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Full Record for Micrograph 160

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Micrograph no
160
Brief description
Glass ceramic, heat treated at 750° C for 3 hours
Keywords
ceramic Link to MATTER Glossary entry for ceramic, glass Link to MATTER Glossary entry for glass
Categories
Ceramic
System
LAS: Li2O-Al2O3-SiO2
Composition
Not specified
Standard codes
Reaction
Processing
Heat treated at 750°C for 3 hours
Applications
LAS glass ceramics are principally used for domestic cooker hobs and cookware. LAS and other glass ceramics can also be used for microwave radomes, vacuum and laser envelopes, telescope mirrors, and in bioceramic applications.
Sample preparation
Thin section
Technique
Transmitted polarised light microscopy, with sensitive tint plate
Length bar
100 μm
Further information
Glass ceramics are materials that are cooled from the melt in the form of a glass, and then heat treated to induce controlled crystallisation of the glass. Heterogeneous nucleation is carried out at a temperature to maximise the nucleation rate (common nucleating agents include TiO2 and ZrO2), and the temperature is then raised sufficiently to cause the nuclei formed to grow rapidly.

Glass ceramics are strong, reasonably tough, transparent to IR radiation, have a low coefficient of thermal expansion, a high resistance to thermal shock and a low thermal conductivity, which makes them very useful in domestic applications such as cookware and cooker hobs.

The most common glass ceramic system is LAS (Li2O-Al2O3-SiO2), but others include MgO-Al2O3-SiO2, Na2O-BaO-Al2O3-SiO2, and Li2O-MgO-Al2O3-SiO2.
Contributor
Dr K M Knowles
Organisation
Department of Materials Science and Metallurgy, University of Cambridge
Date
09/08/02
Licence for re-use
Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales
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