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When used in conjunction, acoustic and electro-acoustic techniques have
significant advantages for characterizing
particle size distribution and zeta potential. As such, an optimum ultrasound
based technique should combine both acoustic and electro-acoustic
spectroscopy together in one instrument. The Acoustic & Electro-acoustic
Spectrometer DT-1202 is such an instrument.
The measuring chamber of DT-1202 contains the both
acoustic and electro-acoustic sensors. As a result this instrument
is capable of measuring an attenuation spectra
(see
acoustic
theory) for particle size, as well as Colloid
Vibration Current (see
electro- acoustic theory) for
zeta potential. This instrument can perform acoustic and electro-acoustic measurements separately and independently. At the
same time, the interpretation software is quite different for the individual
spectrometers, yet provides links
between acoustics and electro-acoustics for improved characterization.
For instance, calculation of
zeta potential from CVI
requires information about particle size distribution, acoustic
impedance and sound attenuation. These
parameters can be extracted from the acoustic attenuation spectra when acoustic and electro-acoustic
spectrometers are combined together. The acoustic spectrometer
provides, in this case, the required information about particle size
and acoustic properties of the system. This correction is
implemented into the DT-1202 software. This software contains also 3 different
ways of estimating weight fraction of solids in concentrated sample: 1) from
attenuation spectra together with PSD; 2) from attenuation spectra for known
a'priori PSD; 3) from the measured sound speed.
The DT-1202 can be supplemented with a set of
Options, which substantially extend this
instrument's capabilities. For instance, it can be supplied with 2 burettes for
titration, capable of measuring zeta potential and particle size at different pH,
surfactant concentration, and ionic strength. Aqueous and non-aqueous conductivity
measurements are also optional. Non-aqueous conductivity is especially important
for characterizing zeta potential in non-polar liquids. The Rheological option is
suitable for characterizing longitudinal rheological properties, such as
compressibility and bulk viscosity. Porous materials Option extends zeta
potential capability for these type of samples. This option includes also
measurement of porosity with high frequency aqueous conductivity probe.
The DT-1202 has a very flexible sample handling system that we
have developed while dealing with complex concentrated systems for over 15 years. This
flexibility has been achieved with a set of standard (included) and optional
(purchased)
Accessories. For
instance, in the case of a stable system, sample volume for zeta potential
measurements can be as little as 0.1 ml, and for particle size measurement - 10 ml.
There are about 50 papers published by users of
the DT-1200, 1201 and 1202 models during last decade. These papers present applications of this instrument for
characterizing particle size and zeta potential in a variety of complex systems,
and
are organized in several groups in the section
Applications. Our own studies of
particle size distributions and zeta potential with this instrument are given in
the section
Newsletters.
The
DT-1202 Acoustic & Electro-Acoustic Spectrometer is much less expensive than the sum of the
prices of the DT-100 (particle size distribution only) and DT-300 (zeta
potential only).
There are 5 US patents that describe several
novel and patented aspects of this instrument:
- Dukhin A.S. and Goetz, P.J. "Particle
size distribution and zeta potential using acoustic and electroacoustic
spectroscopy", patent USA, 6,109,098 (2000)
- Dukhin A.S. and Goetz, P.J. "Method
and device for determining particle size distribution and zeta potential in
concentrated dispersions", patent USA, 6,449,563 (2002)
- Dukhin A.S. and Goetz, P.J. "Method
for determining particle size distribution and structural properties of
concentrated dispersions", patent USA, 6,910,367 B1 (2005)
- Dukhin A.S. and Goetz, P.J. "Method
for determining particle size distribution and mechanical properties of soft
particles in liquids", patent USA, 6,487,894 B1 (2002)
- Dukhin A.S. and Goetz, P.J. "Method
for determining electric properties of particles in liquids by means of
combined electroacoustics and complex conductivity measurements",
patent USA, 6,915,214 B2 (2005)
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