POLYMER PRECURSOR SYNTHESIS OF ALUMINA FIBERS

High strength alumina fibers were fabricated with a polymer precursor process which was monitored with C-13-NMR, elemental analysis, gas evolution, SEM, and X-ray diffraction. Methylaluminoxane was chain extended by reaction with H2O, the unreacted methyl groups were converted to propanoyloxyl and i-propanoyl groups in molar ratios of 0.2:0.8 to 0.4:0.6 to afford spinning dope of adequate fluidity which can be spun into filaments with suitable stability. These precursor fibers were hydrolyzed in two stages at ambient temperatures and at 320-350-degrees-C, and then calcined at 950-degrees-C. The resulting alumina fibers have average tensile strengths up to 1.1 GPa and modulus of greater than 140 GPa.