Glass Ceramic Formation

Glass ceramics are mostly produced in two steps.

Glass ceramic formation. An ordinary ceramic kiln is adequate to fuse glass to ceramics but care must be taken with firing and cooling. Glass formation is an enigmatic phenomenon which is still not properly understood. Glass transition with its associated thermodynamics and kinetics remains an area of active scientific inquisition. Glass ceramics are a solidified body with an amorphous crystal multiphase structure that is obtained by a heat treatment when using a base glass.

In this heat treatment the glass partly crystallizes. In most cases nucleation agents are added to the base composition of the glass ceramic. Fusing glass to ceramics is an ancient craft that is becoming popular again. Glass ceramics consisting of various oxide crystals in a matrix of siliceous residual glass offer properties not available with more common silicate crystals.

These materials are built from base glasses via controlled nucleation and crystal growth. Glass formation usually takes place by rapid cooling of the molten mass past the crystallisation temperature and the solidification starts at the glass transition temperature. Good oseointegration through the formation of apatite on the implant surfaces neo et al 1993 combined with good mechanical properties kokubo et al 1985 1986 perhaps explains why the a w glass ceramic has found promising applications in bone and vertebra replacement kokubo 2008 and it is reported that over 50 000 successful bone. In particular glass ceramics based on spinels and perovskites can be quite refractory and can yield useful optical mechanical and electrical properties.

Sign in to download full size image 7 1. The extent of order of atoms and molecules in a material decides its nature in terms of it being crystalline polycrystalline or glassy. The glass is cooled down and is then reheated in a second step. Glass ceramic components are formed using the same processes that are applicable to glass components.

Melting glass to a glazed surface is the process of merging two separate layers of glass. The traditional glass ceramic route is. I melting homogenizing and refining a batch to form an optically homogeneous glass usually containing one or more nucleating agents. First a glass is formed by a glass manufacturing process.

To convert them from a vitreous glass material into a crystalline glass ceramic material they must be heat treated or devitrified. Glass ceramics consist of at least one glassy phase with at least one embedded crystalline phase.