Mullite Fibers Prepared by Sol-Gel Method Using Aluminum Chloride Aluminum Isopropoxide and Tetraethylorthosilicate

Mullite fibers with good flexibility were prepared from an aqueous water solution of aluminum chloride (AC), aluminum isopropoxide (AIP), tetraethylorthosilicate (TEOS) by the sol-gel process. Aluminosilicate spinnable sol (pH=2) with the stoichiometric mullite composition (Al:Si=3:1, AIP/AC=2:1) was prepared. The removal of organic and chlorine was completed at 800 degrees C. The complete transformation to mullite was observed at 1200 degrees C by X-ray diffraction (XRD). The lateral and circumferential cracks were showed in the results of scanning electron microscopy (SEM) when fibers were sintered at 10 degrees Cmin-1. It was useful for preparation of fibers with smooth surface and uniform diameter by controlling the sintering schedule.