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Full Record for Micrograph 198
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- Micrograph no
- 198
- Brief description
- 96% Alumina
- Keywords
- alumina
, ceramic , engineering ceramic - Categories
- Ceramic
- System
- Al2O3
- Composition
- Al2O3 96%, remainder MgO, CaO, SiO2
- Standard codes
- Reaction
- Processing
- Fine sub-micron oxide powders such as lime, silica and periclase are mixed with the coarser alumina and fired so they melt and partially react with the alumina forming a liquid phase, which acts to densify the ceramic by capillary action (liquid phase sintering).
- Applications
- Seals and bearings in corrosive fluid handling systems. Electrical insulation e.g. in fluorescent light tubes.
- Sample preparation
- Grind and polish. Thermally etch for 10 mins at about 50ºC below sintering temperature.
- Technique
- Reflected light microscopy
- Length bar
- 250 μm
- Further information
- The image shows the classic angular shape of corundum (alumina) grains formed in a liquid medium. The intergranular regions are dark and contain the aluminosilicate glass left from the cooled liquid. This liquid will soften at high temperature and limit the maximum use temperature of the ceramic.
- Contributor
- Prof W E Lee
- Organisation
- Department of Engineering Materials, University of Sheffield
- Date
- 02/09/02
- Licence for re-use
Attribution-NonCommercial-ShareAlike 4.0 International