Student Abstracts: Materials Sciences

Bending Kirkpatrick-Baez Mirrors for Neutron Focusing. ANTHONY FIELDS and JAY PATEL (South Carolina State University, Orangeburg, Sc, 29117) DR. GENE E. ICE (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Neutron scattering is useful for analyzing the atomic structure and defect density of materials. Because neutrons have spin, an isotope-dependent scattering cross-section and are penetrating, neutron beams are particularly well suited for the study of magnetic materials, bulk materials and for the study of low Z or mixed Z structures. Several techniques for directing a beam of neutrons to a sample are available. While guide tubes and collimators work well for large sample sizes, focusing becomes increasingly important as the neutron probe dimension and sample sizes become small. The importance of high-performance nondispersive focusing optics for neutrons has just recently been recognized. In micro-focus experiments, we consider the need for convenient wavelength tuning and/or broad bandpass beams. This favors achromatic methods based on specular reflection. The Elliptical Kirkpatrick-Baez (KB) scheme offers the best flexibility and neutron gathering power, and can nondispersively image neutrons to small spots with high intensity and source-limited brilliance. The KB geometry uses crossed mirrors in grazing-incidence. With perfect elliptical KB mirrors, spherical aberration can be eliminated. We have adopted techniques for producing elliptical neutron mirrors by controlled bending. The need to control the slope errors in the mirrors is very important. The mirrors, the bending control mechanism, and supports are integrated as a unit. Both mirrors are attached to, and bent by a leaf spring mechanism. We have used a laser beam to simulate a thermal neutron beam for system calibrations; we determine the radius of curvature of the mirror as a function of bender settings (coupling force). Results show changes in the focal length (and subsequently in the radius of curvature) with micrometer setting. From these results we can determine the optimum radius of curvature of the mirrors for minimum slope errors. The mirror in the vertical plane sags under gravity and therefore, introduces a mixture of defocus and spherical aberration. We have designed passive corrections by a series of springs under the mirror. A computer program has been written to calculate the gravitational curvatures and slope errors as a function of the number of support springs and loading conditions. Simulation results show that the effect of one spring alone reduces the slope errors by a factor of 10 and with three spring supports, slope errors are reduced by over a factor of 100.

Blends of thiophene-based dendrimers with titania nanoparticles for use in organic photovoltaic devices. TALIA GERSHON (Massachusetts Institute of Technology, Cambridge, MA, 2139) DAVID GINLEY (National Renewable Energy Laboratory, Golden, CO, 89401)

Dendrimers (small branched organic molecules) offer an exciting alternative to typical semiconducting polymers in organic photovoltaic applications, as they are monodisperse and have virtually independently tunable optical, electronic, and architectural properties. Similarly, metal oxide nanoparticles offer a tunable, high-mobility alternative to the established organic electron acceptors. Since nanoparticles are many times larger than typical organic acceptors they may also help address issues in domain size limitations that appear in fullerene-based bulk heterojunctions. To explore these advantages a unique blend of the thiophene-based dendrimer, 4G1-3S, and anatase titania nanoparticles has been studied for use in organic photovoltaic devices. The charge transfer between these two materials was monitored as a function of solvent, drying conditions, and device architecture. Changes in film domain size and morphology were observed via SEM and AFM images. Devices were made under a variety of conditions via solution processing in air. Although no photocurrent was consistently extracted, several key conclusions were drawn regarding how these materials interact, which point toward the realization of a successful device.

Cadmium-doped SiO2 Nanoparticle Label for the Electrochemical Immunodetection of Protein IgG. XIAOHAI ZHANG (University of Washington, Seattle, WA, 98105) JUN WANG (Pacific Northwest National Laboratory, Richland, WA, 99352)

