Pressure Sensitivity for Particle Packing of Aqueous Al₂O₃ Slurries vs Interparticle Potential

Abstract

The relation between relative density and applied network pressure has been determined for aqueous A1,0, 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 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.

Colloidal Processing of Ceramics

“…Because of the weak attraction between particles, such slurries could be consolidated under modest applied pressures to densities approaching those attainable in dispersed systems. 67 In contrast, Gauckler and co-workers 46,47 utilized enzymatic reactions to shift pH toward the IEP of the colloidal system of interest, thereby inducing coagulation, as shown in Fig. 4 (refer to Section V).…”

“…During drying, fluid is removed via evaporative processes (refer to Section VI). Experimental work by the groups of Zukoski 92 and Lewis 3 demonstrated that particlepacking densities rivaling those achieved under applied mechanical loads, e.g., pressure filtration, 67,113 are possible via chemically driven consolidation.…”

“…For example, Lange and co-workers 44,67 produced weakly attractive, aqueous alumina suspensions at pH conditions below the IEP point and found that the yield strength increased with increased electrolyte concentration. These attractive networks were much weaker than those produced by flocculating the system at its IEP (pH ϳ8.5).…”

Dispersion of mixtures of submicrometer and nanometre sized titanias to obtain porous bodies

“…Some authors have demonstrated that it was possible to enhance sintering through green state deformation processing, as stated for alumina submicrometer sized particles [28,29]. When homogeneous dispersions of two phases with very different size or shape are needed, heterocoagulation can be a suitable route to force the uniformity through strong electrostatic interactions.…”

Development of Slurry Characterization Method by Constant Pressure Filtration-Analysis of Cake Forming Behavior-

“…The slurry condensation behavior has been usually characterized by sedimentation or centrifugal sedimentation and there are many reports [12][13][14][15][16] associated with the sedimentation test. However, the experimental time is very long because the particle size is on the submicron order in the ceramics industry, therefore a new evaluation method is required to shorten experimental time.…”