Alumina Ceramics Fabricated by Colloidal Processing

Alumina ceramics were fabricated using an inorganic particulate 801 as a dispersing medium. High purity alumina was dispersed in boehmite sol and the interparticle potential in powder-sol medium was controlled by pH adjustment to obtain a well dispersed alumina suspension. The dispersion stability and suspension viscosity with varying pH in boehmite as well as water medium were .studied and presented. Alumina-boehmite slurry of more than 80 wt% solid content was achieved by controlled flocculation and green compacts were made through slurry compaction. Packing characteristics of alumina particles under slurry compaction and dry pressing were also studied and compared. Alumina slurry containing 14 wt% of boehmite has the maximum theoretical green density of about 63% at 14 MPa and the theoretical sintered density of about 96.9% at 1450°C. The microstructural features of sintered alumina show uniformly distributed grains of 2 (mu)m size. Alumina after sintering has a reasonable hardness of 2500 kg.mm^-2. Slurry compaction is found to be a novel method for producing high dense alumina ceramics.