Transparent alumina

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Transparent alumina is a transparent form of aluminium oxide, Al2O3. In bulk, solid form, alumina is a colourless, transparent solid. Ruby and sapphire are two forms, containing different impurities, which occur naturally.

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As a powder or solid formed by sintering (welding together small particles), alumina is opaque or translucent. Recently, a method of sintering very small particles of alumina has been developed by researchers at the Fraunhofer Institute for Ceramic Technologies and Sintered Materials. This sintered alumina is very hard, nearly transparent, and has a very high melting point (2303 Kelvin), yet like other sintered materials it can be produced at temperatures much lower than its melting point.

In 2004, Anatoly Rosenflanz and colleagues at 3M in Minnesota used a "flame-spray" technique to alloy alumina (aluminium oxide) with rare-earth metal oxides to produce strong glass with good optical properties. The method avoids many of the problems encountered in conventional glass forming and may be extensible to other oxides.

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[edit] References

  • Rolf Apetz and Michel P. B. van Bruggen. "Transparent Alumina: A Light-Scattering Model", Journal of the American Ceramic Society 86, page 480, March 2003.
  • Andreas Krell, Paul Blank, Hongwei Ma, Thomas Hutzler, and Manfred Nebelung. "Processing of High-Density Submicrometer Al2O3 for New Applications", Journal of the American Ceramic Society 86(4):546-553, April 2003. (also online: [1])
  • A Rosenflanz et al 2004 Nature 430 761 (online abstract)

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