Institute for Materials Science and Engineering

-v

*

" Y ipjfli*

NAS-NRC

Assessment Panel

February 2-3, 1 989

NISTIFS 88-3840

U.S. Department of Commerce

National Institute of Standards

and Technology

Technical Activities

1988
The first three-dimensional wear map

of alumina lubricated with paraffin oil showing the relationship between

extent of wear (Z axis), normal force

(x axis) and sliding speed (Y axis).

Ceramics may undergo potentially

catastrophic transitions in wear when

the tribological operation conditions

exceed certain limits. Wear maps

are being developed to understand

these limits.
<

1'J-i &> MO •

Institute for Materials Science and Engineering

CERAMICS

NAS-NRC

Assessment Panel

February 2-3. 1989

NISTIR 88-3840

U S Department of Commerce

National Institute of Standards

and Technology

Technical Activities

1988

TABLE OF CONTENTS

Page

INTRODUCTION 1

TECHNICAL ACTIVITIES 3

STRUCTURAL CERAMICS

Powder Synthesis and Characterization. .. .Alan Dragoo 9

Mechanical Properties David Cranmer 17

Tribology Said Jahanmir 25

FUNCTIONAL CERAMICS

Electronic Materials Stephen Freiman 37

Optical Materials Albert Feldman 47

Synchrotron Radiation Analysis Masao Kuriyama 55

RESEARCH STAFF 61

OUTPUTS AND INTERACTIONS

Selected Technical Publications 69

Selected Technical/Professional Committee Leadership 73

Industrial and Academic Interactions 77

Standard Reference Materials 83

APPENDIX

Organizational Chart

National Institute of Standards and Technology

Organizational Chart

Institute for Materials Science and Engineering

INTRODUCTION

Introduction

1988 marks the third year that the Ceramics Division has been in existence.

Several events occurred in 1988 that have far reaching impact on our future

activities. On August 23, 1988, President Reagan signed the Omnibus Trade

and Competitiveness Act which, among other things, renamed the National

Bureau of Standards to the National Institute of Standards and Technology

(NIST) . Besides the traditional role of standards and measurement

research, NIST will also assist U.S. Industries to develop technology and

enhance competitiveness. This has reinforced the objective of the Ceramics

Division to provide understanding, critical data, reference materials, and

measurement techniques in key technological areas to enable industry to

achieve desired properties through advanced processing. In late summer, we

invited senior industrial representatives to NIST to explore the technical

feasibility of advanced process control through intelligent materials

processing. We have also increased our already strong ties to industry

through mutual visits and discussion over a wide range of technical areas

for possible collaboration. This increased emphasis on awareness of

industry's requirements has been manifested by increased industrial support

of the Division's activities (estimated at approximately $1.5M) through

both direct funding and services in kind such as Research Associates in the

Division.

Concurrently, the Division has been restructured to focus on structural

ceramics and functional ceramics. Within each focus area, the

characterization-property activities have been augmented by a processing

component. Integration of processing- structural-property activities within

a class of material will increase our program impact.

We continue to expand our programs in terms of personnel and equipment. On

January 1, 1988 we were converted into a Personnel Demonstration system

which gave us considerable flexibility in recruitment, hiring, and salary

administration. As a result, we have been successful in recruiting several

key staff members who are crucial in establishing several key competence

areas

.

One area is in surface chemical characterization and measurement. We are

in the process of setting up a solid state NMR (Nuclear Magnetic Resonance)

which when coupled with existing facilities of FTIR (Fourier Transformed

Infrared) microscope and micro-focused, time resolved Raman Scattering

Spectroscopy, will give us an unique capability of characterizing surface

chemistry, phases, and composition of powders, compact and sintered bodies.

Another area is in the surface forces facility. We are now able to measure

surface forces down to molecular levels. Understanding of the nature and

magnitudes of the surface forces has serious technological implications in

ceramic powder dispersion, agglomeration, crack propagation, crack healing,

lubrication, and the control of interface bonding.

Division output continued at a high level with the publication of 174

papers, and the presentation of 213 talks. Recognition of the many

1
contributions of Dr. Sheldon Wiederhorn to the field of mechanical

properties measurement was manifested by his appointment as a Institute

Scientist

.

At this time, we are looking forward to increasing our interactions with

U.S. ceramics industries, and together, we shall accomplish our goals.

S. M. Hsu

Chief, Ceramics Division

September 1988

2
TECHNICAL ACTIVITIES

Technical Highlights

Significant accomplishments by the Ceramics Division in 1988 include:

High Temperature Superconductors - Significant progress has been made in

determining the effects of processing on the grain boundary chemistry and

structure of YBaCuO superconductors. This research has provided insight

which could increase the critical current density which now limits the

application of these materials.

Phase Diagram for Ceramists - The Division, in cooperation with the

American Ceramic Society, has completed Volume 7 of the widely used "Phase

Diagrams for Ceramists". This volume contains approximately 1,000 phase

diagrams of salt systems.

Diamond Film Research - Research on diamond film synthesis has emphasized

the development of understanding of the effects of processing on the

structure and properties of this important class of materials. Significant

progress on identification of defects and impurity sites has been realized

through the development of cathodoluminescence analysis techniques.

Surface Forces Laboratory - A laboratory has been constructed to study the

forces present between solid surfaces in close proximity (10-100 nm) . This

laboratory, one of only a few in this country, will provide data required

for a fundamental understanding of phenomena occurring in fracture and

lubrication of ceramic materials.

Ceramic Composites - Behavior of ceramic composites, which offer the

potential for widespread usage due to their damage tolerance, depends upon

the properties of fiber or whisker to matrix interface properties.

Research on techniques to characterize the chemical, and mechanical

properties of these interfaces has resulted in the ability to optimize

fiber coatings for increased composite toughness.

Ceramic Wear Maps - Wear maps which provide a comprehensive view of the

wear of ceramics in terms of load and contact velocity have been developed

for aluminum oxide and silicon nitride. These maps, the first

characterization of wear by this technique provide design information

required for wear and guidelines for avoidance of the transition to high

wear

.

Ceramic Tensile Tests - Inexpensive techniques have been developed to

determine the creep and creep rupture properties of structural ceramics to

temperatures as high as 1500°C. The use of laser techniques to measure

creep displacements to accuracies of ± 2 Micrometers has allowed evaluation

of silicon carbide and silicon nitride composites with potential for use in

heat engine and heat exchanger applications.

A Computerized Tribology Information System (ACTIS) - The vast volume of

tribological data available to designers has not been widely utilized due

to both the narrow focus of tests and the wide variety of fields of

research publication. ACTIS, a program sponsored by a variety of Federal

and private organizations, attempts to provide a readily accessible and

viable data base for the design community. Computerized formats have been

3
designed and demonstrated and evaluated data for selected ceramic material

has been input to the program.

Time Resolved Micro Raman Analysis - A time resolved Micro Raman technique

has been developed to analyze chemical reactions at tribological contacts.

This facility will provide basic data to determine mechanisms of wear and

lubricant behavior at wear surfaces.

Synchrotron Radiation Analyses - The NBS synchrotron radiation beamline

capabilities for topographic imaging of the interior of crystalline

materials have been used to observe, perhaps for the first time, defects

which may be the "missing link" that materials scientists have been

searching for to explain the performance limits of gallium arsenide single

crystals

.

4
STRUCTURAL CERAMICS

OVERVIEW

The major barrier facing the structural ceramic industry today is

cost/effectiveness. This can be related to the technical capability to

produce reliable and durable ceramics. Reliability can be defined as

consistency in properties while durability is related to corrosion, wear,

and environmental stability under in-service conditions. Both factors can

be controlled through advanced processing and intelligent process control

which requires models, test methods, and sensors capable of real time

measurements. Discussions with industries have identified these needs and

additional requirements in reference materials, easily accessible data, and

in-service performance simulations and predictions. As a result, the

division program has been structured to focus on ceramic powder

characterization, mechanical properties, and wear behavior under different

conditions. The underlying scientific theme is to develop models to

describe the process ing- structure -property relationships of monolithics and

composites

.

Identification and measurement of key powder properties for reliable

manufacturing of ceramics is a difficult but crucial requirement for

process model development for both monolithic and composite ceramics. One

of our key activities in powders has been the leadership role of an

international round robin to compare different methods on several powders

among some 30 laboratories. This effort, under the auspices of the

International Energy Agency, entailed the preparation and distribution of

over 10,000 controlled samples of ceramic powders and analysis of data

developed by the participants. This will be the most comprehensive

compilation of methods and data on ceramic powder characterization, and

would provide industry with a crucial data base for process and product

deve lopment

.

Research efforts in ceramic powder analysis are focused on the

characterization of the surface chemistry of powders and the effect of this

feature on structure and properties. FTIR and Micro Raman techniques now

in use will be augmented in 1989 by solid state NMR analysis. Production

of Ceramic Standard Reference Materials has continued and a standard for

silicon nitride alpha/beta ratios is scheduled for completion in 1989.

Reliability of structural ceramics requires a determination of the

relationship of processing to properties and structure. The availabi lity

and use of methods of property measurement and the development of these

techniques has been a key element of the structural ceramics program.

Development of tensile creep rupture tests has resulted in an inexpensive

procedure now being examined in a round robin.

The increased reliability offered by fiber reinforced ceramic composite

depends upon the behavior of the fiber to matrix interface. In 1988, a comparison of techniques of measurement of fiber to matrix bonding was

conducted. The data from this project will be utilized to further the

development of uniform test methodologies. In 1988, a more fundamental

characterization of the nature of fracture of ceramics was initiated by the

5
establishment of a surface forces laboratory. Data from this latter

research will aid our understanding of the influence of microstructure and

environment on crack propagation.

Durability of ceramics in wear applications has been a primary reason for

the development of structural ceramics. Our focus on the development of

wear test methodologies and the interpretation of data has led to the

development of wear maps which relate system parameters such as load,

speed, and environmental factors to wear. Such maps will allow designers

much better insight into selection of materials and operation conditions to

avoid siezure and premature wear. We have also participated actively in

standard setting activities both internationally and within the U.S. Two

wear test methods have been developed and are undergoing ASTM round robin

testing

.

Lastly, the dissemination of critical data to the technical community has

been emphasized throughout the division programs and is best illustrated by

the development of A Computerized Tribology Information System (ACTIS)

.

ACTIS is an interagency, intersociety joint effort in providing best

judgment values by experts in the computerized data base. This year,

approximately 5,000 evaluated data on triboligical properties of materials

have been established and will undergo user trials in 1989. Similar

programs in phase diagrams and fracture properties are also underway.

6
PROJECT LISTING

Powder Synthesis and Characterization

• Ceramic Powder Synthesis

• Powder Characterization - Physical Properties

• Electron Microscopy/Image Analysis

• X-ray Diffraction

• Chemical Characterization of Ceramics

• Small Angle Neutron Scattering

• Powder Characterization - Colloidal Processing

Mechanical Properties

• Microstructure and Toughness

• Surface Forces

• High-Temperature Deformation and Fracture

• Interfaces in Structural Ceramics

• Processing-Property Relations in Ceramic Matrix Composites

• Sintering Multi-Component Ceramic Systems

• Machining Damage of Si 3 N4

• Structural Ceramics Database

Tribology

• Advanced Ceramics

• Tribological Coatings and Composites

• Advanced Lubrication

• A Computerized Tribology System

7

POWDER SYNTHESIS AND CHARACTERIZATION Alan Dragoo

The Powder Characterization and Processing Group seeks to further the

reliability and reproducibility of advanced ceramic products by the

development of improved starting powders, characterization procedures and

standards, and the science and technology base for ceramic processing. The

group is integrating a broad range of characterization methods with ceramic

processing studies both to advance the understanding of processing effects

and to improve and expand characterization methodology.

For chemical analysis of precursor powders and ceramic materials methods

used within the group to elucidate both bulk and surface characteristics

include x-ray diffraction (XRD) , surface extended x-ray augmented fine

structure (EXAFS), analytical scanning electron microscopy (SEM) and

Fourier transform infrared (FTIR) spectroscopy; and a solid state nuclear

magnetic resonance (NMR) facility is being added. These are complemented

by other methods at the NIST or at universities through cooperative

arrangements. During the past year a procedure was established for

measuring the amount of crystalline and amorphous phases in silicon nitride

powders by FTIR.

Crystalline structure and microstructure of particle ensembles are

characterized with x-ray diffraction and small angle neutron and x-ray

scattering (SANS and SAXS , respectively). The application of SANS to the

characterization of agglomerate microstructures of particles in liquid

media is being explored.

The group continues to play a key role in an international inter laboratory

comparison of powder characterization methods conducted under the auspices

of the International Energy Agency. The results of this program will

provide an important basis for the establishment of measurement procedures

and standards which are needed for the international trade of advanced

ceramic powders. The group has been instrumental in the establishment of

an U.S. Working Group for Powder Characterization which is composed of

industrial and governmental researchers in the fields of powder

characterization and ceramic processing.

Representative Accomplishments

o A numerical descriptor was developed for description of the fiber

distribution in fiber-reinforced composites.

o Work was concluded on a three-year effort in which over 6000

reference powder samples of silicon nitride, silicon carbide,

silicon and yttria-zirconia were prepared and certified for a international powder characterization round-robin.

o Standard Reference Material 1879, cristobalite powder, was

certified as new reference material for quantitative

characterization of silica phases by x-ray powder diffraction.

9
o Demonstrated the application of FTIR analysis for determination

of silicon nitride phase composition.

o Demonstrated the application of FTIR analysis for the

characterization of the surface chemistry of ceramic powders in

aqueous slurries.

o Development of chemical treatment for the passivation of

hydrolytically unstable oxide powders.

o Densif ication of microporous silica analyzed with small angle

neutron scattering to determine the change in porosity.

Ceramic Powder Synthesis

J. Ritter, R. Faltynek

Families of ambiently stable organic molecules containing boron-nitrogen

and silicon-nitrogen bonds were extensively studied as coating agents for

alumina and mullite fibers. Although earlier research indicated that the

compounds were pyrolytic precursors to boron nitride and silicon nitride,

it was unexpectedly found, however, that the nonoxide ceramic precursors

react irreversibly with alumina or mullite, resulting in fiber degradation

and embrittlement. Decomposition was rapid at 700-800°, but solutions of

the precursors in nonreactive solvents slowly attacked the oxide fibers at

room temperature as well. Studies are underway to identify means of both

retarding and enhancing the degradation reaction, leading to methods for

successfully depositing BN or Si 3 NA on fibers, and for removing oxide

coatings from nonoxide substrates.

Powder Characterization - Physical Properties

A. Dragoo, S. Malghan, J. Kelly, D. Minor, L. Lum, C. Robbins, R. Munro 1

1 Ceramics Division Office

Research is carried out to develop measurement procedures and standards for

powder characterization, to support national and international programs in

this area, and to support research on ceramic processing. The

instrumentation includes an x-ray gravitational sedigraph, centrifugal

photosedimentation apparatus, photon correlation (quasi-elastic light

scattering) spectrometer, Brunauer-Emmett-Teller (BET) surface area

apparatus, mercury intrusion porosimeter and automatic helium pycnometer.

Work sponsored under the Department of Energy Heat Engine Program has a key

role in supplying powders and providing data analysis for an international

interlaboratory comparison of powder characterization methods. Research on

powder characterization is coupled to needs of U.S. industry through active

leadership of the U.S. Working Group for Powder Characterization and

through guestworker opportunities.

1C
Electron Microscopy/Image Analysis

J. Kelly, D. Minor, J. Ritter, A. Dragoo

Direct microscopic characterization of ceramic particles provides

fundamental size and shape data not accessible by indirect techniques, as

well as distribution data that serve to verify the indirect measurements.

The capacity for characterizing thousands of individual features has been

developed through the installation of a computer controlled scanning

electron microscope with EDS x-ray and image analysis distributions for

ceramic powders as part of the international round-robin on ceramics

characterization under the auspices of the International Energy Agency.

Small relative changes in the microstructural details of ceramic materials

can result in major changes in their strength. It is therefore important

to understand the relationships between fracture processes controlling

material toughness and microstructure. Toward this end an in situ fracture

stage has being developed to enable real time observation of crack

propagation in ceramic wafers in the SEIM. This capability will enable us

to observe in greater detail the role of grain morphology in the mechanism

of bridging ligaments behind the advancing crack tip. This work is in

collaboration with the Mechanical Properties Group and is supported by the

Air Force OSR.

The dependence of ceramic properties on their microstructural and

compositional homogeneity is well established. Specifically this

homogeneity is an important factor in the properties of YBaCuO, high T c , superconductors. An SEM study of the particle size, shape and chemical

homogeneity of chemically precipitated YBaCuO precursor powders has shown

the relationship between those microscopic properties and the chemical

reactor conditions of concentration and solution pH.

X-rav Diffraction

J. Cline, M. Kuchinski, A. Dragoo, C. Hubbard1

, W. Wong-Ng2, H. McMurdie 3, B. Paretzkin3

, Y. ZhangA

, T. Nakamura 5

, C. Robbins 6

1 Formerly Data Activities Group, Ceramics Division, now at Oak Ridge

National Laboratory

2 Electronic Materials Group

3 Guest scientist

*Guest scientist, University of Maryland

5 Guest scientist, Meiji University, Japan

6 Formerly Powder Synthesis and Characterization Group, now retired.

Research in the field of x-ray diffraction involves its application to

ceramic materials throughout the various fabrication phases for improved

process modeling and process control. The aim is to increase both the

number of sample characteristics that may be measured and the accuracy of

such measurements as they pertain to ceramic research.

The investigation of the accuracy of quantitative analysis by XRD has led

to the isolation of microabsorption and extinction effects. This work has

11
not only led to a greater understanding of how to obtain high quality

analyses of this type, but has also lead the using of these effects to

determine additional aspects of sample character. This knowledge is being

used in conjunction with high temperature x-ray diffraction for in-situ

measurements of grain growth during sintering. The high temperature

diffraction equipment on site incorporates a high speed detection system

which allows us to measure both phase equilibria and the kinetics of phase

transformations. The kinetics of the formation of the BaYCuO

superconducting system as a function of atmospheric composition is one of

the several systems being investigated.

