning, M e q = 6 {\displaystyle M_{eq}=6} in 3D, as there is one equation of equilibrium for translational and rotational modes in each dimension. This yields This can be applied to each node in

8772-444: The number of degrees of freedom per atom in a three-dimensional system. The same condition applies to random packing of spheres, which are isostatic at the jamming point. Typically, the conditions for glass formation will be optimal if the network is isostatic, which is for example the case for pure silica . Flexible systems show internal degrees of freedom, called floppy modes, whereas stressed-rigid ones are complexity locked by

8874-614: The prefactor is 1 / 18 {\displaystyle 1/18} instead of 1 / 30 {\displaystyle 1/30} . Hence, based on the Zaccone–Scossa-Romano expression for G {\displaystyle G} , upon setting G = 0 {\displaystyle G=0} , one obtains z = 2 d = 6 {\displaystyle z=2d=6} , or equivalently in different notation, n c = 3 {\displaystyle n_{c}=3} , which defines

8976-461: The repetition of a finite unit cell. Statistical measures, such as the atomic density function and radial distribution function , are more useful in describing the structure of amorphous solids. Although amorphous materials lack long range order, they exhibit localized order on small length scales. By convention, short range order extends only to the nearest neighbor shell, typically only 1-2 atomic spacings. Medium range order may extend beyond

9078-430: The research. Remarkably, a dimensionless quantity of internal friction is nearly universal in these materials. This quantity is a dimensionless ratio (up to a numerical constant) of the phonon wavelength to the phonon mean free path . Since the theory of tunneling two-level states (TLSs) does not address the origin of the density of TLSs, this theory cannot explain the universality of internal friction, which in turn

9180-424: The selection of the raw materials, e.g., sodium selenite may be preferred over easily evaporating selenium dioxide (SeO 2 ). Also, more readily reacting raw materials may be preferred over relatively inert ones, such as aluminium hydroxide (Al(OH) 3 ) over alumina (Al 2 O 3 ). Usually, the melts are carried out in platinum crucibles to reduce contamination from the crucible material. Glass homogeneity

9282-461: The short range order by 1-2 nm. The freezing from liquid state to amorphous solid - glass transition - is considered one of the very important and unsolved problems of physics . At very low temperatures (below 1-10 K), large family of amorphous solids have various similar low-temperature properties. Although there are various theoretical models, neither glass transition nor low-temperature properties of glassy solids are well understood on

9384-601: The start of the 20th century. By the 17th century, glass in the Venetian tradition was also being produced in England . In about 1675, George Ravenscroft invented lead crystal glass, with cut glass becoming fashionable in the 18th century. Ornamental glass objects became an important art medium during the Art Nouveau period in the late 19th century. Throughout the 20th century, new mass production techniques led to

9486-466: The strength of glass. Carefully drawn flawless glass fibres can be produced with a strength of up to 11.5 gigapascals (1,670,000 psi). The observation that old windows are sometimes found to be thicker at the bottom than at the top is often offered as supporting evidence for the view that glass flows over a timescale of centuries, the assumption being that the glass has exhibited the liquid property of flowing from one shape to another. This assumption

9588-529: The strong-coupling Eliashberg theory of superconductivity. Amorphous solids typically exhibit higher localization of heat carriers compared to crystalline, giving rise to low thermal conductivity. Products for thermal protection, such as thermal barrier coatings and insulation, rely on materials with ultralow thermal conductivity. Today, optical coatings made from TiO 2 , SiO 2 , Ta 2 O 5 etc. (and combinations of these) in most cases consist of amorphous phases of these compounds. Much research

9690-502: The structure of amorphous solids. A variety of electron, X-ray, and computation-based techniques have been used to characterize amorphous materials. Multi-modal analysis is very common for amorphous materials. Unlike crystalline materials which exhibit strong Bragg diffraction, the diffraction patterns of amorphous materials are characterized by broad and diffuse peaks. As a result, detailed analysis and complementary techniques are required to extract real space structural information from

9792-444: The surface, along with interfacial effects, distorts the atomic positions and decreases structural order. Even the most advanced structural characterization techniques, such as X-ray diffraction and transmission electron microscopy , can have difficulty distinguishing amorphous and crystalline structures at short size scales. Due to the lack of long-range order, standard crystallographic techniques are often inadequate in determining

9894-460: The system Al-Fe-Si may undergo a first-order transition to an amorphous form (dubbed "q-glass") on rapid cooling from the melt. Transmission electron microscopy (TEM) images indicate that q-glass nucleates from the melt as discrete particles with uniform spherical growth in all directions. While x-ray diffraction reveals the isotropic nature of q-glass, a nucleation barrier exists implying an interfacial discontinuity (or internal surface) between

9996-500: The system by normalizing by the number of nodes where f = F N {\displaystyle f={\frac {F}{N}}} , n c = N c N {\displaystyle n_{c}={\frac {N_{c}}{N}}} , and the last term has been dropped since for atomistic systems 6 ≪ N {\displaystyle 6\ll N} . Isostatic conditions are achieved when f = 0 {\displaystyle f=0} , yielding

10098-450: The widespread availability of glass in much larger amounts, making it practical as a building material and enabling new applications of glass. In the 1920s a mould -etch process was developed, in which art was etched directly into the mould so that each cast piece emerged from the mould with the image already on the surface of the glass. This reduced manufacturing costs and, combined with a wider use of coloured glass, led to cheap glassware in

10200-400: The year 1268. The study found that the room temperature viscosity of this glass was roughly 10   Pa · s which is about 10 times less viscous than a previous estimate made in 1998, which focused on soda-lime silicate glass. Even with this lower viscosity, the study authors calculated that the maximum flow rate of medieval glass is 1 nm per billion years, making it impossible to observe in

10302-785: Was developed by P. K. Gupta and A. R. Cooper in 1990, where rather than nodes representing atoms, they represented unit polytopes . An example of this would be the SiO tetrahedra in pure glassy silica . This style of analysis has applications in biology and chemistry, such as understanding adaptability in protein-protein interaction networks. Rigidity theory applied to the molecular networks arising from phenotypical expression of certain diseases may provide insights regarding their structure and function. In molecular networks, atoms can be constrained by radial 2-body bond-stretching constraints, which keep interatomic distances fixed, and angular 3-body bond-bending constraints, which keep angles fixed around their average values. As stated by Maxwell's criterion,

10404-552: Was rarely transparent and often contained impurities and imperfections, and is technically faience rather than true glass, which did not appear until the 15th century BC. However, red-orange glass beads excavated from the Indus Valley Civilization dated before 1700 BC (possibly as early as 1900 BC) predate sustained glass production, which appeared around 1600 BC in Mesopotamia and 1500 BC in Egypt. During

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