A cohesive database for predicting long-term corrosion/erosion of steel exposed
to flowing liquid lead/lead bismuth eutectic. JANA JENSEN
(Brigham Young University
- Idaho, Rexburg, ID, 83440)
SOLI KHERICHA (Idaho National Laboratory, Idaho
Falls, ID, 83415)
In connection with:
NING LI and HUIDAN YU(Los Alamos National Laboratory, Los Alamos,
NM 87545). Liquid lead or lead-bismuth eutectic (Pb/LBE) is a good
candidate for the coolant in accelerator-driven systems or advanced
nuclear reactors of the future. However, corrosion of the container
and structural materials that house the Pb/LBE presents a critical
challenge. Experimentally an active oxygen control technique has
been developed to mitigate corrosion and contamination in the liquid.
This technique was developed and researched in many laboratories
and under numerous conditions. In this work, the wide-ranging experimental
test results reported by groups from around the world were collected
and a cohesive database was created. The database categorizes and
compares the type of structural material, oxygen concentration, velocity
of Pb/LBE, characterizations of the different loops, and oxide layer
thickness/weight loss, etc. Through this database, an analysis based
on kinetic modeling of the oxidation and corrosion of steels in Pb/LBE
was preformed. Tedmon’s model of oxidation was used as an oxide growth
model. In connection with the completed database, this model was
used to find the parabolic growth constant(Kp) and the scale removal
rate(Kr) for many of the collected experiments. For instance, the
Kp for Idaho National Laboratory’s loop at 700oC
with Fe-3.82%Si sample was calculated to be 8.97E-17 m2/s. Under the same conditions Kr was 7.47E-12 m/s. Using these
constants it was calculated that the oxide thickness of Fe-3.82%
under the same conditions would stabilize to be 6.0E-6 m. Utilizing
the data sets with different loop conditions, oxidation and corrosion
rates will be extracted and further research will be done to predict
long-term corrosion rates which are very difficult to measure in
the short to medium duration tests. Having this complete and defined
database will assist the finding and development of the optimal steel
and operating conditions based on the short to mid-term tests; long-term
tests and verification will still be needed.
A Novel Approach to Estimating Thermal Conductivity. GORDON
WU (University of California, Berkeley, Berkeley, CA, 94720)
TIM KNEAFSEY (Lawrence Berkeley
National Laboratory, Berkley, CA, 94720)
Scientists at Lawrence
Berkeley National Laboratory (LBNL) are currently researching natural
gas recovery from gas hydrates in hopes that this will one day become
a viable source of energy. Natural gas hydrates are water crystals
located below permafrost and submarine environments that contain
methane gas. Knowledge of heat flow through the hydrate-bearing reservoir
must be understood and thermal conductivity is a fundamental property
of a material that indicates its ability to conduct heat. The technique
for estimating thermal conductivity calls for applying a temperature
changes and using thermocouples to accurately measure the rate of
temperature change. The thermal data were analyzed using Microsoft
Excel and iTOUGH2. The program iTOUGH2 computes a best-fit to our
measured data by optimizing the thermal conductivity through automatic
model calibration. ITOUGH2 estimates the thermal conductivity based
on previous output values and given parameters. The four materials
used were dry sand, polyvinyl chloride (PVC), high density polyethylene
(HDPE) and Pyrex borosilicate glass, and were chosen because they
have thermal conductivities close to that of hydrate bearing sand
(2.7 W/m K). Good matches were obtained between the simulations and
the measured data showing the validity of the technique. It is important
to realize that the substances that we were using can vary in thermal
conductivity depending on the temperature, the porosity of the particular
substance, and the composition of the sample. Now that the technique
is validated, it can be used in other experiments to measure thermal
conductivities.
Atomic Layer Deposition of Tin (IV) Oxide and Indium Tin Oxide Using Tetrakis(Dimethylamino)Tin
Precursor. DAVID
BAKER (University of Illinois
at Urbana Champaign, Urbana, IL, 61802) GREGORY KRUMDICK (Argonne National Laboratory, Argonne, IL, 60439)
Thin films of tin
oxide were deposited on silicon wafers (001) and glass by Atomic
Layer Deposition (ALD) using alternating pulses of Tetrakis(Dimethylamino)Tin
and an oxidizing precursor. Doping tin oxide films with various reagents,
such as indium, can create smooth, optically transparent and conductive
coatings with applications in solar cell, gas sensor, and flat panel
display technologies. Using deposition temperatures between 100oC - 400oC, and exposure times ranging from 0.5 to 8 seconds, growth of
a film was evident on Al2O3 coated substrates. For the silicon and glass substrates, measurements
from the spectroscopic ellipsometer showed the thickness of the film
increased with temperature and increased linearly with the number
of cycles (maximum of 1.5 Ĺ per cycle) during the ALD growth. At
lower temperatures, extending the exposure times of each precursor
demonstrated a self-limiting reaction. Growth at higher temperatures
did not demonstrate a self-limiting reaction. This precursor was
also used to create Indium Tin Oxide (ITO) films also by ALD. As
evident from 4-point probe resistivity measurements, tin oxide and
ITO films are excellent conductors with good optical transmittance.
Characterization of the films was furthered by x-ray diffraction
(XRD), x-ray photoelectron spectroscopy (XPS), x-ray florescence
(XRF), and scanning electron microscope (SEM). Tetrakis(Dimethylamino)
tin precursor demonstrated consistent ALD growth on glass and silicon
surfaces coated with Al2O3.
Characterization of Nano-particles in Mesophase Pitch Derived Graphite Foams. JENNIFER MUELLER (Virginia Polytechnic Institute and
State University, Blacksburg, VA, 24060) JAMES KLETT (Oak Ridge National
Laboratory, Oak Ridge, TN, 37831)
The addition of
nano-particles to a raw material can significantly alter the structure
and therefore properties of a material. A characterization study
was conducted to explore the effects of nano-particle additions on
graphite foam, a material that exhibits very high thermal conductivity
and low density. Carbon nano-particles were added to mesophase pitch
in varying amounts and processed to create graphite foam. Image analysis
was conducted on each sample by using an optical microscope, Scanning
Electron Microscope (SEM), and Transmission Electron Microscope (TEM).
Other analyses included density measurements, compression tests,
permeability tests, and flash diffusivity tests. Results showed that
there were overall trends of decreasing density, thermal conductivity,
and strength with an increasing amount of carbon nano-particles,
but the permeability increased. Through optical image analysis, it
was determined that the ligament size of the graphitic matrix decreased
and that there was a significant disruption of graphitic plane alignment
with greater additions of carbon nano-particles. Additionally, it
was seen with the SEM that the number and size of open pores increased
with an increasing amount of carbon nano-particles. Overall, the
decreased ligament size and disruption of graphitic alignment explains
the decreased strength and thermal conductivity, respectively. Also,
the addition of the nano-particles increased the open porosity and,
therefore, increased the permeability of the foam. As a result, the
graphite foams characterized through this study are suitable for
applications where higher permeability foams are desired. Since the
mixture with the greatest amount of nano-particles had the highest
permeability, a further study should be conducted to determine what
mixture results in the maximum permeability of the graphite foam
without a significant loss in thermal and mechanical properties.
CHEMICAL AND PHYSICAL RESPONSE OF NB-W-CR BASED ALLOYS TO HIGH TEMPERATURE
OXIDATION*. BRENDA MACHADO (University of Texas at El Paso, El
Paso, TX, 79968) KEN NATESAN (Argonne National Laboratory, Argonne,
IL, 60439)
Nickel-based superalloys
are the only high-temperature metallic materials known at this time
that can withstand temperatures up to 1000şC. The binary systems
have not accomplished what is needed for the high-temperature industry.
Therefore, in order to develop an ultra-high temperature metallic
system for gas turbines, aircraft engines, and aerospace materials,
new ternary alloy systems are being explored. Using Nb-W-Cr compositions
with addition of Y, the oxidation performance over 24 hours and the
microstructural characteristics of the alloy were evaluated. Oxidation
curves have been plotted between weight gain per unit area as a function
of time for each temperature. SEM (Scanning Electron Microscope)
has been used to characterize the surface of the alloys and EDS (Energy
Dispersive Spectrometer) to identify the elements and oxides. In
the temperature range from 900 to 1300°C, Nb-W-Cr-Y shows a difference
in microstructural characteristics and oxidation resistance. The
alloy turns into complete powder at 700°C, 800°C and 1400°C, an unexpected
result. We were able to determine that the addition of Y lowered
the temperature range for formation of powder. Also it was found
that Cr in the alloy was good because it produces higher oxidation
resistance than for an alloy with a lower percentage of Cr in it.
This alloy must compete with nickel-based superalloys. The investigation
performed in this summer provides the basis for further work in the
evaluation of the oxidation resistance of the alloys from Nb-W-Cr.
Comparison of Surface Morphologies of Commercial Solar Cell Silicon Wafers
Measured by NREL-Reflectometer and Profilometer Technique. WILLIAM
JOHNSTON (Texas A&M University-Commerce, Commerce, TX, 75429) BHUSHAN SOPORI (National Renewable Energy Laboratory, Golden,
CO, 89401)
The production
of high quality silicon solar cells requires that good quality control
be in place at production facilities. The National Renewable Energy
Laboratory (NREL) has developed a reflectometer that can quickly
measure many solar cell parameters. To increase the applications
of the reflectometer in the solar cell industry research was conducted
to show that the reflectometer could characterize the roughness present
on the surface of a silicon wafer. For comparison silicon wafers
were characterized by the reflectometer and profilometer technique.
