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Formation of Ceramics from Metakaolin-Based Geopolymers. Part II: K-Based Geopolymer

Authors

  • Jonathan L. Bell,

    1. Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
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    • *Member, The American Ceramic Society.

  • Patrick E. Driemeyer,

    1. Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
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    • *Member, The American Ceramic Society.

  • Waltraud M. Kriven

    Corresponding author
    1. Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
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    • *Member, The American Ceramic Society.

    • **Fellow, The American Ceramic Society.


  • C. Jantzen—contributing editor

  • This work was supported by Air Force Office of Scientific Research (AFOSR), USAF, under Nanoinitiative Grant No. FA9550-06-1-0221, through Dr. Joan Fuller.

†Author to whom correspondence should be addressed. e-mail: kriven@illinois.edu

Abstract

The structural evolution and crystallization of potassium-based geopolymer (K2O·Al2O3·4SiO2·11H2O) on heating was studied by a variety of techniques. On heating from 850–1100°C, potassium-geopolymer underwent significant shrinkage and surface area reduction due to viscous sintering. Small, 15–20 nm sized precipitates present in the unheated geopolymer coarsened substantially in samples heated between 900° and 1000°C. However, the microstructural surface texture was dependent on the calcination conditions. Leucite crystallized as the major phase after being heated to >1000°C, although a minor amount of kalsilite was also formed. Prolonged heating for 24 h at 1000°C led to the formation of ∼80 wt% of leucite, along with 20 wt% of remnant glassy phase. The surface of geopolymers heated to 1000°C attained a smooth, glassy texture, although closed porosity persisted until 1100°C. Thermal shrinkage was completed by 1100°C, and the material reached 99.7% of the theoretical density of tetragonal leucite.

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