Semiconducting nanoparticles have garnered enormous attention in the field of biosensor development within the past decade. Due to recent advancements in the control of their growth size and shape, nanoparticles such as silica MCM-41, which have unique structural functionalities, are now an applicable material in creating novel methods of bio-detection. In this report, an amperometric biosensor using biochemically modified silica nanoparticles was developed for the detection of protein IgG via sandwich immunoassay. This novel electrochemical immunosensor is based on the encapsulation of Cadmium ions within mesoporous aluminosilicate nanoparticles (SiNPs) MCM-41. The synthesized silica NPs - antibody conjugates were then characterized with electrochemical detection as well as UV spectrum analysis. Preliminary tests have confirmed that Cadmium ions were immobilized inside the mesoporous shell of the silica NPs; they’ve also shown that the protein antibodies were successfully conjugated. In these experiments, the performance of the electrochemical immunosensor was evaluated via carbon Screen Printed Electrodes (SPE), and a detection sensitivity of 10ppm was achieved. This report has shown that SiNPs has great potential for future research and development of electrochemical bio-sensors; however, optimizations in its synthesis method are still required to increase the detection limit. Cadmium labeled silica NPs offers a viable approach for the rapid, simple, and cost-effective analysis of biological samples.

Cd2SnO4 and ZnMgO: Ternary Transparent Conducting Oxides for Thin Film CdTe and CuInGaSe2 Solar Cells. HANNAH RAY (Wesleyan University, Middletown, CT, 6459) XIAONAN LI (National Renewable Energy Laboratory, Golden, CO, 89401)

The compounds cadmium stannate (Cd₂SnO₄) and zinc magnesium oxide alloy (Zn_1-xMg_xO) are ternary transparent conducting oxides (TCOs) that are promising for use in thin film solar cells. When used in place of the commonly used TCO tin oxide (SnO₂), Cd₂SnO₄ enhances small-scale cadmium telluride (CdTe) solar cell performance. To scale up the deposition area and rate of Cd₂SnO₄, metal organic chemical vapor deposition is used. The commonly used precursors for cadmium oxide and SnO₂ have incompatible deposition temperatures; thus, a different tin oxide precursor with a lower deposition temperature must be found to be used with dimethyl cadmium. A literature search was performed, and tin (II) acetylacetonate was deemed best for this application. Zinc oxide (ZnO) is commonly used in copper indium gallium diselenide (CIGS) solar cells. Alloying ZnO with the insulator magnesium oxide (MgO) allows for band gap (E_g) engineering. However, adding MgO to a ZnO alloy detracts from the film’s electrical conductivity. In this study, a gradient of ZnO:Al and MgO was deposited using RF magnetron sputtering by two ZnO:Al and MgO targets, creating the zinc magnesium oxide alloy Zn_1-xMg_xO. Magnesium (Mg) content of the films varied from 3-30%. The optical and electronic properties of the film were measured every centimeter along the gradient. It was determined that the electrical properties of the Zn_1-xMg_xO alloys are only acceptable for use in a solar cell when the proportion of Mg in the sample is less than 3.5% (x_{g
(Zn1-xMgxO)} = 1.72x + E_g
(ZnO) with the amount of Mg in the alloy. At Mg content between 0-7%, the band gap was higher than this fit line due to the Burstein-Moss effect. As Mg content increased in this region, E_g due to the Burstein-Moss effect decreased until the effect disappeared at x = 0.07. Increasing the deposition temperature improved the electronic conductivity of the films. Increasing the temperature had no effect on the band gap when the Mg content was greater than 7%, but when Mg content was less than 7%, E_g increased with temperature.

Combinatorial Study of Znx Sn1-x Oy: a Transparent Conducting Oxide. DIANA SILVA (University of Colorado, Boulder, CO, 80301) MAIKEL VAN HEST (National Renewable Energy Laboratory, Golden, CO, 89401)