A silicon wafer was characterized in a rough sawn state and after
polishing to understand how the reflectometer measurements and profilometry
measurements change with decreasing surface roughness. As the silicon
wafer was polished the specular reflection off of the surface increased
while the roughness measured by profilometer technique decreased.
Also seen with increasing polishing time was a decrease in diffuse
reflection of short, <500 nm, wavelength light. It was shown that
the reflectometer and profilometer could both measure the presence
of roughness down to 10 micrometers in width. The reflectometer is
shown to also be capable of measuring features of much smaller width.
The reflectometer has been shown to be able to rapidly characterize
the entire surface of a silicon wafer making it a valuable tool to
the silicon solar cell industry.
Composition of Stainless Steel Slurries for Enhanced Structural Support of
the TuffCell. LAURA JANE ELGASS (College of DuPage, Glen Ellyn,
IL, 60517) J. DAVID CARTER (Argonne National Laboratory, Argonne,
IL, 60439)
The "TuffCell" is
a bipolar plate-supported solid oxide fuel cell that produces electrical
power by the galvanic combination of oxygen with hydrogen or other
fuel. The SOFC anode support must be both conducting and porous.
Porosity is required to ensure that hydrogen gas can flow through
the anode support. SOFC anode supports have traditionally been composed
of nickel, but the use of stainless steel as a support while also
using a thinner anode will provide increased structural integrity.
The process for building the support layer starts with making a stainless
steel slurry. The slurry composition includes stainless steel powder,
binder, plasticizer, solvent, and in some cases pore former. The
slurry is allowed to mix thoroughly and is then made into a tape
cast using a doctor blade. The tape cast is dried and then placed
into the dilatometer for twenty hours where it is exposed to air,
nitrogen, and hydrogen to sinter. The weight percent of each slurry
component must be such that the slurry meets certain criteria when
cast and sintered. In casting, these criteria include an even cast
(i.e. the stainless steel cannot separate from the other components
during the cast), a strong and flexible dried cast, and a slightly
grainy texture. In sintering, the stainless steel layer must not
shrink more than the other layers of the cell and must also be porous,
with pores approximately 20 microns in diameter. An even cast is
the result of optimal slurry viscosity for the given components.
Modification of flexibility and strength is accomplished by varying
the binder to plasticizer ratio. Porosity can be achieved with a
large stainless steel powder particle size and no pore former, or
with smaller particles plus pore former (this method warrants varying
the volume ratios of stainless steel and pore former to find the
optimal porosity). In addition to finding the optimal weight percents
of each of the slurry components, it is necessary to determine which
plasticizer/binder/solvent trio best casts, sinters, and interacts
with the other components of the cell. When xylene/butanol is used
for a solvent, compositions with a combination of large stainless
steel mesh size and smaller stainless steel mesh size in conjunction
with 12% solvent and a plasticizer to binder ratio of 1:5 or 1:7
have proved most successful.
Controlled Assembly of Protein-mediated Lipid Multi-bilayers. CONSTANCE ROCO (University
of Virginia, Charlottesville, VA, 22904) GABRIEL MONTAŃO (Los Alamos National Laboratory, Los Alamos, NM, 87545)
Protein-mediated
multilamellar lipid assemblies were created using biotin-streptavadin
conjugation. We are interested in using these assemblies as a platform
for investigating membranes and membrane-protein properties, as well
as towards understanding the relationship between structure and function
in biological multilamellar assemblies, such as the neuron insulating
myelin sheath. Successive lipid bilayers, containing a fraction of
biotinylated lipids, are held together using an intermediate layer
of streptavadin. Control over lipid bilayer assembly was determined
using atomic force microscopy and spectroscopic ellipsometry. Lateral
fluidity of individual layers was characterized by fluorescence recovery
after photobleaching (FRAP). Three successive bilayers, with each
successive bilayer exhibiting fluidity, have been created. We are
currently determining effects of protein concentration and numbers
of bilayers on fluidity by comparing rates of diffusion under the
various conditions. There are many other properties, such as the
substrate and lipid composition, that can affect membrane interactions
that can be altered and studied in future work. The investigation
of these biomimetic assemblies illustrates how guided molecular self-assembling
at the nanometer length scale can improve our understanding of complex
biological systems.
Crystallographic Descriptors of a Metal Surface along a Fracture Line. RYAN GLAMM (Ohio State University, Columbus, OH, 43210)
BARBARA K. LOGRASSO (Ames Laboratory, Ames, IA, 50011)
This work investigated
the feasibility of using electron back scattered diffraction (EBSD)
to associate, or differentiate, metal fracture fragments. The objective
of this work was to determine an empirical basis for the hypothesis
that a minimum sequence of grains can be used to identify a metal
fracture line beyond a reasonable doubt. Crystallographic misorientations
between individual grains were determined using EBSD along several
lines (point-to-origin vectors) of metal crystals within the microstructure
of a 304 stainless steel. From a given starting crystal, a grid of
vectors was used to do relative referencing comparison of the grain
orientation profiles along each vector. A radial grid was used with
5° spacing between vectors at a radius of 11.5 times the average
grain diameter. Misorientation angle between grains was calculated
by averaging the misorientation angles within a single grain and
referencing this average misorientation angle back to the origin
grain. The average vector matched 2.6±2 grains with adjacent vectors
out of 16.9±7 grains characterized per vector. In point by point
matching, vectors placed 5° apart had 83±11% of data points match
in the first 2.5 grains away from the origin, with that falling to
36±10% in the last 2.5 grains characterized in the vector. The extent
of point to point matching confirms that this method can properly
identify when similar or dissimilar profiles are being compared.
This leads to the conclusion that a relatively low number of grains
need to be analyzed to uniquely characterize a fracture line by relative
crystallographic orientations. It also opens the possibility to a
more extensive statistical review of concepts and data.
Density-Functional Theory Investigation of ß-SrRh2O4. GARETH
WILSON-SHORT (North Carolina State University, Raleigh, NC, 27606)
DAVID J. SINGH (Oak Ridge National Laboratory, Oak
Ridge, TN, 37831)
There is a need
of better materials for direct photoelectrolytic hydrogen production.
Requirements are an appropriate band gap (ideally 1.8 eV), flat band
edges, photochemical and aqueous stability, and effective charge
transfer to water. Computational methods are appropriate for studying
the band structures of materials, allowing one to examine the first
two of the above requirements. This study is a theoretical treatment
of (P-62c) ß-SrRh2O4 and its viability for direct photoelectrolysis. Straightforward
calculations are hampered by the disorder of strontium. Linearized-Augmented
Plane-Wave (LAPW) Density Functional Theory (DFT) calculations were
performed on supercells with different occupancies of these strontium
sites as well as virtual crystals that approximate the effect of
Sr2+ by
substituting 2Rb+.
Independent DFT calculations, within either the local density approximation
(LDA) or the generalized gradient approximation, were performed in
order to calculate properties for these structures and relaxed structures
provided by a colleague. A result of interest for ß-SrRh2O4 is the flatness of the t2g band edge as well as the relative narrowness of the eg manifold.
The placement of strontium has a significant effect on the electronic
structures in both virtual crystal approximations and supercells.
Despite the strontium disorder, this study indicates that the bulk
electronic structure of ß-SrRh2O4 is
excellent for the for the direct photoelectrolytic production of
hydrogen. LAPW DFT within the LDA calculates band gaps (1.0-1.2 eV)
in these supercells, lower than those for the virtual crystal approximations
(1.5-1.7 eV). However, this method traditionally underestimates semiconductor
band gaps. A good example being the prediction of a 0.6 eV band gap
in ZnRh2O4 using the same computational methods employed here, while experiment
revealed a 1.2 eV band gap. This study does make two significant
assumptions, namely that the compound is stable in water due to low
ionic mobility of Sr, and that effective charge transfer to water
can occur. These can both be addressed with experiments.
Design, Fabrication and Measurement of Nb/Si Multilayers and Niobium Transmission
Filters. SUNEIDY LEMOS FIGUEREO (University
of Puerto Rico, Rio Piedras, Rio Piedras,
PR, 931) ERIK GULLIKSON (Lawrence Berkeley
National Laboratory, Berkley, CA, 94720)
The extreme ultraviolet
(EUV) region of the electromagnetic spectrum is being used in multilayer
optical systems to design technology projected for use in the fabrication
of nano-electronics. Multilayer optical systems with high reflectivity
have been produced in the soft x-ray and EUV regions of the spectrum.
Due to the limited understanding of the Nb/Si optical systems, our
research group fabricated and measured Nb/Si multilayers and Nb transmission
filters for the soft x-ray and EUV regions. Multilayer optical systems
are used in applications ranging from EUV lithography to synchrotron
radiation. The films were deposited using dc magnetron sputtering
in the Center for X-Ray Optics at the Lawrence Berkeley National
Laboratory. Reflectivity and transmission measurements were performed
at the Advanced Light Source beamline 6.3.2. The Nb/Si multilayer
mirrors fabricated have a reflectivity of approximately 65% in the
extreme ultraviolet region, which makes these systems practical for
applications where a high reflectivity is required, such as Astronomy
and instrumentation development. Transmission measurements of up
to 90% were observed in the soft x-ray and EUV regions as well. Future
work in the research group includes the design and fabrication of
an Nb/Si multilayer with a B4C interface. The Nb/B4C/Si optical systems
are expected to have a higher reflectivity than Nb/Si systems.
