The activation energy of crystallization of amorphous silica was determined from DTA-analysis to be
Ea/k = 42730
K
w0 = 2.9 *1011
s-1.
It was proved by XRD analysis that annealed silica (at 1350 K, 120 h) crystallized into the high temperature phase cristobalite
An extrapolation for the annealing time of amorphous silica using the constants Ea and w0 was performed:
Silica subjected to a temperature of 1000 K would need an annealing time of approx. 150 days to exhibit a crystalline SiO2 component
Therefore, we found only amorphous silica in the laser-ablated smoke annealed at 1000 K!
Experiment:
Sol-gel SiO2 annealed
for 120 minutes at 1350 K.
Crystalline component is cristobalite.
Annealing time of amorphous
silica (extrapolation).