Research in the department is broadly based, following the traditional disciplines of mechanical engineering and industrial engineering on the one hand and exploring emerging areas on the other. These research directions reflect the interests and creativity of the faculty and students. Education of new generations of researchers is integral to the department's research mission.
While the generation of new knowledge remains central, the application of new knowledge and technology transfer are also driving factors in the department's research commitments. The faculty is deeply concerned with meeting the needs of the state of Illinois and the nation.
The department is committed to expanding its cooperative research with state and federal government agencies and, especially, its outreach to industry. Several departmental industry-driven initiatives focus on research and technology transfer: the Manufacturing Research Center; the Institute for Competitive Manufacturing; the Machine Tool Agile Manufacturing Research Institute; and two National Science Foundation industry/university cooperative centers, the Air Conditioning and Refrigeration Center and the Center for Machine-Tool Systems Research.
The department is strongly committed to cross-disciplinary research and works closely with other departments across the College of Engineering. The Beckman Institute for Advanced Science and Technology, the National Center for Supercomputing Applications, the Materials Research Laboratory, and other campus resources add strength and diversity to the department's research.
Much of the department's research involves investigation of the production, conversion, utilization, and conservation of energy along with environmental impact; the problems of creating safer, more efficient, and more cost-effective raw materials, products, and services; and the dynamics of man-machine systems. Area of focus are described on the following pages.
We are attempting to generate microstructures for an artificial bone
from composite particles produced by a method developed in our
laboratory (hydroxyapatite-polypeptide composites). An important
consideration is the surgical delivery of this material as a
deformable mass which hardens within minutes and then integrates with
natural bone by partial biodegradation. We have recently demonstrated
that microstructures partly sintered under high pressure can harden
significantly after exposure to laser beams in the visible range. The
molecular mechanism is thought to involve the simultaneous
polymerization and ionic gelation of two oppositely charged
macromolecules.
Macro-defect-free (MDF) cement pastes are being studied with the
following objectives: (1) optimizing processing parameters, (2)
improving resistance to moisture, and (3) developing alternative
cement-polymer composites. Flexural strengths up to 300 MPa are
achieved in the dry state, with a 0-20% decrease in strength occurring
after immersion in water.
This research focuses on understanding the role of polyelectrolytes
(commonly referred to as superplasticizers) on the rheological
behavior and dispersion of cement-based dispersions. Model cement
powders, beta- and gamma-C2S, have been synthesized for this study.
The influence of several acrylate-based polyelectrolytes, obtained
commercially, with varying molecular weight, branch lengths, and
ionizable side groups have been studied. Experimental observations
will be compared to their theoretically predicted stabilization
behavior to elucidate the mechanisms by which stability is imparted by
this important new class of superplasticizers.
This project investigates the development of new materials we have
termed "organoceramics," which are based on the concept of
inorganic crystal growth in the presence of polymers and/or monomers.
The products of interest are inorganic-organic intercalated structures
in which polymers and/or monomers may participate in setting
reactions. We have been able to synthesize a number of organocalcium
aluminate structures containing poly(alcohols) and cationic
polyelectrolytes. Interestingly, we find that the intercalated
polymers can modulate the crystal structure, crystal habit, and
chemical composition of these cementitious materials.
Studies of the electric-field dependence of the shape of cement-based
materials are being made using interferometric and strain-gauge
techniques. These investigations have already revealed the presence of
large unexpected electrically induced strains. Studies as a function
of composition, pore parameters, water content, and ion content are
being systematically performed. It is hoped that these investigations
will reveal for the first time the nature of the complex nonlinear
electrical, electromechanical, and mechanical properties of cement
materials.
Structural studies of the calcium silicate hydrate gel phase of
ordinary portland cement are being performed by transmission electron
microscopy, high-resolution transmission electron microscopy, and
micromechanical methods. These investigations have already revealed
the presence of a mesostructure in calcium silicate hydrate gels for
the first time. The nature of this mesostructure is currently being
studied as a function of composition, heat treatment, and moisture
history. It is hoped that these investigations might lead to a more
comprehensive understanding of the complex structure property
relationships in cement-based materials.
Strong, dense materials are formed by casting mixtures of calcium
silicate (portland) cement and silica fume at very low water contents.
The chemistry of the cementitious reactions and development of
microstructure are being studied using small-angle x-ray scattering,
trimethylsilylation, and thermal analysis. Improvements in processing
and particle packing are also under investigation.
The interactions between superplasticizing admixtures with portland
cement are being studied. Zeta potential measurements will be combined
with rheological behavior to determine the mechanism of dispersion.
Low-porosity concretes are being evaluated for use as overlays on
existing airport pavements. These materials use high additions of
silica fume and superplasticizers to provide dense concretes of low
permeability, good bonding characteristics, and improved wear
resistance. However, cracking caused by thermal and drying shrinkage
is a concern. This project examines experimentally the properties of
these concretes and models their cracking tendencies. Development of
bond with the existing pavement will also be considered.
Deterioration of repair mortars underneath fiberglass exterior wraps
has been observed in some bridge columns. The cause of this
deterioration is under investigation.
Wasteforms based on a magnesium potassium phosphate binder are being
characterized using x-ray diffraction, mercury intrusion porosimetry,
scanning electron microscopy, and thermal analysis. Model wastes are
Class F and Class C fly ashes and a surrogate waste representing
plutonium-processing wastes at Rocky Flats. The presence of the wastes
influences the physical characteristics of the binding phase, which is
MgKPO4·6H2O.
The first part of the program involves the synthesis of ceramic
precursors via a chemical synthesis route. The precursors will be
characterized using standard procedures such as IR- and NMR-
spectroscopy, phase (XRD), and thermal analysis (DTA/TGA). Solutions
of the precursors will then be spray deposited onto fibers, single and
woven sheet, through a technique called charged liquid beam cluster
deposition to form a coating layer. Adhesion of the ceramic coating
layer onto fibers and the homogeneity of its distribution will be
studied primarily through SEM. Determination of the optimum coating
thickness for useful transformation-weakening applications leading to
fiber/matrix debonding will follow.
This project involves understanding the effect of corrosion scales on
water quality. The cast iron and steel pipes from the Northern
Illinois Water Corporation as well as pipes from on-campus locations
have been assembled into a Pilot Corrosion Tester system. Corrosion
scale analysis is performed using SEM, EDAX, and the x-ray diffraction
techniques. Both surface and cross-sectional analyses are done on the
scales which are first dried and then removed from the pipe surface.
The quantitative and qualitative elemental and the phase composition
information obtained is then interfaced with the results from the iron
uptake studies carried out at the pilot testing experiment in an
effort to understand the underlying mechanisms.
Novel glassy materials are needed for photonics applications. Glass
formation has conveniently been attributed to a kinetic arrest in
structural relaxation, before crystallization can occur. There is,
however, increasing evidence for irreversible transitions in the
molecular configurations to take place. The decisive processes which
need to be understood occur on the time scale of nanoseconds, whether
the origin of glass formation is purely kinetic or involves structural
phase transitions. This time regime has so far been little
investigated. We use Brillouin light scattering to observe structural
dynamics in supercooled liquids. This allows us to determine directly
the coefficients of momentum transport on the molecular scale, as well
as to monitor the structural assembly upon cooling.
Kinetics and mechanisms of fluid-assisted cracking are examined in
Si3N4 and Al2O3 ceramics to elucidate the synergistic effect of stress
and surface chemistry on microfracture. Three different techniques are
being used to measure this effect: the repeated indentation technique,
which follows the development of indentation cracks leading to surface
microfracture, small crack experiments where the growth of penny-
shaped surface cracks is monitored, and fracture mechanics technique
with through-thickness cracks. Possible influences of fluid viscosity,
temperature, grain size, grain boundary phase, and loading rate on
cracking kinetics are investigated.
C in a tube furnace under Ar atmosphere, a pure powder is obtained.
Crystallinity is examined by XRD analysis and the decomposition
behavior of the powder precursor is investigated by thermogravimetric
(TGA) and differential thermal analysis (DTA). For characterization of
powder synthesized, Fourier transform infrared spectroscopy (FTIR),
Auger electron spectroscopy (AES), particle size distribution,
specific surface area, chemical analysis, and density measurement are
carried out.
C for times of 72 h. A volume contraction of 5.6% is accompanied
by the reconstructive transformation.
Fine, pure, high specific area surface powders of dicalcium and
tricalcium silicates will be chemically synthesized using an organic-
inorganic precursor route. Polyvinyl alcohol is used to chemically
bind and sterically entrap component cations in aqueous solution to
produce highly reactive submicron powders. They will be characterized
in terms of crystallinity, specific surface area, particle size and
size distribution, as well as minimum calcination temperature.
Composites will be made using aqueous chemical bonding products at low
temperatures to incorporate alumina platelets and other filler phases.
The relevant mechanical or electrical properties will be measured.
Boron carbide-titanium diboride composites are fabricated by
reactively sintering boron carbide with titanium in the hot-press.
Sintering behavior and microstructural development of the composites
are being studied by analytical and high-resolution transmission
electron microscopy. Kinetics of the phase formation is being
investigated by interrupted growth studies at a wide temperature
range. Fracture toughness data are correlated with microstructure and
phase composition.
Our objective in this project is to identify oxidation modes of
nonoxide particles or fibers that are embedded in a ceramic matrix and
determine the dependence of such modes on the composition and
microstructure of the matrix. A model is being developed, based on
oxygen diffusion rates in matrix and in oxidation products.
Experimental measurements (by TEM) of oxide thickness around particle
vs. depth of particle below composite surface can be predicted by the
model. The matrix can be modified to control oxidation behavior of the
embedded reinforcements.
Ceramic matrix composites based on several different oxide matrix
materials and reinforced with silicon carbide platelets are prepared
by sintering and hot-pressing techniques in an effort to obtain
strong, tough, and dense materials. Densification behavior of mullite,
alumina, and other matrices is examined. Fracture toughness and
strength are measured and related to the microstructure, particularly
the interface characteristics.
C. The effect of BN crystallinity on the possible formation of
compounds and graphitic solid solutions is investigated by high-
resolution transmission electron microscopy.
This research focuses on applying high-performance computing to
simulate the dynamics of interface motion in complex microstructures
and thin-film systems. The approach is based on both sharp interface
and diffuse interface theories, and allows one to track interface
motion readily. A number of thermodynamic driving forces for energy
dissipation, as well as several kinetic mechanisms by which
dissipation occurs, have been included. A diverse set of phenomena can
be studied with this model, and it is currently being used to examine
the growth and coalescence of thin-film islands, Ostwald ripening of
precipitates, and the distribution of absorbed liquid in porous
networks.
Computer simulations of time-dependent processes can be written using
discrete systems of lattice sites whose values are synchronously
updated in discrete time steps as a result of local interactions with
other sites. We are developing cellular automata programs of a wide
variety of physical, chemical, biological, and social phenomena.
Within a Green's function formalism, electronic density-functional
theory (DFT) techniques are used to investigate disordered, partially
ordered, and fully ordered phases of multicomponent alloy systems. The
underlying electronic origin of various materials properties
(electronic, magnetic, thermodynamic, elastic) are then determined.
Additional schemes are being developed to investigate larger-scale
phenomena, such as microstructure and kinetics, which are ultimately
based on such DFT results, thus allowing a connection of length
scales: micro- to macroscale.
We developed algorithms for large-scale molecular dynamic simulations
using massively parallel computing environments, allowing us to study
ensembles up to millions of atoms. This gives us the opportunity to
tackle the long-standing questions of structural characterization
beyond nearest neighbors in amorphous materials. New analytical
concepts are being developed allowing one to analyze large molecular
configurations for topological patterns as well as structural and
chemical heterogeneities.
By using concepts from chaos theory, such as Lyapunov exponents and
Kolmogorov-Sinai entropies, we characterize the dynamic behavior of
large molecular configurations generated by molecular dynamic
simulations. From these measures one can derive conclusions about the
thermodynamic stability of a structure, as well as estimate the
magnitudes of atomic transport coefficients. The goal of this project
is to develop formalisms that allow one to relate the topology of a
structure to the inherent mobility of its constituents, and with this
knowledge improve the design of electrolytes used in batteries, fuel
cells, and sensors.
This research focuses on modeling the removal of volatile species from
particulate ceramic films during drying. Specifically, 2-D and 3-D
cellular automata models have been developed that contain both random
walk and invasion percolation algorithms. These models are being used
to determine the removal kinetics, effective diffusivities, and
geometry of the developing pore front as a function of relative
volatility and composition of the multicomponent fluid, volatile to
particle size ratio, and particle size distribution and loading.
This work encompasses the fabrication and characterization of
ferroelectric Pb(Sc0.5Ta0.5)O3(PST) thin films by metal-organic
chemical vapor deposition (MOCVD) techniques. For infrared detector
applications, we perform noise, blackbody responsivity, and spectral
response and frequency response measurements. The PST detectors'
performance will be compared with commercial state-of-the-art
pyroelectric detectors. The ultimate goal of this work is to develop a
room-temperature infrared radiation detector. We base our work on the
ferroelectric PST system and a novel detection approach which utilizes
both the ferroelectric and the pyroelectric properties of PST. We also
fabricate other perovskite thin films such as PT, PZT, and BST on
various types of substrates and investigate the structure-property-
processing relationships.