Determining Valence Band Maxima for Photovoltaics using Ultraviolet Photoelectron
Spectroscopy. SAKA OKYERE-ASIEDU
(University of Delaware, Newark, DE, 19050) DR. STEVEN HULBERT
(Brookhaven National Laboratory, Upton, NY, 11973)
Photovoltaic solar
cells (PVs) consist of semiconducting materials, which directly convert
sunlight into electricity. In order to make high efficiency solar
cells there is the need to maximize the transport of charge carriers—thus
experiments should reveal energy levels of electrons in the device.
Ultraviolet Photoelectron Spectroscopy (UPS) allows for probing these
energy levels. In UPS, vacuum UV (10-45 eV) radiation is used to
examine valence levels by exciting electrons from those levels. The
valence band is defined as the highest electron energies where electrons
are normally present and determines the conductivity of the semiconductor.
For the experimentation we set three principal goals. The first was
to understand the operation of the U4A beamline on which the experiments
were run. Since the objective was to study bulk not surface phenomena,
it is necessary to understand how to minimize the effects of surface
treatment on the measurement. The second goal was then to determine
the effect of HF surface treatment on valence bands. Under this goal
we needed to identify features in a valence band spectra belonging
to the Si substrate, as well as H, O and defects in the Si film.
Also, the cross-section for electron excitation and the electron
path lengths are incident photon energy dependent. The third goal
was to determine the valence band maximum (VBM) for a series of candidate
materials for solar cells. This series includes amorphous (a) and
crystalline (c) Si, with n-type (n), p-type (p), or intrinsic (i)
doping. The series of i-a-Si, n-a-Si, and p-a-Si was analyzed with
varying energy photon 30eV – 120eV. For experimental controls, we
started with samples of n-c-Si and p-c-Si with expected EF – EV =
0.87eV and 0.225eV. We then compared a-Si films of different p- and
n-doping as well as standard i-layer. Future experiments seek to
maximize the efficiency of solar cells by adjusting the valence bands
using various deposition techniques and doping.
Development of a Low-Cost Pitch-Based Carbon-Carbon Composite for Friction
Applications. ANDREW MELO (The University of the South, Sewanee, TN, 37383)
DR. JAMES KLETT (Oak Ridge National Laboratory, Oak
Ridge, TN, 37831)
Carbon-Carbon (C/C)
composites are materials containing a carbon fiber preform impregnated
with a graphite matrix. These composites have many important physical
characteristics such as excellent specific strength, wear resistance
and low thermal expansion coefficients. Current C/C composites are
often produced by forcing pitch under high pressures and temperatures
into the preform. The pitch fills the voids between the preform fibers,
and the high heat carbonizes the pitch simultaneously. A second step,
called graphitization, involves heating the sample to 2800°C under
an inert atmosphere which causes the carbon within the sample to
form a graphite matrix. Due to the pitch’s viscosity, this process
takes several month-long cycles to conduct. Because of the time and
cost currently required to produce C/C composites, they have seen
limited use outside of aerospace and military applications. A novel
proprietary process for the fabrication of C/C which obviates the
need for high pressure processing has been developed at ORNL. In
the present project, this process was used to fabricate samples made
of a chopped carbon fiber technology called P4 and samples made from
a three dimensional fiber weave. These samples were processed (impregnated,
carbonized and graphitized at least two times) in under a month to
create samples with an average density of 1.3 g/cc compared with
a density of approximately 1.7 g/cc with the old method. Optical
microscogy, scanning electron microscopy, thermal conductivity, flexural
strength, tensile strength, wear testing, and density measurements
were performed on the samples to characterize their properties. Currently,
these parts demonstrate a thermal conductivity of 12.5 W/m K as well
as a flexural strength and modulus of 30.3 MPa and 76 GPa, respectively.
It is hoped that this new process will produce parts with nearly
the same physical characteristics as the old method while dramatically
reducing cost.
Development of Thin Film Diamond Coatings for Mechanical Rotary Pump Shaft
Seals. ELIZABETH ROLLINGS (University of California, Berkeley,
Berkeley, CA, 94720) GREG KRUMDICK (Argonne National Laboratory,
Argonne, IL, 60439)
The key materials
properties necessary for long-term, reliable operation of rotary
pump shaft seals include high hardness, high thermal conductivity,
low coefficient of friction, and high resistance to corrosion. Given
this list of properties, it is clear that diamond is an ideal candidate
material for pump seal surfaces. In this work, three varieties of
diamond thin films grown by hot-filament chemical vapor deposition
are investigated for their viability as smooth, wear resistant coatings
for silicon carbide pump seal surfaces. Scanning electron microscopy
is employed to characterize film surface morphology, and Raman spectroscopy
is developed as a tool to monitor film composition. Signature Raman
spectra are associated with diamond grain size via the relative intensity
of spectral features associated with sp2-bonded carbon versus sp3-bonded carbon in the polycrystalline films. Finally, surface
profilometry measurements are used to quantify the average surface
roughness of the coated seals. It is found that nanoscale grain size
is an essential feature of high-performance diamond pump seal coatings.
Does an Indentation Size Effect Exist in Nickel Titanium Shape Memory Alloy?. ERIN DONOHUE (Brown University, Providence, RI,
2912) EASO P. GEORGE (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)
Hardness is usually
measured by indentation and is considered to be an intrinsic property
of a material. Recently, however, an indentation size effect (ISE)
has been observed, which is manifested as an increase in a material’s
hardness with a decrease in the volume of material probed. This phenomenon
has previously been studied in a variety of materials and is due
to the creation of geometrically necessary dislocations (GND) and
work hardening. In this new work, shape memory alloys (SMA) are examined
to determine if they demonstrate an ISE. After elastic deformation,
instead of going directly into the plastic regime, deformation in
a SMA occurs by the reorientation of the variants of the martensite
phase. As a result, when the SMA is heated above its martensite-to-austenite
transformation temperature, the material returns to its original
shape. Nickel titanium (NiTi), a common SMA, is the material chosen
for this study. Using an Instron machine, a uniaxial compression
test is performed to determine the stress-strain behavior of a bulk
sample of NiTi. Another NiTi sample is tested with spherical indenters
in the Nano Indenter XP. By making indents at a variety of maximum
depths for each of the five indenters of different radii, it is possible
to characterize the size dependence of hardness in NiTi. Fused silica,
a material whose elastic properties are well known, is used to calibrate
the size of each indenter. The indents are also imaged and measured
by the MicroXAM Interferometric Surface Profiler. Finally, the sample
is placed in hot water to see which indents are able to recover.
There is a clear trend of increasing hardness with decreasing radii
of the indenters, i.e., an indentation size effect. However, the
hardness values obtained with the two smallest spheres were similar,
indicating that the size effect breaks down at small length scales.
The hardness values obtained with the two largest spheres agree with
the hardness deduced from uniaxial compression, indicating that they
correspond to the macroscopic hardness of the material. Indent sizes
measured with the Nano Indenter and the Profiler correlate well and
there is no time-dependent shape recovery. When placed in hot water,
all of the indents experience some degree of recovery, with some
of the smaller indents disappearing completely. These results indicate
that the observed ISE cannot primarily be due to a dislocation mechanism.
Effects of Annealing on DC Sputtered Gold Catalyst for Growth of Pinning-Effective
Nanostructures in YBCO Film. JONATHAN
HEBERT (University of South Alabama, Mobile, AL, 36688) DAVID CHRISTEN (Oak Ridge National Laboratory, Oak
Ridge, TN, 37831)
As high temperature
superconductors move more from the laboratory to industry, it is
critical to improve the current carrying capacity. One way to do
this is to introduce controllable flux pinning sites, which prevent
the dissipative motion of superconducting vortices. A method for
this of current interest at ORNL is to embed an ordered array of
nanorods within a superconducting film. In order to be effective,
this method should produce pinning sites with appropriate sizes in
densities comparable to important flux densities, which for most
applications is on the order of one tesla. Also, the nanorod material
must be nonreactive to the superconductor and, in order to be grown
perpendicular to the substrate, have a similar crystal structure
to the substrate material. Magnesium oxide (MgO) is an ideal material
for these nanorods for use with the superconductor yttrium barium
copper oxide (YBCO). Another prerequisite for nanorod growth is the
presence of a catalyst, from which the nanorods will nucleate. One
such catalyst for MgO is gold. Through the method of DC sputtering,
thin films of gold have been fabricated, and by annealing these films, "nanodots" were
created. It is known that four main factors affect the size and density
of these nanodots: film thickness, substrate material, annealing
time, and annealing temperature. In this project the effect of different
annealing times was studied for a sputtering time of eight seconds,
a sufficient time for the growth of a continuous film, and an annealing
temperature of 900°C, the processing temperature of MgO nanorods.
Interestingly, the as-deposited film appears to consist of layers
of nanoparticles, each around 100 nm in size, implying that the gold
is deposited as fairly uniformly sized particles instead of atomically.
Analysis of the films and nanodots is carried out using atomic force
microscopy and scanning electron microscopy. The results show that
an annealing time on the order of tens of minutes is needed for nanostructures
to agglomerate from continuous film. In addition, the smallest particles
were obtained with an annealing time of 60 minutes, while annealing
for 30 minutes produced the most uniformly sized particles.
Electrochemical Characteristics of Secondary Lithium Metal Batteries Containing
(x)LiNi0.5Mn0.5O2•(1-x)LiNi0.5Mn1.5O4 as the Active Material in
the Cathode. JACOB HENDRICKS-HOLTZ (Fayetteville State University,
Fayetteville, NC, 28301) CHRISTOPHER JOHNSON (Argonne National
Laboratory, Argonne, IL, 60439)
As technology progresses,
a search for improved batteries that have higher energy content is
needed to implement Li-ion chemistry in hybrid electric vehicles.
