Synthesis and characterization of silicon carbide powders converted from metakaolin-based geopolymer
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CitationBagci, C., Kutyla, G.P., Seymour, K.C., Kriven, W.M. (2016). Synthesis and characterization of silicon carbide powders converted from metakaolin-based geopolymer. Journal of the American Ceramic Society, 99(7), 2521–2530.
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 ?m to nanosize, as seen by X-ray diffraction as well as SEM and TEM, respectively. © 2016 The American Ceramic Society