EFFECTS OF IMPURITIES ON THE HYDROTHERMAL REACTIONS OF ALUMINA,
EMMANUEL COLL BOSTON MASS ORIENTAL SCIENCE RESEARCH LIBRARY
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Corundum Al2O3 was obtained from boehmite AlOOH under hydrothermal conditions at temperatures above 400C. The grain size of the crystals with definite habits was 10 to 100 microns. The effects of impurity on the crystallization process of corundum were investigated. It was found that the reaction rate, crystal size and habit, and incorporation of added ions were strongly influenced by temperature change, pH change, and addition of impurities into the solution. These observed data were explained as the results of impurity effects on the solvent structure, solution structure, solubility, diffusion process, nucleation process, and growth process. Habit modification of corundum by adding iron-group ions as sulfate, nitrate, chloride, hydroxide or oxide was determined. Copper ion is not solid-soluble in corundum if sulfate ion coexists it is solid-soluble substitutionally as Cu3 in six coordinated sites if it is added as nitrate, oxide or hydroxide.
- Ceramics, Refractories and Glass