PREPARATION OF MULLITE FIBER

Transparent mullite fibers have been prepared using aluminum carboxyla tes (ACs) and tetraethyl orthosilicate (TEOS) as starting materials, T he ACs are derived from the catalyzed dissolution of elemental aluminu m in a mixture of formic acid and acetic acid. The solubility of alumi num in the acids is influenced by the concentrations of the acids, mat er, and additives and the preparation temperature. A 1:4:3:24 molar ra tio of aluminum, formic acid, acetic acid, and mater dissolves the alu minum completely to give a colorless, clear solution suitable for fibe r synthesis. The mixture of the ACs and TEOS, in the presence of ethyl alcohol as a mutual solvent at 50 degrees-60 degrees C, is concentrat ed to give a spinnable dope, from which mullite precursor fibers can b e drawn, Heat treatment of the precursor at 1250 degrees C yields crys tallized and transparent mullite fibers.