Conventional methods of x-ray pattern interpretation use selected areas or

points of diffraction maxima. Profile refinement procedures developed here

utilize peak shape for high accuracy particle size and strain measurements.

Whole patterns analysis by means of the Rietveld refinement technique

allows for the simultaneous elucidation of the broadest range of sample

characteristics. These include the anisotropy and degree of particle size

and strain, crystallographic parameters, texture, as well as quantitative

analysis

.

The techniques and expertise developed here are being used to produce a

variety of Standard Reference Materials relevant to both the ceramic and

diffraction communities. Two SRMs were certified in 1988, SRM 660, a line

profile standard consisting of LaB6 , and SRM 1879, a respirable

cristobalite standard. The recertification of SRM 674 is nearing

completion. The Rietveld method is also being applied to the certification

of an alpha/beta silicon nitride SRM. X-ray line profile analysis is being

used to measure peak breadth for the certification of an ultrafine MgO

powder for use as a crystallite size SRM. Additional SRMs being certified

consist of a high purity alumina and respirable tridymite.

Expansion of the market for new ceramic materials and the use of computer

automation combine to accentuate the needs for improved reference data in

the Powder Diffraction File (PDF). NBS has carried out a two-year program,

supported by the JCPDS - International Centre for Diffraction Data, to

generate high-quality x-ray diffraction patterns for new phases of advanced

ceramic materials. During the past year work has focused on x-ray data for

phases of interested for high Tc and electronic ceramics, approximately 70

experimental patterns were produced.

Chemical Characterization of Ceramics

Pu Sen Wang, R. A. Faltynek, S. M. Hsu

Work has been started on the characterization of the surface chemistry of

ceramic powders, with emphasis on detection of surface additive components.

Surface components were analyzed and quantified for three Si 3 N4 powder

samples by x-ray photoelectron spectroscopy (XPS) . C Is, N Is, 0 Is, Si 2s

and Si 2p photoelectrons were observed. X-ray induced Si KLL Auger

electron (XAES) was also detected. Surface carbon and Si02 layers were

found on all three samples. Two of these powders were found to contain

Y2 03 and one of these two also has Al2 03 additive.

12
Si 3 N4 tribological discs were also analyzed by XPS and AES coupled with an

argon etching technique to profile the surface structure. Both techniques

suggest that the carbon and Si02 films were limited to the first 40 A.

Normal Si 3 NA composition was observed underneath these films. Samples

after wear testing were found to contain phosphorus which is believed to

come from the lubricants used.

Complete phase composition analysis of silicon nitride powders by Fourier

transform infrared (FTIR) spectroscopy was improved by the introduction of

a multiple linear regression program for data reduction. Typical results

are shown below:

% Composition (actual) % Composition (FTIR)

Sample 1q = 56.4 a = 58.6

P = 27.0 CM o

II

<3Cl

amorph = 16.6 amorph = 14.4

Sample 2: a = 22.4 CM o

II a

P = 40.8 P

= 41.8

amorph = 36.8 amorph = 34.2

The technique yields data that correlates well with independent x-ray

powder diffraction analysis, and it promises to be useful in SRM

certification

.

FTIR measurements by attenuated total reflectance (ATR) on aqueous slurry

samples of Si 3 NA and SiC pretreated with surface modifying agents showed

that the technique can directly determine the qualitative chemical

environment of powder surfaces. Analyses were carried out at the request

as part of our industrial collaboration. In terms of application to online process monitoring, it is significant that ATR measurements yield

information on the condition of slurry with no further sample preparation

prior to analysis.

Single-pulse FT-NMR experiments for test mixtures of ceramic powders were

performed for 7 Li, 11 B, 2

9

Si, and 31 P nuclei. Resonance signals in forms

of free induction decay and Fourier transform were observed at 116.640,

96.258, 59.620, and 121,496 MHz for these nuclei, respectively.

Experiments were performed in both stationary and magic angle spinning

states. The configuration for the Division's NMR spectrometer was

designed, specifications written, and purchase order issued.

13
Small Angle Neutron Scattering;

G. Long (420), S. Krueger (440), and R. Gerhardt1

Rutgers University

The sol-gel technique can be used to prepare novel glasses, fibers, thin

and thick films with chemical homogeneity and unique structural and

electrical properties. High purity, crack-free silica bodies with "madeto-order" narrow pore-size distributions have been formed as model systems

for the investigation of the relationships between the physical properties

of this class of material and the amount and character of porosity. The

present research, which is a collaboration between NIST and Prof. R.

Gerhardt of Rutgers University, focuses on the characterization of such

porous bodies by small angle neutron scattering (SANS) and multiple small

angle neutron scattering (MSANS) since it has been demonstrated that

thermal processing and the resultant microstructure bears a strong

influence on the dielectric and other properties of the product material.

MSANS was used to measure the average pore sizes present during the

intermediate stages of thermal processing, where the radii could be

expected to be in the 0.08 - 10 fim range. Total surface areas were

estimated from the single scattering Porod curves. Pore populations were

studied in the late stages of processing by means of diffraction

measurements with 14 A incident neutrons.

The results indicate that densif ication during the intermediate stages is

accompanied by pore coarsening. Although pore coarsening had previously

been observed in the earlier stages of thermal processing, this result was

unexpected since the pores are generally expected to undergo shrinkage in

order for the body to density. The observed pore coarsening eventually

levels off and by the time the material is 95% dense, one cannot detect any

pores with radii greater than 0.08 /xm. SANS measurements on the 95% dense

sample using 14 A incident neutrons reveal the presence of populations of

pores with radii 33 nm and less.

Powder Characterization - Colloidal Processing

S. Malghan, G. Long, A. Dragoo, B. Moudgil 1

1 Faculty member, University of Florida, Gainesville

Ceramic components with a high degree of homogeneity and reliability can be

produced from ultrafine powders using colloidal processing techniques -- slip casting, pressure casting, etc. In colloidal processing, not only

physical (size, surface area, morphology, etc.) but also chemical (bulk,

surface chemical) properties are found to play an active role in obtaining

homogenous dispersions. The specific colloidal properties based on

electrochemical phenomena under investigation are electrokinetic behavior,

rheological behavior, and dispersability . To complement existing equipment

capabilities, efforts are underway to establish high energy attrition mill

for dispersion and size reduction, and acous tophoretic mobility measurement

14
facilities. Some of the powders and whiskers to be included in these

studies are alumina, silicon nitride, zirconia and silicon carbide.

Primary goal of this research is to relate microstructural changes

influenced by the colloidal properties of the powder suspensions. This

includes determination of colloidal properties of powders and whiskers in

liquids of interest, and relationships between colloidal properties and

processing response in green state and after consolidation.

Since particulate arrangements in dense slurries may have an important

bearing on pore size and structure in green state ceramics, and hence on

strength limiting voids in structural ceramic components, a program has

been initiated to investigate methods for characterizing particle

assemblages in dense and flocculated slurries. Preliminary work is in

progress to investigate the use of SANS for in situ characterization of

such assemblages.

15

MECHANICAL PROPERTIES David Cranmer

Our program on mechanical properties has as its broad objectives: (1) the

generation of new theories and data to elucidate fracture and deformation

mechanisms in brittle materials; (2) the development of fracture

methodology for studying the fundamental forces that exist between two near

surfaces; (3) the investigation of ceramic microstructures and their

relationship to mechanical behavior; and (4) the understanding of the

deformation and fracture properties that govern the mechanical response of

ceramics at high temperatures. Specific projects are focussed on the

processing-property relations between microstructurai features and

resulting properties including toughening behavior in structural ceramics

and development of models for the fracture behavior of continuous fiberreinforced, ceramic matrix composites. This latter work involves test

development as well as preparation, characterization, and testing of

composite systems.

Representative Accomplishments

o A laboratory facility for measuring the magnitude of forces

between ceramic surfaces has been constructed and is now

operational. The laboratory is a semi-clean room facility

containing laminar flow cabinets which permit contaminant free

surfaces to be prepared for examination in the surface forces

apparatus

.

o A semi- automated facility for investigating the creep and creep

rupture behavior of ceramic materials in tension has been

constructed. Data collected by laser imaging is used to

calculate deflection- time curves at the completion of each run.

Displacement measurements are accurate to ±l/^m at 1500°C, the

maximum operational temperature of the equipment.

o Tensile creep specimens were designed so that alignment of less

than 1% strain in bending could be achieved at a cost of

approximately $80 per specimen. Creep and creep rupture behavior

of carbide and nitride composite materials intended for use in

high temperature structural applications are being investigated.

o An indentation-strength procedure for determining R-curves for

ceramic materials has been developed. The method involves the

use of a controlled flaw, where an indenter is used to place

well-defined starting cracks into the surfaces of prospective

strength specimens. When coupled with the theoretical model,

microstructures which optimize strength and toughness can be

chosen

.

o Processing techniques were developed for studying residual

stresses and distortions in multi-component ceramic systems, such

as ceramic composites, co-fired ceramic/metal packages, and

multilayer devices.

17
o Facilities were developed for fabricating whisker- toughened

ceramic composites; and a J-integral analysis was developed to

explain their fracture behavior in terms of microstructural

processing variables. This will allow us to make predictions of

the behavior of the material as well as to optimize the

processing conditions and microstructure for a particular

application.

o A fracture mechanics specimen with a simple array of fibers was

developed and used to study influences of processing conditions

and metallic interface layers on the toughening of ceramic matrix

composites. The simplicity of the test method and specimen

geometry allows us to test a broad range of composite processing

variables and coating compositions/thicknesses without the

necessity of producing full-scale composites.

o A fiber coating system involving the ultraviolet curing of a polymer slurry containing the powdered ceramic composition was

developed. A patent has been applied for on this process which

permits the uniform coating of continuous ceramic fibers with a ceramic powder which can later be consolidated to form the

composite matrix.

o Thermal wave analysis was used to determine the extent of surface

damage introduced into Si 3 N A components by grinding, as well as

to characterize the thermal properties of diamond films.

Microstructure and Toughness

B. R. Lawn and S. J. Bennison1

1 Guest Scientist, Lehigh University

During the past year the strength behavior of a number of ceramic materials

has been studied using indentation flaw techniques. In-situ microscopic

observations of crack growth in alumina, revealed a radical new type of

toughening process. We identified interlocking grains and ligaments of

unbroken material in the wake of the crack front as the main cause of

toughening. We have now developed a theory that provides a full fit of the

R-curve for various alumina and other ceramics. Our model is based on a

frictional pullout process in which interlocking grains exert frictional

closure forces on the new crack walls behind the advancing tip. "Lockedin" thermal expansion mismatch stresses in non-cubic structures play a

profound role in enhancing these frictional tractions. The output of this

project has strong implications concerning the microstructural tailoring

required for optimum toughness properties of ceramics. We are embarking on

a systematic processing program to test these implications. A

collaborative program with Dr. M. P. Harmer's ceramics processing group at

Lehigh University is currently underway to explore this prospect.

18
Surface Forces

B. R. Lawn, S. Lathabai 1 and R. M. Thomson

1 Guest Scientist, Lehigh University

In addition to the covalent and ionic cohesive forces that hold brittle

materials together, there are weaker (but longer-range) adhesive forces

which come into play when new surfaces are created, particularly in the

presence of interactive environments: dispersion (van der Waals) , electric

double layer, solvation, and cation-site forces are examples. These are

the surface forces which are of great importance in colloidal chemistry.

We have shown in fracture experiments on mica, glass, and sapphire that

forces of this type are important also in strength properties of ceramics.

Data on the growth of cracks in both the forward and reverse directions

have been collected in various environments and are being analyzed. We

find that cohesive energies for the crack interfacial regions are

considerably higher than might be expected from current theoretical

knowledge of fundamental forces, or from measurements of adhesion in the

surface forces apparatus. The reasons for these divergences are currently

being investigated in terms of the accessibility of the environment species

to the crack interface. These investigations are leading us to new

conclusions concerning the nature of the interaction, particularly in

regard to the geometrical configuration of the interaction zone in both

cracks and adhesion geometries.

High-Temperature Deformation and Fracture

S. M. Wiederhorn, T.-J. Chuang, B. J. Hockey, D. E. Roberts and D. F.

Carroll 1

1 Guest Scientist, Pennsylvania State University

The development of new ceramics provides hope for high efficiency, enhanced

performance of structural systems in high temperature, stress-bearing

environments. However, before ceramics can be used in industrial

applications, issues concerning reliability and service life remain to be

resolved. With this in mind, we have been studying the creep and creep

rupture behavior of model ceramics at elevated temperatures. During the

past year, the creep and creep rupture behavior of a grade of siliconized

silicon carbide having a large grain microstructure was investigated and

compared with a similar grade of material having a uniform fine grain

microstructure. Grain size enhancement resulted in cavity formation at the

boundaries between the large grains of silicon carbide and the silicon.

These cavities grew along the silicon carbide interface, forming large

cracks that limited the amount of deformation allowable in the material and

were the eventual cause of component failure. Although the cavity

nucleation process in the fine grain material was similar, the small size

of the grains limited the size of the cracks that could form as a result of

the creep process. As a consequence, the fine grain material was found to

be more ductile, tolerating a greater degree of creep before failure. Work

on the effect of microstructure on creep is being continued. During the

coming year, tensile creep studies on silicon carbide whisker reinforced

silicon nitride will be conducted.

19
Creep rupture behavior of non-oxide ceramics is also being characterized in

tension and in flexure. During the past year we observed that for both

modes of loading, the rupture time was roughly inversely proportional to

the creep rate prior to failure. Quantitative relations between failure in

flexure and tension were developed, permitting both the creep rate and the

failure time in flexure to be calculated from tensile and compressive creep

data using a maximum strain criterion for failure. This maximum strain

criterion represents a new approach to lifetime prediction. For the coming

year, this method of lifetime prediction will be applied to compressively

loaded "C" -rings to determine the general applicability of the technique to

ceramic materials

.

Interfaces in Structural Ceramics

S. M. Wiederhorn, B. J. Hockey, Ygal Finkelstein1 and J. E. Blendell

1 Guest Scientist, Rafael Laboratories, Haifa, Israel

A new effort has been initiated to study the mechanical behavior of ceramic

interfaces at elevated temperatures. During the past year, the interface

between aluminum oxide and glass was studied in some depth. Interface

migration was investigated by sandwiching presintered polycrystalline

alumina between thin plates of sapphire. The type of bond formed as a

consequence of the joining process and degree of migration was found to

depend on the orientation of the sapphire. The kinetics of migration are

believed to be interface controlled, and the morphologies of the advancing

sapphire interface were rationalized in terms of the interfacial surface

energies of the sapphire plane relative to the average surface energies of

the aluminum oxide grains in the alumina. Work in this area will be

continued to obtain a better insight into the sintering process in alumina.

Processing-Property Relations in Ceramic Matrix Composites

T. W. Coyle, E. R. Fuller, Jr., R. F. Krause, Jr., C. P. Ostertag,

J. Barta 1

, T. R. Palamides 2

. D. C. Cranmer, S. W. Freiman, W. Haller3

, U.

V. Deshmukh2

, and 0. Yeheskel*

1 Guest Scientist, ISCAR Ceramics, Inc.

2 Guest Scientist, Drexel University

3 Research Associate

4 Guest Scientist, NRCN, Negev, Israel

The primary objective of this program is the experimental determination of

the relationships between the fracture behavior of fiber-reinforced,

ceramic matrix composites and the chemistry, structure, and properties of

the fiber-matrix interface. A second objective is to establish mechanical

test procedures appropriate for these composite systems. The increased

understanding of the fracture process will be used to develop strong,

damage- tolerant materials.

Low and high- temperature structural performance of ceramic matrix

composites is controlled to a large extent by the structure, properties and

stability of fiber-matrix interfaces. Techniques to characterize these

20
interfacial properties and to relate them to both processing, and macroscale mechanical behavior are required to develop reliable ceramic composites. Experimental studies were undertaken to process and characterize

such interfaces. A fracture mechanics specimen was fabricated from a model

composite system of SiC monofilaments in a borosilicate glass matrix.

Measurements of the change in applied stress intensity factor as the crack

approaches and passes the monofilaments provided quantitative data on

bridging fiber tractions and the fiber-matrix interfacial bond developed by

the processing conditions.

A recently installed vacuum hot press (loads to 500 kN and temperatures to

2100°C) is being used to fabricate high-density billets of silicon carbide

whisker-reinforced alumina composites. The relation of processing conditions to microstructure, mechanical properties, and performance is being

evaluated with a Research Associate from Iscar Ceramics. The fracture

behavior of similar materials, obtained from Advanced Composites Materials

Corporation, was characterized as a function of porosity (from 0.6% to

11.5%), using a novel analytical method for interpreting the strength of

indented flexure specimens. The materials exhibit a rising fracture

resistance with crack extension (R-curve behavior). A J-integral analysis

was developed to explain this behavior in terms of microstructural features

and processing variables. The creep and creep rupture behavior of these

materials were also measured at temperatures from 1000 to 1300°C. Creep

rupture occurs in two distinct time -regimes , separated by a transition

stress. High stresses cause failure, typically in less than 100 hours,

while the material is still in a primary creep mode. Low stresses produced

not only primary creep, but also a sizeable time-regime of steady-state

creep, generally exceeding 500 hours before failure. Electron microscopy

is used to relate microstructural behavior to these properties.

Several test methods have been used to experimentally characterize the

fiber/matrix interfacial properties in continuous fiber-reinforced ceramic

matrix composites. The methods include double cleavage drilled compression

(DCDC) , indentation push-in and push-out, and single fiber pull-out tests.