Zinc-tin-oxide (ZTO) libraries were co-sputtered from ZnO and SnO₂ by RF magnetron sputtering onto Eagle 2000 glass substrates at temperatures ranging from room temperature to 550°C and analyzed with combinatorial analytical techniques. Samples were deposited in pure argon and in a mixture of argon and hydrogen with 4% and 2% hydrogen. ZTO films were found to be amorphous at a tin content ranging from 30 to 70% when deposited in pure argon gas at 550°C. ZTO films were also amorphous when deposited in a mixture of argon/hydrogen with 4% and 2% hydrogen at 550°C. ZTO films deposited in pure argon had a maximum conductivity of 134 S ⁄cm at a 70% tin content and an optical transparency with transmission 85%. While, ZTO films deposited in a mixture of argon and hydrogen 2% had an optical transparency with transmission 85% across the visible spectrum and a maximum conductivity of only 92 S ⁄cm observed at 75 at % tin content. Thin films of zinc-tin-oxide deposited in a mixture of argon and hydrogen with 4% and 2% hydrogen, did not improve conductivity and optical properties as expected. Key words: zinc tin oxide, transparent conducting oxides, amorphous

Compiling and Organizing RIMS-Related Data. WALTER PETTUS (Hillsdale College, Hillsdale, MI, 49242) DR. MICHAEL R. SAVINA (Argonne National Laboratory, Argonne, IL, 60439)

Control of Carbon Nanofiber Alignment During Growth in Plasma Enhanced Chemical Vapor Deposition Processes. RYAN PEARCE (University of Tennessee, Knoxville, TN, 37916) MICHAEL SIMPSON (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Carbon nanofibers are just recently coming under scrutiny with a number of potential uses such as gene delivery arrays and neuronal interfaces. Nanonofibers have a stacked “herringbone” structure, giving them a very high aspect ratio, which is what lends them such a great range of possible applications. Carbon nanofibers are typically grown using a process called “Plasma Enhanced Chemical Vapor Deposition” (PECVD). In this process, a silicon wafer with nickel deposited on it in a specific pattern is placed on a heater in a vacuum chamber. The heat is turned on and ammonia (NH3) and Acetylene (C2H2) are introduced into the chamber at a specific pressure and flow rate. A plasma is induced which causes the carbon from the C2H2 to deposit on the nickel dots, forming the carbon nanofibers. This process forms vertically aligned carbon nanofibers. Our project aims to find a technique to control the alignment of the nanofibers during growth. The way we do this is by changing the method whereby gas is introduced into the system. Classically, the gas flows into the chamber perpendicular to and far away from the surface of the wafer, so that only the ratio of gases affects the growth, and not the flow rate. What we do is place a nozzle directly over the wafer so that the gas flows directly over it. We devise an optimal regimen for growth where we only vary the total flow, keeping the ratio of gases constant. After growth, we observe the wafer under a scanning electron microscope. We have found that nanofibers respond to the variations in flow by tilting along the flow. There are some aspects of this study that require further investigation. First, we need to determine the correlation between angle of tilt and flow rate, which can be done by setting up a series of experiments keeping the total flow variable in a stepped sequence and measuring the resulting angle formed by the nanofibers and the substrate. Then, flow ratio needs to be varied to determine the resulting effects. Another method of creating tilt in nanofibers is through variance in the electric field during PECVD. Towards the edge of the field, this causes the nanofibers to “bend.” This technique is impractical, however, as only the fibers grown on the very edges of the field are affected. Our study is fundamental in understanding how to control nanofiber growth, which will lead to an overall better understanding of nanoscale fabrication.

Cross-Sectional Polishing for Solar Cell Device Characterization. NATHAN FAST (California State University Northridge, Northridge, CA, 91330) BHUSHAN SOPORI (National Renewable Energy Laboratory, Golden, CO, 89401)

Fabrication of high efficiency solar cells requires a method to study the effects of new processes on the interactions and physical structure within a cell. An improved method for cross-sectional polishing of large areas of solar cells is described. This method produces a highly planar surface compared to the conventional way of preparing a sample by cleaving. The traditional method of cleaving or fracturing a sample works well for single crystalline wafers, however, creates undesirable surface morphologies for polycrystalline wafers or multi-layered devices such as finished solar cells. The discontinuities caused by the fracture mechanics of non-homogeneous samples create patterns that make it difficult to characterize the true nature of the materials under study. Solar cells cross-sectioned by this improved technique can be characterized by very high resolution electron-beam and optical imaging to measure the alloyed regions of front and back contacts, thickness of backsurface field, and other important physical properties of solar cells. In this method, a standard polycrystalline Si solar cell sample is prepared in a specially designed polishing chuck and secured with wax. The sample is sequentially mechanically polished by progressively decreasing the polishing grit size with chemical mechanical polishing (CMP) used as the last step. Optical microscope and scanning electron microscope (SEM) micrographs showing the planar results of this progressive polishing method are presented showing the improvement over the cleaving technique. This large area cross-sectioning permits statistically significant evaluation of many areas of the cell. The planarity of the sample edge makes it possible to perform a variety of atomic force microscope (AFM), conductive atomic force microscope (CAFM), scanning Kelvin probe microscope (SKPM) and other scanning analyses over large areas in addition to more localized investigations such as with SEM.

