Effects of Solids Loading and Dispersion Schedule on the State of Aqueous Alumina/Zirconia Dispersions

Abstract

The effects of solids loading and dispersion order on the state of aqueous slips of either zirconia or alumina, and binary slips of these two powders, have been examined. Since these powders can acquire surface charge when they are dispersed in aqueous media, changes in the ionic composition of the slip can occur as a result of the addition of solids. At higher solids loading, a substantial fraction of the ionic activity within the slip may be attributed to the solid itself. As the solids loading within unary powder suspensions is increased, it is possible to drive the suspension pH toward the point of zero-charge for the powder, resulting in diminished electrostatic stabilization and possible powder agglomeration. An analytical model was constructed to account for the observed results. This embodied a simple surface site complexation model which was augmented to include material and charge balance constraints on ionized surface sites as well as solvated ions. For binary powder dispersions of alumina and zirconia, it was found that the order of dispersing the two components could have a pronounced effect on the overall suspension behavior. The variability in results is attributed to the solubility of the alumina in the basic processing media.

Electrokinetic Properties of Colloidal Zirconia Powders in Aqueous Suspension

“…The zeta potential () is the most prominent parameter used to describe the surface-force interaction and the stabilization behavior of the particles in the suspensions. This potential is influenced by many factors, such as the powder source, [3][4][5] the electrolyte concentration (ionic strength), 3 the particle concentration and size, the solution pH, 6,7 and the state of hydration. 8 Wernet and Feke 4 reported that powder loading possibly drives the acidity of suspension toward the point of zero charge (PZC) and may result in diminished electrostatic stabilization.…”

Electrodeposition of Metal Matrix Nanocomposites: Improvement of the Chemical Characterization Techniques

“…Smaller agglomerated particle groups have a higher attraction force from the electric field that produced effective adsorption (Kuo et al, 2004). The zeta potential of nano-and micro-scaled particles is influenced by many factors, such as the source of particles (variable preparation and stabilization), the treatment with different surfactants, the electrolyte concentration (ionic strength), the particle morphology and size, the pH of the solution, and the state of hydration (Moreno et al, 1988;Wernet & Feke, 1994;Morterra et al, 1994;Leong et al, 1995;Kim et al, 1998;Kagawa et al, 1987). The particles always interact with the electrolyte and therefore chemical and physical adsorption of electrolyte ions onto the particle occurs.…”

Influência do pH sobre a estabilidade de suspensões de alumina estabilizadas eletroestericamente

“…Estes resultados estão de acordo com a literatura, que prevê valores de iep, para a α-Al 2 O 3 , variando de 7 a 9 13 . A partir da Figura 2, observa-se, ainda, maior densidade de cargas em pH ácido.…”