The (x)LiNi0.5Mn0.5O2 (layered)•(1-x)LiNi0.5Mn1.5O4(spinel) (0 <=
x <= 1) composite-structure materials were synthesized and evaluated
as cathodes in lithium metal secondary cells. Various lithium metal
oxides were synthesized and optimized for phase purity and structure.
Electrochemical characteristics are being studied such as current
rate, cycle life, stability, capacity, and safety in "coin cells".
The synthesis method used was precipitation of the metal hydroxide
salts in basic solution, followed by heating the solid with Li2CO3
to 900°C in air. For the battery testing the anode was lithium metal,
and the electrolyte was a 1.2M of LiPF6 in ethylene carbonate (EC)
and ethyl methyl carbonate (EMC) in a ratio of 3:7 respectively as
the solvent. Ten charge/discharge cycles were used, with a fully-charged
voltage of 4.8V and a fully discharged voltage of 2.8V. The current
drawn was 0.16mA with and has a current density of 0.10 mA/cm2. We
used X-Ray Diffraction (XRD) of each metal oxide, (x) LiNi0.5Mn0.5O2
(layered) • (1-x) LiNi0.5Mn1.5O4 (spinel) (0 <= x <= 1), indicated
that composites were formed. The composites have broad peaks showing
crystal strain in their structure.
Electrodeposition of Cobalt and Cobalt-Vanadium Alloy Films on Copper and Iron
Substrates. BENJAMIN TAYLOR (Tennessee Technological
University, Cookeville, TN, 38505)
MARIAPPAN PARANS PARANTHAMAN (Oak Ridge National
Laboratory, Oak Ridge, TN, 37831)
Cobalt (Co) and
its alloys have magnetic and electrical properties that are very
attractive for technological applications. Low coercivity, high magnetic
permeability and relatively high saturation magnetization and electrical
resistivity allow these materials to be used in technical devices
such as transformers, thin film inductors, giant magneto-impedance
sensors, etc. One of the major advantages of Cobalt-Vanadium (Co-V)
alloys is that they can be prepared on different shaped substrates
with controlled composition and magnetic properties by electrodeposition
methods. This study concentrates on developing successful electrodeposition
techniques to grow thin films of Co and Co-V alloys on flat Copper
and Iron substrates and transform the techniques to round wires.
The controlling parameters for electrodeposition of Co and Co-V alloys
on Copper and Iron substrates were investigated; these are temperature,
pH, current density, electrolyte composition, and time. The compositional,
magnetic, electrical, and structural properties of the electrodeposited
films were studied. The electroplated samples were characterized
using x-ray diffraction (XRD), x-ray fluorescence, scanning electron
microscopy (SEM), optical microscopy, atomic force microscopy, and
energy dispersive x-ray diffraction. XRD analysis shows that electrodeposited
Co forms hexagonal close packed (h.c.p.) and face centered cubic
(f.c.c.) structures under the various deposition conditions used
in this study. The addition of vanadium (V) and a divided electrolytic
cell with very negative current densities forms slightly textured
Co films in the (110) and (100) orientations. The division of the
cell increases the current efficiency in solutions containing V.
Co film thickness is found to have linear relationships with both
current density and time. SEM images show dense, uniform Co films
without cracks or porosity. Grain size variation is observed with
changes in current density and time. More negative current density
causes the electrodeposited Co to be deposited f.c.c., which is more
magnetically reversible than the h.c.p. structured Co. The coercive
field is also significantly less in the f.c.c. electrodeposited cobalt
than in the h.c.p. The electrical and magnetic performances of the
electrodeposited wires will be compared with commercially available
Copper and Iron wires. Research efforts are underway to optimize
the growth of Co film alloyed with 2-3 atomic % V.
Evaluation of Friction and Wear of Steel Sliding Surfaces Lubricated by Various
Types of Gear Oils. UTHAM BALACHANDRAN (University
of Illinois at Urbana Champaign, Urbana-Champaign, IL, 61820) GEORGE FENSKE (Argonne National Laboratory, Argonne, IL, 60439)
A vast majority
of critical components in diesel engines and automobiles are lubricated
by oil. Satisfactory performances of these critical components are
achieved through a combination of materials, surface finish, and
lubricant oil formulations. An empirical trial and error approach
is commonly used to formulate lubricants and select materials and
surface treatment strategies. The Tribology Section within the Energy
Systems Division at Argonne National Laboratory is doing research
to progress to a knowledge-based lubricant formulation and component
performance prediction methodology using expertise and unique experimental
capabilities available at Argonne. As part of this on-going activity
we have evaluated the friction and wear of steel sliding surfaces
lubricated by various types of additized gear oils provided by Caterpillar
and Eaton industries. A total of 13 oils were evaluated using a ball-on-disk
tribometer. Friction coefficient as a function of sliding speed and
time using various types of oils are reported in this research paper.
Evaluation of Water-Based Diamond Seeding for UNCD™ Thin Film Growth on Silicon
Wafers. BRENT HAYNAM (University of Missouri - Columbia, Columbia, MO, 65211)
GREG KRUMDICK (Argonne National Laboratory, Argonne, IL, 60439)
Ultrananocystalline
Diamond™ (UNCD™) films are grown on silicon wafers via chemical vapor
deposition (CVD). In preparation for the CVD process the wafers are
seeded with diamond powder. The seeding of each wafer consumes organic
solvents, which are costly and designated by the EPA as hazardous.
The objective of this project is to investigate a viable alternative
method in which the organic solvent based process is replaced with
a low cost water-based process. In order to evaluate the effectiveness
of the proposed method two wafers were seeded using each method.
These wafers then underwent the remainder of the UNCD™ growth process
together in one deposition in the CVD reactor. Four sets of wafers
were coated resulting in 8 UNCD™-coated wafers. These wafers were
characterized to determine whether the proposed method of seeding
wafers yields a diamond film that meets specifications. To accurately
evaluate the quality of films created using the proposed method the
samples underwent optical inspection, profilometry, Raman spectroscopy,
scanning electron microscopy, and nucleation density analysis. Based
on this data, the proposed water-based seeding method produced UNCD™ thin
films that were comparable to the films produced using organic solvent
seeding. The diamond films produced using the alternate seeding method
met specifications. Further research could analyze water-based ultrasonic
seeding of Si wafers.
Influence of Charge State
and Crystal Structure on Properties of Transparent Conducting Oxide
Spinel. ADRIANA
TEODORO-DIER (Lawrence University, Appleton, WI, 54912) GREG EXARHOS
(Pacific Northwest National Laboratory, Richland, WA, 99352)
Solution and vacuum
based deposition approaches have been used to prepare thin transition
metal oxide films that are electrically conductive. To achieve high
conductivity in these materials, processing methods that drive polaron
formation in the oxide have been explored. Research reported here
is focused on optimizing the transparency and conductivity of NiCo2O4 and
the new polaron conductor CuMn2O4 by manipulating film deposition
parameters. This has been achieved by changing the resident metal
cation charge states. Pulsed Laser Deposition (PLD) from a NiCo2O4
target with high substrate temperature and high oxygen partial pressure
followed by post-deposition annealing produced spinel films with
resistivities as low as 4.0 x 10-1 Ω cm. In
the CuMn2O4 system, infrared transparent films were deposited from
alcoholic or aqueous solutions using spin deposition and PLD. Films
deposited from aqueous solutions displayed resistivities of 2.69 Ω cm
while those obtained from alcohol solutions were insulating. Although
the insulating films became conductive when heated in air, the optimum
cation oxidation states to promote conductivity in the films derived
from alcohol solutions have not been realized. PLD films of CuMn2O4
created under conditions similar to those used to deposit NiCo2O4
films displayed resistivities around 0.5 Ω cm. XRD, XPS, Hall
measurements, Raman and transmission spectra were used to further
characterize resident properties. Ongoing work involves optimization
and refinement of deposition conditions for the CuMn2O4 PLD films
in order to achieve the appropriate mixture of cation oxidation states
associated with optimum conductivity.
Miltilayer Mirrors for Extreme Ultraviolet Lithography. JONNY
RICE (Norfolk State University, Norfolk, VA, 23504) DAVID ATTWOOD (Lawrence Berkeley
National Laboratory, Berkley, CA, 94720)
Extreme Ultraviolet
(EUV) lithography promises to be an efficient way to manufacture
faster and more powerful microchips. Using light of wavelength 13-14
nm instead of the currently used range of ~200 nm results in the
ability to produce smaller feature sizes for the silicon network
that makes up the microchip. However, the normal lithography optics
cannot be used with this range of light because the scattering of
light at this wavelength reduces the rate of success of the process.
The answer is multilayer mirrors, mirrors coated with alternating
layers of optical materials, since the internal reflections between
the individual layers and off-phase refractions within them cause
interference that reduces the scatter. The most efficient multilayer
optics reflect at ~70%, which means a multilayer mirror must have
a high reflectance and be durable enough to withstand the intense
energy required for the process, since the initial energy wave will
be reduced by 60-70% at each interaction with one of several multilayer
optics within the system. Current testing for EUV lithography involves
measuring peak reflectance ang uniformity of reflectance of mirror
samples as well as reductions in reflectance caused by prolonged
exposure to radiation. Future research will involve testing new combinations
of materials for multilayers as well as testing coating layers designed
to lengthen the lifespan of the multilayer optics.
