Rheological properties of concentrated alumina slurries, inf

Abstract
The relationship between the pH, the electrolyte concentrations
and the rheological properties of high concentrated alumina slurries
in aqueous medium is of great importance because it is considered to
be the key to control the stability of the slurries from flocculation.
Zeta potential of alumina slurries with and without Duramax C
(dispersant agent) as a function of pH was studied. Two pH’s around
the zero point of charge of alumina slurries were selected for the
investigation of rheological properties. The rheological properties of
aqueous alumina slurries with respect to different parameters, e.g.:
viscosity, elastic modulus (storage modulus G΄) and viscous
modulus (loss modulus G˝), were investigated. Viscosity
measurements of the slurries as a function of Duramax C content at
both pH’s 8.4 and 9.4) were used to determine the state of slurries.
Three states of slurries, termed flocculated, partially deflocculated
and fully deflocculated, were selected for further investigation. The
viscosity of the three slurries at both pH’s as a function of shear rate
was determined. Fully deflocculated slurry shows Newtonian
behavior at all shear rates at both tested pH’s compared by the
partial deflocculated and flocculated system. Results of investigation
of G’ and G’’ at pH of 9.4 as a function of applied stress explored
the critical stress (τc) at which well-deflocculated alumina slurries
can be prepared to cast green body with high bulk density and
uniform microstructure.