ISSN:
1573-4803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The most important single factor responsible for the largely different microstructure and properties of glass-ceramics as compared with fusion cast ceramics is the viscosity conditions during crystallization. Whereas cast ceramics crystallize from liquids almost always in a very fluid condition, i.e., viscosity less than a 103 poise, the controlled nucleation and crystallization of glass normally takes place at viscosities greater than 108 poise, usually between 109 and 1012 poise. Crystallization of ceramic materials from a melt is a time-temperature-pressure dependent process. Factors such as high volume expansion, crystal orientation, solid solution and exsolution control the resulting microstructure and properties of these brittle materials. Non-equilibrium conditions play a major role in affecting the microstructure. The importance of additions of one or more components to each of the following basic ceramic systems will be discussed: (1) ZrO2-Al2O3-SiO2, (2) Al2O3, (3) MgO, (4) carbides, and (5) borides. Glass ceramics are crystalline materials formed through controlled devitrification of glass. The sequence of nucleation, crystal growth, and phase transformation occurring during the thermal treatment of such glasses can be controlled to produce unique microstructures and properties. This is reviewed for several basic composition areas: (1) SiO2-Al2O3-Li2O (spodumene), (2) SiO2-Al2O3-MgO (cordierite), (3) SiO2-Al2O3-MgO-K2O-F (mica), and (4) SiO2-Al2O3-CaO-MgO-Fe2O3 (basalt).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00610628
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