Table Of ContentUnited States Department of Commerce
Technology Administration
National Institute of Standards and Technology '0
A111DM 123=131
NIST Special Publication 856
Electroacoustics for Characterization of
Particulates and Suspensions
Proceedings of Workshop held at the
National Institute of Standards and Technology
February 3-4, 1993
Gaithersburg, Maryland
Subhas G. Malghan, Editor
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//856
1993
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NIST Special Publication 856
Electroacoustics for Characterization of
Particulates and Suspensions
Proceedings of Workshop held at the
National Institute of Standards and Technology
February 3-4, 1993
Gaithersburg, Maryland
Subhas G. Malghan, Editor
Ceramics Division
Materials Science and Engineering Laboratory
National Institute of Standards and Technology
MD
Gaithersburg, 20899
Issued September 1993
U.S. Department of Commerce
Ronald H. Brown, Secretary
Technology Administration
Mary L. Good, Under Secretary for Technology
National Institute of Standards and Technology
Arati Prabhakar, Director
National Institute of Standards U.S. Government Printing Office For sale by the Superintendent
and Technology Washington: 1993 of Documents
Special Publication 856 U.S. Government Printing Office
DC
Natl. Inst. Stand. Technol. Washington, 20402
Spec. Publ. 856
308 pages (Sept. 1993)
CODEN: NSPUE2
PREFACE
Traditionally, interface chemistry of particulates and colloidal stability in liquids has been
characterized by techniques based on microelectrophoresis. Since the conception of the zeta
potential, colloid scientists have utilized microelectrophoresis and moving boundary
electrophoresis extensively for the measurement of electrophoretic mobilities. Significant
progress has been made in developing understanding and scientific data on many particulates
of commercial and technical interests. Some of the major drawbacks of these methods are
the need for use of low concentrations of particulates in the suspensions, the requirement of
optical opacity of particulates, and the exclusive restriction to colloidal size particulates.
The electroacoustic technique, based on physical effects described by Debye, is relatively
new and the laboratory instrumentation has become available only in the last decade. This
new instrumentation by Matec Applied Sciences and Pen Kern Inc. is based on the
application of either electrical fields or ultrasound as external fields to the particles and
measurement of the resulting electrical or ultrasonic response. These instruments, while
addressing the primary drawbacks of electrophoresis instruments, allow the determination of
signals that are related to the electrokinetic zeta potential for colloidal suspensions in polar
and nonpolar media. In recent years, the electroacoustic technique has been extensively
utilized for the characterization of a variety of particulates in dense suspensions of polar and
nonpolar liquids with great success. As a result of this surge in activity, a number of
technical issues have surfaced.
In order to discuss these issues and develop a common understanding of the fundamentals of
electroacousties, a workshop was organized at the suggestion of the user community.
"Electroacoustics for Characterization of Particulates in Suspensions" is the first workshop on
this subject organized by the National Institute of Standards and Technology (NIST). This
workshop was held on February 3-4, 1993 at NIST, Gaithersburg, MD. The primary
purpose of this workshop was to bring together scientists and engineers working in this field
to address relevant scientific and technical issues on the measurement of electroacoustic
parameters in the study of particulates. The participants included leading scientists,
manufacturers of electroacoustics, and researchers from minerals, ceramics, pharmaceutical,
inks, paints, cement and paper industries. The technical content of this workshop included
theoretical understanding of electroacoustics, latest developments in equipment, application of
electroacoustics to different industrial problems, methods and procedures in the measurement
of electroacoustic parameters, interpretation of these measurement parameters, and major
issues in the measurements.
The participants received a compilation of presentation viewgraphs after the meeting. This
proceedings of the workshop has been possible due to the efforts of a number of my
colleagues who not only presented their results but also provided their papers. Without their
dedication, this would not have been possible. This volume contains all but two papers
presented at the workshop. The papers were reviewed by the participants of the workshop.
iii
In addition, the session chairs prepared the attached notes based on the discussions held
under different groups.