The composite systems studied have included glass (borosilicate, soda-limesilica) or glass-ceramic (LAS III) matrices reinforced by SiC monofilaments

(AVCO SCS-6) or Si-C-0 tows (Nicalon)

.

The work is divided into three parts: measurement of the fiber-matrix

interfacial strength, determination of the effects of thermal expansion

mismatch on fiber-matrix interfacial strength, and determination of the

effects of fibers in retarding crack extension. A single fiber pull-out

test was devised to directly determine the interfacial frictional stress

(r) and debond stress of fibers in a glass matrix. r's measured using this

test varied from 2-3 MPa for the SiC/borosilicate system to 4-20 MPa for

the SiC/soda- lime-silica system. The larger value of r for the soda-lime

matrix is due to the greater fiber/matrix thermal expansion difference,

leading to larger clamping stresses of the matrix on the fiber. An

indentation apparatus instrumented to directly measure force and

displacement was used to conduct fiber push-out experiments. These

experiments gave values of r between 1 and 55 MPa for the SiC/LAS-III

composite. This variability in r is directly due to differences in bonding

between the individual fibers and matrix. Results of the DCDC tests showed

increases in the crack tip stress intensity required to grow the crack due

21
to both number of fibers and coating thickness. The increase in Kx due to

bridging of the crack by fibers is about 20% for a single fiber and 35-50%

for two and three fibers. The thickness of Ni coating on SiC fibers was

shown to have a significant effect on the bridging force.

Sintering Multi -Component Ceramic Systems

J. E. Blendell, E. R. Fuller, Jr., C. P. Ostertag, M. D. Vaudin;

Sintering multi -component ceramic systems typically results in the

development of residual stresses and distortions. Important examples

include fiber-reinforced composites, co-fired ceramic/metal packages, and

multilayer devices. These stresses and distortions are usually

undesirable, and approaches for their avoidance are a mandatory aspect of

technology. Processing techniques were developed this past year to study

and minimize these phenomena. In particular, small external loads, applied

during the sintering cycle, were found to influence greatly the degree of

residual stress and resultant distortion.

Uniaxial compressive stresses are applied through rigid platens so that the

dimensions perpendicular to the stress (i.e., along the fiber axis of a unidirectional fiber-reinforced composite) remain constant during

densif ication (constrained sintering). In this manner, the axial tensile

stresses responsible for crack formations are suppressed when a critical

stress is applied. The body is stress free when the constraints are

released (after the heating cycle), and hence, remain undistorted during

the remaining sintering process. Stresses that allowed distortion-free

densif ication are quite small, on the order of 2 to 2.5 MPa, and thus,

constrained sintering is a viable commercial option.

Machining Damage of Si3 N^

G. White

The mirage thermal wave technique is being used to investigate Si 3 N4 surfaces as a function of grinding treatment. Si 3 N4 specimens have been

ground with various grit SiC to simulate levels of machining experienced by

ceramic components during fabrication. The surface finish of the Si 3 NA is

being investigated using two approaches: three dimensional images of

specific surface areas and dependence of the thermal wave signal on the

average thermal properties near the surface. The imaging approach has, so

far, detected residual grinding grooves, many small cracks, and what

appears to be a near surface inclusion. However, because flaws in brittle

materials are both small and numerous, imaging of discrete defects is

impractical. The second approach depends on measurements of the average

surface damage rather than in discrete flaw detection. In particular,

thermal diffusivity, a, appears to vary systematically as a function of

surface grinding. For large thermal wave penetration depths into the

material, the measured value of a is that of bulk Si 3 N4

. As the

penetration depth is reduced, a deviates from the bulk value and the

deviation appears to depend monotonically on the coarseness of the surface

damage. Since both the deviation and the ideal bulk values of a are

determined on the same specimen, the system may be self -calibrating ; i.e.,

22
no standard reference specimen may be needed. The two approaches appear to

fulfill two separate needs. For small critical components or highly

stressed regions in a large component, imaging may be a practical NDE tool.

For general information on the quality of a surface, the averaging approach

is expected to be superior.

Structural Cerami rs Database

R. G. Munro, C. R. Hubbard1

, H. M. Ondik, and F. Y. Hwang2

, S. M. Hsu

Industrial innovation and competitiveness are predicated on the successful

use of technical information. In materials research and development, the

information is complex, and not readily accessible. In cooperation with

the Gas Research Institute and the Center for Advanced Materials at

Pennsylvania State University, the Ceramics Division has launched an effort

to establish a computerized database on critical properties of structural

ceramics. The initial data base will be targeted for use in gas-fired

applications such as heat exchangers and recuperators, radiant tube

heaters, prime movers, and fuel cells.

The properties of potential importance in an advanced ceramics engineering

database may be divided into eight important general categories of data:

(1) materials specification, (2) processing characterization, (3)

structural and microstructural characterization, (4) intrinsic properties,

(5) dislocation and vacancy-dependent intrinsic properties,

(6) microstructural dependent properties, (7) performance properties, and

(8) failure characterization.

Based on the accumulated information, a preliminary computerized database

system, focused on ceramic heat exchangers, has been developed. The

information gathered for heat exchangers and recuperators considered

current candidate materials, processing methods, and other required

characterization information, typical operating conditions, and key design

properties required in these applications.

The preliminary system consists of modules for materials specification,

thermal expansion, thermal conductivity, thermal diffusivity, specific

heat, thermal shock resistance, and a bibliography of data references,

along with program elements for queries and output. Currently, the query

and output programs are rather general, for development purposes, and need

to be streamlined before being used in the eventual prototype. The other

modules are ready for testing in their current forms.

1 Current address: Oak Ridge National Laboratory, Oak Ridge, TN

Guest Scientist, Industrial Technology Research Institute, Taiwan,

Republic of China

23
-

.

'

.
TRIBOLOGY Said Jahanmir

The primary objective of the Tribology Group is the development of the

science and technology base to provide scientific understanding, critical

data, and design guidelines for new and improved tribomaterials . This

information is needed for mechanical systems requiring high performance,

durability, and cost effective designs. Tribology is the science that

deals with friction, lubrication and wear of interacting surfaces that are

in relative motion. The output from the tribology program will allow wider

usage of engineered ceramics, coatings, self- lubricating composites and

advanced liquid lubricants, as well as realistic models for prediction of

performance and reliable data and information for design and selection of

new materials for advanced applications. The research program is divided

into three thrust areas: 1) advanced ceramics, 2) tribological coatings

and composites, and 3) advanced liquid lubricants. The primary focus in

these areas is on the characterization of the tribological interface

including analysis of chemical reactions and formation of tribochemical

films, physical and mechanical behavior of surface films, and the

deformation and fracture process leading to wear and failure. A

comprehensive computerized information system is being established as an

effective vehicle for technology transfer.

Representative Accomplishments

o A wear test procedure was developed and used to obtain reliable

design data and to define the limits and requirements of ceramics

under various conditions of load, speed, temperature and

environmental factors. The data has been represented in a useful

and simple- to-use "Wear Map" configuration.

o A time -resolved micro-Raman test system was developed to analyze

chemical reactions at tribological contacts. The system uses a Nd-YAG laser to provide periodic pulses of monochromatic light

which are focused on the surface to be analyzed. This unique

facility can provide fundamental knowledge on complex chemical

reactions and phase changes that occur on tribological surfaces.

o Wear and friction behavior of electrodeposited , compositionmodulated coatings of nickel-copper on steel have been measured

under both lubricated and unlubricated sliding conditions and

found to offer significant improvement over the pure metals. A

preliminary model explaining features of the wear of compositionmodulated coatings has been developed.

o A demonstration of the ACTIS numeric data base was presented at

the meeting of the Society of Tribologists and Lubrication

Engineers in May and at the ASM World Congress on Materials,

Chicago, IL, in September.
o A specified method for a new pin-on-disk wear test standard

developed at NIST that is being balloted in ASTM. We have also

developed a modified method for measuring wear of coatings using

a crossed-cylinder geometry. A standard test procedure is being

written for evaluation of wear performance of ceramics. These

standards will be significant since previously standard methods

were not available in the U.S. in these important areas.

Advanced r.praini r.s

S. M. Hsu, S. Jahanmir, D. E. Deckman, R. S. Gates, S. Jahanmir, R. G.

Munro, and J. P. Yellets

Advanced engineering ceramics possess a number of unique physical and

mechanical properties that makes them suitable for tribological

applications where high temperatures, chemical inertness and high

resistance to wear are important. Examples may include high speed ball

bearings for machine tool spindles, valves and cylinder liners for advanced

heat engines, mechanical seals in reactive environments such as food and

chemical processing, and valves and flow nozzles in solid particulate

handling. The primary technical problems that inhibits wide spread use of

ceramics are (lack of detailed scientific knowledge on their tribological

performance) reliability and cost effectiveness. Our program is focused on

investigating the relationship between processing and performance, the

effect of microstructure and composition on friction and wear, surface

reactions and formation of lubricating films, atomistic and mechanistic

models for friction and wear, and providing reliable test methods and data

for design and selection of advanced ceramics for important technological

applications

.

The research activities on test methods have focused on the selection of

appropriate test apparatus, contact geometry, specimen preparation

procedure, and assessment of the effect of test variables on friction and

wear performance of several advanced ceramics. Test results on alumina,

silicon nitride and silicon carbide, lubricated with mineral oil have shown

that at a specific load both the friction coefficient and the wear rate

increase to a level comparable with the data in unlubricated tests. The

fundamental mechanisms which control this transitional behavior are

currently under investigation.

The selected test procedure was used to obtain reliable design data and to

define the limits and requirements of ceramics under various conditions of

load, speed, temperature and environmental factors. The data has been

represented in a useful and simple- to-use "Wear Map" configuration. These

data are being used to provide a critical step towards understanding the

wear mechanisms of advanced ceramics and the establishment of predictive

models of wear.

The cover illustration of this Annual Report is one of a series of threedimensional graphs that comprise the wear map representation for alumina.

The cover figure shows a dramatic transition between regions of low wear

and high wear in a ball-on- three - flats wear test with a nonreactive,

paraffin oil lubricant. Results, such as this figure, provide important

26
insights and design guides to applications of ceramic materials. For

example, the operating point of a wear component in an engine is actually

an operating range in which variations of both speed and load are possible.

The operating range must now allow the speed and load variables to cross

any portion of the wear transition zone.

Recent findings on the role of microstructure have shown that the grain

size and porosity exert an important influence on wear. Experimental data

suggest that there may be an optimum grain size for best wear resistance.

This phenomena is being currently investigated; it may be related to the

combined effects of fracture initiation and propagation.

Our extensive data on the friction and wear performance of several

technologically important ceramics have confirmed that lubricants must be

used to control the friction coefficient and the wear rate of ceramics.

The present lubricant technology, however, is based on a vast amount of

basic knowledge on reaction between lubricant species and metallic

surfaces. Similar detailed knowledge for ceramics is not available. One

of our projects is directed towards understanding the reaction mechanisms

between lubricants and ceramics. The research during last year has

provided important insights on reaction and film formation tendencies of

several important chemical functionalities such as phosphates, sulfates,

chlorides, as well as the normal paraffinic hydrocarbons, and moisture in

the environment. Such basic understanding is indispensible for design of

advanced lubricants for future applications using ceramic components.

Tribological Coatings and Composites

D. E. Deckman, L. K. Ives, S. Jahanmir, M. B. Peterson, A. W. Ruff, and E.

P. Whitenton

In many applications it is not possible to use liquid lubricants and thus

the materials themselves must have suitable friction and wear

characteristics. Wear and corrosion resistant tribological coatings, and

composites that contain solid lubricating phases are most promising for

these applications. Mechanical seals, actuators and values, rolling

element bearings, splines and couplings are among the tribological

components where coatings and composites could be used to extend the

practical operating limits. Our research in this area included wear

resistant composition modulated coatings, synthesized diamond films, and

self - lubricating composites.

The composition-modulated coatings made at NIST are prepared as alternate

layers of nickel and copper, deposited on steel, at layer spacings from 10

nm to 100 nm. Sliding wear studies have been completed under both

unlubricated and lubricated conditions. An analytical model of dislocation

behavior in a layer microstructure during the plastic deformation

associated with wear has been developed. The model allows for three

effects associated with these unique microstructures; 1) layer spacing

effects, 2) dislocation line energy difference effects, associated with

composition, and 3) layer interface thickness and structure difference

effects. Efforts are now underway to explore these effects systematically

in different alloy systems and using different coating processing

27
parameters. Longer term wear experiments are planned using a different

test geometry. Plans for research on additional composition-modulated

alloy systems are being made and include alternate metal-ceramic coatings

where improved hardness and toughness are expected.

Self - lubricating composites based on polymers are used in many low speedlow load sliding applications. Their use has been limited because of

temperature limitations of polymers. To reach higher interface temperature

metal or ceramic based materials are required. Such tribomaterials would

have much broader applicability. Research projects include:

microstructural effects on wear and strength; the effect of

matrix/lubricant/counterface variables on wear; mechanics of solid

lubricant film behavior; improved test methods for wear, property, and

operating limits; and the fabrication and evaluation of metal and ceramic

based composites.

Four models of wear behavior were formulated and evaluated in sliding

experiments using copper/graphite and nickel/graphite combinations.

Results showed that the dominate feature of the wear process was the

capture of the copper or nickel wear particles in the graphite phase which

interfered with the transfer process in forming self - lubricating layers.

Diamond is both the hardest material known and the material with the

largest thermal conductivity. In addition, it is chemically inert.

However, scarcity and expense have limited their use. The deposition of

diamond in inexpensive thin film form might remove these limitations.

Diamond films offer the possibility of superior wear resistant, low

friction, and chemically protective coatings. The purpose of our research

is to explore the possible use of diamond films as wear resistant, low

friction materials for tribological applications. Silicon carbide disks

were coated with synthesized diamond films using the hot filament CVD

method, in the Optical Materials Group. Preliminary results indicate that

the diamond films provide a low friction coefficient of 0.07, under

unlubricated conditions, as well as excellent wear resistance. The

scientific issues that are being addressed consist of the mechanisms by

which low coefficients of friction are obtained, the effect of deposition

parameters on the physical and chemical characteristics of the diamond

films, such as surface roughness, interfacial bond strength, and the

percentage of diamond bonds in the film.

Advanced Lubrication

S. M. Hsu, S. Jahanmir, D. E„ Deckman, R. S. Gates, B. E. Hegemann, C. S.

Ku, P. Pei, and J. M. Perez

The development of advanced lubrication systems for future applications is

critical to the advancement of technology. Manufacturing processes and

machining, magnetic recording devices, advanced aerospace engines, more

efficient low heat rejection engines, transportation and power generation

are a few examples of technologies with critical lubrication needs. High

temperature lubrication efforts consist of the following: lubrication of

ceramics using improved synthetic fluids, lubricant interaction with

28
ceramics, high temperature additive chemistry and the mechanism of

oxidation and deposit formation at high temperatures.

Definition of reaction mechanisms at high temperatures involves an

understanding of the relationship between molecular structure and thermal

oxidative stability. Understanding how changes occur at the interface

under severe tribochemical conditions is the first step in controlling the

processes

.

Micro-Raman and /i-FTIR spectroscopy were used to analyze the tribochemical

reactions between advanced materials and lubricants. The spatial

resolutions achieved in these techniques are 2 to 3 |im and 100 /im,

respectively. A major area of application is in the analysis of

tribochemical interaction products with ceramic substrates. An

understanding of the effects of differences in ceramic composition and

information on phase change, occurring under in both lubricated and

unlubricated conditions, is being developed.

To further understand the role of chemical structures on effective high

temperature lubrication, the role of polar constituents of base oils was

pursued in light of their ability to enhance or deter the effectiveness of

additives. Base oils obtained from different sources and processed by

different technologies, may differ significantly in their response to

essential additives. Base oils were separated into compound classes and

then evaluated as to their antagonistic or synergistic effect on selected

antioxidants. The fractions were also chemically characterized to

determine the chemical functionality that may cause the observed effects.

Recent findings indicated that most polar subfractions behave in a synergistic manner with antioxidants to increase the oxidation induction

time. However, the most polar subfractions, containing hydroxyl

functionalities, act in antagonistic manner and decrease the oxidation

induction time.

Many advanced ceramic applications require lubrication to prevent

catastrophic failure. Tribological behavior of four synthetic fluids,

polyalphaolef ins (PAO) , trimethylolpropane tripelargonate (TMP)

,

polyphenylethers (PPE) , and tricresyl phosphate (TCP) were studied on

alumina. It was found that the transition from normal wear to high wear

rates can be affected by lubricant chemistry. Lubricant-ceramic

interaction products were found for TMP and PPE but not for TCP and PAO,

suggesting lubricant effects. Functional groups were identified by /i-FTIR

and changes due to tribochemical reactions at the sliding contacts, played

significant roles. Lubrication behavior on alumina is related to

differences in the oxidation/thermal stabilities and relative volatility of

the synthetic base fluids.

Control of the formation of deposits and thermal-oxidative degradation of

materials at high temperatures is critical to developing advanced engine

technologies. Cooperative studies with industry has resulted in a

promising method to evaluate deposit forming tendencies of lubricants and

additives. Laboratory simulation of engine test results have been

demonstrated with current baseline engine oil technology. Extension of the

technique to evaluate novel additives and lubricant formulations is in

progress

.

29
A Computerized Tribology Information System

S. Jahanmir, A. W. Ruff, S. Harris, R. G. Munro and S. M. Hsu

Research in tribology is attempting to reduce the estimated $100 billion

cost incurred by the U.S. economy each year as a result of friction and

wear processes. The Department of Energy has estimated that as much as

forty percent of those losses could be saved by improved technology

transfer. Research in tribology, however, is a complex, interdisciplinary

effort that involves scientists and engineers of rather diverse areas of

expertise. These researchers report their progress in correspondingly

diverse media. As a result, advances in this field are often hindered by

the inaccessibility of critical data or by the lack of awareness of

parallel and concurrent research efforts.

