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Annealing (glass)
Annealing is a process of slowly cooling hot glass objects after they have been formed, to relieve residual internal stresses introduced during manufacture. Especially for smaller, simpler objects, annealing may be incidental to the process of manufacture, but in larger or more complex products it commonly demands a special process of annealing in a temperature-controlled kiln known as a lehr (glassmaking), lehr.E. F. Collins (1921) Electrically heated glass annealing lehr. Journal of the American Ceramic Society 4 (5), pp. 335–349 Annealing of glass is critical to its durability. Glass that has not been properly annealed retains thermal stresses caused by quenching, which will indefinitely decrease the strength and reliability of the product. Inadequately annealed glass is likely to crack or shatter when subjected to relatively small temperature changes or to mechanical shock or stress. It even may fail spontaneously. To anneal glass, it is necessary to heat it to its annea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kiln
A kiln is a thermally insulated chamber, a type of oven, that produces temperatures sufficient to complete some process, such as hardening, drying, or chemical changes. Kilns have been used for millennia to turn objects made from clay into pottery, tiles and bricks. Various industries use rotary kilns for pyroprocessing—to calcinate ores, to calcinate limestone to lime for cement, and to transform many other materials. Pronunciation and etymology According to the Oxford English Dictionary, kiln was derived from the words cyline, cylene, cyln(e) in Old English, in turn derived from Latin ''culina'' ("kitchen"). In Middle English the word is attested as kulne, kyllne, kilne, kiln, kylle, kyll, kil, kill, keele, kiele. For over 600 years, the final "n" in kiln was silent. It wasn't until the late 20th century where the "n" began to be pronounced. This is due to a phenomenon known as spelling pronunciation, where the pronunciation of a word is surmised from its spelling an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Expansion Coefficient
Thermal expansion is the tendency of matter to change its shape, area, volume, and density in response to a change in temperature, usually not including phase transitions. Temperature is a monotonic function of the average molecular kinetic energy of a substance. When a substance is heated, molecules begin to vibrate and move more, usually creating more distance between themselves. Substances which contract with increasing temperature are unusual, and only occur within limited temperature ranges (see examples below). The relative expansion (also called strain) divided by the change in temperature is called the material's coefficient of linear thermal expansion and generally varies with temperature. As energy in particles increases, they start moving faster and faster weakening the intermolecular forces between them, therefore expanding the substance. Overview Predicting expansion If an equation of state is available, it can be used to predict the values of the thermal expan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glass Engineering And Science
Glass is a non-crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenching) of the molten form; some glasses such as volcanic glass are naturally occurring. The most familiar, and historically the oldest, types of manufactured glass are "silicate glasses" based on the chemical compound silica (silicon dioxide, or quartz), the primary constituent of sand. Soda–lime glass, containing around 70% silica, accounts for around 90% of manufactured glass. The term ''glass'', in popular usage, is often used to refer only to this type of material, although silica-free glasses often have desirable properties for applications in modern communications technology. Some objects, such as drinking glasses and eyeglasses, are so commonly made of silicate-based glass that they are simply called by the name of the material. Despite bei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Warm Glass
Warm, WARM, or Warmth may refer to: * A somewhat high temperature * Kindness Music * Warm (The Lettermen album), ''Warm'' (The Lettermen album), 1967, and the title song * Warm (Johnny Mathis album), ''Warm'' (Johnny Mathis album), 1958, and the title song * Warm (Herb Alpert album), ''Warm'' (Herb Alpert album), 1969 * Warm (Jeff Tweedy album), ''Warm'' (Jeff Tweedy album), 2018 * Warmer (Randy VanWarmer album), ''Warmer'' (Randy VanWarmer album), 1979 * Warmer (Jeff Tweedy album), ''Warmer'' (Jeff Tweedy album), 2019 * "Warm", a song by Majid Jordan from ''Majid Jordan (album), Majid Jordan'', 2016 * "Warm", a song by Charli XCX featuring Haim from ''Charli (album), Charli'', 2019 * "Warmer", a song by Bea Miller from ''Chapter Two: Red'' and ''Aurora'', 2017 * "Warmth", by C418 from ''Music of Minecraft#Minecraft - Volume Beta, Minecraft - Volume Beta'', 2013 Other uses * ''Warm.'', taxonomic author abbreviation of Eugenius Warming (1841–1924), Danish botanist * WARM (foundat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tempered Glass
Tempered or toughened glass is a type of safety glass processed by controlled thermal or chemical treatments to increase its strength compared with normal glass. Tempering puts the outer surfaces into compression and the interior into tension. Such stresses cause the glass, when broken, to shatter into small granular chunks instead of splintering into jagged shards as ordinary annealed glass does. The granular chunks are less likely to cause injury. Tempered glass is used for its safety and strength in a variety of applications, including passenger vehicle windows, shower doors, aquariums, architectural glass doors and tables, refrigerator trays, mobile phone screen protectors, bulletproof glass components, diving masks, and plates and cookware. Properties Tempered glass is about four times stronger than annealed glass. The greater contraction of the inner layer during manufacturing induces compressive stresses in the surface of the glass balanced by tensile stresses in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Float Glass
