Abstract
In this work the colloidal behaviour of three different TiO2 nanopowders
in water is studied. A commercial powder of anatase and another of
rutile were used for this study. For comparison purposes, a cryogel
of anatase synthesised by a particulate sol-gel route and freeze-dried
was also studied. All three powders were characterised by scanning
electron microscopy, specific surface area measurements and X-ray
diffraction. Diluted aqueous suspensions were prepared and characterised
in terms of particle size distribution and zeta potential, using
dynamic light scattering and laser Doppler velocimetry principles,
respectively. All suspensions were prepared using an ultrasounds
probe for mixing times ranging from 0 to 5 min. Colloidal stability
was studied as a function of pH, type and concentration of dispersants
(polyacrylic-based deflocculant and citric acid) and mixing time.
Stable suspensions of commercial nanosized powders were obtained
with polyelectrolyte contents of 1.0-1.5 wt.\%. No stable suspensions
of the cryogel were obtained with polyelectrolyte, requiring in this
case the use of citric acid as deflocculant. It was observed that
neither the size distribution nor the zeta potential values were
affected by the sonication time. (C) 2008 Elsevier Ltd. All rights
reserved.
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