Ceramic powders characterization

516 Pages·1995·20.1 MB·English

by  Malghan, Subhas G.

United States Department of Commerce
Technology Administration
National Institute of Standards and Technol
NAT L INST. OF STAND & TECH R.I.C.
NIST Special Pumcation 879
Ceramic Powders Characterization:
Results of an International
Laboratory Study
S. G. Malghan and S. M. Hsu, Editors
QC
100
.U57
NO. 879
1995
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NIST Special Publication 879
Ceramic Powders Characterization:
Results of an International
Laboratory Study
S. G. Malghan and S. M. Hsu, Editors
Materials Science and Engineering Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899-0001
Contributors:
R. Munro and L.-S. H. Lum, NIST
A. L. Dragoo, DOE
H. Hausner, TUB, Germany
R. Pompe, SCI, Sweden
July 1995
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: 1995 of Documents
Special Publication 879 U.S. Government Printing Office
Natl. Inst. Stand. Technol. Washington, DC 20402
Spec. Publ. 879
510 pages (July 1995)
CODEN: NSPUE2
This report is the result of a cooperative program on ceramics for Heat Engines and other conservation applications by the
Department of Energy. The research was partly sponsored by the U.S. Department of Energy, Assistant Secretary for Energy
Efficiency and Renewable Energy, Office of Transportation Technologies, as part of the Ceramic Technology Project of the
Propulsion System Materials Program, under contract DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc.
FORWARD
Reproducible manufacturing of high quality advanced ceramics components
requires the use of powders having high purity, and consistent physical and
chemical properties. The development and use of technically sound powder
characterization methods is one of the ways to accomplish reproducibility in
manufacturing. In addition, rapid commercialization of the advanced ceramics
can be accomplished by reaching a consensus on the measurement methods on an
international -scale since the raw materials and their processing to
manufacture ceramic components is carried out in different countries. Instead
of carrying out the required research in individual countries , the United
States, Germany and Sweden joined hands in 1979 under the auspices of the
International Energy Agency to initiate a collaborative research program on
advanced ceramics for high performance engines and other energy conservation
applications .
In 1984, under the far-sighted leadership of Messers Al Chesnes , and Robert
Schulz, Office of Transportation Systems in DoE, Mr. Ed Lenoe of the U.S. Army
Materials Command in Watertown, MA, an international cooperative study on
advanced ceramics was launched. With the inputs of the U.S. industries, an
agreement was formulated under the auspices of the International Energy
Agency, lEA, and the countries involved were the United States, Germany, and
Sweden.
The agreement is called "Implementing agreement for a program of research and
development of high temperature materials for automotive engines". The U.S.
Department of Energy is the Operating Agent for the agreement, with the
Kernforschunganlage Julich GmbH in the Federal Republic of Germany, and the
Swedish National Board for Technical Development as the counterparts for the
agreement. The initial technical management was carried out by the U.S. Army
Materials Command under contract to DoE. This was changed to the Oak Ridge
National Laboratory in 1987.
The research in this report was conducted under the lEA Annex II Subtask 2
agreement. The objective of this task was to study the various
characterization methods on ceramic powders. The study was coordinated by the
National Institute of Standards and Technology in cooperation with U.S.
Department of Energy. This report represents the combined efforts of many
people in 25 organizations who participated in the ceramic powders
interlaboratory comparison project. It also represents a landmark for
international cooperation in the fast growing technology. We would like to
express our sincere thanks to all who participated in the project, especially
the national technical leaders: Dr. Alan Dragoo of the United States, Prof.
Hausner of Germany, and Dr. Robert Pompe of Sweden.
To the readers of this report, this document is the first of its kind, and is
the most comprehensive compilation of fine ceramic powder properties to date.
In the future, we plan to prepare reports on the subsequent Subtasks 6 and 8.