An international effort to overcome this technological problem is being

pursued through the development of A Computerized Tribology Information

System (ACTIS). The central project, ACTIS, is an interagency government

program sponsored by the Department of Energy/Energy Conversion and

Utilization Technology/Tribology Program, the National Institute of

Standards and Technology, the U.S. Army/Fort Belvoir, the U.S. Air

Force/Wright Patterson Aeronautical Laboratories, and the National Science

Foundation. Additional support is being provided by the American Society

of Lubrication Engineers, by the American Society of Mechanical Engineers,

and by two distinguished advisory committees.

The system will include six distinct components: numeric data, design

programs, bibliographic search capability, references to tribological

products, research in progress listings, and a newsletter. All the data

bases will be linked together for easy access by the user, and interactive

searches for particular data are possible.

Considerable effort has been placed this year into the implementation of

the ACTIS tribology data and information system. Most of the effort has

concerned the numeric data portion of the system.

A computer scientist attached to the NIST Office of Standard Reference Data

(OSRD) has started working with the data bases. The selected data base

management system is Advanced Revelation. A major effort was placed in

developing a format for the numeric data to be used with the data base.

The format consists of 49 field names in the categories 1) materials data,

2) mechanical data, 3) physical data, 4 ) tribodata, and 5) triboconditions

.

Substantial time was spent in developing entry screens for the data base

using features in Advanced Revelation. Those screens provide the user with

instructions and information on the system, and give the options available

for selecting report output from any data search. Six of the nine numeric

data base efforts underway have been received from the experts involved,

and three of them installed into the prototype ACTIS system.

Additional data gathering activities are currently underway in the areas of

seals and lubricants. Plans for additional activities include areas of

30
coatings and surface treatments, polymers, ceramic, composites, and

lubricated wear.

A demonstration of the ACTIS numeric data base was presented at the

Cleveland, OH, meeting of the Society of Tribologists and Lubrication

Engineers (STLE) in May over a 2 1/2 day period. A second demonstration

was given at the ASM World Congress on Materials, Chicago, IL, in

September

.

31

FUNCTIONAL CERAMICS

OVERVIEW

Since 75-80% of the roughly $4.4B sales of "advanced ceramics" by the U.S.

ceramics industry in 1987 were in electronic and optical ceramics, the

Division's efforts in functional ceramics support an established portion of

the U.S. ceramics industry. The Division's program in electronic ceramics

addresses superconductors, substrate and packaging materials, dielectrics,

and piezoelectrics. The program on optical ceramics currently addresses

thin optical films and planning is underway for possible future work in

other photonic materials. There are also collaborations with other groups

of the Division and other portions of NIST where appropriate.

The current program in superconducting ceramics is part of a much larger

NIST-wide program aimed at providing the nation with part of the technology

base needed for exploiting as soon as possible the recent discovery of

ceramic superconductors with critical transition temperatures (Tc ) above

77K. The Division's program currently emphasizes technology needed for

producing bulk superconductors as opposed to thin films (which are

addressed in efforts in other NIST divisions). The major technological

barriers to the serious consideration of potential applications of these

materials as bulk superconductors are ways of processing the materials into

components which have high current densities (on the order of 10 5 A/cm2

) and

adequate mechanical strengths. The three divisional thrusts are:

determinations of phase diagrams, explorations of chemical routes for

producing powders, and methods of processing the powders into bulk

superconductors with optimal properties; it is anticipated that these three

thrusts will continue to be emphasized in the foreseeable future. We

believe that the phase diagrams provided by the Division over the past two

years have had major impacts in guiding the processing of the new

superconducting compounds.

Substrate and packaging materials, dielectrics and piezoelectrics

constitute about 50-60% of the U.S. advanced ceramics industry sales

mentioned above and the technologies involved are multi-faceted and rather

mature. The major needs are ways to more cost-effectively produce

components with properties as good or better than those currently produced.

The needs require materials with inherently better properties and more

efficient and reliable ways of processing and testing the materials into

components embodying the improved properties over longer periods of

service. Our efforts in these areas, therefore, emphasize use of very

strong or unique expertise within the Division, namely, phase equilibria

analyses, ceramic processing, small angle neutron scattering and x-ray

analyses, and mechanical properties testing and theory. With the advent of

NIST and the mandate to work closely with U.S. industry, we are in the

process of identifying additional activities in this area that should and

could be addressed.

The current efforts in optical ceramics also emphasize applications of

unique or strong divisional expertise. The major emphases are on synthesis

and characterization of thin films of a variety of materials but especially

of diamond. In the diamond thin film technology, the major needs are to

33
develop techniques for cost-effectively producing films, particularly

single crystal films, with properties appropriate to the intended

applications. The Division's current efforts in diamond thin films

concentrate on the development of chemical vapor deposition (CVD)

techniques and development and use of techniques for characterizing the

films. Other work addresses the mechanical properties of infrared

transmitting materials. The area of photonic materials (optoelectronic and

electrooptic) has been recognized as a potential major growth area and

planning is underway.

The synchrotron radiation analysis program includes the development and

exploration of a unique x-ray topographic capability for nondestructively

analyzing the microstructures of crystalline materials under more realistic

conditions than is possible with most methods. These efforts address a

generic need throughout materials science for an in situ capability for

microstructural characterization. Current efforts emphasize the

exploration and use of these techniques for analyses of defects and

microstructures in electronic and electrooptic single crystals and

polycrystalline ceramics. During 1988, this capability allowed observation

of a type of defect not known to exist in GaAs single crystals but which

may be a factor in limiting the electronic performance of the crystals.

Because current sales of the U.S. semiconductor industry are on the order

of $12B per year, the potential implications of this find are significant.

Increased utilization of this facility by other members of the Division,

NIST, and outsiders to resolve fundamental measurement issues, is being

encouraged and is anticipated.

34
PROJECT LISTING

Electronic Materials

• Development of Superconducting Ceramics

• Ceramic Powder Synthesis

• Phase Equilibria Studies

• Structural Phase Transition Studies

• Processing-Property Relations

• Ceramic Phase Diagram Program

• Pressure Induced Sintering and Transformation Toughening

• Mechanical Failure of Piezoelectric Components

• Studies of Residual Strain and Crystallite Size

• Thermal Wave Measurements in Brittle Materials

Optical Materials

• Diamond Film Growth and Structural Characterization

• Properties of CVD-grown Diamond Films and Particles

• Photothermal Radiometry of Ceramic Films

Synchrotron Radiation Analysis

• Analysis of Polycrystalline Materials Individual Particle Imaging

• Spatial Resolution in X-Ray Image Magnification of Diffraction Images

• Diffraction Imaging for Process Control in Commercial Crystal Growth

• Pervasive Antiphase Boundaries in Gallium Arsenide

35
.
ELECTRONIC MATERIALS Stephen Freiman

The Electronic Materials Group performs research in a number of different

areas. A major effort is directed toward an understanding of the

relationships between processing and properties of the high Tc superconducting ceramics. In this task, we are working closely with

personnel in the Powder Synthesis Group, as well as with other scientists

throughout NIST. One of the primary research objectives in the

superconducting ceramics program is the development of phase equilibria

data, leading to phase diagrams for the different systems. Also, phase

transformations are being investigated in various systems using X-ray

diffraction techniques. In addition, techniques are being developed to

determine critical currents in superconducting ceramics. In somewhat

related work, there is an ongoing study on the reliability of piezoelectric

components under cyclic loading including possible effects of electric

fields on fracture.

During this past year, the Ceramics Phase Diagram Program which is

conducted jointly with the American Ceramic Society was incorporated into

this group. The primary objective of this program is the publishing of

edited phase diagrams for use by ceramic scientists worldwide.

Various processing techniques are being investigated for preparing multicomponent ceramic systems such as electronic packages. Pressure induced

densif ication has been studied as a means of obtaining toughened, infrared

transmitting ceramics.

Work in powder synthesis new chemical routes has been explored for the

preparation of precursor powders for high Tc superconductor ceramics. This

work has led to several advances and patent applications in the preparation

BaYCuO and Bi (Pb) SrCaCuO materials, including a ceramic material with a critical current in excess of 800 A/cm2

.

Discovery of conditions for novel chemical synthesis of precursors for high

Tc superconductor materials.

Demonstrated the application of FTIR analysis for determination of silicon

nitride phase composition.

Achieved significant advances in processing high Tc ceramic

superconductors, particularly with regard to compositional

homogeneity, the role of processing on grain-boundary properties, and the

influence of sintering conditions on microstructure and critical current

density

.

Examined influences of heat treatment on the formation of 80 K and 110 K

superconducting components, as well as regimes of partial melting, in a

study of processing conditions for a new class of high- temperature oxide

superconductors in the Bi-Sr-Ca-Cu-0 system.

Finally, there is work ongoing in the development of non-destructive

evaluation techniques for ceramics. This research involves the use of

thermal wave analysis for the determination of surface flaws, possible

delamination of thin films, and inhomogeneities in the thermal diffusivity

of electronic ceramic components.

37
Representative Accomplishments

o A phase diagram for the Y-Ba-Cu-0 superconducting ceramics was

published. This diagram shows those compositions from which

single crystals of the superconducting compound can be grown.

This work has also led to important observations regarding

effects of carbon impurities on the formation of particular

phases in this system.

o Significant advances were made in processing high Tc ceramic

superconductors in both the Ba-Y-Cu-0 and Bi-Sr-Ca-Cu-0 systems,

particularly regarding compositional homogeneity, the role of

processing on grain-boundary properties, and the influence of

sintering conditions on microstructure and critical current

density

.

o Mechanical and magnetic processing techniques were developed to

align the crystalline grains of bulk Ba-Y-Cu-0 superconductors to

exploit the preferred directions of current transport in these

materials

.

o Discovery of conditions for novel chemical synthesis of

precursors for high Tc superconductor materials.

o Examined influences of heat treatment on the formation of 80 K

and 110 K superconducting components, as well as regimes of

partial melting, in a study of processing conditions for a new

class of high- temperature oxide superconductors in the Bi-Sr-CaCu-0 system.

o Pressure - induced sintering and particulate inclusions were used

in processing polycrystalline, infrared- transmitting ceramics to

improve their structural properties, particularly their fracture

toughness

.

o Volume 7 of Phase Diagrams for Ceramists on salt systems was

completed, and will be published in early 1989.

o Dielectric aging studies were conducted on a number of capacitor

ceramics as a function the oxygen partial pressure during

annealing

.

Development of Superconducting Ceramics

Despite intensive worldwide research in high Tc superconducting ceramics,

difficulties in reproducing materials having optimum electronic properties

and lack of a thorough understanding of the origin of the superconducting

mechanism still remain. A major problem limiting the technological

development of these materials is the relatively small currents, Jc, that

these materials will support in the superconducting state. Impurities and

grain- to-grain misalignment play a large part in limiting the current

carrying capability of these ceramics.

38
Orannc Powder Synthesis

J. Ritter, R. Faltynek

Work within the past year has lead to the development of chemical synthesis

methods for three types of high Tc superconductors. The investigations

were prefaced with the synthesis of the binaries Y2 BaA 07 and CaCu02 as

intermediates important to understanding the formation of precursors in the

YBaCuO and BiSrCaCuO systems respectively. Experience gained in the binary

synthesis was used to develop synthetic approaches to ternary and higher

systems. Considerable success was achieved in precipitating homogeneous

YBaCuO hydroxycarbonate precursor to the YBaCuO superconductor. The

precipitated material converts readily to the superconducting phase at

875°C and test bars made from this powder have shown critical current

densities > 800A/cm2 at 77K. In addition, two novel synthetic routes to

the BiSrCaCuO and BiPbSrCaCuO superconductor systems have been developed.

Each of these processes has been the subject of a patent application.

Phase Equilibria Studies

R. S. Roth, C. J. Rawn, J. D. Whitler, J. 0. Anderson1

, W. Wong-Ng, F.

Beech2

, C. K. Chiang, J. J. Ritter3

, and B. Burton*

1 NBS American Ceramics Society Research Assoc.

2 Reactor Radiation Division

3 Powder Characterization Group

4 Metallurgy Division

Phase equilibria studies, to determine the thermodynamic relations and the

primary phase field of the Ba2 YCu3 06+x superconducting compound in the BaY-Cu-0 system have continued. The compound Ba2 YCu3 06 + x was found to melt

in air through a four phase field with BaY2 Cu3 0 5 , BaCu02 and liquid

gradually increasing in amounts from about 975°C to the incongruent melting

point at 1002°C. As four phases cannot coexist in equilibrium, through a temperature range, a fourth component, C02 , is required to explain the

experimental melting data. The compound previously described as

3BaO : 1/2Y2 03

: 2CuO , has been shown to exist as a solid solution region

between, but not including, the 3:1:2, 4:1,: and 5:1:3 compositions. A

series of single phase specimens can be prepared at 950°C with the formula

Ba3 2^0 8

C

u2 - x^6 a - x (0.1<x<0.4). This phase does not form at all when

prepared with Ba02 in a pure oxygen atmosphere; it is concluded that the

compound is structurally and chemically an oxycarbonate . This work

illustrates the importance of carbon impurities in the processing of these

materials

.

Phase equilibria studies in the quaternary system Ba-Sr-Y-Cu-0 have also

been undertaken in order to determine the extent of solid solution of Sr in

Ba2 YCu3 06+x and also to identify any new phases that might be present in

the four component system. The results show that Sr will substitute for Ba

in (Ba, Sr) 2 YCu3 06+x up to about 60%. There are no ternary compounds in the

Sr-Y-Cu-0 system equivalent to the three ternary phases in the Ba system.

Collaborative X-ray diffraction studies have also been carried out with

39
AT&T Bell Laboratories scientists on single crystals grown from different

alkaline earth/metal oxide-cuprate melts.

A systematic study of the quaternary, Bi2 03 -SrO-CaO-CuO system is being

carried out to determine the thermodynamic relations between phases as well

as to develop processing routes to the superconducting phase (or phases)

.

In the SrO-CaO-CuO system, a new binary phase, probably CaCu02 was

discovered. The ternary SrO-CaO-CuO system has extensive regions of solid

solution; complete solution is observed for the 2:1 series (Sr,Ca) 2 Cu03

. Another new ternary phase with a very narrow range of homogeneity was also

reported. Crystals of composition (Ca0 86 Sr0 14 )Cu02 have been grown, and

characterized by X-ray diffraction.

Structural Phase Transition Studies

W. Wong-Ng, L. P. Cook, C. K. Chiang, L. J. Swartzendruber 1

, L. H. Bennett 1 and F. Beech2

.

1 Metallurgy Division

2 Reactor Radiation Division

Understanding of structural phase transitions in solids is of importance

for processing control, and the development of new products. In the case

of Ba2 RCu3 06 + x , where R = yttrium and the lanthanides, phase transition

studies are being used to gain insight into the role of oxygen in

determining the superconducting properties.

Various measurements including x-ray diffraction, thermogravimetric

analysis, and determination of Meissner effects were carried out for

several high Tc superconductors Ba2 RCu3 06+x (where R= Sm, Y, Gd and Er ; x=0

to 1) in order to correlate the phase transition temperature and oxygen

content with the size of R, annealing temperature, and crystallographic

data. The structural phase transition temperature appears to follow a trend anticipated from the dependence of the ionic radius of R on the f

electron count. The crystal structures undergo a transformation, presumed

to be second order, from orthorhombic Ba2 RCu3 07 to tetragonal Ba2 RCu3 06

. The transformation for all four phases takes place in a temperature range

of 625 (Sm) to 770°C (Er) ; and the lanthanide elements of smaller size seem

to stabilize the orthorhombic phase to a higher temperature.

Oxygen stoichiometry is clearly the most important parameter affecting the

Tc depression and the presence of Tc plateaus. Neutron diffraction was

carried out to investigate the oxygen distribution in the basal Cu-0 plane

of a 60K material Ba2 YCu3 06 56 . Within statistical error, no oxygen was

found in the a-axis. When oxygens are being removed from the Cu-0 chain,

which possibly acts as a charge reservoir, the magnitude of Cu2-01 distance

increases and the Cul-01 distance decreases, which diminishes the coupling

between the Cu-0 plane and the Cu-0 chain. By this mechanism, disruption

of oxygen along the Cu-0 chain is a likely cause of the depression of Tc .
Processing-Property Relations

J. E. Blendell, E. R. Fuller, Jr., C. P. Ostertag, S. A. Soulen, L.

C. Stearns, M. D. Vaudin, J. S. Wallace

The interrelations between processing, microstructures, and properties are

particularly important for the new high Tc ceramic superconductors.

Significant advances were made in processing these materials, elucidating

many of the processing-microstructure-properties interrelations. Results

for the Ba-Y-Cu-0 system are discussed below.

Composition control . Grain-boundary chemistry has a major effect on

the current carrying capability of these materials. The presence of second

phases along grain boundaries is a major impediment to current flow. Segregation of impurities below the solubility limit also can limit current

flow. Clean-room processing of high-purity starting materials gave orderof -magnitude improvements in transport critical current density, Jc , as

compared to conventionally processed, reagent grade materials. Values of

transport J c at 77 K increasing from tens of A/cm2 to hundreds of A/cm2

. Transmission electron microscopy indicates that considerable amounts of

second phases remain at many grain boundaries; thus further improvements

are possible. Recent chemically prepared samples have had transport Jc values at 77 K of greater than 800 A/cm2 (sample heating prevented exact

measurements)

.

Grain Alignment . Crystallographically aligned polycrystalline samples

were produced both by sinter- forging and magnetic casting. Due to the

anisotropic nature of these materials, aligned materials exhibit higher

critical current density as compared to unaligned materials. In sinterforging, samples are deformed during unconstrained hot pressing. Alignment

occurs as the grains rotate during the deformation. Although the samples

were observed to align crystallographically, the transport current density

was very low, and in some cases the samples were not conductive at all.

SEM, EPMA and TEM analysis showed that this was due to large scale chemical

segregation that occurred during sinter-forging. The usefulness of this

technique for improving properties of Ba-Y-Cu-0 superconductors is somewhat

doubtful at this time.