The primary objective of this research is to produce oxide thin films
for sensor applications. One is a flammable gas sensor using SnO2 and
the other is a heavy-metal detection sensor in drinking water using
Pb-Ag oxide. These oxide thin films are grown by the MOCVD technique.
Microstructural analysis is also carried out on the grown films using
XRD, SEM, TEM, AES, and XPS. Sensing tests are done for SnO2 using
resistivity measurements with reducing gases such as H2, alcohol, etc.
Whereas for heavy-metal sensors, tests are done using electrolyte
methods in collaboration with Motorola. Models are suggested to
explain the measured sensing properties.
Composites consisting of organic polymers and inorganic glassy phases
are developed for use as electrolyte materials. The organic polymer
contains the charge-carrying species and acts as the conducting phase,
whereas the inorganic glass provides mechanical stability. High ionic
conductivities can be achieved with this constellation because the
conducting phase can be maintained above the glass transition
temperature. The electrolytes are synthesized via a sol-gel process.
This project is concerned with controlling the structure at the
nanoscale to optimize component performance. The electrolytes
synthesized in the laboratory are characterized using impedance
spectroscopy, small-angle x-ray scattering, and thermal analysis.
Solid-state nonlinear optic and electrooptic devices offer many
advantages, including speed, compactness, simplicity, and reliability.
Ferroelectric crystals show the strongest nonlinear properties and
have high optical damage thresholds. The research is directed at the
growth of high-quality single crystals of SrxBa1-xNb2O6 and BaTiO3.
Mechanisms of crystal growth are determined. Methods to control the
ferroelectric domains are developed. Electrical and optical properties
are investigated using structure-property and processing-property
relationships for nonlinear optical and electrooptic ceramics.
Understanding of the role of dopants is pursued with regard to
holographic storage, laser host, and ferroelectric switching
applications.
Lead zirconate titanate (PZT) perovskite materials are of considerable
technological importance, particularly with regard to physical
properties such as pyro- and piezoelectricity and electric field-
induced antiferroelectric-to-ferroelectric phase switching. A
systematic study of the effects of temperature, Sn- and La-
substituents, and Zr/Ti ratio on the evolution of incommensurate
phases in high Zr-content PZT is carried out by hot- and cold-stage
TEM. Particular attention is paid to the possible development of
1/x[110] incommensurate modulations and to the resul-tant influence on
the macroscopic properties. The pur-pose of this investigation is to
obtain a fundamental understanding of microstructure-property
relationships for electroceramics.
Rare earth manganese perovskites doped with divalent cations, such as
Ca, Sr, Ba, and Pb, have been shown to exhibit greatly enhanced
magnetoresistive properties when compared with metallic heterolayers.
Improved magnetoresistive behavior is greatly desired for sensor
applications, such as magnetic read heads, or advanced computer
memories, such as MRAM cells. Current research is concerned with the
electronic behavior and morphological characterization of doped rare
earth manganese perovskite single crystals. Resulting candidate
materials were deposited by low-temperature solution processing and
self-assembled patterning to form integtated structures for devices.
Sol-gel-derived PZT thin layers deposited on silicon were examined for
their shrinkage behavior using in situ ellipsometry. Correlating
densification data with thermal analysis (DTA, TGA), the effect of
pyrolysis and crystallization on layer shrinkage is observed as
experimental parameters such as water of hydrolysis, heating rate, and
layer thickness are systematically varied. The resulting stresses in
the coating are measured as a function of heat treatment by a laser
reflectance technique and related to associated densification
phenomena and substrate/layer thermal expansion mismatch.
Thin-layer ceramics have diverse applications as integrated
capacitors, sensors, display components, and other devices. Solution
processing allows deposition of such layers at greatly reduced
temperatures on metal, oxide, and semiconducting substrates with
control of stoichiometry, doping level, and crystalline order. Current
research is directed at a new selective deposition technique made
possible by functionalization of substrates with self-assembled
layers. Derivitization of metal, oxide, and semiconductor substrates
with hydrophilic or hydrophobic assembled layers enables preferential
wetting of surfaces by solution or vapor deposition techniques.
Lithography-free selective deposition of ceramic thin layers has been
demonstrated.
Recently, bismuth-layered compounds, such as SrBi2Ta2O9 and
SrBi2Nb2O9, have been recognized as potential candidates for
nonvolatile ferroelectric memory applications. However, their basic
structures and intrinsic properties are not well understood. This
research is directed at the growth of sizable single crystrals of
SrBi2Ta2O9, SrBi2Nb2O9 materials. Several crystal growth techniques,
such as Czochralski, top-seeded solution growth, and hydrothermal, are
under investigation. Their structures and ferroelectric and optical
properties will be determined.
The complex piezoelectric properties of lead zirconate titanate based
ceramics are being studied. Investigations are being performed using a
modified Michelson-Morely interferometer, which can measure both the
real and phase components of the response as a function of temperature
and frequency. Investigations are being performed for various ac drive
amplitudes and dc bias levels. It is anticipated that these studies
will lead to a more comprehensive understanding of the fundamental
electromechanical coupling mechanism in ferroelectrics.
The microstructure property relationships in various ferroelectric and
piezoelectric ceramics are being studied by transmission electron
microscopy. Investigations of the phase transformational
characteristics are being performed in situ by hot- and cold-stage
methods. Corresponding bulk property investigations are also being
performed. Compositional systems currently being investigated include
lead zirconate titanate (PZT), La-modified PZT, lead magnesium
niobate, strontium barium niobate, and Sn-modified PZT. It is
anticipated that these studies may lead to a more comprehensive
understanding of the influence of impurities on ferroelectric and
antiferroelectric domain structures and phase transformational
characteristics.
The dielectric, piezoelectric, and electrically induced strain and
polarization characteristics of antiferroelectric Sn-modified lead
zirconate titanate ceramics are currently being investigated.
Corresponding transmission electron microscopy studies are also being
performed. These investigations are revealing the nature of the
complex structure property relationships in these materials for the
first time. An unusual incommensurately modulated polar structure has
been observed. Changes in the modulated structure are being correlated
with changes in the macroscopic response characteristics. Evidence is
indicating that the nonlinear response is controlled by the modulation
of the incommensurate structure by an applied electrical field.
The dependence of the dielectric response characteristics of
ferroelectric, soft ferroelectric, and relaxor ferroelectric materials
is being studied as a function of ac drive amplitude. Investigations
are being performed as a function of temperature, frequency, and
superimposed dc bias. These investigations have already revealed the
presence of strong nonlinearities in critical compositional regions.
The mechanisms underlying the anomalous nonlinearities are currently
being studied and related to microstructural changes by transmission
electron microscopy.
Studies of lead magnesium niobate lead titanate crystalline solutions
are being studied for the purpose of achieving enhanced electrically
induced strains and electromechanical coupling coefficients.
Compositional modifications are being investigated that lead to
improved performance coefficients with reduced hysteresis. Studies are
being performed by dielectric spectroscopy, piezoelectric
spectroscopy, and electrically induced strain and polarization
methods. It is hoped that the investigations will lead to the
development of the next generation of high-performance
transducer/projector materials for underwater acoustical imaging
applications in lateral waters.
Barium titanate is one of the most important ferroelectric materials.
The interrelationships between the structure and properties in this
material are being studied by changing the La and Sn contents. These
investigations are being performed by dielectric spectroscopy and
transmission electron microscopy, with particular attention being paid
to the influence of impurities on the phase transformational
characteristics and domain structure. The purpose of this study is to
develop new lead-free relaxor-like ferroelectric materials for
electrostrictive applications.
Minor amounts of CaO and SiO2 are being added to MnFe2O4 to study
their effects on the electrical transport properties of the ferrite.
The additives are concentrated in the grain boundaries, which is
believed to produce high-resistance grain boundaries, surrounding more
conductive grains, thus reducing eddy current losses at high
frequencies in the ferrite. It is also found that the concentration of
dopant in the grain boundary prevents decomposition of the ferrite in
oxidizing atmospheres, thus maintaining the stoichiometry of the high-
resistance ferrite. Impedance spectroscopy, thermogravimetry, and
electrochemical cell measurements are being used in the study.
The objective of this project is to use surface/interface sensitive x-
ray diffraction/scattering techniques, e.g., grazing incidence
diffraction/scattering/fluorescence, specular reflectivity, standing
and evanescent wave experiments, and truncation-rod experiments (all
of which require the use of the synchrotron radiation) to examine
various materials systems of scientific and technological importance.
Some specific areas of investigation are: studies of the reconstructed
structure, stress fields, relaxations, roughness, and phase
transitions of single-crystal surfaces and interfaces such as
Ag/Si(111), Ge/Si, C60/Si, Cu/Al2O3, SnO2/Al2O3, GaN/Al2O3; the
dynamical structural and compositional evolution associated with
melting, solidification, passivation, and corrosion.
The individual atomic events contributing to the growth of crystals
and films are being explored on the atomic level. Through the use of
the field ion microscope, single atoms are visualized, and processes
such as condensation, diffusion, nucleation, and incorporation into
the lattice are examined quantitatively to reveal how structure and
chemical composition affect growth processes.
The fatigue behavior of mullite fiber reinforced Al-Mg alloy matrix
composites is examined as a function of Mg concentration and fiber
volume fraction. The primary objective is to understand the role of
the interface in the fatigue crack initiation and growth processes.
Several reaction products are found at the fiber/matrix interface in
the as-received composite. Research is in progress to evaluate the
effect of the interfacial reaction on the fatigue properties of the
composite.
Experimental and theoretical studies are carried out to understand the
relationship between microstructure and mechanical properties of bi-
materials interfaces. We have developed new experimental techniques to
measure mechanical properties of interfaces and applied these
techniques to metal-ceramic, metal-polymer, glass-ceramic, and bi-
metals interfaces. We are developing model interfacial microstructures
at graphite-epoxy, alumina-aluminum, polyimide-copper, epoxy-metal,
and solder-copper interfaces by chemical, physical, electrochemical,
and metallurgical surface-modification techniques. We are modeling
several salient mechanisms of crack growth, such as crack sliding,
crack interlocking, and crack tip plasticity, along model interfaces.
The sol-gel processing route was used to synthesize thin layers of
various compositions in the Pb(ZrxTi1-x)O3 system. Low-temperature
crystallization behavior is believed to be influenced by local order
and the coordination of the species in the starting precursor
structure. The aim of this research was to understand how structure
evolves through drying, thermolysis, densification, and
crystallization. The observed transformation from molecular level
heterogeneity at lower temperatures to intermediate range order, and
eventually to the long-range ordered perovskite structure at higher
temperatures, was determined by EXAFS spectroscopy.
To minimize the size of electronic components, a great deal of
research has been carried out to develop new materials with higher
dielectric constants. In addition to the demand for smaller electronic
components, the need for Pb-free dielectric materials is also a major
concern. Because of its high electric-field strength and good
compatibility with microelectronic processing, Ta2O5 is widely used as
an alternative to SiO2 for dielectric layers in thin-film capacitors.
In addition, the dielectric constant can be increased by addition of
Ti and Zr.
This program is applying our knowledge of the mechanisms of hydrogen
embrittlement of metals to develop an understanding of the factors
which strengthen alloys against environmental attack. The systems
studied include high-strength aluminum alloys, beta titanium alloys,
and the high-alloy nickel-based alloys. The experimental techniques
used include mechanical property tests, electron microscopy, in situ
environmental cell TEM, secondary ion mass spectrometry, and Auger
spectroscopy. In most of the above alloys the studies include the
effects of solutes and hydrogen on grain boundary fracture.
The effects of hydrogen on the structure and properties of
intermetallics (nickel and iron aluminides) are being studied using
the environmental cell TEM and other analytical techniques. To
understand the role of the environment on the lack of ductility in
polycrystalline Ni3Al, the effect of boron on the distribution of
deuterium around grain boundaries is being mapped by using SIMS.
The interactions of gaseous hydrogen environments on the properties of
metal systems is being studied directly by using an environmental cell
TEM. Use of this microscope permits gas-solid interactions to be
studied in real time and at high spatial resolution. The focus of the
program is primarily on the effects of aggressive environments on the
mechanical behavior. Specifically, we are investigating the effect of
hydrogen on the stress field of dislocations and on the stacking-fault
energy by monitoring the change in dislocation node spacing in the
presence and absence of gas.
Ti-based alloys are being considered for a wide range of aerospace
applications, and in some uses they will be exposed to elevated
temperatures and harsh chemical environments. This program is aimed at
developing an understanding of the effects of hydrogen on the
mechanical properties of b-Ti alloys. Studies of the effect of
hydrogen on the bulk mechanical properties are coupled to results from
deformation experiments performed in a gaseous environment in situ in
a TEM. This combination of experimental techniques allows the bulk
property changes to be understood from a microscopic point of view.
The ability of ceramic materials to withstand high-temperature and
hostile environments offers great prospects for potential major
improvements in the design performance of high-temperature components
in chemical processing, power generation, and industrial waste
recovery applications. Their use as structural materials, however, has
been limited primarily because of their poor fracture toughness and
lack of damage tolerance. The purpose of this program is to examine
the fundamental micromechanisms of high-temperature subcritical crack
growth in three classes of ceramic-matrix composites chosen to reflect
different primary room temperature toughening mechanisms, namely,
crack deflection, crack trapping, and crack bridging.