Stephen M. Hsu Subhas G . Malghan
PARTICIPANTS*
Chairman, Sub task 2 Stephen M. Hsu
Technical Leader for the United States Alan L. Dragoo
Technical Leader for Federal Republic of Germany Hans Hausner
Technical Leader for Sweden Robert Pompe
Participants from the United States
Richard R. Hengst AC Spark Plug Division of General Motors
Elise Hersenhart, Nancy Fitzgerald Alcoa Technical Center
Bernard J . Busovne Allied- Signal Aerospace Company
Carborundum Company
Wolfgang Boecker
Lawrence P. Boesch, Jo Meglen Engineering and Economics Research
H. Fred Linebarger Elkem Materials
Ford Motor Company
Gary M. Crosbie
Samuel Natansohn, Francis X. Pink GTE Laboratories
Marc Freedman NASA Lewis Research Center
NIST
Alan L. Dragoo, Subhas G. Malghan, Stephen M. Hsu
Norton Company
William Andruchow, Param Tewari, Kamal E. Amin
Mark A. Janney Oak Ridge National Laboratory
Theresa M. Resetar, James W. McCauley U.S. Army Materials
Technology Laboratory
Participants from the Federal Republic of Germany
Gerhard Franz
W. Kraft Robert BosBcahy e rG m bAHG
Gangolf W. Kriechbaum
Gerhard Rehfeld Degussa AG
Dynamit Nobel
Schwetz, Peter Matje Electroschmelzwerk Kempten GmbH
Rolf Priimmer Fraunhofer- Inst i tut fur Werkstof fmechanik
Jiirgen Heinrich Hochst CeramTec AG
A. Naoumidis KFA Julich GmbH
Albert Kerber Lonza Werke GmbH
G. Schwier Hermann C. Starck Berlin GmbH
Hans Hausner, Wolfgang Genthe Technische Universitat Berlin
3. Participants from Sweden
Michael Hatcher KemaNord Indus trikemi AB
Robert Pompe Swedish Ceramic Institute
^Affiliation of participants was during the period in which this Subtask was
implemented.
iv
EXECUTIVE SUMMARY
The application of advanced ceramics In engines depends on developing reliable
and cost-effective ceramics that will withstand harsh engine environments.
Improvement in the characterization of ceramic starting powders is a critical
factor in the control of reliability. Ceramic powders used by manufacturers
of components are increasingly obtained from producers throughout the world.
Consequently, the need for internationally agreed upon measurement procedures
is becoming increasingly critical.
This report contains the results of an international interlaboratory
comparison program ( "round- robin" ) of powder characterization under the
auspices of International Energy Agency (lEA). The results include the
contributions of 25 industrial, university and governmental laboratories in
the Federal Republic of Germany, Sweden and the United States. These
laboratories surveyed a variety of methods for the characterization of
physical properties and chemical characteristics of ceramic starting powders.
For the first time, data from various measurement methods are available for
critical comparison. Results of the same method from different laboratories
are also provided. This represents an important milestone towards
international consensus on powder measurement methodology in advanced
ceramics .
The selected fine powders of silicon nitride, silicon, silicon carbide, and
zirconia were representative of different methods of production and various
types and stages of ceramic component manufacture. Careful preparation of the
samples of the selected powders was carried out by the National Institute of
Standards and Technology (NIST) to assure sample- to -sample homogeneity.
Measurements were carried out by each laboratory according to its customary
procedures. All results and descriptions of methods were reported to NIST.
Data compilation and statistical analysis were performed by NIST personnel.
The three technical leaders then performed analyses and drew conclusions.
These conclusions were sent to individual participants for comments.
This report presents the final results and summarizes the data obtained and
the methods studied under the auspices of lEA/Annex II, Subtask 2, Powder
Characterization. Recommendations for future studies are drawn from results
of the present round- robin. The data obtained in Annex II will no doubt serve
as the basis for designing and conducting future studies as well as for the
development of standard procedures needed in the international arena of
advanced ceramic materials .
Technical Program Description
Samples of the following five powders: silicon nitride (reference), silicon
nitride (test), silicon, silicon carbide and zirconia, were prepared and sent
to the participating laboratories. Each laboratory performed a core group of
analyses using standard methods employed in their respective laboratories. A
summary of properties and methods is presented below.