In contrast, studies on magnetic alignment of calcined superconductor

powders prior to sintering are more promising. Resulting sintered compacts

tend to have their c-axes aligned parallel to the applied magnetic field,

as confirmed by X-ray and neutron diffraction observations. The measured

values of magnetization versus applied field at 77 K were strongly

anisotropic, indicating appreciable crystallographic alignment. Critical

current densities calculated from magnetic measurements were on the order

of 10 3 to 10A A/cm2

. Transmission electron microscopy showed that the

grain boundaries did not contain second phases, and that the (001) planes

were aligned across most of the grain boundaries to within an angle of 10°

.

Lanthanide Substitutions . The use of the lanthanide elements for Y

are being investigated. The initial stages of a study on the effect of La,

Gd, Ho, and Er on the nature and location of second phases in Ba-Ln-Cu-0

have been completed. The effect of these substitutions on the magnetic

alignment will also be investigated.

Ba Precursors . Microstructure and superconducting properties are

intimately related to the processing conditions employed. It has been

determined that the choice of the Ba precursor plays a critical role on the

41
microstructural evolution of the sintered body, particularly in relation to

the density and grain size. Transmission electron microscopy showed marked

inhomogeneity in these fine-grained materials with the same grain in some

instances having both "clean" and "dirty" facets. Investigation of the

effect of using different Ba precursors is continuing, with emphasis on

obtaining clean grain boundaries and high critical current densities.

Ceramic Phase Diagram Program

S. Freiman, C. R. Hubbard4

, H. M. Ondik, R. S. Roth, M. A. Clevinger, L. P.

Cook, P. K. Schenck1

, S. K. Peart2

, K. M. Kessell2

, J.-O. Andersson2, C. G.

Messina2

, H. F. McMurdie2, M. J. Rodtang3

, D. I. Pennington3

, R. Yang3, T. A. Messina3

, R. A. Wilson3, T. J. King3

. Metallurgy Division

2 Research Associate, American Ceramic Society

3 Student Research Associate, American Ceramic Society

4 Oak Ridge National Laboratory, formerly of the Ceramics Division NBS/NIST

The National Institute of Standards and Technology (NIST) -American Ceramic

Society (ACerS) ceramic phase diagram program completed its third full year

of the expansion plan. The driving force for this joint program is

industry's need for current, evaluated phase equilibria data covering a

broad range of ceramic systems. Industrial contributions for the support

of Research Associates at NIST have passed the $2,000,000 mark.

Volume 6 of Phase Diagrams for Ceramists was published by the Society in

November, 1987. Volumes 7 and 8 are in production. Each contains

approximately 1000 phase diagrams. Final review of Volume 7 on salt

systems has been completed and is fully typeset. An early 1989 publication

date is anticipated. Volume 8 on water containing oxide systems at

elevated pressures is fully keyboarded; commentaries and diagrams have been

reviewed and computer typesetting has begun. A mid-1989 publication date

is anticipated. Material for Volume 9 on carbides, nitrides, and borides

is in the hands of the technical editors, and should be published in late

1989.

Databases which permit direct search capability of the data sets of both

graphics and text material have been developed for Personal Computers (PC)

.

Currently, the data files for the graphics and the bibliography-commentary

files corresponding to Volume 6 are in the PC databases. The graphics

capabilities developed by Peter Schenck now include the ability to transfer

the diagrams to a Personal Computer (PC) database, edit them for PC

viewing, and manipulate them on screen.

The PC bibliography and commentary database established in 1987 on a

customized commercial database management system has been upgraded. The

commercial company provided a more complex system which uses menus and popup windows, thereby eliminating the need for the user to learn the rather

tedious original query system. This PC database also contains the

bibliographic data for all the diagrams being considered for future

inclusion in Phase Diagrams for Ceramists .

42
A large effort has been expended in keyboarding the bibliography

corresponding to Volumes 1-5. In early 1989, the files will undergo a final proof check by computer and will be available for data dissemination

by the ACerS

.

The upgraded version of the text-containing database as well as the PC

graphics database were exhibited at the ACerS Annual Meeting in May. Since

then, they have both been distributed to the Industrial Sponsors of the

program for testing.

Pressure Induced Sintering and Transformation Toughening

S. Block, G. J. Piermarini, M. L. Balmer, V. Bean

Ceramics are typically sintered at high temperatures, occasionally with the

assistance of moderate pressures. An interesting alternative for producing

ceramics with potentially superior properties is "high-pressure induced

sintering" at low temperature. Such a process can be accomplished by highpressure compaction of ceramic powders, thereby enhancing interparticle

contact and breaking down aggregates, followed by low- temperature

"sintering" under high pressure.

Extensive studies were undertaken in a diamond anvil cell on pressure

sintering and toughening of materials, which are optically transparent in

the 8-14 nm range. These studies concentrated primarily on ZnS and examined the following processing variables: a) powder source; b) compaction

pressure (to 4 GPa) ; c) sintering pressure (to 500 MPa) and temperature (to

500°C) ; d) transformation toughening additives; and e) temperature excursions. Chemically vapor deposited (CVD) samples of ZnS from Raytheon Corporation were used as a standard of comparison. Results to date are very

interesting. As in ordinary sintering, pressure sintering results are

dependent on powder source. One powder produced fracture toughness values

~ 50 % superior to the standard, while another source gave only about a 20

% improvement. The hardness of both samples is directly proportional to

the initial compaction pressure. In contrast to conventional sintering,

where temperature excursions are insignificant unless they are very large

or involve phase changes, temperature excursions greatly affect compacts

formed by pressure sintering, negating the above-mentioned improvements.

Pressure sintering, therefore, most likely involves a mechanism which is

different from classical sintering.

Work was initiated to fabricate larger samples in collaboration with the

Temperature and Pressure Division (522). A compact, prepared in one of

their large presses, had a fracture toughness which varied from 0.73 to

1.53 MPa. mb with position in the sample. The KIC of the standard ZnS is

about 1.0 MPa. mb. Further improvements in KIC are expected as the pressure

induced processing procedures are optimized.

43
Mechanical Failure of Piezoelectric Components

G. S. White, S. W. Freiman, D. C. Cranmer, and A. M. Wilson1

1 Coop Student, Oberlin College

Experiments were conducted on cyclically loaded lead zirconate titanate

(PZT) to clarify the mechanisms leading to mechanical failure. The work is

directed toward three goals: 1) determining cyclic fatigue mechanisms in

electrically stressed PZT 2) delineating the effects of the electric field

itself on crack extension, and 3) determining possible contributions of the

environment to crack growth. Indentation techniques are used to produce

surface cracks which grow under an electric-field generated load. This

approach permits us to monitor directly the crack interactions with pores

and grains in the material. Preliminary results indicate that cracks tend

to grow from pore to pore in the material rather than in straight lines.

This result suggests that one possible mechanism driving crack growth is

increased strain generated by enhanced electric fields around the pores.

Preliminary data obtained on other piezoelectric ceramics also tends to

support the concept of direct effects of electric field induced strain on

crack extension.

Transformation toughening is a well-known and effective method for

enhancing the fracture toughness of ceramic materials. Transformation

toughening by the retention of high-pressure metastable phases is a concept

that originated at NIST. Necessary criteria for such toughening require

the toughening agent to exist metastably at ambient pressures and

temperatures and to have a rapid, reversible, pressure- induced, phase

transformation

.

This new approach to toughening is currently being applied to toughen

materials optically transparent in the 8-14 /xm range. NiS/ZnS compacts

were made by sintering under pressure to determine whether transformation

toughening occurs. The fracture toughness as measured by an indentation

technique increased by 100 % at 33 % NiS. Infrared transmission is

problematical, probably depending strongly on stoichiometry and particle

size. The two polymorphic forms of NiS, and their toughening effect are

being investigated.

Studies of Residual Strain and Crystallite Size bv X-Rav Diffraction

W. Wong-Ng, Y. Zhang1

, C. R. Hubbard, S. W. Freiman and J. M. Stewart 1

1 Guest Scientist, University of Maryland

Potential applications of the high Tc ceramics, Ba2 RCu3 0 7 _ x , where R are

the lanthanide elements, depend a great deal on their electrical and

mechanical properties. A thorough knowledge of the microstructure of these

materials, in both their ceramic as well as powder forms, is of importance

in order to understand and control the variation of their physical and

mechanical properties with processing parameters.

44
Significant differences in the x-ray diffraction line widths have been

observed for two orthorhombic barium yttrium cuprate powders with

compositions of Ba2 YCu3 07 0 and Ba2 YCu3 06 8

. The former was annealed in

oxygen and the latter in air. It was found that the x-ray diffraction

peaks of the air-annealed sample are *35% broader than those of the oxygen

annealed sample. Since the coherent diffracting domain length (crystallite

size), residual microstrains, and chemical inhomogeneity might all affect

the superconducting and mechanical properties of these materials, x-ray

diffraction line profile analysis using the Warren Averbach and Hall

Williamson methods has been carried out to study these profile differences.

A significant anisotropy in the crystallite size and residual strain for

the air-annealed sample was observed relative to that for the oxygenannealed material in which size and strain broadening were negligible.

Thermal Wave Measurements in Brittle Materials

G. S. White, H. P. F. Frederikse 1

, and Xuan Tong Ying2

1 0ptical Materials Group

2 Guest Scientist, Fudan University, Shanghai, PRC

Thermal Diffusivitv of Diamond Films

Thermal diffusivity, a, measurements have been made on diamond films

produced at NBS and at General Electric. The mirage technique has the

capability to determine a in different directions; therefore, nonuniformities and directional dependence of the specimen's thermal

characteristics can be detected. The value of a in the GE specimen was

found to be about 3 cm2 /s along the sides but only 0.7 cm2 /s along a band

passing through the center of the specimen. Subsequent discussions with

scientists from GE confirmed that the Si substrate on which the diamond had

grown was incompletely etched away along a band in the center of the

specimen. The substrate material was not visible to the eye, but its

thermal diffusivity value, 0.7 cm2 /s, was easily detected in the mirage

experiment

.

45
•

_
OPTICAL MATERIALS Albert Feldman

The objective of the Optical Materials Group is to provide data,

measurement methods, standards and reference materials, concepts, evaluated

data, and other technical information on the fundamental aspects of

processing, structure, properties and performance of optical and

optoelectronic materials for industry, government agencies, universities,

and other scientific organizations. The program supports generic

technologies in crystalline, glassy, and thin film inorganic optical

materials in order to foster their safe, efficient and economical use.

Research in the group addresses the science base underlying new advanced

optical materials technologies together with associated measurement

methodology

.

The principal area of optical materials research being covered is thin

optical films , which addresses the processing/structure relationships of

diamond and other ceramic coating materials and how they affect properties,

optical performance, and optoelectronic performance as related to optical

coatings, light emitting sources, detectors, and integrated optics.

Representative Accomplishments

o A new hot-filament CVD diamond deposition facility has been

constructed. It allows us to observe the deposition, to vary the

substrate/filament distance, and to employ different filament

configurations. A significant accomplishment is the minimization

of filament sagging resulting in much longer filament life.

o Diamond films have been deposited on Si wafers, Si highly doped

with B, Ni, Si 3 N4 , SiC, Si02 , and mullite and on different

crystallographic surfaces of Si. Mismatch of the thermal

expansion leads to film crazing on Si02 substrates. Morphology

appears to be relatively insensitive to the substrate material

and orientation; however, films on Si 3 N4 have finer grains, and

films on SiC appear to grow faster. Deposition on Ni was

unsuccessful. Deposition on Si doped with B showed regions of

continuous film growth and regions of particle growth.

o Substrate temperature (600-850°C) during deposition causes large

variations in film morphology; the cleanest diamond surfaces

occur at nominal substrate temperatures between 700 and 750°C.

The cathodo- and photo- luminescence spectra also show significant

variation indicating that defect center identities and

concentrations are dependent on the substrate temperature during

deposition. These defect centers can be correlated with defects

centers observed in bulk synthetic and natural diamond.

o The thermal conductivities of plasma sprayed barrier coatings of

chromia, alumina, and zirconia have been measured as a function

of specimen temperature by means of photothermal radiometry as

part of the NDE program.

47
o Thermal diffusivity measurements have been made on a diamond

plate provided by General Electric and on a film deposited by us

on mullite. The values obtained are less than those for bulk

diamond but are greater than that of copper and silver.

o A. Feldman is serving on the National Materials Advisory Board

Committee on Superhard Material examining the technological

significance of materials such as diamond, diamond- like carbon

(also called DLC) , cubic boron-nitride, and SiC, and which is to

recommend research priorities for exploiting these materials.

Diamond Film Research

Diamond Film Growth and Structural Characterization

E. N. Farabaugh and A. Feldman

A new hot-filament CVD diamond deposition facility has been constructed which

has significant improvements over our first generation facility. (Our first

facility was upgraded by the installation of flow controllers which allow us

to vary the gas composition.) The new apparatus, shown schematically in

figure 1, allows us to visually observe the deposition. The substrate holder

contains a heater and has provision for movement relative to the filament.

The filament holder allows for different filament configurations. A means was

devised to support the filament thus minimizing filament sagging and resulting

in much longer filament lifetimes. Filament lifetimes of 500 hrs . have been

achieved. This new configuration also allows us to change specimens more

easily without accidentally breaking the filament. All of the deposition

described below were carried out in our first apparatus.

Diamond films have been deposited on a variety of substrates: different

crystallographic surfaces of single crystal Si wafers; Si doped with B; Ni;

Si 3 N4 ; SiC; Si02 ; and, mullite. Except for the Si doped with B, all of the

substrates were prepared by rubbing with diamond paste and cleaned prior to

deposition in order to obtain continuous film growth. Mismatch of the thermal

expansion of the film and the substrate is important; for example, crazing of

the film is observed when deposited on Si02 because the film contains a large

tensile stress due to the higher thermal expansion of diamond. Morphology

appears to be relatively insensitive to the substrate material and

orientation; however, films on Si 3 N4 have finer grains, and films on SiC show

larger grains and appear to grow faster. Deposition on Ni was unsuccessful.

In our previous depositions on Si, we found it necessary to pretreat the

substrate surface with diamond paste, as discussed above, in order to obtain

continuous films. It had been reported that B acts to nucleate diamond. We

therefore wanted to investigate whether continuous films could be deposited on

Si wafers that were heavily doped with E without the diamond paste

pretreatment. Deposition on Si doped with B showed both regions of continuous

film growth and regions of particle growth suggesting that B might facilitate

diamond nucleation.

The effect of substrate temperature on diamond film morphology was examined.

Films were deposited on pretreated Si substrates at nominal substrate

temperatures of 600, 650, 700, 750, 800, and 850°C. The other film deposition

48
parameters were: gas composition, 0.5% methane/99.5% hydrogen; gas pressure,

5xl03 Pa; gas flow rate, 52 seem; filament temperature, ~1800°C. Large

variations in film morphology were observed (see figure 2). At 600°C, grains

with a cube -like habit seem to predominate. At 650 °C the microstructure is

less well defined with triangular facets beginning to develop and mix with the

cube- like habit. At 700°C the triangular faces predominate and the cube-like

faces are absent. Growth spirals become evident on some of the faces. At

750°C the film surface displays well defined triangular faces, the crystal

grains are well defined, and the growth spirals are more distinct. At 800 °C

the crystal grains are less well defined with secondary nucleation occurring

as evidenced by the appearance of small grains growing between the larger

grains. The growth spirals appear to have evolved into steps and ledges. At

850 °C the secondary nucleation is much more pronounced with a greater loss of

definition of the microstructure. The cleanest diamond surfaces occur at

substrate temperatures between 700 and 750°C. Luminescence spectra, discussed

below, have been obtained on these same films.

Future work includes: effect of deposition parameters on growth rate and

diamond perfection; effect of doping on film growth rate and morphology;

dependence of shift of diamond Raman line on particle morphology (icosahedral

vs. cubo-octahedral) ; deposition apparatus using microwave assisted CVD will

be constructed. In addition films will be provided to support thermal

conductivity measurements, luminescence measurements, infrared transmission

measurements, and tribology measurements.

Optical and Optoelectronic Properties of CVD- grown Diamond Films and Particles

L. H. Robins, L. Cook*, E. N. Farabaugh, A. Feldman, and E. Etz**

*Electronic Materials Group

**Gas and Particulate Science Division/Center for Analytical Chemistry

The goals of this project are to identify and develop experimental techniques

for characterizing the properties of diamond films that are relevant to

projected applications in optical and optoelectronic devices, and to gain a better understanding of the relationship between CVD process parameters and

the properties of the as-deposited films. Recent work has focussed on the

influence of imperfections in the diamond lattice, including both native

defects and chemical impurities.

Luminescence, the optical emission arising from electronic recombination at

defect and impurity levels within the bandgap , is the principal technique

currently being used. Two methods of producing luminescence are being

pursued: cathodoluminescence (CL), in which a high-energy (1-30 keV) electron

beam is the excitation source; and, photo luminescence (PL), in which photons

(visible or ultraviolet light) are the excitation source.

A CL experiment has been set up in a scanning electron microscope. By using

the imaging capability of the scanning electron optics, the spatial

distribution of luminescent defects can be mapped, complementing the

information about electronic structure provided by luminescence spectroscopy.

Several interesting results have already emerged from this experiment. By

comparing the CL spectra in our diamond films to spectra reported in the

49
literature for bulk natural and synthetic diamonds, we have tentatively

identified defects associated with nitrogen impurity atoms, interstitials,

atomic vacancies, and dislocation lines. In a series of films grown at

different deposition temperatures, the nitrogen-related CL was most intense in

films grown at low temperature, the dislocation-related CL dominated at

intermediate temperatures, and the atomic vacancy CL was most intense at the

highest temperature. Variations in the intensity of these CL bands appear to

be correlated with changes in film morphology. CL imaging of single-crystal

particles suggests that the concentration of luminescent defects is high on

(100) crystal planes and low on (111) planes; secondary electron imaging

showed that, at least in large isolated particles, the [100] planes have

smooth surfaces while the [111] planes show growth steps.