This report is divided into six sections based on the sessions held at the workshop. The first
session constituted papers on theoretical aspects and new data on electroacoustics
phenomenon, followed by application of this theory to the development of new
instrumentation. Prof. Hunter described the results of verification of electrophoretic mobility
and dynamic mobility for mono and polydisperse particles. In addition, data on
measurements with the Matec Applied Science's new prototype version of Acoustosizer were
presented to illustrate the accuracy of determination of magnitude and phase of the dynamic
mobility over a frequency range of 0.3 to 11.1 MHz. Prof. Pendse presented the analysis of
MHz
high density suspensions by analyzing attenuation coefficient spectra over 1.0 to 100
frequency range to determine particle size distribution. In the area of new instrumentation,
both theory and experimental results of Matec Applied Sciences and Pen Kem Inc. were
presented by Messrs. D. W. Cannon and P. Goetz, respectively. The second generation of
these instruments have the capability to measure both particle size distribution and zeta
potential in dense suspensions.
In the second session, papers related to applications and procedural aspects of using
electroacoustics were presented. Dr. R. O. James discussed the calibration of Electrokinetic
Sonic Amplitude instrumentation using lattices and oxide colloids as a function of volume
fraction. Excellent precision of the ESA technique in comparison with the classical
electrophoresis techniques was demonstrated. The application of ESA technique to
concentrated suspensions of carbon black in apolar liquids was used to study charging
mechanisms and influence of dispersants by Dr. R. E. Kornbrekke, I. D. Morrison and T.
Oja. Their results showed that particle charging was due to a combination of selective acid-
base type interaction coupled with ion-pair dissociation. In a paper by Dr. Valdes, the
application of the ESA technique to the characterization of colloidal diamond particles as
applied to the development of an electrophoretic coating process for selected area nucleation
and patterning of diamond thin films was presented. Background electrolyte correction in the
measurement of ESA was discussed by Dr. F. N. Desai. Under high ionic concentrations,
these effects become significant. If not corrected for, the results might indicate an apparent
shift in the iso-electric point.
In the third session, two papers were presented by Drs. J. Pollinger and V. A. Hackley on
the application of ESA measurements for silicon nitride powder processing. The powder
behavior in aqueous environment was studied by Dr. Pollinger to evaluate aging of powders
in slurries, characterization of dispersion of powders, development of multiple powder
dispersions, and correlation of ESA measurements with other suspension characterization
methods. The primary focus of Dr. Hackley's paper was on the role played by solution ionic
species in modifying surface charge behavior and the ionic contribution to the ESA signal of
the silicon nitride particles.
iv
The fourth session was devoted to the application of ESA measurements to minerals such as
clays, coal, and cements. Dr. N. D. Sanders presented the results of ESA measurements on
precipitated calcium carbonate for surface charge measurements. These results were
supported by calorimetric and Theological measurements in improving the understanding of
the coating behavior of this material. Prof. Chander discussed the role of ESA
measurements in studying the electrokinetic behavior of coal particulates. The ESA
measurements were used in the interpretation of surface charge and strength of adsorption of
species from an aqueous environment. In the study of portland cement, Dr. Darwin
presented a comparative data on electroacoustics, microelectrophoresis, and streaming
potential in the development of superplasticizers. Lack of strong agreement between the data
from these methods and difficulties in the determination of true zeta potential in such
complex systems was discussed. Prof. Moudgil presented the results of the application of
ESA measurements in mineral systems where solid-liquid or liquid-liquid interface chemistry
data are required.
The primary theme of the fifth session was coatings, though two related papers were
presented in other sessions. Dr. Krishnan's paper (not presented at the workshop) deals with
the application of the ESA technique in improving the performance of solvent based gravure
inks. A maximum value of ESA corresponded to a minimum in the particle size distribution,
thus providing a measure to control the coating process. The application of ESA
measurements was employed in the characterization of phosphors by Dr. A. Dutta. This
study involved the investigation of electrokinetic behavior of phosphors in the presence of
non-luminescent additives, surface coatings, and polyelectrolytes. An investigation on
mechanisms of charging of liquid toner by ESA were presented by Dr. J. R. Larson, Besides
presenting a model for micelle ionization and particle charging in these systems, the ESA
technique was used in the study of liquid toner particles.
