Silica glass was synthesized form TEOS and deionized water using sol-gel process. To introduce the physicochemical effects of ultrasonic waves, an ultrasonic homogenizer was used to mix reactants instead of adding cosolvents. 2-step method was chosen to separate hydrolysis reaction and condensation reaction, and thus to control the microstructure of wet gels. Wet gels were dried in 5-8 hours without cracks using supercritical drying with ethanol at 300°C and 10.34 MPa. Aerogels thus obtained have hydrophobic surfaces due to the reesterification reactions during supercritical drying. Aerogels were sintered in a tube furnace in the changing atmosphere from N2 through O2 to He. Sudden volume change was started at 1050°C and sintering was completed at 1100°C as expected. Large pores of aerogels allowed fast sintering in 16 and a half hours. Incomplete extraction in supercritical drying step produced crystals during sintering.
- silica glass