The influence of solid loading in suspensions of a submicrometric alumina powder on green and sintered pressure filtrated samples

The present work deals with preparation of stable suspensions of a submicrometre alumina powder with different contents of solid for pressure filtration. The optimum dispersant content (2.2 wt.% of Darvan C-N) was determined by sedimentation tests and viscosity measurements. By modification of the solid loading and dispersant content two kinds of aggregation were observed. One type of aggregates is related to the use of excessive solid loading in suspension. In samples prepared from these suspensions only minor effect on sintered microstructure was observed, which increased with increasing volume fraction of hard aggregates. In case of excess dispersant addition weak aggregates formed as the result of depletion flocculation. Weak aggregates had stronger negative effect on green microstructure, with consequent negative impact on sinterability.