Data Processing and Analysis for the Superconductivity Program. MICHAEL DUITSMAN (University of Evansville, Evansville, IN, 47722) VICTOR MARONI (Argonne National Laboratory, Argonne, IL, 60439)

Development of an ASTM Graphite Oxidation Test Method. TYLER GULDAN (The University of Tennessee, Knoxville, TN, 37996) TIMOTHY D. BURCHELL (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Graphite, one of the three allotropes of carbon, is a very useful material because of its unique chemical structure and properties such as mechanical strength, chemical inertness, and electrical conductivity. In order to advance our knowledge of various graphite brands, further research must be conducted to gain a greater insight into the process and effects of oxidation on graphite properties. Although the key processes and controlling elements of graphite oxidation have been identified, the behavior of this material during and after oxidation is not well established. Knowledge of this behavior is crucial in understanding what happens to the various graphite components in nuclear reactors. Thermogravimetric analysis in a vertical furnace of large samples of NBG-18 graphite at the Oak Ridge National Laboratory (ORNL) has been used to characterize the oxidation resistance of this material, and to increase the scientific understanding of the relationship between the rate of oxidation and the flow rates of gases, temperature, and the intrinsic reactivity of graphite. This helps to identify the more oxidation resistant forms of graphite. In addition, comparative analysis of data collected on other graphite materials has been conducted, in order to identify a more expedient procedure for analysis of graphite oxidation data. The information gathered from these experiments and calculations is geared towards the development of an American Society for Testing and Materials (ASTM) test method for the oxidation of graphite. More research on all of the types of graphite is needed, but such results suggest that the current ORNL procedure using the vertical tube furnace may become a reliable ASTM test method.

Doping of TiO2 (with C and S) for visible-light absorption. ROHIT BIYANI (Washington State University, Pullman, WA, 99163) THEVA THEVUTHASAN (Pacific Northwest National Laboratory, Richland, WA, 99352)

Hydrogen proves to be a very clean and efficient fuel source; unfortunately obtaining large quantities of it is not cheap. One of the potential methods of obtaining hydrogen involves photocatalytic splitting of water molecules with Ultraviolet light using Titanium Oxide (TiO2) as the catalyst. However, an Ultraviolet light source is expensive; a cost efficient substitute is visible light or sunlight. Band engineering of TiO2 single crystals with appropriate dopants can facilitate photocatalytic activity for visible-light absorption. Anion dopants such as Nitrogen, Carbon and Sulfur have been implanted into the TiO2 substrate, and it has been demonstrated that some of these implanted materials can absorb visible light for photochemistry. Our overall objective is to develop fundamental scientific understanding about the mechanisms associated with photochemistry in these materials. In this study, we used ion accelerator to implant C and S dopants in single crystal TiO2 (110) samples and to investigate the structural changes in the materials. The samples were implanted at various temperatures and doses, the lattice site location of the dopants were analyzed using ion beam capabilities. The implanted TiO2 substrates were characterized using Nuclear Reaction Analysis (NRA), Rutherford Backscattering Spectrometry (RBS), and Proton Induced X-ray Emission (PIXE) methods in random and channeling geometries. Although PIXE is extremely sensitive to trace elements, S quantification could not be made using PIXE due to the domination of the signal from Ti. The signal from S could not be collected without too many uncertainties. The RBS along channeling and random geometries showed that the greater the temperature of implantation, the less the damage was on the surface. Also a lower Carbon dose at a high temperature of 900° C shows some substitutional behavior of the Carbon atoms replacing possibly Oxygen in the TiO2 lattice. The samples were finally annealed at 900oC in air for several hours and as expected, the implantation damage was significantly reduced in the annealed samples. In addition, the angular yield curves show that the C atoms moved to interstitial positions during annealing. Further experiments are necessary to understand the influence of C dose on this behavior of C location in TiO2 lattice.