PL excited by an argon ion laser has been studied in a Raman microprobe

system. The initial results of the laser PL have shown that there are

correlations between CL and PL spectra in films grown under the same

conditions. In particular, the atomic vacancy related luminescence band was

observed by both CL and PL in a film grown at high temperature, but was not

observed by either method in films grown at lower temperatures. A broad,

featureless spectrum at energies higher than the vacancy band has also been

seen in laser PL; preliminary results suggest that the featureless spectrum is

associated with polycrystalline films rather than single-crystal particles.

We plan to extend our experimental capabilities for PL and CL as techniques

for characterizing defects in diamond. In the CL system, spectrally resolved

imaging will be used to compare the spatial distributions of different types

of luminescent defects. Possible linear polarization effects in the images

will also be investigated. The spectral range of the CL detection system will

be extended further into the ultraviolet, beyond the energy of the diamond

bandgap , to allow the detection of near-band-edge as well as deep- level

luminescence. In the PL experiment, a variable- temperature liquid-helium

cryostat will be used to measure the temperature dependence of luminescence

intensities and linewidths. Spectral lines of the ion laser, as well as

tunable arc- lamp and flash- lamp light sources, will be used to investigate the

dependence of PL on excitation photon energy. Related characterization

techniques such as photoconductivity spectroscopy will also be started.

The coupling between film deposition and optical characterization activities

in the Optical Materials Group is being strengthened. For example,

luminescence is being used to compare the defects present in single-crystal

diamond particles and continuous polycrystalline films. The influence of

various deposition parameters on the optically active defects will be

investigated in greater detail. One parameter that may be investigated is the

addition of chemical dopants intended to produce electrically and optically

active donor or acceptor levels; luminescence is expected to be a valuable

technique for characterizing such impurity levels.

50
Photothermal Radiometrv for Monitoring of Ceramic Film Quality

H. Frederikse, X. T. Ying*, A. Feldman, and E. N. Farabaugh

*Guest Scientist from Fudan University, Shanghai, PRC

Ceramic films . The purpose of this project is to inspect the thermal behavior

and mechanical integrity of non-metallic coatings using the propagation of

thermal waves. Such coatings play an important role in many technological

areas: optical components, engines and combusters, corrosion protection,

electronic devices, etc. Thermal wave techniques have gained considerable

attention and popularity during the last 10-12 years. Both thin and thick

layers, from a few microns to several millimeters, can be probed conveniently

by thermal waves because the thermal diffusivity length can be adjusted to

these depths by varying the modulation frequency. Several detection schemes

can be used to determine the temperature variations in time or in space; a

number of these techniques do not require contact with the material being

probed and hence lend themselves well for Non-Destructive Evaluation.

We have investigated the heat resistance of a number of oxides coatings at

temperatures up to 900°C. The coatings, deposited by plasma spraying to a thickness of 50-100 ^m, were chromia, zirconia, and alumina; the substrates

were stainless steel plates in all cases. The previous year we had developed

Photo Thermal Radiometry (PTR) as a noncontact method to monitor the thermal

quality of ceramic coatings at room temperature.

The experimental set up is similar to that described in last year's Annual

Report. The only difference is that the sample is positioned inside a horizontal cylindrical furnace, about 6-8 cm from the opening at one end.

Measurements were made at six temperatures between 20 and 900°C. Two infrared

detectors were employed over this temperature range: a liquid nitrogen cooled

InSb detector for temperatures up to 500°C and a Ge photodiode for

temperatures between 500 and 900°C. The detector was needed because the InSb

detector saturates above 500°C due to a large background thermal signal. Even

in the range of 200-500°C small apertures had to be inserted to limit the

amount of radiation falling on the sensitive InSb area. At the highest

temperatures, the Ge photodiode also required aperturing.

At each temperature, the magnitude of the signal, |s|, and the relative phase,

A4>

,

were measured as a function of the modulation frequency which was varied

from 9-333 Hz. Analysis of the A^-vs-Vf plot yielded the thermal diffusivity

a and the thermal conductivity k of the coatings. The values of a and k are

about a factor two smaller than the Handbook data for bulk ceramic specimens

and much smaller than the single crystal values. This is not surprising

considering the high degree of disorder and the relatively low density of

plasma sprayed coatings. Another indication of large thermal scatter is the

temperature dependence; a and k show a nearly constant behavior rather than

the predicted 1/T dependence.

Thermal Properties of Diamond . In the last few months we have turned our

attention to the thermal properties of diamond films. One of the properties

of great importance is the high thermal conductivity of diamond. Consequently

it is important to determine this property both as a measure of diamond film

quality and as a specimen parameter for a particular use. In recent months we

51
have studied several Thermal Wave Techniques in order to determine the most

suitable method for diamond coatings. Results have been obtained on a 1/2 mm

thick film (obtained from G.E. Laboratories). In this case, PTR was the

preferred method. Other promising approaches are a longitudinal method - propagation of the heat wave along a film of diamond deposited on a narrow

strip of thermally insulating ceramic - and the optical beam deflection

technique (mirage effect)

.

Preliminary measurements of thermal conductivity

indicate values less than that of the best diamond but greater than that of

copper. In addition, optical beam deflection measurements indicated thermal

inhomogeneity.

52
Figure 1. Schematic diagram of redesigned hot filament chemical vapor

deposition apparatus for depositing diamond films.
Figure 2. Scanning electron micrographs of the surface morphologies of

diamond films prepared at different substrate temperatures. Two levels of

magnification are shown.

54
SYNCHROTRON RADIATION ANALYSIS Masao Kuriyama

New materials with enormous practical interest are now being produced in

industry by far more sophisticated processing methods than utilized a

decade ago. These materials are made with control of their buildup

designed at the atomic level. Success with such materials primarily

requires the knowledge of new ways to arrange the atoms in order to achieve

the desired properties. But such knowledge, while important and necessary,

is insufficient by itself. The structure of all materials, when formed, is

non uniform locally over regions of the order of a micrometer. Heterogeneity occurring as grain boundaries, phase interfaces, interacting

dislocations, local compositional variations, regionally homogeneous

strains (plastic deformation), and inhomogeneous strains, etc., often

alters the performance of materials designed for sophisticated and

demanding applications. Thus, successful fabrication of such materials by

atomic design or ultra-molecular engineering of structures depends entirely

on structural details and their influence on properties.

The Synchrotron Radiation Group's objective is to develop and use new

measurement technology for the characterization of such advanced materials

and better starting materials for traditional materials particularly by

applying recent advances of synchrotron radiation diffraction imaging

techniques. This effort aims at the fundamental understanding of the

genesis of imperfections and the processing mechanisms of advanced

materials, in particular, modern ceramic materials. This fundamental

knowledge will directly assist U.S. industrial scientists and engineers to

make high quality advanced microcircuits and electrooptic communications

devices competitive in the world market. In this support of intelligent

processing, the group's current activity emphasizes efforts to improve

generic measurement technology and to provide basic data that will lead to

the production of advanced materials with superior properties for devices

of higher quality and improved reliability, in collaboration with U.S.

industrial scientists.

Representative Accomplishments

o Discovery of novel microstructural features in undoped semiinsulating LEC gallium arsenide by monochromatic synchrotron

diffraction imaging, and explanation of this new

phenomenon in terms of antiphase platelets (or

interfaces)

.

o Proposal of a unified theory of defect generation based on

the antiphase structure in undoped semi - insulating LEC

gallium arsenide; this provides an understanding of the

crystal growth mechanism.

o Establishment of a new analysis method for polycrystalline

materials by imaging individual particles in synchrotron

radiation diff ractometry , and its application to alumina and

silicon particles.

55
o Completion of a new experimental station, A2 , at NIST/IMSE

beam line for EXAFS , standing wave, and total reflection

analysis of interfaces in collaboration with CEEE.

o Development and implementation of collaborative research

programs with industrial and governmental laboratories, such

as Westinghouse , Grumman, Rockwell International (Science

Center), EG&G , U. S. Army Materials Technology Lab, and

business firms interested in crystal growth of liquid

encapsulated Czochralski grown gallium arsenide and

temperature -gradient freeze-Bridgman grown gallium arsenide,

and cadmium telluride.

o Application of the x-ray image magnification technique to

electronic device materials in diffraction imaging, reaching

submicron resolution.

New Analysis Method of Polvcrvstalline Materials bv Imaging Individual

Particles in Diffraction

D. R. Black, R. Spal and M. Kuriyama

The determination of particle size, orientation, strain, and distribution

normally requires elaborate analyses of x-ray diffraction data obtained

from line profiles or small angle scattering (SAXS) profiles. These

analyses are dependent entirely on mathematical models which are chosen by

investigators. With a highly parallel (a few arc-second divergence) beam

prepared from synchrotron radiation, dependence on these models is no

longer necessary. Diffraction lines actually consist of numerous small

spots, although they are grouped to form a ring, historically called

"Debye-Scherrer" ring. The individual spots are, in fact, diffracted from

individual grains and particles, as shown in Figure 4a. From samples

provided by other groups in the Ceramics Division, diffraction images have

been obtained with 10 /im spatial resolution. The relative orientation of

individual particles has been determined, as shown in Figure 4b. The beam

was 2 arc-seconds wide in the vertical direction and 30 arc-seconds in the

horizontal direction, and had a 1 mm X 0 . 2 mm cross section. These conditions can be adjusted for each measurement as required. The acquisition of

the total profile for all particles in one diffraction line can be achieved

within 20 minutes. The relative orientation of particles can be recorded

within 5 minutes by rotating the sample while a detector is at a fixed

position. In the demonstration experiments on a silicon standard sample

and an alumina disk using 8.048 KeV radiation, particles of slightly less

than 10 /im can clearly be separated. This resolution can be improved as

experiments progress. Within each particle, one can see fine structure,

namely, crystal imperfections and subgrain boundaries. The diffraction

profile of a single particle, typically called its rocking curve, can be

obtained within a minute to give an estimate of the magnitude of

inhomogenous strains. The next objective is to determine accurately the

magnitude of homogeneous strains in individual particles, that is, the

determination of residual strains. The information obtained from this new

type of model- independent measurement has proven to be useful for the

characterization of green state materials and sintered materials. Diamond

56
films, superconducting pellets, and powder of superconducting materials are

being investigated in the current beam time at X23A3.

Spatial Resolution in X-Rav Image Magnification of Diffraction Images

R. C. Dobbyn, R. Spal and M. Kuriyama

There have been many advances in obtaining direct images and diffraction

images in real-time. An important question has been what is the limit of

spatial resolution? Is it limited by diffraction effects of samples and/or

x-ray optical elements that prepare the beam and images? An x-ray image

magnifier of 30 X to 40 X was used to obtain diffraction images from

electronic device features on gallium arsenide. The device was set in the

(400) symmetrical diffraction condition in the surface reflection (Bragg)

geometry. The magnifier was aligned in the non-dispersive geometry with

9.3 KeV radiation. As shown in Figure 5a and 5b, the details of the device

down to approximately 3/10 of a micrometer can clearly be visible, although

diffraction effects due to crystalline imperfections are evident along with

the device image. The present result indicates that the resolution has not

been limited by diffraction effects, and the increase of magnification

factors will be useful to achieve real-time imaging with submicron resolution, along with efforts to develop high sensitivity 2D detectors. For the

evaluation of devices, diffraction images demonstrate the uniqueness in

identifying the role of crystalline imperfection in relation to individual

device areas.

Diffraction Imaging for Process Control in Commercial Crystal Growth

B. Steiner, M. Kuriyama, R. C. Dobbyn and H. E. Burdette

The uniqueness of the NIST/IMSE Synchrotron Radiation Beam line, X-23A3 at

National Synchrotron Light Source, is based on unconventional parallel

monochromatic beam optics combined with the distinctive advantage of the

small source size of the storage ring. Diffraction imaging at this unique

facility is leading to an understanding of various defects and strain

fields and of their genesis and interactions during growth and subsequent

device fabrication. This capability has now been put in full use with

industrial scientists for the production of better semiconductors and

optoelectronic materials. In collaboration with EG&G , Grumman, Rockwell

International (Science Center), Westinghouse , and other firms, the group

has been investigating undoped and indium doped LEC gallium arsenide,

temperature-gradient freeze -Bridgman gallium arsenide, cadmium telluride,

mercury iodide and other epitaxial layers.

57
Figure 3. Enlarged portion of a transmission (400) diffraction image

through a 0 . 7 mm thick undoped gallium arsenide single crystal, taken at 10

KeV on the NIST Materials Science Beam Line at NSLS . Typical cellular

structure is accompanied by streaking images running diagonally in the

[100] direction.

Figure 4a. Diffraction lines, magnified 2.5 times, from a-Al2 03 , indicating individual particles undergoing diffraction, taken at 8.048 KeV with a

parallel (2 arc-seconds) monochromatic synchrotron radiation beam. Film

was perpendicular to the (113) line. The film-sample distance is 5 cm.

58
Angle (deg)

Figure 4b. The relative angular orientation of individual particles is

shown as the sample is rotated. The detector is set to receive the (113)

diffraction line of aAl2 03 .

Figure 5a. (400) diffraction image in the surface reflection geometry

taken from a device on a gallium arsenide (100) substrate at 9.3 KeV, using

an x-ray image magnifier, 30 X.

59
Figure 5b . Enlarged portion of the device of Figure 3a, showing details of

approximately 0.3 /im.

Discovery of Pervasive Antiphase Boundaries in Liquid Encapsulated

Czochralski -Grown Semi -insulating Undoped Gallium Arsenide

M. Kuriyama, B. Steiner, and R. C. Dobbyn

Novel, pervasive, streak- like features restricted to the direction of the

scattering vector have been observed in diffraction images of monochromatic

synchrotron radiation (8-10 KeV) transmitted through LEG -grown (liquid

encapsulated Czochralski) semi- insulating undoped gallium arsenide (Figure

3) . The appearance of such features is not predicted by commonly accepted

dynamical diffraction imaging theory, but can be interpreted by dynamical

theory that had been generalized to include scattering by imperfect

crystals. As a result, these observations have been shown to be caused by

the disruption of diffraction by very thin {110} boundaries characterized

by lattice coherence but incorporating a phase (atomic) shift. Of the

various possible crystal defects, only antiphase boundaries are consistent

with these observations as well as with the other aspects of the new high

resolution diffraction images: cellular structure, linear and very lowangle subgrain boundaries in <110> directions, surface stripes in a <110>

direction, and systematic differences in the acceptance angle for images

involving various diffraction vectors. Some of the individual features had

been observed at lower resolution, indicating that the crystals in this

study are typical of undoped LEG gallium arsenide. However, a unified

interpretation had not been achieved. The observation of pervasive

antiphase regions suggests that approaches to greater crystal perfection,

which is required for commercial exploitation of gallium arsenide crystals

for high speed information processing, must be fundamentally reconsidered.

The new observations have been carried out on the NIST/IMSE materials

science beam lines (X23A) at the National Synchrotron Light Source.

60
RESEARCH STAFF
-'

.

*
Powder Synthesis and Characterization

Cline, James P.

Dragoo, Alan L.

Faltynek, Robert A.

Hegemann, Bruce E.

Kelly, James F.

Long, Gabrielle G.

Lum, Lin-Sien H.

Malghan, Subhas G.

Minor, Dennis B.

Pei, Patrick

Ritter, Joseph J.

Wallace, Jay S.

o High- temperature x-ray diffraction

o Microstructural effects in x-ray diffraction

o Standard reference materials

o Powder characterization

o Ceramic process characterization

o X-ray characterization

o Chemical synthesis of ceramic powders

o Organometallic synthesis of ceramic precursors

o FTIR characterization of powders

o Spectrophotometry

o Time-resolved micro-Raman spectroscopy

o Micro-FTIR spectroscopy

o Laser- induced fluorescence spectroscopy

o Quantitative scanning electron microscopy

o Image analysis

o Microstructure analysis

o In-situ crack propagation studies

o Small angle neutron scattering

o Small angle x-ray scattering

o Surface EXAFS

o Powder characterization

o Instrumental analysis

o Powder characterization

o Presintering studies

o Colloidal processing

o Analytical SEM of ceramics and particulates

o Powder test sample preparation

o Powder characterization

o High temperature ceramic synthesis

o Chemical instrumental analysis

o Separation of complex organic mixtures

o Characterization of lubricants and lubricant

products

o Trace organic compound identification

o Ceramic powders from organometallic precursors

o Ceramic powders from solution precipitation

reactions

o Processing-microstructure -property relationships

o Forming, compaction and sintering

o Processing of high Tc ceramic superconductors

o Processing of structural ceramics

61
Wang, Pu Sen

Mechanical Properties

Blackburn, Douglas H.

Chuang, Tze-jer

Coyle, Thomas W.

Cranmer, David C.

Hockey, Bernard J.

Horn, Roger G.

Kauffman, Dale A.

Krause, Ralph F. Jr.

Lawn, Brian R.

Ostartag, Claudia P.

o Solid state NMR

o Nuclear magnetic imaging of materials

o Surface characterization by x-ray photoelectron

and Auger spectroscopy

o Glass properties

o Melting of glasses

o Ceramics

o Diffusional crack growth

o Finite element analysis

o Creep theory

o Processing/microstructure/fracture relations

o Toughening mechanisms in ceramics

o Processing and properties of ceramic composites

o Stress induced transformations

o Ceramics and glasses

o Ceramic matrix composites

o Viscosity

o Ceramics

o Scanning and transmission electron microscopy

o Interfaces

o Microstructure

o Surface forces

o Tribology

o Colloidal science

o Glass melting?

o Fracture mechanics of ceramics

o Creep and creep rupture behavior

o Hot pressing and composite fabrication

o Vaporization Equilibria

o Microstructure/strength relations

o Fracture mechanics

o Contact phenomena

o Surface forces in fracture

o Influence of heterogeneities on sintering

o Processing and sintering of reinforced ceramics

o Processing & reinforcing ceramic superconductors

o Grain alignment of high Tc ceramic

superconductors

62
Roberts, D. Ellis o Mechanical Properties

Schantz, Kevin

Smith, Douglas

Wiederhorn, Sheldon M.

