In-depth characterization of the early sintering stages of an amorphous silica powder

The consolidation and densification mechanisms occurring in the early sintering stages within a pure silica-based glassy material have been thoroughly investigated. Dilatometry curves were studied through several analytical approaches. In isothermal conditions at 1200°C, the identified m exponent value (correlating relative shrinkage to dwell time) is equal to 1.02 ± 0.08, which agrees with the analytical model of Coble for viscous flow sintering. Apparent activation energy and viscosity for sintering process were determined by applying the constant heating rate method and cyclic loading dilatometry respectively. The measured evolutions of specific surface area and relative density at the macroscale were correlated to microstructural features (i.e. pore size and interparticle neck radius). As shown, the silica material undergoes first a consolidation stage without significant shrinkage, before the occurrence of densification through particles coalescence. The shrinkage-neck growth trajectory characteristic of viscous flow sintering was established for this real glassy material, and compared to predictions of numerical models at the meso-scale from the literature.