The fracture mechanisms of particulate-reinforced metal-matrix
composites are examined in several aluminum- and titanium-matrix
composites at room and elevated temperatures. Most composite systems
show a low-temperature fracture behavior controlled primarily by the
reinforcing particles, with the matrix playing an inactive role in
resisting the crack growth. The fracture properties of these
composites are characterized by low fracture toughness, relatively
flat R-curves, and weak dependence on the composition and
microstructure of the matrix alloy. It is shown that a more efficient
use of the matrix plasticity, which makes the fracture process more
matrix-dominated, can lead to significant improvement in the fracture
properties of these composites.
This research project studies the effect of high stresses on the
intrinsic properties of solids. A particular emphasis is on the
collective formation of crystal defects in the presence of high
stresses and the implications of these special defect formation
mechanisms for the brittle failure of materials and the transition to
ductility. The experiments involve testing dislocation-free crystals
in tension and probing the defect content dynamically with electrical
resistivity and x-ray diffraction. The collective nucleation of
dislocations is modeled with analytical methods and computer
simulations. The materials studied include TiAl and NiAl
intermetallics, Si, and metal whiskers.
g/a2 two-phase alloys based on intermetallic compound TiAl are high-
strength, low-density materials for applications at high temperatures,
e.g., as turbine and compressor blades in aircraft engines. This
research investigates (1) the relationship between microstructure and
the mechanical properties such as yield strength, creep resistance,
and toughness and (2) the control of microstructures by means of heat
treatment and mechanical working. The experiments involve microscopy
characterization of microstructure over the nanometer to micrometer
range and mechanical property tests. The relationship between the
microstructure and mechanical properties is modeled, based on the
dislocation pile-up mechanism and the continuum theory of
dislocations.
The origin of dimensional anisotropy and tape movement is studied
using rheological techniques and in situ stress measurements.
Rheological properties of tape casting suspensions are characterized
to probe their relaxation behavior. Stress measurements based on a
laser interferometry technique are carried out on tape-cast layers of
varying thickness and composition. Our goal is to develop a
fundamental understanding of property evolution during drying of these
complex colloidal systems.
The techniques of in situ TEM deformation and hot-stage microscopy are
being used to study the interaction of dislocations with grain
boundaries, the operation of grain boundary dislocation sources, and
the interaction of mobile grain boundaries with obstacles such as
precipitates. These studies are being undertaken to provide an
understanding of the physical processes controlling grain boundary
cavitation, grain boundary sliding, grain boundary dislocation
interactions, and grain nucleation at precipitates.
Severe plastic deformation can force immiscible elements into solid
solution, as observed during ball milling of Cu-Co or Cu-Ag powder
blends. We are developing a program that uses analytical techniques
with atomic resolution to elucidate the mechanisms controlling such
transformations. This is combined with modeling and computer
simulation to develop tools for rationalizing existing behavior and
for anticipating possible new microstructures or properties.
This is a comprehensive interdisciplinary program of basic research on
displacive transformations in ceramics. The ultimate aim is to raise
the level of understanding of these transformations to that comparable
with martensitic transformations in metallic systems. The program
involves studies concerning precursor phenomena and phonon effects,
elasticity properties, transformation crystallography, static
displacements, chemical and structure ordering, and kinetics. Systems
currently being studied are KNbO3, PbTiO3, and BaT:O3, as well as
relaxor ferroelectrics PMN, PST, and PLZT.
The Materials Research Laboratory is engaged in a collaborative effort
with personnel from the Oak Ridge National Laboratory, National
Institute of Standards and Technology, and UOP Research Inc. for the
development of two beam lines of the Advanced Photon Source (APS)
being constructed at the Argonne National Laboratory. The foci of this
effort are to do research and to educate new generations of scientists
and engineers at the cutting edge of the science and engineering in
various disciplines. Particular efforts presently underway and planned
are in surface/interface diffraction, magnetic scattering, inelastic
scattering, Mössbauer effect, diffuse scattering, and
macromolecular crystallography. H. Chen is the director of this APS
beam-line development project.
The principal means by which Ni-based superalloys strengthen
themselves is precipitation hardening. Recent years have seen a
renewed interest in the phenomena of Ostwald ripening. The classical
theory has recently been modified to incorporate the effect of finite
volume fraction and the coherency stresses due to lattice mismatch.
These factors can have profound effect on the precipitates' growth
kinetics and their final size distribution. There is an acute need for
experimental verification, which is the principal goal of this
research. We have found for the first time enhanced coarsening rate
due to lattice misfit strain via small-angle neutron scattering
measurements. Further study is being conducted using TEM to confirm
the scattering results.
Anomalous x-ray scattering studies of a lead-magnesium-biobate (PMN)
single crystal were carried out to study its superstructure. Ordering
was observed by the presence of 1/2(111) type superlattice peaks. By
tuning the energy of the synchrotron radiation to values close to the
Pb LIII absorption edge, the superstructure was shown to include Pb,
either by atomic exchange or large displacements. Recent synchrotron
x-ray data show the Bragg peak intensities changed not only with
temperature but also with aging time. Further work is needed to
separate these two effects and to understand the ordering-temperature
relationship.
Zeolites find wide applications in petrochemical industries owing to
their unique properties, such as absorbents, catalysts, and ion
exchangers. Many studies have concentrated on the synthesis of new
zeolite types and possible applications for zeolites. The underlying
molecular events which govern crystallization are still poorly
understood. With the brilliant synchrotron radiation source at APS
available as well as state-of-the-art position-sensitive detectors, it
becomes possible to carry out the in situ studies using SAXS and WAXS
techniques to monitor the whole process of zeolite crystallization,
with the precursor gel transformation monitored by SAXS and
crystallization by WAXS simultaneously.
The degree to which ordering exists in high-temperature alloys can be
probed by diffuse scattering experiments in which pair-correlations
for compositional and/or magnetic order are measured. We will develop
and apply a first-principles theory of alloys which directly
determines these correlations, based on the underlying electronic and
magnetic interactions. For the first time, the results of the
scattering experiments can be related directly to the electronic
structure of metallic alloys, thereby elucidating the microscopic
reasons for the structural ordering. Identifying the underlying
mechanisms responsible for the observed short-range order provides
valuable guidance in the design of new and improved alloys and
represents a significant advance in alloy theory.
Large-scale molecular dynamic simulations of inorganic compounds are
carried out to study the mechanisms of phase transformations. Phase
transitions are induced by simulated pressure or temperature changes.
The unstable modes of motion on a local scale are identified by
Fourier filtering particle trajectories and by performing normal mode
analysis on static structure. Because of the size of the systems, it
is possible to study the propagation of transformation fronts and the
formation of domains. This research targets issues which arise in
conjunction with wear-resistant hard coatings, high-temperature
structural ceramics, amorphization under pressure, and relaxor
ferroelectrics.
Fundamental studies aimed at understanding the mechanism of adsorption
and desorption of contaminants in activated carbons is being pursued.
This includes determining factors that control pore diameter, pore
diameter distribution, and surface character (acidity vs. basicity).
With this kind of basic knowledge it is anticipated that one can
design greatly improved adsorption systems to control a wide range of
atmospheric pollutants, including CO2, freons, SOx, and indoor air
contaminants. Carbon particles measuring 130Å to 1000Å
will be chemically functionalized and then reacted to form cross-
linked structures. These macrostructural polymers will be examined in
terms of their structural features, thermomechanical properties, and
potential use as advanced filtration systems.
A broadly based program to develop improved matrices for advanced
ceramic composites based on boron nitride is being pursued. The
borazine oligomer used to form the boron nitride is also being
examined as a precursor to BN in the form of a thin-film dielectric
insulator as well as adhesion for high-temperature ceramics.
Single-crystal flakes of aluminum diboride in an epoxy matrix have
been shown to yield outstanding planar mechanical properties far in
excess of those achievable with graphite fiber epoxy composites. The
current program is directed at exploring AlB2 aluminum matrix
composites to develop an understanding of the crystallization kinetics
of the flakes, ability to process directly into shapes, and
establishing the strength-limiting characteristics of such composites.
It has been shown for two families of flexible segment containing
thermotropic main chain liquid crystal polymers, that chain-folded
lamellae develop during crystallization from the liquid crystal state
in quiescent and sheared thin films, annealed solution grown (folded
chain) single crystals, and on the surfaces of bulk samples. Extended
chain lamellae, when formed, are suggested as developing from a chain-
folded morphology by sliding diffusion. Simultaneous polymerization
crystallizations, on the other hand, lead to the growth of lamellar
extended chain crystals. Electron diffraction has permitted
characterization of the crystal structure and transition behavior.
The morphology, crystal structure, and changes therein with
temperature of a wide variety of homopolymer and both random and
alternating copolymer lamellar (100Å thickness) single crystals
and single disclination domains have been characterized by electron
microscopy and diffraction. Polymers include many rigid polyester
LCPs, PET, PBT, PEN, Kevlar, Kapton, polyethers, and polyanhydrides.
The high-temperature lattices for poly(p-oxybenzoate) and their
relationship to the low-temperature lattices have been clarified.
Crystal structures of many of the polymers have been determined by the
use of electron diffraction aided by modeling. The polymers are
prepared by a unique, low-temperature, confined, thin-film melt
polymerization process.
Macrocrystals (up to 0.1 mm) of several liquid crystal homo- and
copolymers have been prepared by a variation of the confined thin-film
polymerization technique. They are composed of lamellae ca. 100Å
thick, presumably extended chain in nature, and all with a common
alignment. Their chemical structure (alternating vs. random) and
transition behavior are being characterized by infrared
microscopy/thermal analysis for comparison with electron diffraction
studies. Growth rates are being observed by hot-stage optical
microscopy as a function of film thickness, temperature, and
composition.
C) yields morphologies varying from single-crystal whiskers (up to 50
m length) to hexagonal platelet crystals (2-5 m thickness and up to
100 m lateral size). Effects of time, temperature, concentration, and
stirring have been characterized. The platelets are suggested to form
by a mechanism similar to that described by Bassett (University of
Reading) for extended chain platelets of linear polyethylene, i.e.,
transformation from a hexagonal columnar liquid-crystal state to an
orthorhombic lattice. Electron diffraction is used to characterize the
relative arrangement for the crystalline domains after the
transformation.
Electron diffraction patterns from the confined thin-film melt
polymerized lamellar crystals and solution-grown whisker single
crystals have been used for ab initio direct phasing crystal structure
studies. Current emphasis is on poly(p-oxybenzoate) (phase I and II)
and poly(terephthalate anhydride). Excellent agreement has been
obtained for poly(p-oxybenzoate) in comparison to molecular Cerius2
program.
C, 70 degrees below the monomer melting point. The polymer formed
consists of lamellae, ca. 100 Å thick, composed of extended
chains. Rapid chain extension occurs on heating to the polymer's
nominal Tk-m. Incorporation of glass fibers or polymer whiskers
results in overgrowths with excellent adhesion; the molecules are
normal to the plane, parallel to the whiskers. Applications as
nanocomposites, normal composites, coatings, and adhesives are being
explored.
A high polymer can adsorb tightly from solution to a surface even if
its individual monomers do not, by virtue of a large aggregate free
energy of sticking. The focus of experimental work has been to measure
equilibrium effects. The dynamic aspects of polymer adsorption are not
understood. In this work, polymer populations at a surface are
measured by infrared spectroscopy. By measuring the kinetics of
adsorption, desorption, and surface diffusion at well-characterized
surfaces, our goal is to understand the dynamics of mass transfer in
thin interfacial regions.
The objective of this research is to probe the tribology of polymer
and surfactant boundary layers on a molecular level. We have developed
new methods for measuring frictional forces between surfaces that are
close to one another (a few angstroms), but not actually touching.
With these methods, we measure the viscosity and static shear strength
of liquids of thickness comparable to molecular dimensions.
The project revolves around the tribology of perfluoroether fluids
under extreme but nonetheless well-defined conditions of shear rate
and confinement. This will allow one to understand the surface
chemical and rheological components of perfluoroether friction, as
distinct from the classical ones that are rooted in the solid-solid
contact. Interpretation from molecular viewpoints is emphasized.
This collaborative research between Exxon and the University of
Illinois involves work in both laboratories. The conceptual objectives
are to establish specific science connections beween microscopic
observables and tribological properties of fluids at interfaces in
chemically reactive environments. Specifically, we will integrate
spectroscopic probes and rheological measurements in model asperity
contacts.
Underway are systematic studies of surface-surface interactions based
on the rational design of known protein and polymer interfaces. We are
interested in the effects of peptide composition, electrostatic and
hydrophobic properties, and especially conformations and specific
interactions with polymers.
The adsorption of polymers with infrared-active vibrations in the
skeletal backbone is studied by infrared spectroscopy in attenuated
total reflection to give direct information about chain flattening
through dichroic measurements. Of particular interest is the
dependence of surface rearrangement rates on the surface coverage.
History dependence is expected to be related to the high local
density.
