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Glass Cutters
Glass is a noncrystalline material that can maintain indefinitely, if left undisturbed, its overall form and amorphous microstructure at a temperature below its glass transition temperature. more...
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Glass synthesis is achieved by quenching a glass-forming liquid through its glass transition temperature sufficiently fast enough to avoid the formation of a regular crystal lattice, producing an amorphous solid. Amorphous solids may also be formed by methods other than melt quenching, such as vapour deposition or the sol-gel method. Silica glass may be produced by using sand as a raw material (or "quartz sand") that contains almost 100 % crystalline silica in the form of quartz. Glass is sometimes created naturally from volcanic magma. This glass is called obsidian, and is usually black with impurities. Obsidian is a raw material for flintknappers, who have used it to make extremely sharp knives since the stone age. The known manufacture of glass dates back to 3000 BC and glass technology is widely used in the modern day in household objects such as bottles, mirrors, windows and light bulbs. The most common method for glass pane production is using molten tin, where the molten glass floats on top of the perfectly flat molten tin, thus giving it the name "float glass". The refractive, reflective and transmission properties of glass make specific chemical compostitions suitable for technological applications such as optics and optoelectronics. The manipulation of heated glass enables it to be shaped into different forms and the incorporation of additives at the manufacturing stage produces different colors which enable glass to be used as an art medium for display purposes.
The Physics of Glass
The standard definition of a glass (or vitreous solid) requires the solid phase to be formed by rapid melt quenching. Glass is therefore formed via a supercooled liquid and cooled sufficiently rapidly from its molten state through its glass transition temperature, Tg, that the supercooled disordered atomic configuration at Tg, is frozen into the solid state. Generally, the structure of a glass exists in a 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 . By definition as an amorphous solid, the atomic structure of a glass lacks any long range translational periodicity. However, by virtue of the local chemical bonding constraints glasses do possess a high degree of short-range order with respect to local atomic polyhedra. It is deemed that the bonding structure of glasses although disordered has the same symmetry signature (Hausdorff-Besicovitch dimensionality) as for crystalline materials.
Read more at Wikipedia.org
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