Effect of Al₂O₃ Particle Size on Mullite Formation by In-Situ Reaction of Aluminosilicate Castables

The total output of unshaped refractories has been increasing in recent years due to its short production cycle, safety and energy saving, good integrity and so on. Among them, aluminosilicate castables have been widely used. In order to improve the high temperature properties of castable, Al₂O₃ micro powder and SiO₂ micro powder are usually used. However, few researchers have reported the effect of particle size in matrix on in-situ formation of mullite. In this paper, a mass dissolution rate model and a solution nucleation shrinkage model are established based on the control of the rate of in-situ mullite formation, which takes place by the dissolution of Al₂O₃ to the liquid phase formed by melting of SiO₂ powder containing impurities at high temperature.The results show that with the increase of Al₂O₃ particle size, the mass dissolution rate of independent particles was accelerated, and the nuclear shrinkage rate of Al₂O₃ particles decreased fastest when the particle size is 1-10μm. The dissolution rate increases with the increase of service temperature. Moreover, the complete dissolution time is shortened with the decrease of particle size of Al₂O₃. When the particle size is 80μm, it takes 100.31 seconds for a single particle to dissolve completely, but only 1.00 second when the particle size of Al₂O₃ decreases to 8μm. (paper)