This work brings together two laboratories in university-industry
cooperation to (1) employ a newly designed tribometer to examine
energy dissipation at intermediate length scales, between molecularly
thin films and the continuum limit and (2) integrated spectroscopic
and newly designed tribological measurements to "see" what
actually occurs at the interface while sliding takes place.
Systematic studies are underway of particle-particle nanorheology
based on the concurrent measurement of static and dynamic forces in
both the shear and normal directions. This is relevant to an enormous
range of fine powder applications based on rheological properties in
an environment that is not dry (among them fluidization and rapid
shear flow in riser reactors, segregation processes, and mixing and
pneumatic conveying).
Microscopic statistical mechanical theories of diblock copolymer melts
and solutions are being developed and applied to understand single-
chain conformation, collective concentration fluctuations, small-angle
neutron scattering measurements, and the molecular factors that
control phase separation. The influence of chain branching, backbone
stiffness, and intermolecular attractive forces on the order-disorder
microphase separation transition of polyolefins have been determined.
Excellent agreement with recent x-ray and neutron scattering
experiments has been demonstrated. Micelle and aggregate self-assembly
in dilute selective solvents is also under investigation.
Microscopic theories of the dynamics of nonlinear macromolecular
solutions and melts are being developed based on modern statistical
dynamical methods. The mechanical response, diffusion, and
conformational relaxation times of macromolecules modeled by fractal
mass distributions are studied. Detailed applications to experimental
systems such as polymer rods, macromolecular rings, and spherical
microgel fluids are in progress. Generalization of the theory for
linear chains to treat self and tracer diffusion and shear viscosity
in solutions, melts, and gels is being pursued.
Microscopic theories for the conformation and structure of self-
assembling multiblock copolymers and ionomers are being developed. The
influence of block length and composition on long wavelength
concentration fluctuations, microdomain formation, and phase
separation temperature have been systematically explored. Application
to address small-angle scattering and the microphase behavior of
multiblock polyurethane melts and ionomer melts have been carried out.
The role of water, nonpolar solvents, and blending with homopolymers
on ionomer structure physical clustering and bulk properties are of
interest.
Microscopic, off-lattice integral equation theories of dense polymer
mixtures are being developed and applied. The influence of density
fluctuations, molecular architecture, and interchain forces on
collective fluctuations, thermodynamic properties, interchain packing,
and phase diagrams is being established via analytic and numerical
approaches. Detailed applications to blends of hydrocarbon chains are
being carried out and compared with small-angle neutron scattering
measurements. Generalizations of the theory to treat specific
interactions, lower critical solution type phase separation, and the
blend equation-of-state are being pursued.
A microscopic statistical dynamical theory of self and tracer
diffusion in polymer blends and diblock copolymer solutions and melts
has been developed. Long wavelength concentration fluctuations and
microdomain formation are predicted to result in slowing down of
diffusion and in enhanced entanglement coupling in a manner which
depends on alloy composition, distance from the phase boundary, tracer
and matrix polymer molecular weight, and overall polymer density.
Generalizations to treat chain dynamics, rheology, and dielectric
response are also under study.
Microscopic liquid state theories of mixtures of polymers and colloids
are being developed. The role of macromolecular structure, colloid
size, composition, and intermolecular interactions on equilibrium
properties are being systematically explored. A prime goal is to
develop a microscopic understanding of the influence of controllable
suspension variables on structure, clustering, and colloid
flocculation.
Microscopic statistical mechanical theories of the structure,
thermodynamics, and phase diagrams of mixtures of polymers and
spherical particles are being developed. The particles may be
nanometer-sized proteins or micelles, larger objects such as
dendrimers, or micron-sized colloids. The complex influences of
particle size, polymer concentration and molecular weight, and steric
and specific attractive forces on mixture equilibrium properties are
under study.
This project investigates molecular conformation and phase structure
in blends consisting of flexible polymers dissolved as guests in a
liquid crystal polymer host. The experimental work involves
measurements by broad-line proton NMR, polarized light microscopy, and
differential scanning calorimetry. We have discovered that a number of
polymers can acquire orientation parallel to the director axis of the
liquid crystal polymer host. A very significant observation has been
the guest's induction of liquid crystalline order in highly mobile
(possibly isotropic) molecular segments of the host. This may be an
example of liquid crystallinity induced by a binary interaction.
This project investigates the synthesis and properties of novel
polymers containing paramagnetic organometallic structural units in
their backbone structure. One of the systems synthesized is a
copolymer of diamagnetic chemical sequences and paramagnetic units
containing tetradentate copper II complexes. This system was found to
form a liquid crystalline phase above its melting point and therefore
acquires molecular orientation in the presence of an external magnetic
field. At the present time we are studying both its orientation
kinetics and solid-state structure. We are using the system's
paramagnetic nature not only to study magnetic properties of organic
polymers but also to probe cooperative phenomena.
This project investigates several systems that order spontaneously
into specific microscopic patterns or molecular structures in the
specific topologies. One system under investigation is the binary
alloy of two chemically periodic nematic polymers. We are interested
in this system's phase diagram and its microscopic patterns of phase
separation. Other systems of interest are self-assembling monomers for
the formation of molecular sheets, ladders, and combs.
This project investigates the synthesis of comb homopolymers and
copolymers containing chiral centers in side chains. It is of interest
here to study the ability of such polymers to form selective membranes
for chiral separation. So far copolymers have been synthesized that
exhibit smectic mesophases with phase transitions that can be
controlled by achiral co-monomers.
Over the past few years our laboratory initiated research with the
specific objective of focusing on the use of functionalized liquid
crystal polymers as the molecular components on the interface. We
succeeded in synthesizing a prototype system containing functions
reactive toward surfaces and matrices. Interestingly, these self-
ordering comb polymers were found to order spontaneously on the
surfaces of carbon fibers over thousands of molecular layers. Very
recently we have been able to place a "single molecular
layer" of these polymers on a carbon surface and have observed
the remarkable result that this monomolecular layer generates to
macroscopic evidence of improved load transfer across a carbon fiber-
epoxy interface.
This research focuses on the synthesis of new molecules and new
molecular architectures of interest in the nonlinear optical
phenomenon known as second harmonic generation (SHG). A system has
been investigated that contains 2-D polymers synthesized in our
laboratory. The 2-D architecture of polymer molecules in these films
leads to excellent temporal stability of the noncentrosymmetric
structure as required for SHG photonic materials. We have also
discovered recently that a derivative of the precursor to these 2-D
polymers self-assembles into noncentrosymmetric
"macroscopic" films with remarkable second order
susceptibility.
A synthetic pathway is described to construct "in bulk" 2-D
polymers shaped as molecular sheets. A chiral oligometic precursor
containing two reactive sites, a polymerizable group at one terminus
and a reactive stereogenic center placed near the center of the
molecule, is used. The 2-D molecular objects form through molecular
recognition by the oligomers, which self organize into layers that
place the reactive groups within specific planes. The oligomers become
catenated by two different stitching reactions involving the reactive
sites. This observation suggests that the transformation of common
polymers from a 1-D to a 2-D architecture may produce generations of
organic materials with improved properties.
We have synthesized a polymer consisting of a monodisperse, rod-like
segment coupled to a monodisperse coil-like segment and have observed
it to form microphase separated structures. The rod-like segment, an
aperiodic sequence containing aromatic units, and the coil-like
segment, polyisoprene, share the same molecular backbone. When not
attached covalently to the coil, the aromatic rod-like segment forms a
compound that melts into a liquid crystalline phase demonstrating the
stiff segment's high aspect ratio. A film of the "rodcoil"
polymer when cast from a selective solvent exhibits microphase
separation, forming ribbons or strips as well as small aggregates that
have dimensions in the range of the rod-like molecular segments.
This research is being conducted to examine the relationship between
microstructure and mechanical performance in the Al2O3-ZrO2 eutectic
system. The study will concentrate on densification processes, thermal
instability associated with phase distribution of zirconia in this
eutectic composite. The effect of processing on the microstructural-
mechanical properties will be evaluated.
Stabilized zirconia is a fast oxygen conductor and as such is widely
used in solid oxide fuel cell applications. Microstructural defects
like grain boundaries raise the ac impedance in this material. We are
investigating the effects on electrical properties of placing a second
oxygen-conducting phase at the grain boundaries, which we attempt to
achieve by coating zirconia powders with that phase prior to
consolidation. The goal of the work is to tailor the temperature-
dependent oxygen conductivity by adjusting the type and thickness of
this secondary phase.
We are experimentally examining the energetics and kinetics of
microstructure evolution in heterophase systems by patterning simple,
controlled-geometry microfeatures of ceramic phases onto crystalline
substrates. By exploring the influences of the initial geometry and
heteroepitaxy on equilibrium morphology and on coarsening and
coalescence rates, we should be able to derive quantitative data on
relative interfacial energies and on the rate-controlling mass
transport mechanism governing the evolution. Such information is
crucial to understanding the processing of materials ranging from thin
ceramic layers to structural composites.
During sol-gel processing, structural developments occur as a result
of network condensation. Consequently, the rigidity of the structure
and the resistance it offers to the escaping solvent increase.
Pressure gradients build and the gels risk fracture. Using Brillouin
light scattering in the course of the drying process, we monitor the
complex mechanical modulus, characterizing the dynamic response of
these gels on a molecular scale. This yields information concerning
the change of elastic properties and viscous dissipation, as
controlled by chemical composition and drying rates.
We are carrying out rheological measurements (stress viscometry and
oscillatory measurements) to probe the effects of free (nonadsorbed)
polymeric species in concentrated, nonaqueous suspensions. Free
polymer species influence particle-particle interactions, and, hence,
suspension "microstructure" through depletion phenomena.
However, relatively little is known about such phenomena even though
free polymeric species are often present in significant amounts in
these systems. Our observations have highlighted the importance of
depletion stabilization in such systems. Ultimately, we aim to develop
a theoretical model for this effect.
Gel casting is a near-net shape-forming process suitable for complex
3-D components. We are studying the gelation behavior of aqueous
suspensions that contain high solids volume fraction in the presence
of low molecular weight polymeric additives (e.g., polyvinyl
alcohols). Such systems are environmentally benign and produce
consolidated bodies with low organic content facilitating subsequent
debinding processes.
Solid free-form fabrication enables the production of prototypes and
parts directly from CAD files, without the need for hard tooling, and
is presently explored for the production of ceramic components. Our
objectives are to develop the polymer/ceramic mixtures suitable for
controlled fused deposition of specific ceramic materials and to
investigate the debinding, sintering, and microstructure development
processes in components produced by this technique.
The goals of this study are (1) to develop the basic understanding of
the behavior of interfaces in materials submitted to radiation field
and (2) to investigate the consequences for the microstructure-
properties relationship in these materials. Two types of behavior are
currently being investigated by atomistic computer simulations and
irradiation experiments: the coarsening of ordered domains and the
shape of precipitates in two-phase materials. In these two cases, the
evolution of the alloy is mostly controlled by dynamical processes
taking place at interfaces, such as atomic mixing and interface
roughening. We have determined that irradiation can induce a
nonequilibrium roughening as well as a nonequilibrium faceting of
precipitates at steady-state.
The focus of this program is to provide an understanding of the basic
processes of damage formation by heavy-ion irradiation of metal
systems. Transmission electron microscopy is used extensively to
characterize the damage structure as a function of ion dose and
irradiation temperature. The experimental information obtained is used
to evaluate current damage models and to provide a better
understanding of how material properties are affected in a nuclear
reactor and how irradiation with energetic heavy-ions modifies the
surface properties of a material.
Fundamental aspects of ion-beam-induced amorphization and layer
intermixing in III-V semiconductor heterostructures are being studied
by using a combination of low-temperature ion channeling and
transmission electron microscopy techniques. Specifically, we are
interested in understanding the effect of increasing the Al content on
the ion dose needed to cause amorphization in the AlGaAs system and
the mechanisms of mixing in AlGaAs-GaAs heterostructures.
Ion implantation is used extensively in the semiconductor industry to
introduce dopants. The accompanying damage must be removed before
devices can be activated. The focus of this effort is on understanding
the mechanisms of solid-phase epitaxial crystallization of amorphous
material in simple and compound semiconductors. The regrowth process
can be stimulated by means of an energetic electron beam, which
allows, through variation of the electron energy, the role of defects
created in the crystalline material (interstitials and vacancies) or
interface defects (dangling bonds or charged kinks) to be directly
assessed.
High-purity group Va and VIa metals exhibit the so-called anomalous
slip behavior at low temperatures (e.g., <200 K in Nb and 77 K in
Ta). To understand this transition in deformation behavior, samples of
high-purity tantalum will be deformed in situ in the transmission
electron microscope as a function of temperature. Such studies will
also yield direct information on the relative mobilities of edge and
screw dislocations and their interactions with each other and with
other obstacles as a function of temperature.
Basic aspects of ion beam modifications of materials are being
investigated. These studies include ion beam mixing, defect
production, radiation-enhanced diffusion, and ion beam-assisted film
growth. The work combines molecular dynamics computer simulation with
experimental studies using MBE grown films and 1 keV to 3 MeV ion
beams and various surface analysis methods. Metals, intermetallic
compounds, oxide ceramics, and compound semiconductors are of
interest.