The sixth session was devoted to discussions and identification of issues. Based on the group
discussions, the session chairs were responsible for the development of the issues identified
in the last chapter of this report
We
are pleased that Ceramics Division at the National Institute of Standards and Technology
sponsored this workshop. Our sincere thanks to Stephen W. Freiman, Division Chief, for
his support and encouragement. Special thanks to Margaret Robinson who was responsible
for workshop arrangements and preparation of the workshop proceedings. Also, thanks to
Vincent A. Hackley for his assistance in organizing the workshop and reviewing papers.
Most of all, our thanks go to Lori Phillips and her colleagues at NIST for the excellent
arrangements of the workshop and help with registration.
Subhas G. Malghan
National Institute of Standards
and Technology
v
DISCLAIMER
Information on product names, manufacturers, or suppliers are included in this report for
clarification. This does not imply endorsement of the products or services by the National
Institute of Standards and Technology.
vi
TABLE OF CONTENTS
Preface
iii
Session I. Fundamentals ofElectroacoustics and Instrumentation
Chairman: R. O. James, Eastman Kodak Co.
Determining Charge and Size with the AcoustoSizer 1
Richard W. O'Brien, William N. Rowlands and Robert J. Hunter
University of Sydney
Theoretical Considerations in Acoustophoretic Analysis of Concentrated
Colloids 23
Hemant P. Pendse, Terry A. Strout and Arvind Shanna
University of Maine
New Developments in Electroacoustic Methods and Instrumentation 40
David W. Cannon, Matec Applied Sciences
Session II. Applications and Procedures
Chairman: H. P. Pendse, University of Maine
Calibration of Electroacoustic (ESA) Apparatus Using Lattices and Oxide
Colloidal 67
R. O. James, Eastman Kodak Company
Electrokinetic Measurements of Concentrated Suspensions in Apolar
Liquids 92
R. E. Kornbrekke, I. D. Morrison and T. Oja, Lubrizol Corp.
Acoustophoretic Characterization of Colloidal Diamond Particles Ill
AT&T
J. L. Valdes, Bell Laboratories
Session III. Advanced Ceramics Applications
Chairman: R. Mountain, NIST
ESA Measurements for Silica and Alumina: Background Electrolyte
Corrections 129
F. N. Desai, H. R. Hammad and K. F. Hayes
Department of Civil and Environmental Engineering
Oxide and Non-Oxide Powder Processing Applications Using Electroacoustic
Characterization 143
J. P. Pollinger, Garrett Ceramic Company
vii
Investigation of Parameters and Secondary Components Affecting the
Electroacoustic Analysis of Silicon Nitride Powders 161
Vincent A. Hackley and Subhas G. Malghan, NIST
Session IV. Clays, Cements and Coa!
Chairman: B, M. Moudgil, University ofFlorida
The Impact of Surface Chemistry on Particle Electrostatic Charging and
Viscoelasticity of Precipitated Calcium Carbonate Slurries 180
Yan C. Huang, Nigel D. Sanders, Frederick M. Fowkes and Thomas B.
Lloyd
Lehigh University and Specialty Minerals Inc.
Characterization of Coal Slurries by Electrokinetic Sonic Amplitude
(ESA) Technique 200
H. Polat, M. Polat and S. Chander, Penn State University
Surface Charge Characterization of Minerals by Electroacoustic
Measurements 219
B.M. Moudgil and R. Damodaran, University of Florida
Surface Charge Characterization of Portland Cement in the Presence of
Superplasticizers 238
&
David C. Darwin, Roger Y. Leung and Trevor Taylor, W.R. Grace
Company
Session V. Coatings
Chairman: N, Sanders, Minerals Inc.
Role of Particle Size and Electrokinetic Sonic Amplitude in Performance
of Solvent Based Gravure Inks 263
R. Krishnan, Sun Chemical Corp.
Electrokinetics of Phosphors 274
Arunava Dutta, Osram Sylvania Inc.
Advances in Liquid Toners Charging Mechanism: Electroacoustic
Measurement of Liquid Toner Charge 301
James R. Larson, Xerox Corporation
Session VI. Subgroups Discussions and Identification of Issues
Discussion Leaders Summary 315
VII. List ofParticipants 324
viii
