Kinetics of Cristobalite Formation in Sintered Silica

The kinetics of the cristobalite transformation are reported for sintered silica glass from 1200°C to 1650°C and plotted as a time–temperature–transformation diagram. The 1200°C–1350°C transformation data were fit to the Johnson–Mehl–Avrami–Kolmogorov expression with an time exponent of 3.0 ± 0.6 and an apparent activation energy of 555 ± 24 kJ/mol for the kinetic constant. The temperature of maximum transformation rate was found to fall between 1500°C and 1600°C. Seeding amorphous silica powder with cristobalite resulted in accelerated transformation kinetics. Silica glass powder containing residual quartz had faster transformation kinetics than fully amorphous powder seeded with cristobalite.