Growth Rate of Reaction Layer between SiO₂ and Molten Al above 1473 K

Abstract

Growth rate of reaction layer between molten Al and SiO₂ was measured in a temperature range between 1473 K and 1723 K, and was compared with the reported rates between molten Al and mullite. A maximum growth rate was obtained at 1623 K, above which the rate decreased and the reaction halted with formation of an initial thin layer. The same phenomenon had been reported for the reaction between Al and mullite, however, temperatures of the maximum reaction rate were lower than the present (SiO₂) case.
According to the observation of microstructures in the reacted layer, gradient of Si concentration became larger as an increase of the reaction temperature up to 1573 K, and closure of the Al phase occurred at 1723 K. Growth rate of the reaction layer was large at 1573 K, however, the residual Si concentration in the reacted layer was also large, indicating that the growth rate is not determined by the rate of Si removal.
Relationship between the microstructure and the growth rate was discussed in comparison with the mullite reaction cases, not only considering the competition between the rates of the reaction and the mass transfer of Al and Si in the reacted layer, but also considering the Al₂O₃ network structure change.