V
I. Physical Properties
Density
Bulk density (helium pycnometer)
Tap density
Specific surface area
Single point BET
Multi -point BET
Particle size and size distributions
Gravitational sedimentation
Centrifugal sedimentation
Light scattering
Fisher sub -sieve
Photon correlation spectroscopy
Electrical sensing zone
Particle Morphology
Scanning Electron Microscopy
Transmission Electron Microscopy
Phase Composition
X-ray diffraction
II. Chemical Properties
Major Methods
X-ray fluorescence (XRF)
Atomic absorption (AA)
Inductively coupled plasma (ICP)
Direct current plasma (DCP)
Gravimetry
Major Non-Metallic Impurities
Total carbon in SisN^, SiC (Combustion)
Free carbon in SiC (Combustion)
Total carbon in Zr02 (Combustion)
Nitrogen in SiC, Si, SisNz, (Combustion)
Oxygen in SisN^, SiC, Si (Fast Neutron Activation Analysis)
Sulfur in SisN^ (Combustion)
Fluorine in SigN^, SiC (Ion Chromatography and
Electrochemical Method)
Chlorine in Si, SiC (Ion Chromatography)
Sulfur in Zr02 (Inductively Coupled Plasma)
(Combustion)
(Mass Spectrometry)
(Ion Chromatography)
v.i
Chlorine in Zr02 (Ion Chromatography,
Neutron Activation and
Argentometric Titration)
Major Metallic Impurities
Free Si in SijN^ (Electrochemical Titration)
(Volumetric Analysis)
Al.Fe.Ca in SigN^, SiC, Si (Atomic Absorption)
(Inductively Coupled Plasma)
(Direct Current Plasma)
(X-ray Fluorescence)
(Mass Spectrometry)
Minor Impurities
S,F,Cl,Na,Mg,K,Ti,Cr,Mn
Ni.W.B in SigN^, Si (Inductively Coupled Plasma)
(Atomic Absorption)
(Mass Spectrometry)
(Direct Current Plasma)
Results and data collected from the participants were analyzed statistically
at NIST by Dr. R. Munro to identify outliers and the primary sources of
variance. Binary comparisons of data and methods were also performed.
Conclusions
Average particle size, density, and surface area are in good agreement not
only among different laboratories but also among the various methods used.
This is somewhat contrary to the previous experience on ceramic powder
interlaboratory comparison. The major difference this time is the
extraordinary care taken in sample preparation and packaging. This resulted
in a minimum sampling error.
Particle size distributions from six methods showed a wide range of variation.
The cause of the variation had been determined to be mainly from the following
three sources: sample pretreatment method and severity, different sensitivity
ranges from various instruments, and different measurement principles.
The chemical analysis of major elements and minor trace impurities presented a
higher than normal deviation. The source of error can be traced to: the lack
of standard reference materials for calibration; different sample pretreatment
methodology associated with different instruments; the choice of instruments
and methods .
vii
Specific conclusions are as follows:
1. Sample preparation methods influence the results of particle size
measurements. Consequently for a set of methods to be compared, a
universal prescription for sample preparation is required so that a stock
slurry is obtained which satisfies (1) the volume requirement of the
method with the largest volume requirement and (2) the concentration
requirement of the method with the most concentrated suspension. Volumes
and concentrations for other methods to be compared would be obtained by
taking suitable aliquots and by making the appropriate dilutions.
2. A bias between specific surface areas determined by single point and
multipoint BET measurements was apparent. However, accurate evaluation
of this bias was obscured by the variability in the data. One source of
variability was the use of different outgassing times and temperatures.
Establishment of a common preparation procedure is recommended.
3. A limited amount of quantitative x-ray diffraction data for phase content
determination was obtained. Several methods for analysis of the data
were used by the laboratories. Concentration (in percent) of secondary
phases typically varied by about 2%. Some of the methods used were
outdated or contained measurement biases. A wider base of test data for
methods based on the best measurement assumptions and protocols is
needed. The use of silicon nitride as the initial test powder is
suggested,
4. Results showed low precision (relative standard deviation > 25 %) for the
analysis by AAS , ICP and DCP of the major metallic impurities Al , Ca and
Fe in SigN^ and SiC. Better interlaboratory agreement (i.e.,
reproducibility) and intermethod consistency were obtained with acid
digestion rather than with flux dissolution of SigN^ and SiC. More
problems were evident in the analysis of SiC than of SisN^. Within-
laboratory uncertainty (i.e., repeatability) was improved by the use of
an internal standard, such as Sc for ICP, and by the use of synthetic
calibrating solutions.
5. Limited data on halide impurities in SigN^, and SiC were obtained. Two
sample preparation methods were used for extraction of halides: hot-water
leaching and flux decomposition. Leaching methods were employed in a
limited manner, mostly for F and CI impurities. Both hot water and
boiling water leaching were used. However, insufficient data were
obtained for detailed analyses. Principal detection methods used were:
ion chromatography, specific ion electrode, argentometric titration for
CI" and potentiometric titration. Concentrations determined after
leaching were somewhat less than those obtained after decomposition.
6. Oxygen in SigN^ and SiC was determined by combustion/decomposition using
either thermal conductivity or IR absorption detection. The results of
most laboratories were in agreement with results from fast neutron
activation analysis; however, some results for 0 in SisN/, (both reference
and test samples) were inexplicably high.
viii