Abstract
The synthesis of fibrous mullite followed by the KDC (Knead-Drying-Calcination) process, that is used for the synthesis of potassium titanate fibers was developed. Ammonium alum was mixed with hydrated halloysite clay to make bubbles in the fired body and to control the Al2O3 content, then was heated at 1500°C for more than 5h. The obtained bubbled mixture was treated with hydrofluoric acid to dissolve excess glass, then fibrous mullite was obtained. The following effects of additives were determined. Ammonium alum shortened the mullite fibers. Boric acid or borix, which is simultaneously mixed with ammonium alum, produces longer mullite fibers. In addition, the fiber was grown to about 30-70μm by doping with boric acid or borix by about 5-10mass%, fired at 1500°C for 10h.
