Dissemination of IT for the Promotion of Materials Science (DoITPoMS)

DoITPoMS Micrograph Library Full Record for Micrograph 151

Full Record for Micrograph 151

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Micrograph no
151
Brief description
Alumina-graphite brick
Keywords
alumina Link to MATTER Glossary entry for alumina, aluminium Link to MATTER Glossary entry for aluminium, antioxidant Link to MATTER Glossary entry for antioxidant, brick Link to MATTER Glossary entry for brick, carbon, ceramic Link to MATTER Glossary entry for ceramic, composite material Link to MATTER Glossary entry for composite material, graphite Link to MATTER Glossary entry for graphite, oxygen Link to MATTER Glossary entry for oxygen, silicon Link to MATTER Glossary entry for silicon
Categories
Ceramic, Composite
System
Al2O3-C-Si
Composition
Al2O3, C up to 30 (wt%), Si few%
Standard codes
Reaction
Processing
Powders and flake graphite mixed and granulated with phenolic resin or pitch binder. Heated <400°C to decompose binder leaving behind a fine C bond. Antioxidising additives (e.g. Al, Si, SiC, B4C) used to protect the C and graphite flakes. Granulated mix is hot isostatically pressed and fired in reducing atmosphere.
Applications
Hollow-ware for steel continuous casting e.g. submerged entry nozzles and shrouds and sliding gate valves.
Sample preparation
Polished but unetched.
Technique
Reflected light microscopy
Length bar
400 μm
Further information
The fused alumina ceramic grain and natural graphite flakes (seen edge on in the micrograph) are held together by a polymer-derived carbon bond and protected from oxidation by a metal (bright Si) which betters oxygen in use to form e.g. SiO2. A true composite material.
Contributor
Prof W E Lee
Organisation
Department of Engineering Materials, University of Sheffield
Date
10/05/02
Licence for re-use
Attribution-Non-Commercial-Share Alike 2.0 UK: England & Wales