SYNTHESIS OF FIBROUS MULLITE BY THE KDC P ROCESS

The synthesis of fibrous mullite followed by the KDC (Knead-Drying-Cal cination) process, that is used for the synthesis of potassium titanat e fibers was developed. Ammonium alum was mixed with hydrated halloysi te clay to make bubbles in the fired body and to control the Al2O3 con tent, then was heated at 1500 degrees 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 ad ditives were determined. Ammonium alum shortened the mullite fibers. B oric acid or borix, which is simultaneously mixed with ammonium alum, produces longer mullite fibers. In addition, the fiber was grown to ab out 30-70 mu m by doping with boric acid or borix by about 5-10 mass%, fired at 1500 degrees C for 10h.