Effect of rheological properties of zircon-alumina suspensions on density of green casts

Abstract

Rheological properties of aqueous suspensions (48 vol%) of zircon-alumina mixtures containing different amounts of polyelectrolyte as dispersant were studied. Slip casting in a plaster mold and pressure filtration at 8 MPa experiments were performed to correlate the rheological properties of the suspensions with the relative density of green casts. Flow curves fitted satisfactorily to the Casson model. The Casson viscosity values remained nearly constant whereas Casson yield stress parameter decreased to a minimum and then increased with increasing the amount of dispersant added. The influence of particle size distribution (PSD) of the powder mixtures on Casson yield stress parameter and on the minimum viscosity was also examined. Green densities increased as yield stress Casson parameter decreased. The mixture of alumina and zircon as fine and coarse powders produced bimodal PSD which maximized the green density of the compacts. Some weakly flocculated suspensions having low apparent viscosity and small yield stress produced casts with relatively high densification. This is attributed to a slight higher viscosity at low shear rates of these suspensions in which settling of particles and /or segregation of components can not occur

Characterization and production of slip casts mullite–zirconia composites

“…To enhance particle packing, small particles must fit the interstices between large ones. Similar to the study carried out by Garrido et al [30,31] in our study experimental results have confirmed that bimodal or a continuous broad particle size distribution can be used to achieve Fig. 13 EDX analysis of mixed (MZC55) composition a high particle packing efficiency and to minimize the viscosity (Fig.…”

“…At the same time, two types of zirconia grains are present one of which is intergranular zirconia located between the mullite grains and the other one is intragranular zirconia present within mullite matrix. Many researchers [19,[31][32][33] put forth that spherical-shaped intragranular particles are tetragonal ZrO 2 , while the intergranular ZrO 2 is mainly monoclinic.…”

Applications in Complex Systems

“…In water, solids such as alumina can interact through interparticle forces to form flocs leading to non-Newtonian rheological behavior. These flocs immobilize some liquid essentially increasing the effective solid volume and thus the viscosity of the solidliquid mixture increases (Garrido & Aglietti, 2001). Dispersants are added to improve the flow and handling characteristics of the slurry.…”

Determination of dispersion efficiency of cement suspensions by method of centrifugation

“…Using compressive rheology, Garrido and Aglietti23 achieved improvement of the rheological properties of aqueous suspensions (48 vol %) of alumina‐zircon mixtures and polyacrylate‐based dispersant by controlling the degree of dispersion. Further work was developed by Tsetsekou et al,24 who stabilized slurries of high‐solid content for the production of slip‐cast objects through the addition of aqueous solution of commercial dispersants (carbonic acid‐based, alkali‐free polyelectrolyte, and ammonium salts of polymethacrylic acid and acrylic polymer).…”