Multiple-Differential-Aperture X-Ray Microscopy. OMBREYAN
BROADWATER & VIRGIL GREENE (South Carolina State University, Orangeburg, SC, 29117)
DR. GENE E. ICE (Oak Ridge National Laboratory, Oak
Ridge, TN, 37831)
A truly non-destructive
tool (X-ray microbeam) for three-dimensional (3-D) characterization
of mesoscopic and nanoscopic material structures has been developed
and is in use. A major breakthrough towards the study of crystal
structure distribution in 3-D is the development of Differential
Aperture X-Ray Microscopy (DAXM). It provides a way to decode the
location of scattering from sites along the incident x-ray microbeam.
A single wire DAXM is currently in use. This method has one major
drawback; it requires a huge increase in data collection time. In
this project, a multiple wire DAXM has been designed and constructed
to accelerate 3-D measurements of crystal structure. The design considers
beam penetration-depth into the sample, angle of sample surface with
respect to beam direction, spacing between the sample surface and
the wires, wire size, and wire spacing. An appropriate holder that
allows all reflected rays to be detected by the X-ray area detector
without interference was also designed and constructed. For a 50-µm
diameter size wire, theoretical and computer program data show that
data collection time is accelerated by at least a factor of 2.5 compared
to a single wire for a 1-µm resolution. Also, a 30 degree angle between
sample surface and beam direction resulted in fewer steps and lower
minimum wire spacing compared to the 45 degree angle that is currently
used. A similar effect is observed as the wires move closer to the
sample surface. Multiple-wire Differential Aperture X-ray Microscopy
not only accelerates data collection time, but also allows studies
of dynamic processes in which short data collection time enables
real time resolution. It provides better signal-to-noise conditions
and less sensitivity to instabilities compared to a single wire.
This system was tested on the 3D X-ray crystal microscope (station
34-ID-E) at the Argonne National laboratory’s Advanced Photon Source
and it worked as designed. Detailed analysis and development of software
to decode the diffraction information is underway. This result further
illustrates the potential for accelerated data collection with multiple
differential apertures.
Nanostructured Artificial Nacre. DEANNA
BRITTON (University of Tennessee, Knoxville, TN, 37996) APRIL MCMILLAN (Oak Ridge National Laboratory, Oak
Ridge, TN, 37831)
Many structured
organic-inorganic composites exist in nature. An example of this
mother-of-pearl, or nacre, was investigated in this study. Nacre
possesses an ordered brick-and-mortar arrangement composed of alternating
layers of inorganic aragonite (CaCO3) approximately 500 nm in thickness
(the bricks), and an organic protein matrix, 50 nm thick, (the mortar).
Nacre is well known for its excellent mechanical properties in particular
its high toughness and strength. These superior qualities can be
attributed to the arrangement of the organic/inorganic elements which
combines the elasticity and toughness of the protein layers and the
strength and hardness of the aragonite. In order to develop an understanding
of how organic and inorganic structures assemble, a synthetic approach
was utilized to reproduce the structure of nacre. This study evaluated
the work of Dr. Nicholas Kotov, Oklahoma State University. Kotov
fabricated the layered structure through demonstration of a technique
called layer-by-layer assembly. Layer-by-layer assembly involves
alternate immersions of glass slides in solutions of negatively-charged
clay called montmorillonite, the bricks, and positively-charged polyelectrolyte
called poly(diallydimethylammonium) chloride (PDDA) which serves
as the mortar. Currently, a calibration curve for layer thickness
versus immersion time is being generated in order to understand the
growth kinetics of the layers. The ability to manufacture artificial
nacre may provide lightweight, rigid composites for biological tissues
that possess a similar structure such as bone and teeth.
Nitride Membranes: Surface Debris Prevention and Strength Testing. PATRICK BENNETT (University
of California, Berkeley, Berkleey, CA, 94720)
ERIK ANDERSON (Lawrence Berkeley
National Laboratory, Berkley, CA, 94720)
Fresnel Zone plate
lenses are used to focus soft x-rays through a series of alternating
zones of opaque and transparent material. Nitride membranes act as
a support upon which zone plates are manufactured. The membranes
are created by coating a silicon wafer with nitride and then etching
away the silicon with potassium hydroxide (KOH) to form a window.
Since window strength is an important factor in throughput, it would
be desirable to identify and optimize production factors that affect
strength. To perform analysis of window strength, an apparatus was
designed and constructed that would increase pressure on nitride
membranes until breakage, allowing for comparative analysis between
different production steps. During testing, it was found that the
windows being produced were contaminated with debris. In order to
reduce contamination, sources were identified using a process of
elimination. By replacing contaminating production steps, surface
debris was greatly reduced. Furthermore, debris was eliminated completely
using a solution of hydrogen peroxide and sulfuric acid. This is
not an ideal solution, however, as it is hazardous and its effects
on window strength are unknown. Preliminary results from pressure
testing indicate that strength of membranes is dependant on mount
orientation. While these results were unexpected, more testing needs
to be done to determine the nature of this relationship. Most likely,
window strength will be related to both the absolute window size
as well as the relative size of window to surrounding silicon support
frame.
Non-Destructive Measurement of Residual Stresses in Finished Carburized Gears
Using X-ray Diffraction. BRYAN BOGGS (University
of Tennessee at Martin, Martin, TN, 38238)
DR. CAMDEN HUBBARD (Oak Ridge National Laboratory, Oak
Ridge, TN, 37831)
Carburization is
a common method for improving fatigue strength and wear resistance
of gears found in transportation systems. Compressive residual stresses
develop as a result of phase transformations from post carburization
heat treatments, which improve fatigue strength. Conversely, these
phase transformations cause surface distortions to develop in the
gear geometry and a loss of surface finish. A finishing process such
as grinding or skiving is implemented in order to remove these distortions
and improve the finish. This research seeks to quantify the change
in residual stress in a carburized gear as it progresses through
the finishing process. X-ray diffraction was used to characterize
both a finished and unfinished carburized gear to map the residual
stresses across and along the face width of a gear tooth. At ten
radial positions along the gear tooth, the compressive stresses were
measured across the width of the tooth. The unfinished gear showed
little variation of residual stresses while the finished gear showed
a significantly larger variation of residual stresses. In the unfinished
gear the average of the stresses varied slightly and had an average
value of 150 ksi compression. However, the finished gear yielded
an average compressive residual stress at each radial position that
varied linearly from 70 ksi to 130 ksi and then back to 70 ksi. This
significant variation is presumed to be a result of the amount of
material removed during grinding. Additional tests are planned to
determine whether the trends observed from these tests are repeatable
for other gear samples. Metrology studies are also in progress to
determine the amount of material removed by grinding, with the intent
to correlate this loss to the change in residual stress. This research
is part of a larger research project in which neutron diffraction
will be used to penetrate deeper into the specimen and to compliment
the near surface x-ray stress data.
Non-Destructive Measurement of Residual Stresses in Finished Carburized Gears
Using X-ray Diffraction. JEFFREY BUNN (University
of Tennessee at Martin, Martin, TN, 38238) CAMDEN
HUBBARD (Oak Ridge National Laboratory, Oak
Ridge, TN, 37831)
Carburization is
a common method for improving fatigue strength and wear resistance
of gears found in transportation systems. Compressive residual stresses
develop as a result of phase transformations from post carburization
heat treatments and therefore improve fatigue strength. Conversely,
these phase transformations cause surface distortions that develop
in the gear geometry as well as a loss of surface finish. A finishing
process such as grinding or skiving is implemented in order to remove
these distortions and improve the finish. This research seeks to
quantify the change in residual stress in a carburized gear as it
progresses through the finishing process. X-ray diffraction was used
to characterize both a finished and unfinished carburized gear to
map the residual stresses across and along the face width of a gear
tooth. At ten radial positions along the gear tooth, the compressive
stresses were measured across the width of the tooth. The unfinished
gear showed little variation of residual stresses while the finished
gear showed a significantly larger variation of the residual stresses.
In the unfinished gear the average of the stresses varied slightly
and had an average value of 150 ksi compression. However, the finished
gear yielded an average compressive residual stress, at each radial
position, that varied linearly from 70 ksi to 130 ksi and then back
to 70 ksi. This significant variation is presumed to be a result
of the amount of material removed during grinding. Additional tests
are planned to determine whether the trends observed from these tests
are repeatable for other gear samples. Metrology studies based on
data from a coordinate measuring machine (CMM) are also in progress
to determine the amount of material removed by grinding, with the
intent to correlate this loss to the change in residual stress. This
research is part of a larger research project in which neutron diffraction
will be used to penetrate deeper into the specimen and to compliment
the near surface x-ray stress data.
Orientation and Ordering of Spherical Nanoscale Particles in a Magnetic Field. JASON STRAINS (Valparaiso University, Valparaiso, IN, 46383) DAVID SCHULTZ (Argonne National Laboratory, Argonne, IL, 60439)
Nanoparticles are
known to exhibit special electrical, optical and magnetic properties.
Ferrofluids are a subset of nanoparticle colloidal suspensions. Ferrofluids
an important area of scientific research. Ferrofluids are also known
to exhibit interesting properties, especially when a magnetic field
is introduced. Our purpose is to study the change in orientation
of spherical nanoparticles in a magnetic field. A sample of spherical,
monodisperse ferromagnetic particles was studied using the known
techniques of small angle x-ray scattering and wide angle x-ray scattering.
The spherical particles were found to exhibit little difference in
orientation or ordering when a magnetic field was applied. This sample
was compared to a previously studied sample of needle-like, more
polydisperse particles. The needle-like particles had previously
been shown to align when a magnetic field was applied. It was concluded
that shape of the nanoparticles plays an important role in determining
whether or not they are affected by a magnetic field. Future studies
should focus on testing a better, more monodisperse sample of needle-shaped
particles and studying the effects of an applied field in more detail.
