Anisotropic grain growth in seeded and B2O3-doped diphasic mullite gels

Anisotropic grain growth in mullite was investigated in B2O3-doped diphasic gels seeded with either mullite particles or whiskers. Anisotropic grain growth was observed in all systems. The largest anisotropic grains were obtained with a system seeded with 2 wt% mullite whiskers and doped with 2 wt% B2O3. The mullite whiskers act as sites for multiple nucleation and subsequently as templates for mullite overgrowth. B2O3 lowered the mullite formation temperature by 150 C and significantly enhanced anisotropic grain growth, independent of the presence of seed particles. This enhancement was attributed to increased dissolution of alumina. 23 refs.