Mullite transformation kinetics in P 2O 5-, TiO 2-, and B 2O 3-doped aluminosilicate gels

Seong Hyeon Hong, Gary L. Messing

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Mullite transformation kinetics of sol-gel-derived diphasic mullite gels doped with P 2O 5, TiO 2, and B 2O 3 were studied using quantitative X-ray diffraction and differential thermal analysis (DTA). The mullite transformation temperature initially increased with P 2O 5 doping because of phase separation and formation of α-alumina and cristobalite. In TiO 2-doped samples, the mullite transformation temperature decreased with TiO 2 doping, and the transformation rate increased with decreasing TiO 2 particle size. Kinetic studies showed that titania reduced the activation energy for both nucleation and growth relative to pure diphasic mullite gels by lowering the glass viscosity and/or enhancing the solid-state mass transport through lattice defects. B 2O, doping decreased the mullite transformation temperature and lowered the activation energy for both nucleation and growth but especially affected the mullite nucleation process, as indicated by the much smaller grain size.

Original languageEnglish (US)
Pages (from-to)1551-1559
Number of pages9
JournalJournal of the American Ceramic Society
Issue number6
StatePublished - Jun 1 1997

All Science Journal Classification (ASJC) codes

  • Ceramics and Composites
  • Materials Chemistry

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