Hybrid gels, defined as gels from mixtures of polymerically and colloidally derived sols, offer many opportunities for crystalline microstructure development upon heating. In this study, hybrid mullite gels are formed by mixing a colloidal boehmite—silica sol with a polymeric aluminum nitrate—tetraethoxysilane‐derived sol. The polymeric gel crystallizes in situ to form mullite that acts as seed crystals for homoepitactic nucleation during the subsequent transformation of the colloidal component of the hybrid gel. Compared with the entirely colloidal gel, the introduction of a 30 wt% polymeric gel fraction results in an increase in apparent nucleation frequency from ∼5x1011 to ∼1x1014 nuclei / cm3 at 1375°C, a reduction in high‐temperature grain size from 1.4 to 0.4 μm at 1550°C, and an increase in the degree of microstructural homogeneity, as evidenced by intragranular pore removal.
|Original language||English (US)|
|Number of pages||5|
|Journal||Journal of the American Ceramic Society|
|State||Published - Sep 1989|
All Science Journal Classification (ASJC) codes
- Ceramics and Composites
- Materials Chemistry