General Acoustics and Electroacoustics, method verification.
There are several published paper verifying basic principles of Acoustics and Electroacoustics for characterizing concentrated dispersions and emulsions.
Particle size characterization of small nano-particles is very challenging because sound attenuation caused by these particles is comparable with attenuation of water. Nevertheless we have measured successfully many systems with particle size below 100 nanometers. There are many examples published in the papers that are listed below.
There is a big advantages of Acoustics over light based methods in ability of characterizing broad particle size distributions. which include nano-size fractions. Our recent studies show that Acoustics could monitor presence of nano-particles with precision of 1%. This is important for nano-ecology and nano-toxicology.
Characterization of zeta potential of nanosize particles is simpler than for particles with micron size. There is no need in particle size correction. Electroacoustic spectrometer measures basically Smoluchowski electrophoretic mobility.
Zeta potential probe can also be used for monitoring presence of small amounts of large sedimenting particles in opaque dispersions of nano-particles
Mende, S. “Representarive on-line measurement of comminution results for nanogriding in stirred media mill”, NETCH, doctoral thesis
Stenger, F. Mende, S. Schwedes, J. and Peukert, W. “Nanomilling in stirred media mills ”, Chemical Engineering Science . 60, 4557-4565 (2005)
Dukhin, A. S. “Observation of sol-gel transition for carbon nanotubes using electroacoustics. Colloid vibration current versus streaming vibration current.” JCIS, vol.310, 1, 270-280 (2007)
Bio-Sciences and Pharmaceuticals
There are several developed applications with results published in the papers presented below. This includes:
· characterization of electric properties of chromatographic resins for proper control of their interactions with proteins
· particle size and evolution of micelles
· particle size of cells
· electric charges (valency) of proteins
Acoustics is also suitable for characterizing pharmaceutical emulsions and microemulsions with no dilution. Dilution is critical for such systems because it affect equilibrium there and can change droplet size distribution.
Acoustic measurement at a single frequency and single gap can be used for very fast monitoring kinetics of dissolving and crystallization. It offers several measurements per second.
Dukhin, A. S. Goetz, P.J. and Theo G.M. van de Ven, “Ultrasonic characterization of proteins and blood cells ”, Colloids and Surfaces B, 52, 121-126 (2006)
Acoustics can characterize particle size and zeta potential in ceramic slurries with no dilution. There are several paper published on this subject and listed below.
There is also possibility to characterize mixtures of different oxides, such as alumina and zirconia, see Chapter 8 in the book by Dukhin and Goetz. This can answer question regarding aggregation between particles of different nature.
Takeda, S. Harano, H. Tari, I. “P article size characterization of highly concentrated alumina slurries by ultrasonic attenuation spectroscopy”, in Improved Ceramics through New Measurements, Processing and Standards, Ceramic Transactuions . vol. 133, 59-63 (2002)
Takeda, S. Suenaga, H. and Tari, I. “P article size characterization of highly concentrated barium titanate slurries by ultrasonic attenuation spectroscopy”, in Improved Ceramics through New Measurements, Processing and Standards, Ceramic Transactuions . vol. 133, 53-59 (2002)
There are two papers published on subject of applicability of ultrasound for characterizing CMP slurries, see below. There are also 2 newsletters, # 1 and # 13 on the same subject.
Acoustics provides accurate particle size that agrees well with independent data. It can monitor presence of 1% large particles on the background of small nano-particles.
Electroacoustics yields very precise value of zeta potential
These measurements can be done with no dilution, which opens possibility for continuous on-line control of the slurry properties. However, calculation of the particle size and zeta potential requires information on the volume fraction. This parameter must be independently measured.
Both ultrasound based methods, Acoustics and Electroacoustics, can be used for monitoring effects of the plastisizer on the properties of cement slurry, as proved in the papers listed below. With no dilution.
Elimination of dilution is critical for accurate measurement of the cement zeta potential Cement slurry could be affect very strongly by dilution. Zeta potential probe offers zeta potential measurement with precision 0.1 mV.
Hackley, A.V. Lum, Lin-Sien, Ferraris, C.F. “Acoustic sensing of Hydrating Cement Suspensions: An explanatory study”, NIST Technical Note 1492. (2007)
Application of Acoustics and Electroacoustics for characterizing minerals dispersions are described in the papers listed below.
Titration option DTI instruments is suitable for determining optimum dose of surfactant for stabilizing clay dispersions, as described in the ref. 3.
Dukhin, A.S. Goetz, P.J. and Truesdail, S.T. “Surfactant titration of kaolin slurries using z eta potential probe”, Langmuir, 17, 964-968 (2001)
There are several experimental studies of the properties of concentrated oxides dispersions (rutile, zirconia, alumina, zinc oxide, etc) presented in the book by Dukhin and Goetz, Ultrasound for Characterizing Colloids”.
Zeta potential at extreme ionic strengths
Electroacoustics could be used at the extremely high ionic strength above 1 M, as well as for non-polar liquids with conductivity below 10 -10 S/m.
This method yields not only zeta potential at these extreme conditions, but also electric surface charge and even size of ions in non-polar liquids.
Kosmulski M. and Rosenholm, J.B. “High ionic strength electrokinetics”, Adv. in Colloid and Interface Science ”, 112, 93-107 (2004)
Zeta potential in porous bodies.
Propagation of ultrasound through a porous body creates motion of liquid inside of the pores relative to the solid matrix. This, in turn, causes relative motion of ions that are located in the diffuse layer and on the pores surfaces. This shows us as an electric current. This current is similar to the Streaming Current, with the difference that it oscillates in time. It is called Streaming Vibration Current. There have been 3 papers already published reporting experimental observation of this effect. The first theoretical paper was published in 1983.
This effect can be used for very fast and simple measuring electric surface properties of porous bodies.
Mueller, E. and Mann C. “Resin characterization by electroacoustic measurements”, J. of Chromatography A., vol. 1144, issue 1, 30-39 (2007)
Williams, M. “An Electrokinetic Transducer”, The review of scientific instruments, 19, 10, 640-646 (1948)
Dukhin, S.S. Mischuk, N.A. Kuz’menko, B.B and Il’in, B.I. “Flow current and potential in a high-frequency acoustic field”, Colloid J. 45, 5, 875-881 (1983)
Acoustics is shown as a suitable tool for characterizing coating dispersions. Particle size distribution measured for intact concentrated dispersion agrees very well with independent data.
Schoelkopf, J. Gantenbein, D. Dukhin, A.S. Goetz, P.J. Gane P.A.C.“Novel Particle size characterization of coating pigments” OMYA
Detail study presented in the paper listed below indicates that Acoustics yields a proper Particle size distribution in various dairy products. This can be achieved with no dilution.
In addition, Acoustics yields information for calculating fat content.
Emulsions and microemulsions
Acoustics makes possible measurement of Particle size of the emulsion and microemulsion droplets with no dilution, which is critical for these systems. Papers presented below indicate very good agreement between this method and independent data.
Combination of Acoustics and Electroacoustics could reveal peculiar mechanisms controlling emulsion stability, such as ion exchange in water-in-oil emulsion, see Ref. 4.
Geers, H. Witt, W. and Babick, F. “Stability analysis of emulsions and suspensions with photon cross-correlation spectroscopy”, PARTEC 2007
Richter, A. Voight, T and Ripperger, S. “Ultrasonic attenuation spectroscopy of emulsions with droplet size greater than 10 microns”, JCIS. 315, 482-492 (2007)
Acoustics provides opportunity for characterizing content of nano-particles in cosmetic dispersions with broad Particle size distributions. Precision is about 1% of the total solids content.