Basic aspects of diffusion and radiation-induced defects in model
ceramic oxide materials are investigated. Specimens especially grown
by MBE methods, tailored to specific experiments, ion beam analysis,
and x-ray diffraction and SIMS comprise the methods of study.
Nanophase processing is a novel technique by which metallic and
ceramic materials can be produced in the form of ultrafine powders
with sizes in the range of 5 to 50 nm. The resulting powder particles,
called nanophase or nanocrystalline powder, can be cold compacted at
or near room temperature to near theoretical density. The novel
microstructure of ceramics thus produced can impart several useful
engineering properties. Ongoing research on these nanophase ceramics
includes sintering kinetics, fracture strength and toughness, and
superplastic deformation. The goal of the research program is to
identify useful engineering properties of the nanophase ceramics and
to understand their structure and property relationships.
The structure of nanoparticles and their interactions with one another
and with substrates are examined on an atomic scale using high-
resolution transmission electron microscopy and molecular dynamics
computer simulations. Sintering of small assemblies of nanoparticles,
epitaxial relationships between the particles and substrates, and the
dependence of size on alloy phase stability are investigated.
This research involves preparation of chemically stabilized b-
crystobalite powders synthesized by the solution polymerization
technique employing Pechini resin and PVA solution as a polymeric
carrier and consideration of mullite-cordierite composites with b-
cristobalite interfaces showing the optimum phase transformation
weakening behavior at the laminate/matrix interface. We are
investigating grain size effects on the bÆa transformation of
cristobalite and fabricating laminate structure by the tape-casting
process including the control of thermal and co-firing conditions
between them.
Amorphous fibers synthesized by laser-heated, containerless methods
are being tested to develop a process to convert them into single-
crystal fibers. These fibers are projected to have important
applications for reinforcing ceramic matrix composite materials. The
kinetic parameters of the crystallization process have been determined
using differential thermal analysis (DTA). The measured kinetic
parameters were then used to determine rates of crystallization as a
function of temperature and time. Additionally, the crystallinity of
the fibers and their microstructure have been evaluated using various
spectroscopic techniques including TEM, optical microscopy, and SEM.
Strength values of the fibers have been measured using tensile testing
techniques.
Modern ceramic fabrication techniques are being applied to inexpensive
raw materials to produce strong lightweight building panels. Emphasis
is on common clays, fly ash, bottom ash, and diatomaceous earth as raw
materials. Lignin sulphonate, a by-product of the paper industry, is
used as a foam-stabilizing agent in fabricating foamed ceramic
construction materials. Sol incorporation and gellation, with careful
control of pH and rheology, is similarly being evaluated in
fabrication, as is phosphate bonding. Combustible additives, such as
sawdust, and expansive additives, such as vermiculite, are also being
studied as means of decreasing density. Extruded honeycomb structures
will be produced and evaluated.
Detailed microstructural and microchemical investigation of polymer-
derived fibers and matrices is being performed. In particular, the
amorphous/crystalline nature of the materials and the presence of
second phases are being studied. The effect of various processing
conditions and exposure to various environments on fibers and
fiber/matrix interfaces is being investigated using a variety of
microanalytical techniques.
We are investigating mechanisms of high-temperature oxidation of hot-
pressed SiC-AlN compositions. The dense materials are either
composites or solid solutions, depending on processing conditions. The
oxidation is strongly affected by the formation and further reaction
of several layers found at the outer surface, such as SiAlON and
mullite, and by microstructural factors. High-resolution and
analytical TEM, as well as SEM and XRD, are used in the investigation.
The current-carrying capability of bulk polycrystalline
superconductors is limited because of their "weak link"
behavior. This behavior results from misorientation of individual
grain boundaries, unfavorable grain boundary chemistry, porosity, or
the presence of microcracks. We have developed a novel technique to
produce grain-aligned YBa2Cu3O7-x that couples magnetic alignment with
partial melt processing. Magnetically aligned films are densified near
the peritectic temperature to promote partial melting. The oriented,
unmelted Y123 grains then act as seeds for textured growth during
recrystallization. We are currently investigating the role of second
phase additions on the peritectic decomposition reaction,
microstructural development, and properties of YBa2Cu3O7-x thick
films.
A new high-pressure facility provides a unique capability for high-Tc
research. Work is directed at synthesis and growth of layered
structure compounds and on new exploratory studies of superconducting
structures. Attention is paid to the hole-doped materials of possible
d-wave nature, which are believed to give the highest Tc's. In
addition to high pressure synthesis, electrochemical crystal gowth
also gives rise to the high oxidation capability, which is important
for the formation of hole-doped high-Tc superconductors. Experiments
are designed to improve the quality of crystals and to explore new
layered-structure compounds for high-Tc superconductivity.
This project involves characterization of corrosion growths in water
pipes. Sample sections of pipes are removed from working drinking
water systems in various cities. Water treatments are run through the
systems for a period of time ranging from six months to two years, and
then another sample section is removed from the system. These sections
are shipped to the University of Illinois, where qualitative
characterization of before-treatment and after-treatment pipes is done
to determine the effectiveness of the water treatments used.
Characterization techniques used include light microscopy, SEM, EDS,
and XRD.
While not altogether new, anodic spark deposition (ASD) is a most
promising and versatile process for the application of a wide range of
novel ceramic coatings that has yet to be exploited. It is a
comparatively rapid, subconventional temperature process that occurs
at the positive electrode of an electrolytic cell via a complex set of
reactions that involves sparking. The aim of this research is to
determine the feasibility of the application of diamond and/or
diamondlike carbon films by ASD. Such films have also been put down in
connection with this program by chemical vapor deposition techniques.
Gas tight layers of stabilized zirconia are being deposited on carbon
from vapors of the chlorides by means of the local electrochemical
cell set up by the electrolytic properties of the growing ceramic
coating. The electrolytical properties of the coating are being
evaluated as a means of protecting the carbon from oxidation at
elevated temperatures in an oxidizing atmosphere. Polarization
processes at the carbon electrode are being evaluated by
potentiometric measurements, and the volume of oxidation reaction
products is being monitored by means of a Bunsen tower.
C suitable for fabrication on plastic substrates.
Our goal is to develop a low-temperature growth process for thin-film
hydrogenated amorphous silicon (a-Si:H) and silicon nitride (a-SiNx:H)
layers, which are used as the semiconductor and dielectric materials
in thin-film transistors, respectively. The films are grown using
reactive magnetron sputter deposition, fabricated into field-effect
devices, and analyzed. We recently demonstrated a record high mobility
using a buried channel configuration.
We are investigating a new method for the deposition of titanium
nitride thin films: remote plasma processing from metal-organic CVD
precursors. The remote plasma approach has the potential to bring
together the best features of the chemical and physical vapor
deposition routes for the synthesis of ultrahard coatings: the high
growth rates, low temperatures, and conformal coverages characteristic
of CVD and the dense, polycrystalline microstructure of the PVD
process. A major component of this research is an investigation of the
chemistry using in situ reflection-absorption infrared spectroscopy
and modulated mass spectroscopy with isotopic labelling experiments.
We study the nucleation and growth of polycrystalline silicon (px-Si)
thin films on glass substrates at relatively low substrate
temperatures ( C) using real-time, in situ spectroscopies. The goals
are to determine the kinetics of hydrogen and silicon hydride
adsorption, diffusion, reaction and elimination from the growing
surface, and the effects of fast particle bombardment on these
processes; to develop realistic models of px-Si film deposition; and
to improve px-Si growth methods based on this knowledge. We seek a
reaction pathway which yields high-quality px-Si in the as-deposited
state, as opposed to the deposition of an amorphous silicon (a-Si) or
fine-grained px-Si film followed by thermal recrystallization.
This work is intended to elucidate the electronic stability of thin-
film silicon devices that have been passivated by deuterium instead of
by hydrogen. The impetus for this work comes from the recent discovery
that the use of deuterium sharply decreases the rate at which MOS
transistors degrade by electron-impact reactivation of interface
states at the SiO2/Si interface and the rate at which amorphous
silicon photovoltaic devices degrade under illumination. The goal of
our project is to establish the existence, magnitude, and kinetics of
the deuterium passivation effect in a third class of silicon-based
materials, namely, polycrystalline silicon thin-film transistors.
We are interested in studying solid-state reactions involving thin
films of metals deposited on semiconductor substrates (Si or GaAs).
The samples are characterized using standard thin-film analysis tools
such as TEM and x-ray diffraction. In order to study the kinetics of
the reaction, the sheet resistance of the film is monitored in situ
during the annealing process using a four-point probe assembly. By
monitoring the changes in the sheet resistance versus time we can
attempt to understand the rate-determining mechanisms of the reaction.
We plan to use this technique in both traditional furnaces and rapid
thermal annealing (RTA) systems.
We plan to explore several areas related to small metal structures in
a typical integrated circuit. The first area is the measurement of
metal-to-metal contact resistance of small-area interconnect
metallization systems. The second area of interest explores the
reactions induced by local heating using a small resistance heater
(microheater) fabricated with photolithography techniques. These
heaters act as "fuses" in some IC systems. We are also
exploring the possibility of building a scanning tunnelling
potentiometer to electrically characterize these small structures.
C) SPE growth of Si-Ge films on Si(100). This is accomplished by
thermally annealing a-Ge/Au bilayers deposited on Si(100) using
thermal evaporation. RBS, TEM, ion channeling, and AES were used to
characterize the microstructure of the films. The process of the
growth is studied using XTEM and in situ resistivity measurements.
Ti metallization plays an important role in state-of-the-art MOS
processing technology. Not only is it used extensively for SALICIDE
formation for source/drain contacts, but it is also used to form
conductive TiN diffusion barriers needed for reliable contacts with
aluminum metallization. We investigate the reaction sequence in this
system using both in situ measurements such as differential
resistivity measurements and ex situ microstructure analysis,
including TEM and XRD.
We are developing a new technique that is potentially a very powerful
method for directly obtaining quantitative values for small enthalpy
of reactions at interfaces, surfaces, and near surface regions. This
microcalorimeter is expected to have high sensitivity, capable of
measuring extremely small amounts of heat generated during solid/solid
reactions and surface processes as well as low enthalpy of internal
microcrystalline processes. This technique will be useful for
measuring the kinetics of interface reactions, such as the nucleation
of silicides at buried interfaces, and the study of near-surface
processes, such as point-defect annihilation and coalescence of
vacancies in Si following ion implantation.
C in the melting point of Sn nanostructures, which agrees with the
liquid-shell model describing the size-dependent melting point
depression.
A wide variety of techniques for the deposition of thin films utilize
bombardment of the growth surface by low-energy ions to enhance film
properties. We are studying the deposition of metal films using a low-
energy metal ion beam with a well-defined energy that can be varied
between 5 eV and 200 eV. In situ scanning tunneling microscopy is used
to characterize the surface morphology. When we combine this technique
with ex situ x-ray diffraction and transmission electron microscopy
studies, we form a nearly complete picture of the dependence of film
microstructure on the energy of depositing atoms.
Ceramic coatings are widely used as thermal barriers to increase the
maximum operating temperature of metal alloys. Our research project
seeks a greater understanding of the role of atomic-sized defects,
internal interfaces, and porosity on the thermal conductivity of oxide
coatings. Experimental coatings are deposited using magnetron
sputtering. Our newly developed measurement technique enables us to
measure the thermal conductivity of films only 100 nm thick over a
wide temperature range, 80-800 K.
Thermal plasma processing shows great promise as a technology for the
remediation of toxic wastes. Unfortunately, the extremely high
temperatures produced in plasma-arc melting can lead to significant
loss of metals from the molten slag by evaporation. The Plasma Arc
Facility at the University of Illinois is extensively instrumented to
allow real-time monitoring and control of plasma-arc processing of
model systems for contaminated wastes. We are studying the kinetics of
metal evaporation and particle generation using optical probes.
Our experiments on the fundamentals of crystal growth by molecular
beam epitaxy (MBE) and etching by low-energy ions take place in the
EpiCenter, a collaborative facility for research in physics,
electrical engineering, and materials science. We use in situ scanning
tunneling microscopy (STM) to quantify the surface structure and
morphology of a wide variety of semiconductors and metals. The STM
studies include atomic resolution imaging as well as systematic
studies of morphology evolution during low-temperature processing.
We use molecular dynamics calculations and scanning tunneling
microscopy to study collective behavior during energetic ion impacts
with solid surfaces. Collective behavior such as thermal spikes can
produce qualitative differences in the morphology and microstructure
produced by ion implantation in comparison to the predictions of
binary collision models. The experiments take advantage of the
EpiCenter facility to produce clean surfaces of a wide variety of
materials and quantify the morphologies produced by ion impacts.
For improved hardness, corrosion resistance, and decorative purposes,
titanium nitride has received a wide range of applications.
Fundamental problems involving adhesion, interface strength, effect of
residual stress on strength, texture effect on properties, etc., are
some of the significant topics that still require systematic
investigation. Moreover, refining coating procedures to improve the
aforementioned properties by introducing new microstructure remains a
great challenge. This program involves the deposition and
characterization of TiN thin films obtained by ion beam assisted
deposition (IBAD) and laser ablation depostion (LAD) methods. A
variety of microstructure/microchemistry techniques along with
mechanical and corrosion testing are carried out.
We use ex situ and in situ electron microscopy to study thin films.
