PROJECT TITLE: Electroacoustic Characterization of Ceramic Powder Slurries
PROGRAM TITLE: Intelligent Processing of Materials
Principal investigator(s):
NIST Staff:
Designated Project Leader: Hackley, Vincent A.
Mailing Address: NIST
Materials (223), A256
Gaithersburg, MD 20899
Telephone: (301) 975-5790
Fax Number: (301) 990-8729
E-mail Address: vince.hackley@nist.gov
Other NIST Principal Investigator: Mountain, Raymond
Mailing Address: NIST
Physics (221), A105
Gaithersburg, MD 20899
Telephone: (301) 975-2484
E-mail Address: raymo@rdm.phy.nist.gov
Technical Description:
This project is focussed on the application of non-destructive electroacoustic techniques for
characterizing particle size and charge in aqueous ceramic powder slurries, the development of
data, measurement science and computational tools to support these applications, and the
optimization of advanced ceramic processing by improvement of interfacial chemical control of
slurry properties.
Technical Objectives:
The objective of this research is to develop measurement methods and an understanding of the
surface density of ceramic powders of relevance to slury processing control.
Outcomes:
Two primary outcomes are expected to derive from this research: (1) development of
electroacoustic analysis for process control in powder processing, (2) improved understanding of
component interactions during aqueous processing of complex highly concentrated slurries.
Accomplishments:
Extensive testing and evaluation of a novel electroacoustic technique has demonstrated the
capabilities of this method for characterizing ceramic powder systems. Improvements were
derived from cooperative interaction with the instrument manufacturer.
Polyelectrolyte dispersants, commonly used additives in aqueous processing of powders, were
studied and evaluated using electroacoustic methods in the model Si3N4/water system.
Measurements in moderately concentrated slurries provided agglomerate size and zeta potential
as a function of polymer concentration, molecular weight and suspension pH. This data will be
used to optimize conditions for improved dispersion of Si3N4 powders.
Electroacoustic measurements, along with several other surface chemical techniques, were used
to investigate the aqueous reaction-bonded silicon nitride system. This processing route begins
with metallic silicon dispersed in aqueous suspension in a complex mixture with sintering aids,
nitriding agent, dispersants and binders. The aging of unstable silicon in water was characterized
under various conditions using electroacoustic measurements of the changing surface potential
as a function of time and pH. The interaction of dispersants and binders with the primary silicon
phase was examined extensively, leading to improvement of dispersion via chemical control of
suspension conditions. This research is on-going.
A consortium was formed in September 1993 between NIST, five manufacturers that produce
ceramic powders or components, an instrument company and a federal laboratory, in a joint effort
to improve processing of ceramic powders. Participants in this Consortium on Intelligent
Processing of Powders and Slurries include Cercom Inc. (Vista, CA), Coors Ceramics Co.
(Golden, CO), Eaton Corp. (Southfield, Mich), Kerr-McGee Corp. (Oklahoma City, OK), St.
Gobain/Norton Industrial Ceramics Co. (Northboro, MA), and instrument manufacturer, Matec
Applied Sciences Inc. (Hopkinton, MA). The Metals and Ceramics Division of the U.S.
Department of Energy's Oak Ridge National Laboratory is a participating partner.
Outputs:
"Electroacoustic Characterization of Particle Size and Zeta Potential in Moderately Concentrated
Suspensions", Hackley, V.A. and Malghan, S.G., in Ceramic Transactions, Volume 56, Advanced
Synthesis and Processing of Composites and Advanced Ceramics (American Ceramic Society,
Westerville, OH, 1995) p 283.
"Techniques for Characterization of Advanced Ceramic Powders", Malghan, S.G., Wang, P.S.
and Hackley, V.A., in Chemical Processing of Ceramics, Lee, B.I. and Pope, J.A., Eds., (Marcel
Dekker, NY, 1994).
"Surface Chemical Interactions of Si3N4 with Polyelectrolyte Deflocculants", Hackley, V.A.,
Premachandran, R. and Malghan, S.G., Key Engineering Materials, 89-91, 679 (1994).
"Intelligent Processing of Ceramic Powders and Slurries", Malghan, S.G., Hackley, V.A. and
Wang, P.S., in Ceramic Eng. and Sci. Proc. (American Ceramic Society, Westerville, OH, 1994)
p 527.
"The Surface Chemistry of Silicon Nitride Powder in the Presence of Dissolved Ions", Hackley,
V.A. and Malghan, S.G., J. Mat. Sci., 29, 4420 (1994).
Research results were also presented at two scientific meetings, the First International Symposium
on Advanced Synthesis and Processing of Composites and Advanced Ceramics in Cocoa Beach,
Florida, and the 1995 American Ceramic Society Annual Meeting in Cincinnati, Ohio.
Impact:
Research performed at NIST and reported to the consortium participants under the auspices of
a Cooperative Research and Development Agreement has provided new and improved
information regarding the aqueous suspension behavior of metallic silicon powders. This will
have a direct impact on processing formulations for reaction-bonded silicon nitride. NIST testing
and evaluation has provided feedback to the instrument manufacturer which resulted in system
improvements. NIST measurements have provided necessary information regarding the
application of electroacoustic methods to characterizing ceramic powders which is currently being
employed for the analysis of materials used by consortium participants. The impact of NIST
research in this area is demonstrated by the formation of new collaborations with industry which
are currently in the development stage.
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Last modified: Fri Jul 19 10:13:18 1996