Densification and anisotropic grain growth were investigated in sol-gel derived, boria-doped diphasic mullite. Boria enhanced viscous flow densification by reducing the viscosity and also produced a fine grain microstructure. Whisker-like mullite grains evolved from the dense, equiaxed microstructure. The onset temperature was ~1500°C. Chemical leaching was employed to characterize the anisotropic grains. Growth kinetics showed that anisotropic grains followed the empirical equation Gn-Gon=Kt with n=3 and n=4 for the length and thickness directions, respectively. The activation energies for grain growth were 660kJ mol-1 for elongation and 800 kJ mol-1 for thickening.
All Science Journal Classification (ASJC) codes
- Ceramics and Composites
- Materials Chemistry