PRESSURE SENSITIVITY FOR PARTICLE PACKING OF AQUEOUS AL2O3 SLURRIES VS INTERPARTICLE POTENTIAL

The relation between relative density and applied network pressure has been determined for aqueous Al2O3 slurries prepared with different in terparticle potentials and consolidated by centrifugation. Attractive interparticle potentials were obtained by either changing the pH to th e isoelectric point or adding an excess electrolyte. A range of centri fugal speeds produced consolidation pressures between 10(-3) and 10 MP a. At lower speeds, the density gradient was determined with an X-ray absorption technique. The maximum packing density (0.62 +/- 0.02) was achieved for both dispersed and coagulated slurries at network pressur es >0.5 MPa. At lower pressures, the packing density of these slurries was pressure-dependent, where the coagulated (salt added) slurries ha d a relative density between that of the dispersed and flocced slurrie s. Slurries flocculated by adjusting the pH to the isoelectric point n ever reached the highest packing density at the largest pressure.