Thin films are grown by molecular beam epilaxy, or gas reaction, in
specially built ultrahigh-vacuum transmission electron microscopes.
Quantitative measurements from images are used to extract stress
magnitudes or examine ordering in films.
We use in situ transmission electron microscopy to understand the
growth of Ga and Al nitrides on sapphire substrates. The growth method
is reactive molecular beam epitaxy.
Multitarget sputtering techniques have been developed to allow the
sequential deposition of ultrathin (10-100 Å) alternating layers
of metastable (GaAs)1-x (Si2)x and GaAs. Preferential sputtering has
been investigated and excellent control over film chemistry has been
demonstrated. The structural perfection and electronic properties of
such intercalated structures are being studied. Superlattice x-ray
scattering techniques are also being used to study thermal and ion
bombardment enhanced diffusion in these materials.
The growth of high-quality, mixed, III-V ternary and higher order
single-crystal thin films by MBE incorporating reactive species using
low-energy accelerated ion beams is being investigated. Structural
perfection, optoelectronic properties, and composition of deposited
alloy films are related to growth conditions. An understanding of this
relationship may allow the development of new classes of
multicomponent materials by exploiting the fact that sputtering is
basically a physical rather than a chemical growth technique.
The primary objective of this research is to develop a detailed
understanding of energetic particle/surface interactions for
controllably altering nucleation and growth kinetics, microchemistry,
and physical properties of metal and semiconductor films during
deposition from the vapor phase by a variety of techniques including
ion-assisted MBE, plasma-assisted CVD, sputter deposition, and
primary-ion deposition. Low-energy ion/surface interactions allow the
crystal grower additional dynamic control, at the atomic level, over
microchemistry and microstructural evolution. Kinetic energy can be
efficiently coupled to the growth surface thereby altering surface
reactivity as well as adsorption, adatom diffusion, and nucleation
kinetics.
We are developing a general model for the prediction and analysis of
elemental incorporation probabilities and depth distributions of
dopants in vapor phase deposited films as a function of experimental
parameters such as film material, dopant, film growth temperature,
growth rate, and the flux and kinetic energy of dopant species
incident at the growing film surface. The model accounts for dopant
diffusion, surface segregation, and low-energy ion bombardment
effects. Model predictions are tested using accelerated-beam MBE as
well as glow discharge and ultrahigh vacuum ion beam sputter
deposition in which actual doping profiles will be determined by
secondary ion mass spectrometry (SIMS) and, where applicable,
capacitance/voltage and Hall effect measurements.
Chemical reaction paths can be affected by laser-induced
photochemistry. We are investigating semiconductor crystal growth
using focused laser beams to initiate heterogeneous reactions at
substrate surfaces as well as by gas-phase photodissociation. LCVD
offers a unique opportunity to probe the thermodynamics and kinetics
of controlling gas phase and gas-surface reactions during film growth
due to the spatial, temporal, and wavelength selectivity of coherent
light sources.
Transition-metal nitrides such as TiN are used extensively as hard and
wear-protective coatings for mechanical components, as abrasion-
resistant optical coatings, and as diffusion barriers in integrated
circuits. We have grown the first single-crystal TiN layers, using
ultrahigh vacuum reactive magnetron sputter deposition on MgO, and
have investigated their mechanical, electrical, and optical
properties. We have also grown the first epitaxial nitride strained-
layer superlattices, TiN/VN, and have found that they have mechanical
and electrical properties that are a strong function of the
superlattice period. Recently, we have grown metastable NaCl-structure
(Ti, Al)N alloys and have found that they have greatly enhanced high-
temperature oxidation resistance.
This program addresses three fundamental issues in CuInSe2 (CIS) solar
cell technology: (1) grain boundaries and their effects on second-
phase populations, bulk grain conductivity, and heterojunction
behavior; (2) stoichiometry and point defects; and (3) control of
electronic properties and carrier collection of the heterojunction
through the CIS chemistry. Experiments involve (1) growth of single-
crystal and polycrystalline layers as a function of thickness,
composition, substrate, and growth parameters; (2) testing of the
structural, chemical, electronic, and optical properties of the
fabricated materials; and (3) modification of the chemistry of the
layers.
CuInSe2 semiconductor coatings are being deposited by combining
sputtered fluxes of Cu and In with an evaporated flux of Se. This
approach takes advantage of the strengths of both the sputtering and
evaporation processes while removing the requirement for using H2Se as
a working gas. The project also involves studies of CuInSe2 deposition
where a portion of the evaporated Se flux is ionized and accelerated
in the direction of the substrate. Emphasis is on the basic mechanisms
of coating growth and the resultant electronic properties of the
coatings. The coatings are examined both by direct measurement and by
fabricating and testing CuInSe2/CdS heterojunction devices.
Bioceramics
LEE, S. J., W. M. KRIVEN, and H. M. KIM. Shrinkage free, alumina-glass, dental composites by aluminum oxidation. J. Amer. Ceram. Soc., 80, 2141-2147 (1997).
Cementitious Materials
OLSON, R. A., P. D. TENNIS, D. BONEN, H. M. JENNINGS, T. O. MASON, B. J. CHRISTENSEN, A. R. BROUGH, G. K. SUN, and J. F. YOUNG. Early containment of high-alkaline solution simulating low-level radioactive waste in blended cement. J. Hazardous Waste, 52, 223-236 (1997).
Ceramic and Glassy Solids
LIPOWITZ, J., J. A. RABE, A. ZANGVIL, and Y. XU. Properties of SYLRAMIC silicon carbide fiber--a polycrystalline, stoichiometric b-SiC composition. Ceram. Engr. Sci. Proc., 18:3, 147-57 (1997).
YOUNGMAN, R. E., J. KIEFFER, J. D. BASS, and L. DUFFRÈNE. Extended structural integrity in network glasses and melts. J. Non-Cryst. Solids, 222, 190-198 (1997).
Computer Simulations of Materials
GAYLORD, R. J. Cellular automata explorations: chemotaxis. Mathematica Educ. Res., 6:3, 41-45 (1997).
GAYLORD, R. J. Cellular automata explorations: driven diffusion of two species. Mathematica Educ. Res., 6:2, 37-42 (1997).
GAYLORD, R. J. Cellular automata simulations in materials science: solidification. Mathematica Educ. Res., 6:1, 34-36 (1997).
GAYLORD, R. J. Cellular automata simulations in materials science: spinodal decomposition. Mathematica Educ. Res., 5 4, 22-26 (1997).
GAYLORD, R. J. A cellular automata programming toolkit. Mathematica Educ. Res., 5:3, 61-67 (1997).
GAYLORD, R. J. and K. NISHIDATE. Modeling Nature: cellular Automata Simulations Using Mathematica. (TELOS/Springer-Verlag, 1997) (Japanese Ed.).
JOHNSON, D. D. and M. ASTA. Energetics of homogeneously-random fcc Al-Ag alloys: a detailed comparison of computational methods. Comput. Mater. Sci., 8, 54 (1997).
REARDON, B. J. and J. KIEFFER. Atomistic mobility in supercooled liquids via normal mode analysis and molecular dynamic simulations. Ceram. Trans., 69, 195-202 (1997).
Electrical Ceramics
CHO, C. R., D. A. PAYNE, and S. L. CHO. Solution deposition and heteroepitaxial crystallization of LaNiO3 electrodes for integrated ferroelectric devices. Appl. Phys. Lett., 71, 3013-3015 (1997).
KALINECHEV, A. G., J. D. BASS, B. N. SUN, and D. A. PAYNE. Elastic properties of tetragonal PbTiO3 single crystals by Brillouin scattering. J. Mater. Res., 12, 2623-2627 (1997).
LEE, S. W., P. P. TSAI, and H. CHEN. H2 sensing behavior of MOCVD derived SnO2. Thin Films Sensors Actuators, B41, 55-61 (1997).
SCHWARTZ, R. W., J. A. VOIGHT, B. A. TUTTLE, T. L. REICHERT, R. S. DASALLA, and D. A. PAYNE. Comments on the effects of solution precursor characterization on crystallization behavior of sol-gel derived PZT thin films. J. Mater. Res., 12, 444-456 (1997).
SENGUPTA, S. S., S. M. PARK, and D. A. PAYNE. Integrated electroceramics: densification and stress development in sol-gel derived thin layers. Integ. Ferroelectr., 14, 193-200 (1997).
Interfaces
CHEN, X. and J. M. GIBSON. Dramatic effect of postoxidation annealing on (100) Si/SiO2 roughness. Appl. Phys. Lett., 70, 1462 (1997).
GIBSON, J. M., X. CHEN, and O. POHLAND. Transmission electron microscopy of surface and interfacial steps. Surf. Rev. Lett., 4, 559 (1997).
PEDDADA, R. S., I. M. ROBERTSON, and H. K. BIRNBAUM. Growth of Ti thin films on sapphire substrates. J. Mater. Res., 12:7, 1856-1865 (1997).
Materials Chemistry
CLEM, P. G., N. L. JEON, R. G. NUZZO, and D. A. PAYNE. Monolayer mediated deposition of Ta2O5 thin film microstructures from solution precursors. J. Amer. Ceram. Soc., 80, 2821-2827 (1997).
JEON, N. L., P. G. CLEM, D. Y. JUNG, W. LIN, G. S. GIROLOMI, D. A. PAYNE, and R. G. NUZZO. Additive fabrication of integrated ferroelectric thin-film capacitors using self-assembled organic thin-film templates. Adv. Mater., 9, 891-895 (1997).
SINGHAL, A., J. M. GIBSON, and J. C. YANG. Stem-based mass spectroscopy of supported Re clusters. Ultramicroscopy, 67, 191 (1997).
Mechanical Behavior of Solids
LUNT, M. J. and Y. Q. SUN. Slip creep of Ni3Ga. Scr. Met., 36, 599 (1997).
SUN, Y. Q. An explanation of the small strain-rate sensitivity of Ni3Al. Acta Met., 45, 3527 (1997).
VETRANO, J. S., S. M. BRUEMMER, L. M. PAWLOWSKI, and I. M. ROBERTSON. Influence of the particle size on recrystallization and grain growth in Al-Mg-X alloys. Mater. Sci. Engr., A238, 101-107 (1997).
Phase Transformation and Characterization
ALTHOFF, J. D. and D. D. JOHNSON. Concentration-wave analysis of atomic pair correlations in disordered ternary alloys: application to Cu2NiZn. Comput. Mater. Sci., 8, 71 (1997).
ASTA, M. and D. D. JOHNSON. Thermodynamics of fcc-based Al-Ag alloys: implications for the formation of Guinier-Preston zones. Comput. Mater. Sci., 8, 64 (1997).
ATHENES, M., P. Bellon, and G. Martin. Identification of novel diffusion cycles in B2 ordered phases by Monte-Carlo simulations. Phil. Mag. A, 76, 565-585 (1997).
GIBSON, J. M. and M. M. J. TREACY. Diminished medium range order in annealed amorphous semiconductors. Phys. Rev. Lett., 78, 1074 (1997).
KITA, E., S. KONDO, H. IWO, M. FURUSAKA, K. SIRATORI, H. Y. LEE, and H. CHEN. Neutron and x-ray small angle scattering studies of rapidly quenched La-Fe alloys. J. Phys. Soc. Japan, 66:2, 451-454 (1997).
McCORMACK, R., M. ASTA, J. J. HOYT, B. C. CHAKOUMAKOS, S. T. MISTURE, J. D. ALTHOFF, and D. D. JOHNSON. Experimental and theoretical investigations of order-disorder in Cu2AlMn. Comput. Mater. Sci., 8, (1997).
MURALIDHARAN, G., M. C. PETRI, J. E. EPPERSON, and H. CHEN. Interaction of Si and Al during interdiffusion in Ni-Al-Si alloys. Scr. Mater., 36:2, 219-225 (1997).
MURALIDHARAN, G., J. W. RICHARDSON, JR., J. E. EPPERSON, and H. CHEN. Lattice parameters and compositions of g and g¢ during coarsening in the Ni-Al-Si system: a neutron powder diffraction study. Scr. Mater., 36:5, 543-549 (1997).
POCHET, P., L. CHAFFRON, P. BELLON, and G. MARTIN. Phase transformations under ball-milling. Ann. Chim. Sci. Mater., 22, 363-372 (1997).
POPOOLA, O. O. and W. M. KRIVEN. Phase transformation in KNbO3 perovskite ceramic. Phil. Mag. Lett., 75, 1-5 (1997).
STAUNTON, J. B., M. F. LING, and D. D. JOHNSON. A theoretical treatment of atomic short-range order and magnetism in iron-rich bcc alloys. J. Phys.: Cond. Matter, 9, 1281 (1997).
Polymers
DALEY, M. D., C. L. MANGUN, J. A. DEBARR, S. SIHA, A. A. LIZZIO, G. L. DONNALS, and J. ECONOMY. Adsorption of SO2 onto oxidized and heat treated activated carbon fibers. Carbon, 35:3, 411 (1997).
DAVID, E. F. and K. S. SCHWEIZER. Liquid state theory of thermally driven segregation in conformationally asymmetric diblock copolymer melts. Macromolecules, 30, 5118 (1997).
