Synthesis and Characterization of Silicon Carbide Powders Converted from Metakaolin-Based Geopolymer

Cengiz Bagci, Gregory P. Kutyla, Kevin C. Seymour, Waltraud M Kriven

Research output: Contribution to journalArticlepeer-review


Silicon carbide (SiC) ceramic powders were synthesized by carbothermal reduction in specific geopolymers containing carbon nanopowders. Geopolymers containing carbon and having a composition M2O·Al2O3·4.5SiO2·12H2O+18C, where M is an alkali metal cation (Na+, K+, and Cs+) were carbothermally reacted at 1400°C, 1500°C, and 1600°C, respectively, for 2 h under flowing argon. X-ray diffraction and microstructural investigations by SEM/EDS and TEM were made. The geopolymers were gradually crystallized into SiC on heating above 1400°C and underwent significant weight loss. SiC was seen as the major phase resulting from Na-based geopolymer heated to ≥1400°C, even though a minor amount of Al2O3 was also formed. However, phase pure SiC resulted with increasing temperature. While a slight increment of the Al2O3 amount was seen in potassium geopolymer, Al2O3 essentially replaced cesium geopolymer on heating to 1600°C. SEM revealed that SiC formation and a compositionally variable Al2O3 content depended on the alkaline composition. Sodium geopolymer produced high SiC conversion into fibrous and globular shapes ranging from ~5 μm to nanosize, as seen by X-ray diffraction as well as SEM and TEM, respectively.

Original languageEnglish (US)
Pages (from-to)2521-2530
Number of pages10
JournalJournal of the American Ceramic Society
Issue number7
StatePublished - 2016


  • geopolymers
  • nanoparticles
  • silicon carbide
  • synthesis

ASJC Scopus subject areas

  • Ceramics and Composites
  • Materials Chemistry


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