Micrograph 148 and full record
- Micrograph no
- 148
- Brief description
- Magnesia-chrome refractory brick
- Keywords
- aluminium , bond , brick , calcium , ceramic , chromia, chromite, chromium, grain , iron, magnesia, magnesium, silicon
- Categories
- Ceramic
- System
- MgO-Cr2O3
- Composition
- MgO 70, Cr2O3 19, Al2O3 4, Fe2O3 4, CaO 1, SiO2 1 (wt%)
- Standard codes
- Reaction
- Direct bonded brick i.e. fine MgO and Cr<sub>2</sub>O<sub>3</sub> react to form MgCr<sub>2</sub>O<sub>4</sub> spinel bonds
- Processing
- MgO and Cr2O3 grain and finer bond powders pressed with organic binder and fired to 1850 °C in neutral atmosphere.
- Applications
- Secondary steel making e.g. high wear areas of vacuum degassers. Were used extensively in cement kiln linings but formation of carcinogenic Cr<sup>6+</sup> in use means they are no longer used.
- Sample preparation
- Polished but unetched.
- Technique
- Reflected light microscopy
- Length bar
- 1 mm
- Further information
- The micrograph shows the large sintered MgO aggregate (grey) with white chromite and dark pores. In particular, small (5mm) Cr2O3 precipitates are seen in the MgO. Fine particles react to form spinel which directly bond the aggregates conferring high temperature strength.
- Contributor
- Prof W E Lee
- Organisation
- Department of Engineering Materials, University of Sheffield
- Date
- 10/05/02
- Licence for re-use
- Attribution-NonCommercial-ShareAlike 4.0 International
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