SOL-GEL PREPARATION OF SIO2 GLASSES CONTAINING AL2O3 OR ZRO2

Glasses containing up to 15 mol% Al2O3 or ZrO2 were prepared by the sol-gel process. Gels synthesized through the hydrolysis of alkoxide complexes were concluded to consist of Al-O-Si or Zr-O-Si bonds from SAXS data. Gels shrunk by the dehydration-condensation of hydroxyl groups bonded to Al or Zr atoms in the temperature range of 300-800 degrees C. The glasses were crystallized to precipitate mullite or tetragonal zirconia near the porous-nonporous conversion temperature. The Young's modulus increased with increasing content of Al2O3 or ZrO2 and reached 100 GPa at the composition of 15Al(2)O(3).85SiO(2).