Centrifugal Consolidation of Al₂O₃ and AI₂O₃/ZrO₂ Composite Slurries vs Interparticle Potentials: Particle Packing and Mass Segregation

Abstract

Dispersed ceramic slurries with high concentrations of indifferent electrolyte have been shown to effectively eliminate mass segregation effects in composite materials. Furthermore, high packing efficiencies have been achieved with these systems. It has been suggested that the addition of high concentrations of indifferent electrolytes to an otherwise dispersed ceramic slurry modifies the interaction potential so that the short-range adhesive attraction is diminished by additional repulsive forces. This lower attractive force is still high enough to cause coagulation which raises the viscosity, but small enough to allow easy particle rearrangement during filtration or centrifugation. This rearrangement leads to high packing densities. The effectiveness of this behavior on the improvement of ceramic powder processing of composites is demonstrated with Al2O3 and ZrOz.[

Strongly Degenerate Parabolic-Hyperbolic Systems Modeling Polydisperse Sedimentation with Compression

“…Some more treatments that less closely refer to a particular mathematical model support the similar idea of "en masse" sedimentation of multispecies suspensions at high concentrations [5,29,121]. Zeng and Lowe [121] consider rigid-sphere suspensions (not forming compressible sediments) but postulate the existence of a "critical concentration," in the sense of the quantity φ * (not φ c ) introduced above, at which change in sedimentation behavior from differential settling (size fractionation) to "enmasse settling of the entire suspension" occurs [121], and they indicate that values of φ * ranging from 0.3 to 0.55 are suitable, depending on the material.…”

Layer orientation effects on the R-curve behavior of multilayered alumina–zirconia composites

“…Centrifugal casting is a particle consolidation process in which particles in a colloidal suspension settle under centrifugal acceleration [13][14][15][16][17]. Multi-layered aluminazirconia composites having uniform layer thickness and parallel stacking were produced by sequential centrifugal consolidation of flocculated aqueous alumina-zirconia slurries (alumina; A16SG, ALCOA and ceria-partially stabilized zirconia: CEZ-12, American Vermiculite Corp., Marietta, Georgia) as described previously [18] and briefly described here.…”

Consolidation of nanoparticle suspensions by centrifugation in non-porous moulds

“…The drawback of the centrifugal consolidation method is the possible particle size segregation and microstructural gradient development in the deposit due to different settling of particles of different sizes and/or densities. This can be eliminated by using weakly flocculated suspensions (prepared from dispersed suspensions by adding a large amount of indifferent electrolyte) that are characterised by high viscosity with a pronounced yield stress [6]. Such an approach, however, results in a lowdensity deposit often with an inhomogeneous density profile [7][8][9].…”