Fine spherical premullite particles were prepared by employing partial hydrolysis to control the difference in reaction rate of two alkoxides and by controlling the solvent composition, considering the difference in solubility of the double alkoxide. Final particles were formed via aggregation of the growing particles in the droplets and fine particles generated from the dissolved alkoxide. The optimum conditions for the preparation of spherical premullite particles were [Si(OC 2 H 5 ) 4 ] ) 0.033 mol/L, ([Al(OC 4 H 9 sec ) 3 ] ) 0.1 mol/L, [H 2 O] ) 0.5 mol/L, volume fraction of acetonitrile ) 40 vol %, and amount of HPC ) 0.1 g/L. The Al 2 O 3 /SiO 2 molar ratio of the premullite particles determined by XRF analysis was about 3:2. The premullite particles were found to be amorphous by XRD analysis, and DTA analysis of all premullite powders showed an exothermic peak associated with crystallization to the spinel phase at around 990 °C. The samples that passed through the spinel phase were transformed into the tetragonal mullite at around 1100 °C, and a transformation to orthorhombic mullite took place at about 1250 °C. The ratio of added H 2 O to Si(OC 2 H 5 ) 4 in the partial hydrolysis reaction had a significant effect on the mullitization mechanism of premullite particles and the composition of the crystal.
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