Tribology

Duvall, William W.

Hegemann, Bruce E.

Ives, Lewis K.

Jahanmir, Said

Ku, Chia-Soon

Munro, Ronald G.

Pei, Patrick

Perez, Joseph M.

Peterson, Marshall B.

o Fracture

o Surface forces

o Ceramics

o Fracture

o Reliability

o Creep rupture

o Wear test analysis

o Time-resolved micro-Raman spectroscopy

o Micro-FTIR spectroscopy

o Laser- induced fluorescence spectroscopy

o Wear of materials

o Transmission electron microscopy

o Mechanical properties

o Wear mechanisms

o Boundary lubrication

o Mechanical behavior of materials

o Lubrication of ceramics

o Lubricant oxidation, thermal stability and

volatility

o Lubricant degradation mechanisms

o Theory and modeling

o Molecular dynamics of phase stability

o Temperature modeling of ceramic pairs

o Characterization of lubricants and

lubrication products

o Separation of complex organic mixtures

o Trace organic compound identification

o Additive chemistry and deposits

o Thermal and oxidation stability of fluids

o Fuels, lubricants and diesel engines

o Wear of materials

o Solid film lubricants

o Mechanical behavior

63
Ruff, Arthur W.

Strakna, Timothy J.

Whitenton, Eric P.

Electronic Materials

Balmer, Mari Lou

Blendell, John

Block, Stanley

Chiang, C. K.

Clevinger, Mary

Cook, Lawrence P.

Freiman, Stephen W.

Ondik, Helen M.

o Wear of materials

o Microstructure effects

o Mechanical behavior

o Wear test analysis

o Self lubricating components

o Electronics

o Computer science

o Surface measurement

o Mechanical Property Testing

o Fiber processing

o Ceramic processing and clean-room

processing

o Sintering and diffusion controlled

processes

o Processing high Tc ceramic

superconductors

o Activation chemical analysis

o Ceramic processing and high-pressure

sintering

o Pressure- induced transformation

toughening

o High-pressure physical properties &

structures

o High-pressure X-ray diffraction and

spectroscopy

o Electronic ceramics

o Superconductivity

o Phase Diagrams for Ceramists

o Computerized data

o Thermodynamics

o Electron microscopy

o Phase diagram evaluation

o Electronic ceramics

o Mechanical properties

o Composites

o Phase Diagrams for Ceramists

o Database Management Systems

64
Piermarini, Gasper

Rawn, Claudia

Raynes, Alan

Roth, Robert

Stearns, Laura C.

Vaudin, Mark

White, Grady S.

Wong-Ng, Winnie

Optical Materials

Farabaugh , Edward

Feldman, Alberto

Frederikse, Hans P. R

o Ceramic processing and high-pressure

sintering

o Pressure- induced transformation

toughening

o High-pressure physical properties &

structures

o High-pressure X-ray diffraction and

spectroscopy

o Phase Diagrams

o X-ray Diffraction

o Fracture

o Microstructure

o Crystal Chemistry

o Phase Diagrams

o Phase Equilibria

o Ceramic processing and sintering

o Electronic properties of ceramics

o Electron microscopy of ceramic

superconductors and of ceramic

ceramic and ceramic-metal composites

o Microscopy and diffraction studies of

interfaces

o Computer modelling of grain-boundary

phenomena

o Micros true tural properties of advanced

ceramics

o Ceramics and glass

o Nondestructive evaluation

o Subcritical crack growth

o X-ray analysis

o X-ray standards

o Thin film deposition and analysis

o X-ray diffraction analysis

o Scanning electron microscopy

o Surface analysis

o Diamond films

o Optical films

o Guided waves

o EXAFS

o Diamond films

o Thin film thermal wave analysis

65
Robins, Lawrence H. o Photoluminescence spectroscopy

o Cathodo luminescence spectroscopy

o Photoconductivity

o Diamond films

Synchrotron Radiation Analysis

Black, David R. o Inelastic x-ray scattering

o Energy dispersive diffraction

o Fluorescence and absorption

Burdette, Harold E. o X-ray optics engineering

o Crystal growth

o Instrumentation

Dobbyn, Ronald C. o X-ray imaging

o X-ray optics

o Microradiography

Kuriyama, Masao o Scattering physics

o Condensed matter physics

o Crystallography

Spal, Richard D. o X-ray optics

o X-ray image detectors

o Condensed matter physics

Steiner, Bruce W. o X-ray diffraction imaging

o Optoelectronic materials

o Crystal growth

66
GUEST SCIENTISTS AND GRADUATE STUDENTS

Baker, Theresa L. Ohio St. University

Balasubramanian , Raghuraman Mr. Clarkson University

Barta , J . , Dr

.

ISCAR Ceramics, Inc.

Bennison, S. J., Dr. Lehigh University

Brandon, D. , Dr. Technion, Israel

Carroll, D. F. , Dr. Pennsylvania State University

Cho , Seong-Jai Korea Standards Research Institute

Deckman, Douglas E. Pennsylvania State University

Deshmukh, U., Dr. Drexel University

Dong, Jie-Yi E. China University

Dong, Xiaoyan University of Tsinghua

Duvall, William W. University of Maryland

Finkelstein, Y. Rafael Lab., Israel

Gartstein, Efim Dr. Georgia Institute of Technology

Gates, Richard S. Pennsylvania State University

Gerhardt, R. A. Rutgers University

Inglehart, L. , Dr. Johns Hopkins University

Kruger, Jerome Johns Hopkins University

Laor, Uri Dr. Nuclear Research Center, Israel

Lathabai , S . , Dr

.

Lehigh University

Lee, Soo W. University of Illinois

Lim, Dae-Soon University of Illinois

Liu , D

.

University of Delaware

Liu, W. Tsinghua, U., PRC

Miller , P . J . , Mr

.

Naval Surface Warfare Center

Mizuhara, Kazuyuki Ministry of Inti. Trade, Japan

67
Moudgil, Brij University of Florida, Gainsville

Nakamura, T. Meiji University, Japan

Palamides, T. Drexel University

Ritter, Andrew, Dr. Martin Marietta

Stewart, J. Dr. University of Maryland

Strakna, Timothy J. University of Maryland

Tanaka, D. K. Johns Hopkins University

Vandiver, P. B., Dr. Smithsonian Labs

Wan, K-T. Lehigh University

Wang , Yusha University of Tsinghua

Whitler, John D. University of Maryland

Wilson, Annie, M. , Ms. Oberlin University

Yellets, Jeffrey P. Pennsylvania State University

Ying, Tsi-Ning University of Tsinghua

Ying, X. T. , Mr. Fudan University

Zhang, Y. University of Maryland

Zhang, Z. Johns Hopkins University

Zheng, Pei-Yi Research Institute of Petroleum

Processing, Beijing, PR

68
OUTPUTS AND INTERACTIONS
*
SELECTED TECHNICAL PUBLICATIONS

Powder Synthesis and Characterization

Faltynek, R. A. Lanthanide Coordination Chemistry: Spectroscopic

Properties. Submitted to J. Coord. Chem.

Long, G. G.; Fischer, D. A.; Kruger, J.; Black, D. R. ; Tanaka, D. K. and

Danko, G. A. Surface -EXAFS Experiments at Atmospheric Pressure by Means of

a Photocathode Proportional Counter with Monolayer Sensitivity. Physical

Review B. Accepted for publication.

Long, G. G. and Kruger, J. "Surface X-ray Absorption Spectroscopy, EXAFS

and NEXAFS for the in-situ and ex-situ Study of Electrodes," Chapter in

Techniques for the Characterization of Electrodes and Electrochemical

Processes . In press.

Wallace, J. S.; Bender, B. A.; Lawrence, S. H. and Schrodt, D. J. Reaction

Sintering High-Density, Fine-Grained Ba2 YCu3 06 5+x Superconductors Using

Ba(0H) 2 -H2 0. Proc . of ACerS Symposium on Ceramic Superconductors, M. F.

Yan, ed. ; Ceram. Trans.; Am. Ceram. Soc., Westerville, Ohio; in press.

Wallace, J. S.; Ritter, J. J.; Fuller, E. R. Jr.; Bennett, L. H.; Schull,

R. D.; and Swartzendruber , L. J. Synthesis and Magnetic Properties of the

BiSrCaCu2 Ox 80 and 100K Superconductors. Phys . Rev. (rapid comm.), in

press

.

Mechanical Properties

Alpert, C. P.; Chan, H. M. ; Bennison, S. J. and Lawn, B. R. J. Am. Ceram.

Soc., 7_1 C-371 (1988) "Temperature Dependence of Hardness of Alumina-Based

Ceramics"

.

Chan, H. M. and Lawn, B. R. J. Am. Ceram. Soc., 71 . 97 (1988),

"Indentation Deformation and Fracture of Sapphire".

Chuang, T.-J. and Wiederhorn, S. M. J. Am. Ceram. Soc. 7JL» 595-601 (1988).

"Damage Enhanced Creep in a Siliconized Silicon Carbide: Mechanics of

Deformation"

.

Cranmer, D. C. A Perspective on Fiber Coating Technology. Ceramic Eng.

and Sci. Proc. 1988.

Horn, R. G.; Clarke, D. R. and Clarkson, M. T. J. Mater. Res. 3., 413-416

(1988) "Direct Measurement of Forces Between Smooth Sapphire Surfaces in

Aqueous Solutions".

Hubbard, C.R.; Dapkunas , S.J.; Munro , R.G.; Hsu, S.M. Advanced ceramics:

A critical assessment of database needs for the natural gas industry,

NBSIR 88-3706, National Bureau of Standards, May 1988.

69
Jakus, K. ; Ritter, J. E. ; Choi, S. R. ; Lardner, T. and Lawn B. R. J. NonCryst. Solids, 102 82 (1988) "Failure of Fused Silica Fibers With

Subthreshold Flaws".

Krause, R.F. Jr.; Fuller, E.R. Jr. and Rhodes, J.F. Fracture toughness

behavior of silicon-carbide-whisker/alumina composites of different

porosities. J. Am. Ceram. Soc . , in press.

Lawn, B. R. ; Roach, D. H. and Thomson, R. M. Mater. Sci., 22 4036 (1987).

"Thresholds and Reversibility in Brittle Cracks: An Atomistic Surface Force

Model".

Munro, R.G. and Hubbard, C.R. Computerized critical data for gas -fired

applications of advanced ceramic materials, CAM Newsletter, Pennsylvania

State University, 1988.

Roach, D. H.; Lathabai, S. and Lawn, B. R. J. Am. Ceram. Soc., 7_1 97

(1988). "Interfacial Layers in Brittle Cracks".

Wiederhorn, S. M. ; Chuang, T.-J.; Roberts, D. E. and Chuck, L. 71 . 602-

608 (1988) "Damage Enhanced Creep in a Siliconized Silicon Carbide:

Phenomenology"

.

Wiederhorn, S. M. ; Hockey, B. J. and Krause, R. F. , Jr. pp . 795-806 in

Ceramic Microstructures "86. Edited by J . A. Pask and A. G. Evans, Plenum

Publishing Corporation, 1988, "Influence of Microstructure on Creep

Rupture "

.

Wiederhorn, S. M. and Krause, R. F. , Jr. "The Effect of Slag Penetration

of the Performance of Magnesia Chrome Refractories in Slagging Gasifiers,"

and J. Sun, pp . 121-128 in Materials for Coal Gasification, W. T. Bakker,

S. Dapkunas , V. Hill, eds. ASM International, 1988.

Wiederhorn, S. M.; Krause, R. F. Jr. and Sun, Jing. Bull. Am Ceram. Soc.

67 . 1201-10 (1988), "Coal Slag Penetration in a Magnesium-Chromite

Refractory"

.

Tribology Group

Gates, R. S. and Hsu, S. M. "Tribochemical Mechanism of Alumina with

Water," Tribology Transactions, in press.

Hsu, S. M. ; Lim, D. S. and Munro, R. G. "Ceramic Wear Maps," Proceedings

of the Third International Symposium: Ceramic Materials 6c Components for

Engines, American Ceramic Society, November 27-30, 1988.

Ives, L. K. ; Peterson, M. B. and Whitenton, E. P. "Galling: Measurements

and Mechanisms , " Proceedings of ASM Conference on Engineered Materials for

Advanced Friction and Wear Applications," in press.

70
Jahanmir, S.; Deckman, D. E.; Ives, L. K. ; Feldman, A.; and Farabaugh, E.

"Tribological Characteristics of Synthesized Diamond Films on Silicon

Carbide," Wear, in press.

Jahanmir, S.; Ruff, A. W. and Hsu, S. M. "A Computerized Tribology

Information System," Proc . ASM Conference on Engineered Materials for

Advanced Friction and Wear Applications, Gaithersburg, MD, March 1988, in

press

.

Munro, R. G. Munro and Hsu, S. M. "Advanced Ceramics: A Critical

Assessment of Wear and Lubrication, NBSIR 88-3722, National Bureau of

S tandards , 1988.

Perez, J. M. ; Ku, C. S.; Pei, P. Pei; Hegemann, B. E. and Hsu, S. M.

"Characterization of Tricresyl Phosphate Lubricating Films by MicroFourier Transform Infrared spectroscopy," Tribology Transactions, in press

Ruff A. W. and Wang, Z. X. "Sliding Wear Studies of Nickel-Copper

Composition-Modulated Coatings on Steel," Wear, in press.

Electronic Materials

Blendell, J. E. Handwerker, C. A. Vaudin, M. D., and Fuller, E. R. Jr.,

Composition Control of the Microstructure of Ba2 YCu3 06 + x

. J. Crystal

Growth 89: 93-100; 1988.

Block, S., Piermarini, G. J., Munro, R. G., and Fuller, E. R. Jr.,

Isothermal Phase Behavior of Ag3 SbS 3 , ZnGeP2 , and ZnS . Physica A (special

honorary issue); in press.

Freiman, S. W. Brittle Fracture Behavior of Ceramics. Bull. Am. Ceram.

Soc. 67: 392; 1988.

Melmed, A. J.; Shull, R. D., Chiang, C. K.; Fowler, H. A. Possible

Evidence for Superconducting Layers in Single Crystal YBa2 Cu3 07

_ x by Field

Ion Microscopy. Science 239: 176; 1988.

Wallace, J. S., Ritter, J. J., Fuller, E. R. Jr., Bennett, L. H. Schull, R

D., Swartzendruber , L. J. Synthesis and Magnetic Properties of the

BiSrCaCu2 Ox 80 and 100K Superconductors. Phys . Rev. (rapid comm.), in

press

.

White, G. S.; Freiman, S. W. ; Fuller, E. R. , Jr.; Baker, T. L. Effects of

Crystal Bonding on Brittle Fracture. J. Mater. Res. 3: 491; 1988.

Cranmer, D. C. A Perspective on Fiber Coating Technology. Ceramic Eng.

and Sci. Proc. 1988

Wong-Ng, W. ; Roth, R. ; Davis, K. L. ; Beech, F. X-ray Study of the Ba0-Y2 03 CuOx System. Advances in X-ray Analysis. 1988

Wong-Ng, W. ; Cook, L. P.; Chiang, C. K. ; Swartzendruber, L. J.; Bennett,

L. H.; Blendell, J.; Minor, D. Structural Phase Transition Study of

Ba2 YCu3 07

_ x

. J. Mater. Res. 1988.

71
Optical Materials

Farabaugh, E. N. ; Feldman, A.; Robins, L. H. and Etz , E. S. Growth of

diamond films by hot filament chemical vapor deposition, Proceedings of the

SPIE, in press.

Feldman, A.; Farabaugh, E. N.; Sun, Y. N. and Etz, E. S. Diamond, A

Potentially New Optical Coating Material; Laser Induced Damage in Optical

Materials: 1987 . NBS Special Publication, in press.

Feldman, A. ; Sun, Y. N. and Farabaugh, E. N. Bonding structure of silicon

oxide films; J. Appl. Phys . 63, 2149 (1988).

Frederikse, H.; and Ying, X. T. Heat Conductivity of Oxide Coatings by

Photothermal Radiometry Between 293 K and 1173 K; in press.

Sun, Y. N.; Feldman, A. and Farabaugh, E. N. X-Ray photoelectron

spectroscopy of 0 Is and Si 2p lines in films of SiOx formed by e-beam

evaporation; Thin Solid Films 157, 351 (1988).

Synchrotron Radiation Analysis

Kuriyama, M. Synchrotron Diffraction Imaging for the Characterization of

Advanced Electronic and Optoelectronic Materials Proceedings of the

International Conference and Exhibition on Optoelectronics (OPT '88 Hyogo,

Japan) (submitted)

.

Kuriyama, M. ; Steiner, B.; Dobbyn, R. C.; Laor, U. Streaking Images that

Appear Only in the Plane of Diffraction in Undoped GaAs Single Crystals:

Diffraction Imaging (Topography) by Monochromatic Synchrotron Radiation J.

Physical Review B (accepted for publication)

.

Spal, R. A CAMAC Handler for RT-11 Nuclear Instruments and Methods in

Physical Research A270 (1988) 462-466 North-Holland , Amsterdam.

Steiner, B.; Kuriyama, M; Dobbyn, R. C.; Laor, U. Diffraction Imaging

(Topography) with Monochromatic Synchrotron Radiation Journal of Research,

NIST (to be published, Sept/Oct 1988).

Steiner, B. ; Kuriyama, Dobbyn, R. C.; Laor, U. ; Larson, D. ; Brown, M.

