Glass Manufacturing).Glass-Ceramics )

Ordinary glass is non-crystalline. Glass-ceramics however, are manufactured through the controlled crystallization of a specially formulated glass.

For the production of glass ceramics, a high density of crystalline nuclei is generated in the molten glass, either by the droplet phase-separation mechanism or by the addition of nucleating agents such as titanium, zirconium, or phosphorus pentoxide. After the nucleation process is carried out for a predetermined time, the crystals are allowed to grow to maturity at an increased temperature. It is also named crystallite glass. Glass-ceramics are useful in thermally hazardous conditions. This 'glassy' material contains crystalline lattices, which give it specific properties. Glass-ceramics are commonly used in thermally hazardous environments, such as in cookware. With lower density like aluminium, glass-ceramics are also used in high precision equipment such as high speed cutting reamers and to cover radar appliances on rockets because some types have the property of near-zero expansion. Some others have a high physical strength and can be machined like metals. Good resistance to erosion and pressure, as well as excellent hardness, also makes glass-ceramics widely used in industrial purposes. Moreover, glass-ceramics are very good electrical insulators. article source http://www.glassonweb.com