Understanding the effect of magnetic fields on ferrofluids has promise
in applications such as MRI enhancement and particle activation.
The latter could be an important discovery for the medical field,
potentially leading to targeted drug delivery.
Preparation and Characterization of Self-Assembled Molecular Films. KYAL WRIGHT (Norfolk State University, Norfolk, VA, 23504)
MIQUEL SALMERON (Lawrence Berkeley
National Laboratory, Berkley, CA, 94720)
Industrial laboratories
and semiconductor manufacturing companies have implemented an initiative
to investigate the structure-property relationships, specifically
the electrical and mechanical property relationships, of island structures
(islands) of organic ultra thin films. Before these properties can
be studied, reproducible methods of island formation must be developed
to promote controlled structure-property studies. This project will
study island formations from alkanethiol self-assembled monolayers
(SAM) and conduct preliminary mechanical property tests. There are
many parameters that affect the formation of SAM islands. Some of
these parameters include the surfactant concentration in solution,
the solution temperature, the substrate cleanliness, the substrate’s
grain sizes and the duration of deposition. This project used Atomic
Force Microscopy (AFM) to investigate the relationships between solution
concentrations, substrate deposition times, and substrate grain sizes
for the control of SAM island domains. To test the effects of deposition
time and material concentration on the formation of the SAM islands
on gold substrates, alkanethiol molecules in ethanol solution were
used in 2 µM, 5µM, 10µM and 20µM concentrations. Experiments dependent
on deposition time used time periods ranging from 30 seconds to 6
minutes. Preliminary tests on the effects of flame annealed gold
substrates resulted in the use of substrates annealed for 45 passes
at one pass per hertz for the tests involving solution concentration
and deposition time. The results of the preliminary substrate investigation
and structural investigations support that SAM island domains larger
than 100nm can be formed on annealed gold substrates when alkanethiol
solutions greater than 10µM concentration are deposited on the substrate
between 45 seconds and one minute. Results from the mechanical property
investigation indicated that the islands formed from 20µM solution
at a deposition time of 45 seconds are quite robust when a maximum
load corresponding to 8 volts from the AFM system was applied to
a 150nm region. While the results from all the investigations support
the theory that the first phase of SAM island formation can be controlled,
further investigations and trials for each experiment are still needed
to confirm this claim.
Processing and Analysis of YBCO Film Spectroscopy Data Using the GRAMS Series
of Computer Software. MICHAEL DUITSMAN (University
of Evansville, Evansville, IN, 47722)
VICTOR MARONI (Argonne National Laboratory, Argonne, IL, 60439)
The Superconductivity
for Electric Systems Program at Argonne is performing detailed characterization
studies on Y1Ba2Cu3O7 (YBCO)
superconducting films deposited on long-length metal substrate tapes.
One of the important tools used in this research is Raman microspectroscopy,
which makes it possible to determine phase composition and texture
quality of the YBCO films. A large number of Raman spectra are collected
in this program and each one has to be processed to remove background
effects, so that a pure Raman spectrum extrapolated to a horizontal
baseline can be obtained for further analysis. Due to the long period
of time required to perform even simple mathematical processes on
spectroscopy data, there have been many computer programs created
to assist in the performance of these tasks. This report discusses
the use of one such series of programs-the GRAMS series. The work
focused on processing groups of spectra from step-milled samples
by applying the software for baselining, noise smoothing, spectral
subtraction, and curve-fitting of such spectra. The results show
that the GRAMS series facilitates rapid, simple, reproducible processing
of spectral data of the type generated by Raman microspectroscopy.
The processing of many sets of spectra from a group of six related
samples has shown an interesting correlation between the performance
behavior of the superconductor and certain types of defects that
Raman can detect.
Production of Micro- and Nanocrystalline Diamond Stripper Foils for the Spallation
Neutron Source Using Microwave Plasma Chemical Vapor Deposition. MARK JENSEN (Brigham Young University, Provo, UT, 84602)
ROBERT W. SHAW (Oak Ridge National Laboratory, Oak
Ridge, TN, 37831)
Preliminary testing
at Brookhaven National Laboratory predicted that diamond stripper
foils will have a longer lifetime in the Spallation Neutron Source
(SNS) H- beam
(38 mA at 1 GeV) than conventional carbon stripper foils. The design
of the SNS requires that foils be supported by a single 12 mm edge
and extend 20 mm of freestanding foil. Also, the SNS design estimates
the ideal areal density to be 280 µg/cm2 or
~0.8 µm thick. However, testing at Los Alamos National Laboratory
showed that increasing foil thickness should provide increased stripping
efficiency. Foils were produced using microwave plasma chemical vapor
deposition (MPCVD) onto silicon substrates. Substrates were pretreated
by the use of ultrasonication in a diamond-methanol slurry. The slurry
consisted of 0.3 g each of 35 µm and 4 and
98-99% H2 at
50 torr. Nanocrystalline diamond films were grown at 900-1000 W in
an atmosphere of 1-2% CH4,
8-9% H2,
and 90% Ar at 130 torr. The foils’ substrates were then etched using
a standard Nitric-HF-Acetic Acid etching solution. Due to thermal
expansion mismatch of diamond and silicon, foils originally scrolled
upon etching the silicon. To keep the freestanding foil flat, a photolithography
technique was used to pattern ~6 µm deep U-shaped channels in the
substrate before pretreatment. The channels terminated on the supported
edge. Foils showed inconsistent and low nucleation densities that
resulted in pinholes and weak areas. Nucleation density increased
and became more uniform by frequent stirring of the diamond slurry
during pretreatment. This enhancement of the scratching procedure
resulted in smoother surfaces and decreased the likelihood of holes.
It is anticipated that the usable lifetime of both micro- and nanocrystalline
diamond foils will greatly exceed that of conventional stripper foils.
The performance of different foils in the SNS will provide direction
into which properties and crystal size are the most important for
long lasting foils.
Protection of Aluminum from Saltwater Corrosion by
Superhydrophobic Films. PHILIP
BARKHUDAROV (Utrecht University, Utrecht, ND, 0) JAROSLAW MAJEWSKI (Los Alamos National Laboratory, Los
Alamos, NM, 87545)
The damaging effects
of corrosion cost billions of dollars each year in metal replacements
and repairs. Unfortunately, corrosion cannot be completely stopped;
the natural state of most metals on earth is in oxide form. Fortunately,
it is possible to slow the oxidation process or to redirect it, and
with ever more advanced technology, especially on the nano-scale,
corrosion prevention is becoming more and more effective. This research
focused on the corrosion of aluminum in salt-water environments.
In dry air, aluminum develops a thin surface oxide layer that prevents
further corrosion. However, in the presence of water and salt, this
layer is broken and rapid corrosion ensues. In this study, superhydrophobic
films were layered onto the metal, repelling water and slowing corrosion.
These superhydrophobic films consisted of a highly nano-porous silica
framework together with hydrophobic organic ligands. To study the
effectiveness of such protective layers, the neutron reflectometry
method was used. By taking neutron reflection measurements over time
on samples of layered aluminum/superhydrophobic film/salt-water,
it was possible to observe and quantify the rate of oxide growth
in the aluminum. From the relatively short period of measurement,
it was possible to predict corrosive behavior on a longer time scale
and to show the effectiveness and feasibility of using superhydrophobic
films to protect aluminum in marine environments, i.e. ships, off-shore
platforms, aircraft, and coastal regions.
Pulsed Laser Deposition of Precursors for Ex Situ BaF2 Growth of YBCO Superconducting
Film. ALI MORADMAND (University of South Alabama, Mobile, AL, 36688) DAVID CHRISTEN (Oak Ridge National Laboratory, Oak
Ridge, TN, 37831)
Various methods
exist for the deposition of thin films used in materials research
of yttrium barium copper oxide (YBCO) superconductors. One common
method is in situ pulsed laser deposition (PLD), in which a target
is subjected to a pulsed laser beam and ablated into a plume of particles
which deposit reactively on a substrate. Another technique used to
make high-quality YBCO film for the application of so-called "coated
conductor" technology is the ex situ physical vapor deposition
of precursors containing BaF2 at room temperature - unlike in situ
PLD where the deposition takes place at elevated temperatures. The
precursors are then converted in a furnace to form superconducting
YBCO. The focus of this study is to develop a new ex situ PLD method,
in which the substrate is kept at room temperature and the deposition
of the fluoride-containing YBCO is done using PLD. By optimizing
parameters such as ambient gas species, chamber pressure of background
gas, and laser energy, YBCO precursors can be formed with the desired
thickness, surface morphology, and ratio of the elements in the precursor.
The converted films are analyzed for the crystalline YBCO structure
using x-ray diffraction and the surface is imaged using atomic force
microscopy and scanning electron microscopy. The samples are then
tested for superconductivity in a superconducting quantum interference
device. Analysis on various samples deposited under different conditions
shows that lower laser energy and introduction of background gas
can produce film with more favorable surface structure for conversion.
