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 interparticle potentials and consolidated by centrifugation. Attractive interparticle potentials were obtained by either changing the pH to the isoelectric point or adding an excess electrolyte. A range of centrifugal speeds produced consolidation pressures between 10(-3) and 10 MPa. 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 pressures >0.5 MPa. At lower pressures, the packing density of these slurries was pressure-dependent, where the coagulated (salt added) slurries had a relative density between that of the dispersed and flocced slurries. Slurries flocculated by adjusting the pH to the isoelectric point never reached the highest packing density at the largest pressure.