Soda-lime glass, containing around 70% silica, accounts for around 90% of manufactured glass. 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. Glass is most often formed by rapid cooling ( quenching) of the molten form some glasses such as volcanic glass are naturally occurring. So the chief engineer goes out and inspects the batch through the windows.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. People seem to like old war stories, as long as, being fascinating in their. How To: Remove Non-Existent Network Adapters Windows Server When migrating a virtual machine from one physical node to another and adding a network adapter, you may receive the following error: The IP address XXX.XXX.XXX.XXX you have entered for this network adapter is already assigned to another adapter Name of adapter.
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. Extruded glass fibres have application as optical fibres in communications networks, thermal insulating material when matted as glass wool so as to trap air, or in glass-fibre reinforced plastic ( fibreglass).Main article: Structure of liquids and glassesThe standard definition of a glass (or vitreous solid) is a solid formed by rapid melt quenching. In our previous publication,5.The refractive, reflective and transmission properties of glass make glass suitable for manufacturing optical lenses, prisms, and optoelectronics materials. Glass can be coloured by adding metal salts or painted and printed as enamelled glass.It is usually very difficult to measure the viscosity of a supercooled liquid in broad temperature and pressure (T, P) ranges.
Laboratory measurements of room temperature glass flow do show a motion consistent with a material viscosity on the order of 10 17–10 18 Pa s. The notion that glass flows to an appreciable extent over extended periods of time is not supported by empirical research or theoretical analysis (see viscosity in solids). Due to chemical bonding constraints, glasses do possess a high degree of short-range order with respect to local atomic polyhedra. As in other amorphous solids, the atomic structure of a glass lacks the long-range periodicity observed in crystalline solids. Although the atomic-scale structure of glass shares characteristics of the structure of a supercooled liquid, glass exhibits all the mechanical properties of a solid.
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 the glass transition range. Generally, a glass exists in 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. This ability can be predicted by the rigidity theory. The tendency for a material to form a glass while quenched is called glass-forming ability.
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Archaeological evidence suggests that the first true synthetic glass was made in Lebanon and the coastal north Syria, Mesopotamia or ancient Egypt. Glassmaking dates back at least 6000 years, long before humans had discovered how to smelt iron. Furthermore, it does not describe the temperature dependence of Tg upon heating rate, as found in differential scanning calorimetry.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. The equilibrium theory of phase transformations do not hold for glass, and hence the glass transition cannot be classed as one of the classical equilibrium phase transformations in solids.
The term glass developed in the late Roman Empire. Much early glass production relied on grinding techniques borrowed from stoneworking, such as grinding and carving glass in a cold state. Archaeological finds from this period include coloured glass ingots, vessels, and beads. During the Late Bronze Age there was a rapid growth in glassmaking technology in Egypt and Western Asia. 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 in Mesopotamia and 1500 in Egypt. Early glass 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.
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. Examples of Roman glass have been found outside of the former Roman Empire in China, the Baltics, the Middle East, and India. Glass objects have been recovered across the Roman Empire in domestic, funerary, and industrial contexts.
From 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. Anglo-Saxon glass has been found across England during archaeological excavations of both settlement and cemetery sites. Glass was used extensively in Europe during the Middle Ages.
Throughout the 20th century, new mass production techniques led to widespread availability of glass in much larger amounts, making it practical as a building material and enabling new applications of glass. Ornamental glass objects became an important art medium during the Art Nouveau period in the late 19th century. In about 1675, George Ravenscroft invented lead crystal glass, with cut glass becoming fashionable in the 18th century. By the 17th century, glass in the Venetian tradition was also being produced in England. Towards the end of the 17th century, Bohemia became an important region for glass production, remaining so until the start of the 20th century.
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Laminated glass has been widely applied to vehicles for windscreens. Modern multi-story buildings are frequently constructed with curtain walls made almost entirely of 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. This reduced manufacturing costs and, combined with a wider use of coloured glass, led to cheap glassware in the 1930s, which later became known as Depression glass.
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