Reduction of laser power by modifying the optics reduces the problem
of "splashing", which is a known obstacle in PLD. Under
an optical microscope, reduction of laser energy shows a significant
decrease in surface irregularity. Magnetometry tests show a critical
temperature of 88K for these converted YBCO precursor films and critical
current densities of 2.9MA/cm2 at 5K. Future goals are to further
improve film uniformity and quality to increase these values. Because
PLD can also make good multilayering films, the long-term goal is
to conduct rare-earth substitution into the precursors. Alternating
layers of rare-earth material can be deposited in the precursor,
and the substitution of the yttrium in YBCO with other rare earth
elements has been known to improve flux pinning and raise the critical
temperature of such superconductors. By optimizing the parameters
for ex situ PLD of a single layer, the method can be extended to
rare-earth substituted multilayered precursors as a versatile method
of deposition of precursors for high-quality high temperature superconducting
films.
Purification of N@C60. CHANDA ROGERS
(Benedict College, Columbia, SC, 29204) DR. JOHN SCHLUETER (Argonne National Laboratory, Argonne, IL, 60439)
Currently, research
is being conducted to produce and purify the endohedral molecule
N@C60, which will act as the basic quantum bit (qubit) for the next
generation of computers. With these qubits, quantum computers will
become more effective in the areas of large database searches, large
number factorization, and quantum mechanical simulation of physical
systems. Therefore, there is a need to develop methods to increase
the yield and purity of N@C60. The method that was chosen for the
purification of N@C60 was high performance liquid chromatography
(HPLC). Electron paramagnetic resonance (EPR) was used to confirm
the presence of N@C60. In utilizing these two methods together, the
sample of N@C60 in C60/toluene was separated with the HPLC instrument,
and then each fraction from the fraction collector was concentrated
down to about 1mL of solution and placed inside of EPR tubes. Next,
an EPR spectrum was recorded, and the fraction that gave an EPR spectrum
of the clearly defined triplet characteristic of N@C60 was reinjected
into HPLC. This will be continued until a pure sample of N@C60 is
identified. It will then enter into the next stage of the research,
which includes it being formed into the qubits.
Retained Austenite in SAE 52100 and 1045 Steels Post Magnetic Processing and
Heat Treatment. NATHANIEL PAPPAS (Ball State University, Muncie, IN, 47306)
THOMAS R. WATKINS (Oak Ridge National Laboratory, Oak
Ridge, TN, 37831)
Steel is an iron-carbon
alloy that contains up to 2% carbon by weight. Understanding which
phases of iron and carbon form as a function of temperature and percent
carbon is important in order to process/manufacture steel with desired
properties. Austenite is the face center cubic (fcc) phase of iron
that exists between 912° and 1394° C. When hot steel is rapidly quenched
in a medium (typically oil or water), austenite transforms into martensite.
The goal of the study is to determine the effect of applying a magnetic
field on the amount of retained austenite present at room temperature
after quenching. Samples of SAE 52100 steel were heat treated then
subjected to a magnetic field of varying strength and time, while
samples of SAE 1045 steel were heat treated then subjected to a magnetic
field of varying strength for a fixed time while being tempered.
X-ray diffraction was used to collect quantitative data corresponding
to the amount of each phase present post processing. The percentage
of retained austenite was then calculated using the American Society
of Testing and Materials standard for determining the amount of retained
austenite for randomly oriented samples and was plotted as a function
of magnetic field intensity, magnetic field apply time, and magnetic
field wait time after quenching to determine what relationships exist
with the amount of retained austenite present. In the SAE 52100 steel
samples, stronger field strengths resulted in lower percentages of
retained austenite for fixed apply times. The results were inconclusive
when applying a fixed magnetic field strength for varying amounts
of time. When applying a magnetic field after waiting a specific
amount of time after quenching, the analyses indicate that shorter
wait times result in less retained austenite. The SAE 1045 results
were inconclusive. The samples showed no retained austenite regardless
of magnetic field strength, indicating that tempering removed the
retained austenite. It is apparent that applying a magnetic field
after quenching will result in a lower amount of retained austenite
but that the exact relationship, linear or other, is inconclusive.
This project is a part of a larger, ongoing project investigating
the application of a magnetic field during heat treatment and its
influence on the iron-carbon phase-equilibria.
Search for Mechanically-Induced Grain Morphology Changes in Oxygen Free Electrolytic
(OFE) Copper. JENNIFER SANDERS (Westminster College, Fulton, MO, 65251)
ROBERT KIRBY (Stanford Linear Accelerator Center, Stanford, CA, 94025)
The deformation
of the microscopic, pure metal grains (0.1 to > 1 millimeter)
in the copper cells of accelerator structures decreases the power
handling capabilities of the structures. The extent of deformation
caused by mechanical fabrication damage is the focus of this study.
Scanning electron microscope (SEM) imaging of a bonded test stack
of six accelerating cells at magnifications of 30, 100, 1000 were
taken before simulated mechanical damage was done. After a 2ş - 3ş twist
was manually applied to the test stack, the cells were cut apart
and SEM imaged separately at the same set magnifications (30, 100,
and 1000), to examine any effects of the mechanical stress. Images
of the cells after the twist were compared to the images of the stack
end (cell 60) before the twist. Despite immense radial damage to
the end cell from the process of twisting, SEM imaging showed no
change in grain morphology from images taken before the damage: copper
grains retained shape and the voids at the grain boundaries stay
put. Likewise, the inner cells of the test stack showed similar grain
consistency to that of the end cell before the twist was applied.
Hence, there is no mechanical deformation observed on grains in the
aperture disk, either for radial stress or for rotational stress.
Furthermore, the high malleability of copper apparently absorbed
stress and strain very well without deforming the grain structure
in the surface.
Solid Oxide Fuel Cell Based on Proton Conductor. KATHRYN
FENSKE (University of Illinois
at Urbana Champaign, Champaign, IL, 61820) DR. U. BALACHANDRAN (Argonne National Laboratory, Argonne, IL, 60439)
Thin films of SrCe0.95Yb0.05O3-d (SCYb5)
are prepared on porous substrates of SCYb5/NiO by a casting method.
Dense, crack-free SCYb5 substrates films with a thickness of approximately
10-30µm are successfully deposited on porous NiO/SCYb5 substrates.
Scanning Electron Microscopy (SEM) shows uniform thickness of the
films and is bonded to the substrate. The prepared cells were tested
to determine their performance as a fuel cell at 800°C.
Solvent-induced Bandgap Effects in Poly(3-hexylthiophene). RENEE
GREEN (University of Pittsburgh, Pittsburgh, PA, 15213) GARRY RUMBLES (National Renewable Energy Laboratory, Golden,
CO, 89401)
Poly(3-hexylthiophene)
is a well-studied semiconducting polymer whose absorbance, and thus,
optical bandgap, can be altered via formation of thin films or addition
of poor solvent. These methods are known to change the color of the
polymer from yellow (“Y-form”) to red (“R-form”). The change in absorbance
of the two forms of polymer results in the widening of its optical
bandgap, but the resulting alteration of the electrical bandgap is
poorly understood. Absorbance spectra were taken on dilute solutions
of poly(3-hexylthiophene) dissolved in THF as methanol was added
to bring about the absorbance transition. The resulting absorbance
wavelengths were then converted into electron-volts to determine
the polymers’ optical bandgaps. Cyclic voltammetry was then performed
on the solutions containing varying methanol volume fractions to
evaluate the polymers’ electrical bandgaps. Y-form polythiophene
was found to have an approximate optical bandgap of 2.3eV, while
that of the R-form was found to be 1.9eV. The electrical bandgap
of only the Y-form of the poly was able to be determined, at approximately
1.8eV. Solvent oxidation interference is suspected to be the cause
of poor R-form electrochemical data, thus other solvents will be
tested. Furthermore, while it is assumed that both phases of R-form
polythiophene are energetically analogous, we aim to eventually demonstrate
this concept by comparing the electrical and optical bandgap data
of the polymer in solution and in thin-film.
Stainless Steel Support Layer For Solid Oxide Fuel Cells (SOFC). MATTHEW HAMEDANI (College
of DuPage, Glen Ellyn, IL, 60137) DAVE CARTER (Argonne National Laboratory, Argonne, IL, 60439)
The solid oxide
fuel cell (SOFC) is a type of fuel cell that operates at high temperatures
and employs ceramics as functional elements of the cell. Each cell
is composed of a cathode and an anode separated by a solid impervious
electrolyte, which during operation conducts oxygen ions produced
by reduction of oxygen from the cathode to the anode where they react
with hydrogen gas supplied to the anode. This investigation focuses
primarily on developing a reliable cell support using stainless steel
434 (SS 434) instead of a nickel cermet support because it is expected
to be more cost effective and structurally and chemically durable
in hydrogen/steam atmosphere. Ultimately, the cell support layer
should have the combined properties of porosity and high electrical
conductivity. Layers were made by tape casting onto a Mylar sheet
from a pre-made slurry containing metal particles, solvent, binder,
plasticizer, and pore former when needed. The binder holds the cast
together and makes it viscous, the plasticizer makes the cast flexible,
and the pore former which generates porosity in the metal layer once
it is sintered. The composition of the slurry was changed so that
the cast from it would exhibit the desirable properties of being
flexible, smooth, porous, electrically conductive, and sturdy. We
found such slurries to be well dispersed, free from foaming and air
bubbles, chemically stable, and rheologically optimal for casting.
Shrinkage of casts that exhibited desirable properties was measured
using a dilatometer. Results indicate that slurries made using butanol
as the solvent and B-79 as the binder gave more flexible and sturdy
casts than slurries made with Xylene/Butanol as the solvent and AT
746 as the binder. Successful fabrication of multilayer cells containing
an electrolyte, anode layers, and two layers of a metal slurry was
achieved. Sintering of these multilayer cells at high temperature
under controlled atmosphere yielded products in which the electrolyte
layer was impervious and free of cracks, while the stainless steel
layer displayed the high porosity. Further work will optimize slurry
composition and tape casting process.