Structural Anomalies in Undoped Gallium AP.senide Indicated in High

Resolution Diffraction Imaging with Monochromatic Synchrotron Radiation

Journal of Applied Physics (accepted for publication)

.

72
SELECTED TECHNICAL/PROFESSIONAL COMMITTEE LEADERSHIP

American Ceramics Society

Glass Division

S. W. Freiman

Committee on Glass Standards Classification and

Nomenclature

M. J. Cellarosi, Chairman

Editorial Committee

S. M. Wiederhorn, Subchairman

Basic Science Division

Editorial Committee

B. R. Lawn, Chairman

Program Committee

E. R. Fuller, Jr., Chairman

Communication of the American Ceramic Society

E. R. Fuller, Jr., Contributing Editor

American National Standards Institute (ANSI)

Committee 43.1--Safety Standards for X-ray Diffraction and

Fluorescence Analysis Equipment

S. Block, Chairman

American Physical Society Editorial Board

Review of Scientific Instruments

P. K. Schenck

ASM International

Energy Division

S. J. Dapkunas , Vice Chairman

Journal of Engineering Materials

S. J. Dapkunas, Associate Editor

American Society for Testing and Materials

C14: Glass and Glass Product

M. J. Cellarosi, Chairman

C14.01: Nomenclature of Glass and Glass Products

M. J. Cellarosi, Chairman

D2 : Petroleum Products and Lubricants

D2.09G: Response of Base Oils to Oxidation Inhibitors

J. M. Perez, Chairman

C. S. Ku, Secretary

E29.01: Advanced Ceramics, Organizational Meeting

M. J. Cellarosi

E49.01.02 Computerization of Materials Property Data

C. R. Hubbard, Chairman

FI: Electronics

FI: 02: Lasers

A. Feldman, Subcommittee Editor

G2 : Erosion and Wear

G2.2.02: Solid Particle Erosion

73
A. W. Ruff, Task Group Leader

G2.4.04: Pin-on-Disk

A. W. Ruff, Chairman

American Society of Mechanical Engineers

Research Committee on Tribology

S. Jahanmir, Chairman

Tribology Textbook Editorial Committee

S. Jahanmir, Chairman

American Society for Testing and Materials

Wear of Materials Conference Steering Committee

A. W. Ruff

COMAT Subcommittee on Structural Ceramics

S. M. Hsu, Member

COMAT Subcommittee on Superconductivity

S . J . Dapkunas , Member

Department of Energy

ECUT - Tribology Program, Guidance and Evaluation Panel

S. Jahanmir, Member

Materials Review Board for Nuclear Waste

H. P. R. Frederiske, Member

Gordon Research Conference on Tribology

S. M. Hsu, Chairman

Implementation Task Force on the U.S. Japan Agreement on

Cooperation in Research and Development in Science & Technology

J. J. Ritter

International Commission for Optics

U. S. National Committee

B. Steiner, Chairman

International Energy Agency

Task II - International Standards

Assignment II-0-2 Powder Characterization Working Group

A. L. Dragoo, Chairman

Assignment II-0-3 Ceramic Characterization

E. R. Fuller, Jr., Member

International Union of Crystallography (IUCr)

Commission on Crystallographic Studies at Controlled

Pressures and Temperatures

G. J. Piermarini, Chairman

International Union of Pure and Applied Chemistry

Commission 1 1 - 3 : High Temperature and Solid State Chemistry

J. W. Hastie, U.S. A. Associate Member

NAS Assessment Committee on Ceramic Tribology

S. M. Hsu, Member

74
National Academy of Sciences/National Research Council

Solid State Sciences Panel

H. P. R. Frederiske, Member

National Materials Advisory Board, National Academy of Sciences

Committee on Ceramic Tribology

S. M. Hsu, Member

S. Jahanmir, Member

Committee on superhard Materials

A. Feldman, Member

National Synchrotron Light Source

General Users Oversight Committee

G. G. Long, Chairman

Proposal Study Panel

G. G. Long, Member

Oak Ridge National Laboratory

High Temperature Materials Laboratory Advisory Committee

S. M. Wiederhorn, Chairman

Society of Automotive Engineers

Task Group on Recommended Practices for the Measurement of Unregulated

Diesel Emissions

J. M. Perez, Chairman

Society of Professional Engineers

Mining Processing Division

Concentration Committee

S. G. Malghan, Vice Chairman

Mining and Metallurgical Processing Journal

Editorial Board

S. G. Malghan, Member

Society of Tribologists and Lubrication Engineers

Annual Meeting Program Committee

S. M. Hsu, Chairman

Board of Directors

S. M. Hsu, Director

Ceramics Activity

S. Jahanmir, Paper Solicitation Chairman

Tr ibomaterials Committee

S. Jahanmir, Chairman

Wear Technical Committee

S. Jahanmir, Paper Solicitation Chairman

Ceramics and Composite Committee

S. Jahanmir, Chairman

Superconductor Applications Association

E. R. Fuller, Jr., Member of Advisory Board

75
Versailles Project on Advanced Materials and Standards (VAMAS)

International Round-Robin in Ceramic Working Area

S. W. Freiman, Co-chairman

E. R. Fuller, Jr., Co-chairman

Subcommittee on Wear

S. Jahanmir, U. S. Representative

76
INDUSTRIAL AND ACADEMIC INTERACTIONS

The Ceramics Division actively participates with Industry, Academia and

other Government Laboratories in research programs of mutual interest. The

following examples are illustrations.

INDUSTRIAL

1. ISCAR Ceramics, Inc. (Dr. Joseph Barta)

A research associate from ISCAR Ceramics is working with Division

personnel on the processing (blending and hot pressing) of

silicon carbide whisker-reinforced alumina composites.

Processing conditions are correlated with both microstructural

and mechanical properties.

2. Norton Company (Dr. P. Tewari)

An FTIR study of aqueous slurries and surface treatments of S^N^ and

SiC is in progress.

3. Naval Research Laboratory (D. Schrodt, B. Bender)

The project is on the thermochemical treatment of polymer-derived SiC

fibers and the degradation mechanisms of these fibers during hightemperature heat treatments.

4. Oak Ridge National Laboratory (Dr. T. M. Besmann)

The project is on the microstructural and structural

characterization of ceramic matrix composites produced by

chemical vapor infiltration (CVI). Mechanical properties are

correlated with microstructure and processing.

5. 3M, Inc. (M. S. Leitheriser)

This is a collaborative project to examine the surface chemistry of

ceramic powders.

6. Advanced Composite Materials Corporation (Dr. James F. Rhodes)

The project is to characterize the microstructures of silicon

carbide whisker-reinforced alumina composites. Mechanical

properties (fracture toughness and creep behavior) are correlated

with microstructural properties and processing conditions.

77
7. E.I. DuPont De Nemours and Company (Drs. David Roach, P. Morris,

F. Tabbe , and R. French)

Research is being conducted for the DuPont Co. to evaluate the static

fatigue behavior of polycrystalline aluminum oxide fibers intended for

reinforcement of other ceramic materials. In this project, the

strength, toughness and resistance of these fibers to environmentally

induced fracture will be evaluated at room temperature. The NIST

clean room is being used in joint research projects addressing

production of barium titanate and sintering of ultra high purity

alumina

.

8. Southwest Research Institute (Dr. R. Page)

The project is to conduct SANS beam broadening experiments to follow

pore evolution during early and intermediate stages of alumina

sintering.

9. Boeing Company

An activity has begun with Boeing Company, Seattle, WA, to

examine the wear characteristics of SiC-coated carbon composites

at high temperatures. Specimens have been prepared, and have

been examined so far in the high temperature microindenter

system. A significant temperature dependence of microhardness

was found which should assist in interpreting the wear data to be

obtained

.

10. Gas Research Institute and Pennsylvania State University

(Dr. R. Tressler)

The Division is leading an effort with GRI and PSU to develop a materials property computerized database targeted for gas-fueled heat

exchangers and recouperators as well as conducting research addressing

the tribological properties of materials for gas-fired applications.

11. Cummins Engine Co. (Dr. D. Steuhower)

A simple bench test method to evaluate diesel engine oil

performance was developed in cooperation with Cummins Engine Co.

Validation of the method was performed using samples from Detroit

Diesel Allison Division, GMC and Caterpillar, Inc.

12. John Deere and Company (Dr. P. Swanson)

This program is concerned with investigating problems connected

with the measurement of galling damage and the development of

tests to evaluate alloys used in agricultural and industrial

equipment where severe wear is a serious problem.

78
13. Battelle Columbus Laboratories (Dr. W. Glaeser)

A joint activity is underway to prepare a wear atlas from

selected literature and research findings at Battelle Columbus

Laboratories and NIST. Battelle and NIST are evaluating 250

publications in wear and friction to select authoritative

findings that relate wear and friction with materials properties

and surface morphology. The findings will be published as an

atlas under a cooperative effort that also includes the West

German Bundesanstalt fur Mater ialprufung

.

14. VAMAS Standardization

An international round-robin to develop test procedures for

determining the stress corrosion susceptibility of advanced ceramic

materials are conducted. Approximately 20 laboratories in 6 countries

are participating in the interlaboratory testing program. A second

cooperative program is underway to evalute the tribology of structural

ceramics

.

15. Max Planck Institute, Stuttgart, Federal Republic of Germany

Collaborative research with the processing group of Max Planck

Institute on the clean-room processing of advanced ceramic

material is in progress. The influence of clean-room processing

on chemical and phase composition of ceramic superconductors in

the barium-yttrium-copper-oxide system and in similar systems

with lanthanide (rare earth) substitutions for yttrium has been

examined

.

16. AT&T Bell Labs (Dr. P. Gallagher)

This is a joint research on the phase relations in

superconducting ceramics.

17. Electric Power Research Institute (Mr. W. Bakker)

EPRI is funding a program in the Electronic Materials Group to

develop more economical superconducting ceramics for conductor

applications

.

18. Applied Physics Laboratory (Dr. Moorjani)

This is to study the laser-ablated thin films of both the BiSrCaCuO

and BiPbSrCaCuO high Tc superconductor systems. Initial results

indicate an improvement in superconductivity in the thin films when

compared to this property in the target from which they are derived.

79
19. AVX Corporation (Dr. Bharet Rawal)

The joint effort is to understand the mechanical properties of

multilayer ceramic capacitors. AVX is preparing specimens of

differing composition and properties. These are subsequently tested

at NIST.

20. W. R. Grace (Dr. L. Dolhert)

This research addresses sintering properties of barium-yttriumcopper-oxide superconductor materials which have been prepared by

chemical routes and milled to different size fractions.

21. Applied Physics Laboratory (Dr. K. Moorjani)

This is an investigation of the processing conditions and

superconducting properties of Bi-Sr-Ca-Cu-0 materials. Emphasis has

been on fabricating thin films using a laser ablation technique and

measuring the properties of the resulting films.

22. Raytheon Corporation

A joint activity has been initiated to examine the toughness of

CVD and HIPed zinc sulfide materials by a microindentation

technique

.

23. Clarkson University

This is a consortia program to study electrooptic material crystal

growth

.

24. Accumetrix Corporation (Dr. D. Greenspan)

This is a program to study the thermal and adhesive properties of

plasma sprayed ceramic films. The films are prepared at

Accumetrix and their properties were measured at NIST by means of

photothermal radiometrv.

25. Naval Surface Weapons Center (Dr. P. Miller)

This research characterizes the influence of pressure on the

decomposition kinetics of energetic materials by a combination of

FTIR and x-ray diffraction techniques.

UNIVERSITIES

1. University of Minnesota (Dr. D. Pui)

This is a collaborative project on the aerodynamic sizing of fine

ceramic powders and on computer fitting of standard particle size

distribution functions to particle size distribution data.

80
2. Florida State University (Dr. B. Moudgil)

This is a project on SANS characterization of the structure of

agglomerates in dense slurries.

3. Rutgers University (Dr. R. Gerhardt)

This is a collaboration on the characterization by SANS of microporous

silica as a function of thermal processing.

4. Lehigh University (Prof. M. Harmer)

Joint research on the effect of microstructure on the fracture

resistance of ceramic materials. The materials under study will be

manufactured at Lehigh University and will be characterized and tested

at the National Institute of Standards and Technology.

5. University of Michigan (Dr. T. Y. Tien)

This is joint research on the creep and creep rupture behavior of

SiAiON composites at high temperature. These materials were

manufactured at the University of Michigan and characterized both

microstructurally and mechanically at NIST.

6. Drexel University (Dr. M. Koczak)

This is a joint program with Dr. M. J. Koczak of Drexel University on

the fracture behavior of ceramic matrix composites.

7. Northwestern University (Prof. H. Cheng)

Joint research involves lubrication modeling. The research focuses on

the microelastohydrodynamic theories under wearing conditions. This

is the first attempt at combining surface chemistry with surface

mechanics to create a predictive wear model.

9.

University of Illinois (Dr. S. W. Lee)

The project centers on an investigation of the fundamental mechanisms

of friction, wear, and surface damage in tribological applications of

advanced ceramics.

10. University of Maryland (Profs. J. Dally, and J. Stewart)

Two projects are underway; one a joint research project on wear models

of ceramics; and, the other on the determination of residual stresses

in ceramics by x-ray techniques.

11. University of Pennsylvania (Prof. P. Davies)

This is a collaborative project on the properties and structure of

microwave dielectrics and high Tc superconductors.

81

STANDARD REFERENCE MATERIALS

The Division provided science, industries, and government a central source

of well-characterized materials certified for chemical composition of

physical or chemical properties. These materials are issued with a

certificate and are used to calibrate instruments, to evaluate analytical

methods, or to produce scientific data which can be referred to a common

base

.

SRM

DESCRIPTION NUMBER

Alumina Elasticity 718

Alumina Glass Anneal Point 714

Alumina Glass Anneal Point 715

Alumina Melting Point 742

Aluminum Magnetic Susceptibility 763-1

Aluminum Magnetic Susceptibility 763-2

Aluminum Magnetic Susceptibility 763-3

Barium Glass Anneal Point 713

Borosilicate Glass Composition 93(A)

Borosilicate Glass Thermal Expansion 731L1

Borosilicate Glass Thermal Expansion 731L2

Borosilicate Glass Thermal Expansion 731L3

Cadmium Vapor Pressure 746

Chlorine in Base Oil 1818

Container Glass Composition 621

Container Glass Leaching 622

Container Glass Leaching 623

Copper Thermal Expansion 736L1

Fused Silica Thermal Expansion 739L1

Fused Silica Thermal Expansion 739L2

Fused Silica Thermal Expansion 739L3

Glass Analytical Standard 1835

Glass Dielectric Constant 774

Glass Electrical Resist 624

Glass Fluorescence Source 477

Glass Liquidus Temperature 773

Glass Refractive Index 1820

Glass Sand (High Iron) 81A

Glass Sand (Low Iron) 165A

Glass Stress Optical Coefficient 708

Glass Stress Optical Coefficient 709

Glass Viscosity Standard Renewal 717

Gold Vapor Pressure 745

High Boron Glass Viscosity 717

Intensity XRD Set 674

Lead Barium Glass Composition 89

Lead Glass Anneal Point 712

Lead Glass Viscosity 711

Line Profile 660

83
Liquids Refractive Index 1823

Low Boron Glass Composition 92

Lube Oil Oxidation Test Kit 1817

Lube Oxidation Catalysts 8500

Lubricant Oxidation Research Test Kit 8500a

MNF2 Magnetic Susceptibility 766-1

Mica X-Ray Diffraction 675

Neutral Glass Anneal Point 716

Nickel Magnetic Susceptibility 772

Opal Glass Composition 91

Palladium Magnetic Susceptibility 765-1

Palladium Magnetic Susceptibility 765-2

Palladium Magnetic Susceptibility 765-3

Platinum Magnetic Susceptibility 764-1

Platinum Magnetic Susceptibility 764-2

Platinum Magnetic Susceptibility 764-3

Refractive Index Glass 1822

Respirable Cristobalite 1879

Respirable Quartz 1878

Ruby EPR Absorption 2601

Sapphire Thermal Expansion 732

Silicon X-Ray Diffraction 640(b)

Silver Vapor Pressure 748

Soda Lime Flat Glass Composition S620

Soda Lime Float Composition 1830

Soda Lime Glass Viscosity 710

Soda Lime Sheet Composition 1831

Sulfur in Base Oil 1819

Toluene 5 ML 211C

Tungsten Thermal Expansion 737

84
APPENDIX

U.S.

DEPARTMENT

OF

COMMERCE

National

Institute

of

Standards

and

Technology

Institute

for

Materials

Science

and

Engineering

L.

H.

Schwartz,

Director

H.

L.

Rook,

Deputy

Director

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FOAM NBS-1 14A (REV .11-84)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NISTIR 88-3840

2. Performing Organ. Report No. 3. Publication Date

February 1988

4. TITLE AND SUBTITLE

Ceramics Division - Technical Activities 1988

5. AUTHOR(S)

S. M. Hsu

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instruction s)

NATIONAL BUREAU OF STANDARDS

U.S. DEPARTMENT OF COMMERCE

GAITHERSBURG, MD 20899

7. Contract/Grant No.

8 . Type of Report & Period Covered

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City . Stole, ZIP)

NIST - Ceramics Division 420

Building 223, Room A257

Gaithersburg, MD 20899

10. supplementary notes

I

! Document describes a computer program; SF-185, FlPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here)

Current programs of the Ceramics Division are reviewed.

12. KEY WORDS (Six to twelve entries; alphabet! cal order; capitalize only proper names; and separate key words by semicolons)

Advanced Ceramics; Data Bases; Electronic Ceramics; Mechanical Properties;

Optical Materials; Powder Processing/Characterization; Tribology; Superconductors;

Synchrotron Radiation

13. AVAILABILITY

£X] Unlimited

|

; For Official Distribution. Do Not Release to NTIS _ Order From Superintendent of Documents, U.S. Government Printing Office, Washington, DC

20402.

Order From National Technical Information Service (NTIS), Springfield, VA 22161

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