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Journal of Materials Science

, Volume 29, Issue 12, pp 3261–3268 | Cite as

Solid-solution range of mullite up to 1800 °C and microstructural development of ceramics

  • B. Saruhan
  • U. Voβ
  • H. Schneider
Article

Abstract

Tetraethoxysilane (TEOS) and Al-sec-butylate (Al-O-Bu) were used for the sol-gel synthesis of mullite ceramics. The starting materials had bulk compositions corresponding to values between 72 and 78 wt% Al2O3, and 28 and 22 wt% SiO2, respectively, and were calcined at 400 °C (A-series) and 1100 °C (B-series). B-series samples, despite their higher green densities, could only be sintered to about 65–70% TD (theoretical density) at 1650 °C, whereas A-series samples achieve values of about 93–98% TD. Ceramics with relatively high amounts of glass phase from large tabular mullite crystals, which are embedded in a finer-grained mullite matrix. As soon as the bulk Al2O3 content increases, equiaxed mullite grains appear and the mean grain size becomes smaller, showing a significant difference between the nucleation and crystal growth mechanisms of mullites formed in samples with the lower and higher Al2O3-bulk compositions. Depending on the bulk composition of the samples, the temperature-controlled solid-solution of mullite ranges between about 72.7 and 74.3 wt% Al2O3 at 1600 °C and 74.1 and 75.4 wt% Al2O3 at 1800 °C, indicating that the solid-solution region bends over towards the Al2O3-side of the Al2O3-SiO2 phase diagram.

Keywords

Al2O3 Microstructural Development Bulk Composition Theoretical Density Glass Phase 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Chapman & Hall 1994

Authors and Affiliations

  • B. Saruhan
    • 1
  • U. Voβ
    • 1
  • H. Schneider
    • 1
  1. 1.Department of CeramicsGerman Aerospace Research Establishment (DLR), Institute for Materials ResearchKölnGermany

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