As. Dukhin et Pj. Goetz, New developments in acoustic and electroacoustic spectroscopy for characterizing concentrated dispersions, COLL SURF A, 192(1-3), 2001, pp. 267-306
Citations number
61
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
There are two different techniques (acoustics and electroacoustics), both o
f which employ ultrasound instead of light for characterizing properties of
liquid-based dispersions. Acoustic and electroacoustic techniques offer a
unique opportunity to characterize concentrated dispersion in their natural
states because ultrasound can propagate through samples that are not trans
parent for light. Elimination of a dilution step is crucial for an adequate
characterization of liquid dispersions, especially when the high concentra
tion leads to structured systems. The last 2 years have been very successfu
l for these new techniques. We give a short overview of the new development
s during this time. It includes first of all a new electroacoustic theory w
hich is valid for concentrated dispersions. So far this theory works only f
or thin double layer but for any value of the Dukhin number. Acoustic theor
y has been expanded as well due to incorporation of the 'structural losses'
in addition to the existing mechanisms of the particles interaction with t
he sound field. There is a version now which is supposed to work in the str
uctured dispersions. We give here the first example of this new application
for acoustics. Another important new application for acoustics is a 'mixed
dispersions', which is dispersed system with several dispersed phases. A s
pecially developed 'effective media' approach allows us to tackle successfu
lly these very complicated systems. Hardware has been improved during last
2 years as well. We mention here just one new device: zeta -potential probe
. It makes electrokinetic measurement very simple, fast (down to 15 s), pre
cise (0.1 mv) and accurate. It can work on-line. We give here some examples
of the results obtained with this probe. (C) 2001 Elsevier Science BN. All
rights reserved.