Float glass is a sheet of glass made by floating molten glass on a bed of molten metal, typically tin, although lead and other various low- melting-point alloys were used in the past. This method gives the sheet uniform thickness and very flat surfaces. Modern windows are made from float glass. Most float glass is soda-lime glass, although relatively minor quantities of specialty borosilicate and flat panel display glass are also produced using the float glass process. The float glass process is also known as the Pilkington process, named after the British glass manufacturer Pilkington, which pioneered the technique in the 1950s at their production site in St Helens, Merseyside. History Until the 16th century, window glass or other flat glass was generally cut from large discs (or rondels) of crown glass. Larger sheets of glass were made by blowing large cylinders which were cut open and flattened, then cut into panes. Most window glass in the early 19th century was made usin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fabrication And Testing (optical Components)
Optical manufacturing and testing spans an enormous range of manufacturing procedures and optical test configurations. The manufacture of a conventional spherical lens typically begins with the generation of the optic's rough shape by grinding a glass blank. This can be done, for example, with ring tools. Next, the lens surface is polished to its final form. Typically this is done by lapping—rotating and rubbing the rough lens surface against a tool with the desired surface shape, with a mixture of abrasives and fluid in between. Typically a carved pitch tool is used to polish the surface of a lens. The mixture of abrasive is called slurry and it is typically made from cerium or zirconium oxide in water with lubricants added to facilitate pitch tool movement without sticking to the lens. The particle size in the slurry is adjusted to get the desired shape and finish. During polishing, the lens may be tested to confirm that the desired shape is being produced, and to ensure ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bologna Bottle
A Bologna bottle, also known as a Bologna phial or philosophical vial, is a glass bottle which has great external strength, often used in physics demonstrations and magic tricks. The exterior is generally strong enough that one could pound a nail into a block of wood using the bottle as a hammer A hammer is a tool, most often a hand tool, consisting of a weighted "head" fixed to a long handle that is swung to deliver an impact to a small area of an object. This can be, for example, to drive nails into wood, to shape metal (as w ...; however, even a small scratch on the interior would cause it to crumble. It is created by heating a glass bottle and then rapidly cooling the outside whilst slowly cooling the inside. This causes external compression and internal tension such that even a scratch on the inside is sufficient to shatter the bottle. The effect is utilized in several magic effects, including the "Devil's Flask". Manufacture To create the desired effect, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Annealing (metallurgy)
In metallurgy and materials science, annealing is a heat treatment that alters the physical and sometimes chemical properties of a material to increase its ductility and reduce its hardness, making it more workable. It involves heating a material above its recrystallization temperature, maintaining a suitable temperature for an appropriate amount of time and then cooling. In annealing, atoms migrate in the crystal lattice and the number of dislocations decreases, leading to a change in ductility and hardness. As the material cools it recrystallizes. For many alloys, including carbon steel, the crystal grain size and phase composition, which ultimately determine the material properties, are dependent on the heating rate and cooling rate. Hot working or cold working after the annealing process alters the metal structure, so further heat treatments may be used to achieve the properties required. With knowledge of the composition and phase diagram, heat treatment can be used to ad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Viscous Liquid
In condensed matter physics and physical chemistry, the terms viscous liquid, supercooled liquid, and glassforming liquid are often used interchangeably to designate liquids that are at the same time highly viscous (see Viscosity of amorphous materials), can be or are supercooled, and able to form a glass. Working points in glass processing The mechanical properties of glass-forming liquids depend primarily on the viscosity. Therefore, the following working points are defined in terms of viscosity. The temperature is indicated for industrial soda lime glass: Fragile-strong classification In a widespread classification, due to chemist Austen Angell, a glass-forming liquid is called strong if its viscosity approximately obeys an Arrhenius law (log η is linear in 1/''T'' ). In the opposite case of clearly non-Arrhenius behaviour the liquid is called fragile. This classification has no direct relation with the common usage of the word "fragility" to mean brittlene ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Conductivity
The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k, \lambda, or \kappa. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity. For instance, metals typically have high thermal conductivity and are very efficient at conducting heat, while the opposite is true for insulating materials like Rockwool or Styrofoam. Correspondingly, materials of high thermal conductivity are widely used in heat sink applications, and materials of low thermal conductivity are used as thermal insulation. The reciprocal of thermal conductivity is called thermal resistivity. The defining equation for thermal conductivity is \mathbf = - k \nabla T, where \mathbf is the heat flux, k is the thermal conductivity, and \nabla T is the temperature gradient. This is known as Fourier's Law for heat conduction. Although commonly expressed as a scalar, the most general form of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lehr (glassmaking)
In the manufacture of float glass, a lehr oven is a long kiln with an end-to-end temperature gradient, which is used for annealing newly made glass objects that are transported through the temperature gradient either on rollers or on a conveyor belt. The annealing renders glass into a stronger material with fewer internal stresses, and with a lower probability of breaking. The rapid cooling of molten glass results in an uneven temperature distribution throughout the material. This temperature differential results in mechanical stresses throughout the molten glass, which may be sufficient to cause the material to crack as it cools to ambient temperature or to make it susceptible to cracking during later use, either spontaneously or due to mechanical or thermal shock. To prevent such material weaknesses, objects made from molten glass are annealed by gradual cooling in a lehr oven, from the annealing point, a temperature just below the solidification temperature of the glass. In t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
