An aluminum/Al2O3 composite body is produced by a displacement reaction between SiO2 and molten aluminum. The growth rate of the reaction layer possesses negative (anomalous) temperature dependence at 1000-1300 K. This study compared reported reaction-kinetic data and investigated causes for this temperature dependence. The reaction product, Al2O3, changed from the γ-/θ-Al2O3 phase to the α-Al2O3 phase in this temperature range and α-Al2O3 became the dominant phase at > 1273 K. Isothermal transformation of the γ-/θ-Al2O3 product phases to the α-Al2O3 phase was also observed. Morphologies and scales of the Al2O3 phases change drastically at 1173 K; this transition occurred in a spatially discontinuous manner. Reaction-rate retardation was interpreted in terms of occurrence of the competitive and simultaneous reactions to produce different Al2O3 phases in this temperature range. It was also found that the hydrogen release from the raw SiO2 and the SiO2 phase transformation were not related to the negative temperature dependence.
|Number of pages||8|
|Journal||Journal of the American Ceramic Society|
|Publication status||Published - 2002 Jul|
ASJC Scopus subject areas
- Ceramics and Composites
- Materials Chemistry