Enhanced Densification of Boehrmte Sol‐Gels by α‐Alumina Seeding

Boehmite sol‐gels were seeded by adding <2.0 wt%α‐alumina powder to a 20% boehmite hydrosol at pH =3. The seeded gel sintered to 98% of theoretical density after 100 min at 1200°C, whereas the unseeded gel had to be sintered at 1600°C to reach 94% of theoretical density. This difference results primarily from nucleation by the α‐alumina seeds and enhanced transformation of the boehmite to α‐alumina, such that a uniform, well‐ordered, fine‐grained α‐alumina micro‐structure forms prior to densification.