Analysis of isothermal sintering data reveals that the viscosity of a gel increases with time. If the experiment is continued long enough, a limiting value of viscosity, η (final), is reached at each temperature. The increase in viscosity is attributed to two concurrent processes: condensation of hydroxyl groups and structural relaxation. Analysis of heat capacity (Cp) data permits an estimate of the viscosity (η) of the sintered glass. The results are in good agreement with η (final) from the sintering data. The approximate dependence of viscosity on hydroxyl content ([OH]) was established using η obtained from (Cp) data and [OH] from IR transmission spectra. The results indicate that structural relaxation contributes significantly to the rise in η during sintering.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Materials Chemistry