DEAN, D. and P. H. GEIL. Unique morphology of poly(azomethine ethers) sheared in the liquid crystalline state. Acta Polym., 48, 149 (1997).
DEPPISCH, C. L., J. K. LIU, J. K. SHANG, and J. ECONOMY. Processing and mechanical properties of AlB2 flake reinforced Al alloy composites. Mater. Sci. Engr. A, 225, 153 (1997).
DHINOJWALA, A. and S. GRANICK. Micron-gap rheo-optics with parallel plates. J. Chem. Phys., 107, 8664 (1997).
DHINOJWALA, A. and S. GRANICK. Relaxation time of confined aqueous films under shear. J. Amer. Chem. Soc., 119, 241 (1997).
DHINOJWALA, A. and S. GRANICK. Surface forces in the tapping mode: permeability and hydrodynamic thickness of adsorbed polymer brushes. Macromolecules, 30, 1079 (1997).
DOUGLAS, J. F., H. M. SCHNEIDER, P. FRANTZ, R. LIPMAN, and S. GRANICK. Origins and characterization of conformational heterogeneity in adsorbed polymers. J. Phys. Cond. Matter, 9, 7699 (1997).
ECONOMY, J., D. FRICH, and L. A. SCHNEGGENBURGER. LCP polyesters vs thermosetting polyesters: a paradigm for research in the 21st century. Macromol. Symp., 118, 11-22 (1997).
FRICH, D and J. ECONOMY. Thermally stable liquid crystalline thermosets based on aromatic copolyesters: preparation and properties. J. Polym. Sci. A, Chem. Ed., 35:6, 1061 (1997).
FRICH, D. and J. ECONOMY. Optimizing adhesion properties of thermosetting aromatic copolyesters. Polym. Engr. Sci., 37:3 (1997).
FRICH, D., C. GORANOV, L. A. SCHNEGGENBURGER, and J. ECONOMY. Novel high temperature aromatic copolyester thermosets: synthesis, characterization and physical properties. Macromolecules, 29, 7734 (1997).
FUCHS, M. and K. S. SCHWEIZER. Mode-coupling theory of slow dynamics of polymeric liquids: fractal macromolecular architectures. J. Chem. Phys., 106, 347 (1997).
FUCHS, M. and K. S. SCHWEIZER. Polymer mode-coupling theory of finite-size-fluctuation effects in entangled solutions, melts and gels. I. General formulation and predictions. Macromolecules, 30, 5133 (1997).
FUCHS, M. and K. S. SCHWEIZER. Polymer mode-coupling theory of finite-size-fluctuation effects in entangled solutions, melts and gels. II. Comparison with experiments. Macromolecules 30, 5156 (1997).
GUENZA, M. and K. S. SCHWEIZER. Fluctuation effects in diblock copolymer fluids: comparison of theories and experiment. J. Chem. Phys., 106, 7391 (1997).
GUENZA, M. and K. S. SCHWEIZER. Local and microdomain scale fluctuation effects in block copolymer solutions. Macromolecules, 30, 4205 (1997).
GUENZA, M., H. TANG, and K. S. SCHWEIZER. Suppression of entangled diblock copolymer diffusion at and below the order-disorder transition. Macromol.-Commun., 30, 3423 (1997).
HUGGINS, K. E., S. SON, and S. I. STUPP. Two-dimensional supramolecular assemblies of polydiacetylenes. I. Synthesis, structure and third order nonlinear optical properties. Macromolecules, 30:18, 5305 (1997).
LI, L. S. and S. I. STUPP. Two-dimensional supramolecular assemblies of polydiacetylenes. II. Morphology, structure and chromic transitions. Macromolecules, 30:18, 5313 (1997).
LIU, J. and P. H. GEIL. Crystal structure and morphology of poly(ethylene terephthalate) single crystals prepared by melt polymerization. J. Macromol. Sci. (Phys.), B36, 61 (1997).
LIU, J. and P. H. GEIL. Electron diffraction and computer modeling studies of the crystal structure of poly(butylene terephthalate) a-form single crystals. J. Macromol. Sci. (Phys.), B36, 263 (1997).
LIU, J. and P. H. GEIL. Electron diffraction and computer modeling of poly(naphthalic anhydride) crystal structure. J. Polym. Sci., Polym. Phys., B35, 1575 (1997).
LIU, J., B. L. YUAN, P. H. GEIL, and D. L. DORSET. Chain conformation and molecular packing in poly(p-oxybenzoate) single crystals at ambient temperature. Polymer, 38, 6031 (1997).
LUCERO, A., F. RYBNIKAR, T. C. LONG, J. LIU, P. H. GEIL, B. WALL, and L. KOENIG. Lamellar macrocrystals of nascent liquid crystal polymers. Polymer, 38, 4387 (1997).
LUENGO, G., J. N. ISRAELACHVILI, A. DHINOJWALA, and S. GRANICK. Generalized effects in confined fluids: new friction map for boundary lubrication. Wear, 205, 246 (1997).
RADZILOWSKI, L. H., B. O. CARRAGHER, and S. I. STUPP. Three-dimensional self assembly of rodcoil copolymer nanostructures. Macromolecules, 30:7, 2110 (1997).
RYBNIKAR, F. and P. H. GEIL. Morphology, crystal structure and orientation of poly(p-oxybenzoate) on mica. J. Polym. Sci., Polym. Phys., B35, 1807 (1997).
SCHNEGGENBURGER, L. A., P. OSENAR, and J. ECONOMY. Direct evidence of sequence ordering of random semi-crystalline copolyesters during high temperature annealing. Macromolecules, 30, 3754-3758 (1997).
SCHWEIZER, K. S. and J. G. CURRO. Integral equation theories of the structure, thermodynamics and phase transitions of polymer fluids. Advances in Chemical Physics, 98, chapt. 1 (1997).
SCHWEIZER, K. S., M. FUCHS, G. SZAMEL, M. GUENZA, and H. TANG. Mode-coupling theory of the slow dynamics of entangled macromolecular fluids. Macromolec. Theory Simulat., 6, 1037 (1997).
SHI, F. and J. ECONOMY. Aliphatic/aromatic copolyester thermoset adhesives: synthesis and characterization. Polym. Engr. Sci., 37, 549 (1997).
SING, C. and K. S. SCHWEIZER. Coupled enthalpic-packing effects on the miscibility of conformationally asymmetric polymer blends. Macromolecules, 30, 1490 (1997).
SOGA, I., A. DHINOJWALA, Y.-K. CHO, and S. GRANICK. Direct measurement of the molecular orientation of confined molecules under shear. Dynamics in Small Confining Systems (Drake, Troian, Kopelman, Klafter, eds.) Mater. Res. Soc., 89 (1997).
STUPP, S. I., V. LE BONHEUR, K. WALKER, L. S. LI, K. HUGGINS, M. KESER, and A. AMSTUTZ. Supramolecular materials: self organized nanostructures. Science, 276, 384 (1997).
STUPP, S. I. The challenge of assembling molecules into materials. Macromol. Symp., 117, 1 (1997).
STUPP, S. I. and P. V. BRAUN. Molecular manipulation of microstructures: biomaterials, ceramics, and semiconductors. Science, 277, 1242 (1997).
SUKHISHVILI, A. and S. GRANICK. Formation and characterization of covalently bound polyelectrolyte brushes. Langmuir, 13, 4935 (1997)
TOHVER, V., P. V. BRAUN, M. U. PRALLE, and S. I. STUPP. Counterion effects in liquid crystal templating of nanostructured CdS. Chem. Mater., 9, 1495 (1997).
Processing
LEE, S.-J., W. M. KRIVEN, J.-H. PARK, and Y.-S. YOON. Bonding behavior of a Cu/CuO thick film on a low-firing ceramic substrate. J. Mater. Res., 12, 2411-2418 (1997).
YANG, J. C., M. YEADON, D. OLYNICK, and J. M. GIBSON. Anomalous desorption of copper oxide observed by in-situ transmission electron microscopy. Micros. Microanal., 3, 121 (1997).
YEADON, M., J. C. YANG, M. GHALY, D. OLYNICK, ET AL. In-situ observations of classical grain growth mechanisms during sintering of copper nanoparticles on (001) copper. Appl. Phys. Lett., 71, 1631 (1997).
Radiation Damage in Metals
SIMEONE, D., O. Hablot, V. Micalet, P. Bellon, and Y. Serruys. Contribution of recoil atoms to irradiation damage in absorber materials. J. Nucl. Mater., 246, 206-214 (1997).
Structural Ceramics
HUANG, C. M., D. ZHU, C. X. DONG, W. M. KRIVEN, R. LOH, and J. HUANG. Carbon-coated glass fiber reinforced cement composites: I. Fiber push-out and interfacial properties. J. Am. Ceram. Soc., 80:9, 2326-2332 (1997).
HUANG, C. M., C. Y. YUH, M., FAROOQUE, D. ZHU, Y. XU, and W. M. KRIVEN. Properties and microstructure of MoSi2 - ߢ SiAlON particulate ceramic composites. Amer. Ceram. Soc., 80:11, 2837-2843 (1997).
KELLY, W. H., A. N. PALAZOTTO, R. RUH, J. K. HEUER, and A. ZANGVIL. Thermal shock resistance of mullite and mullite-ZrO2-SiC-whisker composites. Ceram. Engr. Sci. Proc., 18:3, 195-203 (1997).
KIM, S. and W. M. KRIVEN. Preparation, microstructure and mechanical properties of silicon carbide-dysprosia composites. J. Amer. Ceram. Soc., 80:12, 2997-3008 (1997).
KRIVEN, W. M., D. ZHU, M. H. JILAVI, K. R. WEBER, B. CHO, J. FELTEN, and P. C. NORDINE. Synthesis and microstructure of mullite fibers grown from deeply undercooled melts. Ceramic Microstructures '96 (Tomsia and Glaeser, eds.; Plenum Pub.) 173-180 (1997).
KUO, D. H. and W. M. KRIVEN. A strong and damage-tolerant oxide laminate. J. Amer. Ceram. Soc., 80, 2421-2424 (1997).
KUO, D. H. and W. M. KRIVEN. Microstructure and mechanical evaluation of yttrium phosphate-containing and lanthanum phosphate-containing zirconia laminates. Ceram. Engr. Proc., 18, 129-136 (1997).
KUO, D. H., W. M. KRIVEN, and T. J. MACKIN. Control of interfacial properties through fiber coatings: monazite coatings in oxide/oxide composites. J. Amer. Ceram. Soc., 80:12, 2987-2996 (1997).
MULLNER, P. and W. M. KRIVEN. On the rod deformation twinning in domain reorganization and reorientation in ferroelastic crystals. J. Mater. Res., 7, 1771-1776 (1997).
XU, Y., A. ZANGVIL, and A. KERBER. SiC nanoparticle-reinforced Al2O3 matrix composites: role of intra- and intergranular particles. J. Euro. Ceram. Soc., 17:7, 921-28 (1997).
ZHU, D., H. CHUNG, M. JILAVI, W. M. KRIVEN, and J. MAZUMDER. Microstructure and interfacial properties of a laser ablation coated, fiber-reinforced ceramic composite. Ceram. Engr. Proc., 18, 105-112 (1997).
ZHU, D., M. H. JILAVI, and W. M. KRIVEN. Synthesis and characterization of mullite and YAG fibers grown from deeply undercooled melts. Ceram. Engr. Process., 18, 31-38 (1997).
Superconductivity
LEWIS, J. A., A. C. READ, and T. K. HOLMSTROM. Transport properties of magnetic field/liquid assisted texturing of YBa2Cu3O7-x tape-cast films. IEEE Trans. Appl. Supercond., 7:2, 1440-1442 (1997).
Thin-Film Electronics
ALLEN, L. H. and S. L. LAI. MEMS based scanning calorimetry for thermodynamic properties of nanostructures. Microscale Thermophys. Engr., 2, 40 (1997).
BERGSTROM, D. B., I. PETROV, L. H. ALLEN, and J. E. GREENE. Aluminide formation in polycrystalline Al/W metal/barrier thin-film bilayers: reaction paths and kinetics. J. Appl. Phys., 82, 201 (1997).
CHEY, S. J. and D. G. CAHILL. Surface defects created by low energy (20-240 eV) ion bombardment of Ge(001). Surf. Sci., 380, 377 (1997).
HAMDANI, F., A. BOTCHKAREV, W. KIM, H. MORKOC, ET AL. Optical properties of AgN grown on ZnO by reactive MBE. Appl. Phys. Lett., 70, 467 (1997).
KARR, B. W., I. PETROV, D. G. CAHILL, and J. E. GREENE. Morphology of epitaxial TiN(001) grown by magnetron sputtering. Appl. Phys. Lett., 70, 1703 (1997).
KIM, H., G. GLASS, T. SPILA, N. TAYLOR, S. Y. PARK, J. R. ABELSON, and J. E. GREENE. Si(001):B gas-source molecular-beam epitaxy: boron surface segregation and its effect on film growth kinetics. J. Appl. Phys., 82:5, 2288-2297 (1997).
KIM, H., N. TAYLOR, T. SPILA, G. GLASS, S. Y. PARK, J. E. GREENE, and J. R. ABELSON. Structure of the Si(011) 16x2 surface and hydrogen desorption kinetics investigated using temperature programmed desorption. Surf. Sci., 380:2-3, L496 (1997).