Structural Investigation of Voids and Al Nanoparticles in 20% Al-80% MoO3 Thermite
Pellets. JOSHUA HAMMONS (Texas Tech University, Lubbock, TX, 79409)
JAN ILAVSKY (Argonne National Laboratory, Argonne, IL, 60439)
Aluminum and molybdenum
tri-oxide thermites have a very high energy density and thus are
a very attractive energetic material. Explosion of these thermites
is a result of the oxidation of Al by MoO3 and some O2. To enhance
the contact of Al particles with the MoO3, a mixture of 80% MoO3
and 20% Al was compressed into pellets. When the Al and MoO3 powders
were compressed into pellets, burn rates decreased. The purpose of
this research is to gain some insight into the structure of the Aluminum
particles and or voids that are in the pellet. Scanning electron
microscopy was used to examine the surface of the pellets and compared
to ultra-small angle x-ray scattering (USAXS) data performed at Argonne
National Laboratory (33-ID beamline). Results indicate the possibility
that low density samples contain two separate void phases; the two
phases consist of one large void population that is separate from
much smaller voids that surround the Al nanoparticles. As the density
is increased, the Al particles may penetrate these large voids resulting
in a random dispersion of the Al particles in a single void phase.
To verify these conclusions additional information is needed. BET
analysis should provided additional information about the surface
to volume ratio of the void space in these samples. Additional USAXS
data should also be obtained on samples that range from 30% TMD to
100 %TMD.
Superplastic Forming of Structures Fabricated Using Friction Stir Welding and
Friction Stir Spot Welding. CASSANDRA
DEGEN (South Dakota School
of Mines and Technology, Rapid City, SD, 57701)
GLENN GRANT (Pacific Northwest National Laboratory, Richland, WA, 99352)
Superplastic forming
(SPF) is becoming an increasingly popular metal forming process as
parts with more complex shapes are needed. SPF exhibits the ability
to form complex near-net shapes, reducing both cost and weight. Welded
structures can also be superplastically formed, however the welding
method used is critical to the success of the later forming operation.
Fusion welded aluminum cannot be superplastically formed because
the fusion weld metal is not superplastic. Friction stir welding
(FSW) is a new joining method in which the metal is not melted and
the microstructure remains fine after welding, an essential requirement
for later SPF. In this work, the feasibility of fabricating complex
structures using FSW and friction stir spot welding (FSSW) prior
to SPF was studied. Coupons of FSW and FSSW were made using different
parameters. The coupons were tested in tension at the SPF conditions.
Multisheet packs were also made using FSW and FSSW. The packs were
then superplastically formed in a superplastic forming press. The
results of the coupon and multisheet testing were analyzed and compared
to the metallurgy of the welds before and after SPF. Nearly all samples
showed abnormal grain growth (AGG), a condition detrimental to the
superplastic forming of the weld metal, resulting in low deformation
of the weld metal as compared to the parent metal. From these results,
recommendations are given concerning which FSW and FSSW parameters
should be used to give the best superplastic formability. Future
work will include optimizing the weld parameters for SPF and performance
testing of the multisheet structures.
Synchrotron X-Ray Diffraction Studies of Single Crystals with Varying High Pressure. DANIEL SCOTT (Eastern Illinois University, Charleston, IL, 60193)
YU-SHEN CHEN (Argonne National Laboratory, Argonne, IL, 60439)
Three single crystals
were studied using a synchrotron resource to understand the change
in lattice structure with varying high pressures. The crystal compositions
of H2C2O4•2H2O, Na4SiO4, and C49H40N3PS were determined by their
X-ray diffraction patterns while in the synchrotron beam. The cell
parameters of each crystal came out as expected and verified previous
research [H2C2O4•2H2O: a = 6.100(12), b = 3.500(7), c = 11.850(2), ß =
104.0°(3), Na4SiO4: a, b, c = 24.875(2), a, ß, = 90.00°, C49H40N3PS:
a = 14.624(3), b = 27.343(6), c = 9.982(2), ß = 102.31°(3)]. To apply
high pressure to the crystals, ruby fluorescence from an Argon laser
was used to determine the pressure calibration of a four-screw Diamond
Anvil Cell (DAC). The DAC was calibrated to apply 13.610(5) GPa of
pressure over a spectrographic shift of 4.851(7) nm. Due to equipment
complications with the DAC, the high pressure lattice determination
could not be finished in the specified research time. Future extensions
of this research will be to observe how the unit cell of each crystal
changes when inside the DAC while being exposed to a synchrotron
source.
Synthesis of a Self-Assembled, Nanostructured Polymer for Organic Photovoltaic
Cells (OPVs). LA'TISHA WILSON (Tougaloo College, Tougaloo, MS, 39174) DR. DOLLY BATRA (Argonne National Laboratory, Argonne, IL, 60439)
Organic photovoltaic
cells (OPVs) differ from conventional silicon-based photovoltaics
(PVs) because they offer increased flexibility and cheaper costs;
however, the efficiency of OPVs (3-5%) is considerably lower than
that of traditional, inorganic PVs. The development of nanostructured,
organic polymers where electron transport can be easily controlled
offers an approach for fabricating a more efficient OPV framework.
This project targeted the synthesis of a photopolymerizable ionic
liquid monomer that upon polymerization, would lead to a nanostructured
poly (ionic liquid) incorporating both an electron accepting imidazolium
group and an electron donating thiophene group.
SYNTHESIS OF PEG - LIPID CONJUGATES FOR STIMULI RESPONSIVE COMPLEX FLUIDS. KAMIL HILL (Tougaloo College, Tougaloo, MS, 39174) CHRISTOPHER T. BURNS (Argonne National Laboratory, Argonne, IL, 60439)
Complex fluids
are a class of materials composed of a saturated phospholipid, a
polymer often introduced as a lipid conjugate (such as n-isopropylacrylamide,
NIPAM), and a cosurfactant (detergent molecule) dispersed in water.
Polyethylene glycol (PEG)-grafted, lipid based complex fluids can
serve as the framework for the encapsulation of a bioinorganic molecule,
i.e. proteins, allowing the manipulation of the properties of the
material through external stimuli (temperature, pH, photo, etc.)
without denaturing the molecule allowing the possibility of controlled
and variable transmission of energy and information. In order to
develop a pH responsive complex fluid, a spiropyran -PEG - lipid
conjugate is being synthesized. This presentation will focus on the
synthesis of a carboxylated derivative of a 6-nitrospiropyran, and
a thiol protected PEG, which will be used in the synthesis of the
spiropyran-PEG-lipid conjugate.
Temperature Measurements of Lage-Area TCOs under Vacuum. JENNIFER
GADDIS (University of Illinois
at Urbana Champaign, Urbana, IL, 61801) BRENT NELSON (National Renewable Energy Laboratory, Golden,
CO, 89401)
The National Center
for Photovoltaics (NCPV) has developed new standards for deposition
and characterization tools in order to facilitate process development
and integration. The first tool designed to these specifications
is a sputtering tool for transparent conducting oxides. One such
specification dictates that all systems must hold 6”x 6” substrates.
Concerns were raised internally at the NCPV about temperature uniformity
across the substrates and the performance of large-area heaters.
In this study, large area heater characteristics were studied using
Type-K thermocouples and an Infrared camera; preliminary work on
verifying temperature uniformity and creating intentional non-uniformity
was also conducted. Both optical and direct contact measurement techniques
were used to create a heater calibration curve for Corning 1737F
glass substrates. However, the temperature measured optically was
significantly higher due to radiation from the back-plate of the
substrate holder. Using the thermocouple measurement, the temperature
of the glass was found to achieve only about one half of the heater
temperature (°C). For combinatorial deposition, the ability to produce
both uniform and intentionally non-uniform heating is desired. An
infrared camera was used to create temperature maps of glass substrates.
The uniformity of the substrates from 100-400 °C was verified to
within a standard deviation of 2.6% of the substrate temperature.
Intentional temperature reduction of 15% over a specified area of
the substrate was produced using a Tantalum radiation shield. Future
work will focus on creating a standard temperature measurement method
for 6”x 6” substrates, exploration of other materials and thicknesses
for the substrate platen, and manipulations of temperature for combinatorial
deposition.
The Effect of Phthalocyanines on Solution-Processed Organic Photovoltaic Devices. TALIA GERSHON (Massachusetts Institute of Technology, Cambridge, MA, 2139) DR. SEAN
SHAHEEN (National Renewable Energy Laboratory, Golden, CO, 89401)
Organic photovoltaics
(OPVs) are one mode of renewable energy utilization that promises
to provide a cleaner energy alternative to fossil fuels. Initial
devices called bulk heterojunctions are commonly made using an active
layer composed of a blend of a p-conjugated polymer and a fullerene,
in our case poly(3-hexylthiophene) (P3HT) or Poly[2-methyl,5-(3*,7**
dimethyl-octyloxy)]-p-phenylene vinylene (MDMO-PPV) and [6,6]-phenyl
C61 butyric acid methyl ester (PCBM). These devices have optical
band gaps approximately equal to 1.9 eV where an optimal device would
have a band gap closer to 1.4 eV, thus adding a third component to
red-shift absorption should increase the amount of light absorbed
as well as improve the efficiencies of these devices. Liquid crystalline
zinc-phthalocyanine (Zn LC PC) and liquid crystalline copper phthalocyanine
(Cu LC PC) are materials that have peak absorbances around 650 nm,
which would enhance absorption in the active layer in this way; because
of the
