چكيده لاتين :
Dispersion and rheological behaviors of ionically stabilized aqueous alpha alumina
suspensions were investigated in various pH values (3, 11) and solid volume fractions (4, 7, 10,
15) Vol% using sedimentation experiment as well as viscosity measurement. Interface separating
porous-packed sediment from a relatively clear supernatant at pH 11 was measured over 20
hours with the aim ofobtaining linearity range, initial settling velocity, final sediment height and
suspension sensitivity factor, whilst it failed to be observed in the case ofpH 3 for its turbid
supernatant. Thus, the final sediment level instead of interface location was taken into
consideration. For all solids loading, final sediment level in the case ofpH 3 was smaller than
those in pH 11. The interface was observed to be moving downward in a linear fashion, with the
steady drive toward an equilibrium state, which was substantiated to be pH and solid loading
dependent. As (PHI) increased, linearity time changed in an ascending order. pH 11 suspensions
showed good agreement with the well-known Richardson-Zaki equation and displayed dramatic
variations in initial settling velocity, whilst it was not the case for pH 3 as understood generally by
turbidity observations. In addition, pH and (PHI) appeared to be more effective in giving stability to
the suspending systems. On the other hand, rheological behaviors ofthese suspensions were taken
into consideration for better indication of suspension stabilization degree in which suspension
yield stress derived using viscosity values was focused. The results showed that Ty at pH 3 is much
lower than that of at pH 11. This is a further indication of hetter dispersion at pH 3. It was also
found that for all (PHI) values, pH 3 suspensions were more stable than the flocculated pH 11 ones.