KIM, W., M. YEADON, A. E. BOTCHKAREV, S. N. MOHAMMED, ET AL. Surface roughness of nitrided (0001) Al2O3 and AlN epilayers grown on (0001) Al2O3 by reactive MBE. J. Vac. Sci. Technol., B15, 921 (1997).
KUO, H., J. KUO, Y. WANG, C. LIN, H. CHEN, and G. E. STILLMAN. Determination of the band offset of GaInP-GaAs and AlInP-GaAs quantum wells by optical spectroscopy. J. Electron. Mater., 26:8, 944-948 (1997).
LAI, S. L. and L. H. ALLEN. Thin-film nanocalorimetry for nano-scaled systems. Electrochem. Soc. Proc., 97-11, 59 (1997).
LAI, S. L., G. RAMANATH, P. INFANTE, and L. H. ALLEN. Heat capacity measurements of Sn nanostructures using a thin-film differential scanning calorimeter with 0.2 nJ sensitivity. Appl. Phys. Lett., 70, 43 (1997).
LEE, S.-M. and D. G. CAHILL. Heat transport in thin dielectric films. J. Appl. Phys., 81, 2590 (1997).
LEE, S.-M. and D. G. CAHILL. Thermal conductivity of Si-Ge superlattices. Appl. Phys. Lett., 70, 2957 (1997).
LU, Q., M. R. SARDELA, N. TAYLOR, G. GLASS, T. BRAMBLETT, T. SPILA, J. R. ABELSON, and J. E. GREENE. B incorporation and hole transport in fully-strained heteroepitaxial Si1-xGex grown on Si(001) by gas-source MBE from Si2H6, Ge2H6, and B2H6. J. Cryst. Growth, 179:1-2, 97 (1997).
C by dc reactive magnetron sputtering. Appl. Phys. Lett., 70:2, 226 (1997).
McCORMICK, C. S., C. E. WEBER, J. R. ABELSON, G. A. DAVIS, R. E. WEISS, and V. AEBI. Low-temperature fabrication of amorphous silicon thin film transistors by dc reactive magnetron sputtering. J. Vac. Sci. Technol., A15:5, 2770 (1997).
NELSON, A. J., G. BERRY, A. ROCKETT, D. K. SHUH, J. A. CARLISLE, D. G. SUTHERLAND, and L. J. TERMINELLO. Observation of core-level binding energy shifts between (100) surface and bulk atoms of epitaxial CuInSe2. J. Appl. Phys., 70:14, 1873-1875 (1997).
NURUDDIN, A. and J. R. ABELSON. Does a dipole layer at the p-i interface reduce the built-in voltage of amorphous silicon p-i-n solar cells? Appl. Phys. Lett., 71:19 (1997).
PARK, D.-G., Z. CHEN, D. M. DIATEZUA, Z. WANG, A. ROCKETT, H. MORKOC, and S. A. ALTEROVITZ. Thermal stability of Si3N4/Si/GaAs interfaces. Appl. Phys. Lett., 70:10, 1263-1265 (1997).
SCHROEDER, D. and A. A. ROCKETT. Electronic effects of sodium in epitaxial CuIn1-xGaxSe2. J. Appl. Phys., 82:10, 4982-4985 (1997).
SENGUPTA, D. K., W. FANG, J. I. MALIN, A. CURTIS, T. HORTON, H. C. KUO, D. TURNBULL, C. H. LIN, K. C. HSIEH, S. L. CHUANG, I. ADESIDA, M. FENG, S. G. BISHOP, G. E. STILLMAN, J. M. GIBSON, H. CHEN, J. MAZUMDER, and H. C. LIU. Effects of rapid thermal annealing on the device characteristics of quantum well infrared photodetectors. J. Electron. Mater., 26:1, 43-51 (1997).
SENGUPTA, D. K., T. HORTON, W. FANG, A. CURTIS, J. LI, S. L. CHUANG, H. CHEN, M. FENG, G. E. STILLMAN, A. KAR, J. MAZUMDER, L. LI, and H. C. LIU. Redshifting of a bound-to-continuum GaAs/AlGaAs quantum-well infrared photodetector response via laser annealing. Appl. Phys. Lett., 70:26, 3573-3575 (1997).
SENGUPTA, D. K., W. FANG, J. I. MALIN, J. LI, T. HORTON, A. P. CURTIS, K. C. HSIEH, S. L. CHUANG, H. CHEN, M. FENG, G. E. STILLMAN, L. LI, H. C. LIU, K. M. S. V. BANDARA, S. D. GUNAPALA, D. GUNAPALA, and W. I. WANG. GaAs/AlGaAs quantum-well infrared photodetector on GaAs-on-Si substrates. Appl. Phys. Lett. 71:1, 78-80 (1997).
SENGUPTA, D. K., S. L. JACKSON, W. FANG, J. I. MALIN, T. U. HORTON, A. P. CURTIS, H. C. KUO, A. MOY, J. MILLER, K. C. HSIEH, K. Y. CHENG, H. CHEN, I. ADESIDA, S. L. CHUANG, M. FENG, and G. R. STILLMAN. Growth and characterization of InP/InGaAs p-quantum well infrared photodetector with extremely thin quantum wells. J. Electron. Mater., 26:12, 1382-1388(1997).
SENGUPTA, D. K., S. L. JACKSON, W. FANG, J. I. MALIN, T. U. HORTON, Q. HARTMAN, A. P. CURTIS, H. C. KUO, S. THOMAS, J. MILLER, K. C. HSIEH, I. ADESIDA, S. L. CHUANG, M. FENG, G. E. STILLMAN, Y. C. CHANG, H. CHEN, J. M. GIBSON, J. MAZUMDER, L. LI, and H. C. LIU. Growth and characterization of n-type InP/InGaAs quantum well infrared photodetectors for response at 8.93 mm. J. Electron. Mater., 26:12, 1376-1381 (1997).
THEIL, J. A., E. KUSANO, and A. ROCKETT. Vanadium reactive magnetron sputtering in mixed Ar/O2 discharges. Thin Solid Films, 298:1, 122-129 (1997).
VON KEUDELL, A. and J. R. ABELSON. Evidence for atomic hydrogen insertion into strained Si-Si bonds in the a-Si:H sub-surface from in-situ IR spectroscopy. Appl. Phys. Lett., 71:26 (1997).
WANG, Z., G. RAMANATH, L. H. ALLEN, A. ROCKETT, J. P. DOYLE, and B. G. SVENSSON. Kinetics of thin film reactions of Cu/a-Ge bilayers. J. Appl. Phys., 82:7, 3281-3286 (1997).
YEADON, M., F. HAMDANI, G. Y. XU, A. SALVADOR, ET AL. Surface morphology and optical characterization of GaN grown on a-Al2O3 (0001) by radio frequency assisted molecular beam epitaxy. Appl. Phys. Lett., 70, 3023 (1997).
Cementitious Materials
AI, H. and J. F. YOUNG. Mechanism of shrinkage reduction using a chemical admixture. Proc. 10th Int. Congr. on the Chem. of Cements. Paper no. 3iii018. Inform Trycket AB. (Gothenburg, Sweden, Jun. 1997)
BAKHAREV, T., A. R. BROUGH, R. J. KIRKPATRICK, L. J. STRUBLE, and J. F. YOUNG. Chemical evolution of cementitious materials with high proportion of fly ash and slag in mechanisms of chemical degradation of cement-based systems. Mater. Res. Soc. Symp. Proc., Mechanisms of Chem. Degradation of Cement-based Syst. (Scrivener and Young, eds.) (Chapman and Hall, E & FN Spon) 307-314 (1997).
BAKHAREV, T., A. R. BROUGH, R. J. KIRKPATRICK, L. J. STRUBLE, J. F. YOUNG, R. OLSON, P. D. TENNIS, D. BONEN, H. JENNINGS, T. MASON, S. SAHU, and S. DIAMOND. Durability of cement stabilized low-level wastes in mechanisms of chemical degradation of cement-based systems. Mater. Res. Soc. Symp. Proc., Mechanisms of Chem. Degradation of Cement-based Syst. (Scrivener and Young, eds.) (Chapman and Hall, E & FN Spon) 350-357 (1997).
MATSUYAMA, H., J. A. LEWIS, and J. F. YOUNG. Dispersion mechanisms in processing of cement pastes. 2nd Ann. RILEM Conf. (Dijon, France, 1997).
SCRIVNER, K. L. and J. F. YOUNG (eds.). Mechanisms of Chemical Degradation of Cement-based Systems. Mater. Res. Soc. Symp. Proc. (Chapman and Hall, E & FN Spon, 1997).
Ceramics and Glassy Solids
GUILBERT, E., F. LI, J. D. BASS and J. KIEFFER. Complex mechanical response and pore structure of silica gels. Glass and Opt. Mater. Div., Amer. Ceram. Soc. Fall Mtg. (Williamsburg, Va., Oct. 1997).
KIEFFER, J. Structural assembly in glass-forming melts. Amer. Crystallog. Assn. Ann. Mtg. (St. Louis, Mo., Jul. 1997).
KIEFFER, J., R. E. YOUNGMAN, and J. D. BASS. Brillouin light scattering as a structural probe for inorganic glasses and melts. 30th Amer. Chem. Soc. Great Lakes Regional Mtg. (Chicago, Ill., May 1997).
REARDON, B. J., J. KIEFFER, J. E. MASNIK, and J. D. BASS. Relaxation processes in borate melts. Proc. 2nd Int. Conf. on Borate Glasses, Cryst., and Melts (Soc. of Glass Technol.) (Wright, Feller, and Hannon, eds.) 349-356 (1997).
YOUNGMAN, R. E., J. KIEFFER and J. D. BASS. Brillouin scattering studies of strong glass formers: B2O3 and GeO2 glasses and melts. 99th Ann. Mtg., Amer. Ceram. Soc. (Cincinnati, Ohio, May 1997).
YOUNGMAN, R. E., J. KIEFFER, and J. D. BASS. Brillouin light scattering studies of strong glass formers: boron oxide, germanium oxide, and silicon dioxide. 30th Amer. Chem. Soc. Great Lakes Regional Mtg. (Chicago, Ill., May 1997).
YOUNGMAN, R. E., J. KIEFFER, and J. D. BASS. Extended-range structural integrity in network glasses and melts. 14th Univ. Conf. on Glass Sci. (Bethlehem, Pa., Jun. 1997).
YOUNGMAN, R. E., J. KIEFFER, B. O'NEIL, and J. D. BASS. Pressure and temperature effects on the structure and glass transition behavior of boron oxide by Brillouin light scattering. Glass and Opt. Mater. Div., Amer. Ceram. Soc. Fall Mtg. (Williamsburg, Va., Oct. 1997).
YOUNGMAN, R. E., J. KIEFFER, and J. D. BASS. Structural developments upon glass formation. Glass and Opt. Mater. Div., Amer. Ceram. Soc. Fall Mtg. (Williamsburg, Va., Oct. 1997).
Computer Simulations of Materials
GAYLORD, R. J. Cellular automata modeling with Mathematica. Int. Conf. on Complex Syst. (Nashua, N. H., 1997).
JOHNSON, D. D. and W. A. SHELTON. Electronic origins for the short-range order and energetics in Ni-Fe INVAR alloys. Invited paper, The INVAR Effect--A Centennial Symp. (Wittenauer, ed.) (Minerals, Metals, and Materials Soc.) 63 (1997).
KIEFFER, J. Time-space-correlations of cation motion in alkali silicates. Mater. Res. Soc. Symp. Proc., 455, 331-336 (1997).
KIEFFER, J. and B. J. REARDON. Manifestations of chaos in atomic trajectories. 3rd Int. Discussion Mtg. on Relaxations in Complex Syst. (Vigo, Spain, Jun./Jul. 1997).
REARDON, B. J. and J. KIEFFER. Characterization of phase stability and transitions using normal mode analysis. 99th Ann. Mtg., Amer. Ceram. Soc. (Cincinnati, Ohio, May 1997).
REARDON, B. J. and J. KIEFFER. The role of chaos in molecular dynamics. Amer. Crystallog. Assn. Ann. Mtg. (St. Louis, Mo., Jul. 1997).
Electrical Ceramics
GOSULA, V. and H. CHEN. High-temperature study of PMN by x-ray diffraction. Int. Symp. on Dielectr. Ceram.: Process., Properties and Appl., ACS Mtg. (1997).
GOSULA, V., H. CHEN, S. TESLIC, and T. EGAMI. Ordered structure in lead magnoniobate (PMN) by resonant x-ray scattering. Mater. Res. Soc. Symp. Proc., Appl. of Synchrotron Radiation to Mater. Sci. III (San Francisco, Calif., 1997).
LEE, S. W., P. P. TSAI, and H. CHEN. Thin and thick film gas sensors. 99th Ann. Mtg., Amer. Ceram. Soc. (Cincinnati, Ohio, May 1997).
LIN, C. H., B. M. YEN, H. CHEN, T. B. WU, H. C. KUO, and G. E. STILLMAN. Characterization of highly textured PZT thin films grown on LaNiO3 coated Si substrate. Mater. Res. Soc. Fall Mtg. (Dec. 1997