Effect of Chemistry Variations on the Microstructure and Mechanical Properties of Creep Strength Enhanced Ferritic Steels. KEELY WILSON (Michigan Technological University, Houghton, mi, 48128) JOHN SHINGLEDECKER (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Grades 91, 92, and 122 steels (9-12% Chromium) are known as Creep Strength Enhanced Ferritic steels. These grades of steel are finding increased usage in the pressure retention components of advanced fossil energy systems (Ultrasupercritical Steam Boilers, Heat Recovery Steam Generators, etc.) because of their superior performance in high temperature, high stress environments. The chemical specifications for these grades are very broad, which may affect the mechanical properties and long-term performance of the alloy in service. Ideally in the normalized and tempered condition, Gr 91, 92, and 122, will have fully martensitic structures with no ferrite forming. In an earlier study, two compositions of each grade were produced by varying the amounts of austenite formers (C, Mn, Ni, N) and ferrite formers (Si, Cr, Mo, V, Nb) within the current specification range. These chemistry changes were guided by computational thermodynamics to alter the intercritical temperatures, the temperatures at which steel changes phase, and to cause the formation of ferrite under standard processing conditions. In this study, the mechanical properties of these samples were evaluated, and are compared to literature results for commercially produced material. High temperature (650°C) creep tests were run with loads ranging from 100 to 140 MPa for times exceeding 1000 hours. Tensile tests were run at both high temperature (650°C) and room temperature (25°C). Digital Imaging software was used to analyze the steel microstructures to determine the amount of martensite and ferrite present in each alloy. It was found that both the tensile strength and the creep strength of the alloys decreased substantially with the presence of ferrite in the material. This critical finding clearly shows that the specification range for these alloys is too broad which may result in commercially produced materials with properties far from expectations. A limited evaluation of thermodynamic predictions and microstructural findings was also conducted. The data collected in this study, combined with data from other tests, such as long term creep tests, thermo-mechanical simulation, and thermodynamic modeling will later be used to create more specific standards for Gr 91, 92 and 122 alloys.

Elaboration on the Hexagonal Grid and Spiral Method for Data Collection via Pole Figures. ANTHONY RIZZIE (Ball State University, Muncie, IN, 47306) THOMAS WATKINS (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

A pole figure provides a representation of the distribution of a particular set of atomic planes for data acquired through diffraction and is used for analyzing crystallographic texture or preferred orientation. Pole figures are constructed from a collection of data points, each with a prescribed azimuthal angle (phi) and sample tilt angle (chi) (as specified by the goniometer) and measured intensity (counts or counts per second). Traditionally, the Schulz method (5°x5° grid) is employed to acquire the necessary data, but this leads to a high concentration of data points for small chi values, low concentration for large chi values, and consequently an inefficient use of time. Two alternative data collection methods, the hexagonal grid and spiral, have been previously proposed but only tersely documented in terms of both construction and implementation. The goal, therefore, is to provide a practical description of the mathematics required to implement the hexagonal and spiral data collection schemes. Applying the concepts of equal area and stereographic projections and geometry, spreadsheets were created to formulaically develop hexagonal and spiral grids, which are then related to angular movements of the goniometer. Using the generated data points, the hexagonal grid and spiral methods were programmed by “brute force” into the existing x-ray software and employed to collect data for a sample of aluminum foil. The resulting (111) pole figures compared favorably to typical rolling textures for aluminum foil collected with the conventional Schulz method. The hexagonal grid has been shown to reduce the number of data points and time needed to complete a pole figure, while providing equal area sampling. The spiral method was shown to use only a quarter as many data points as the 5° x 5° grid. In the future, LabVIEW software will be utilized to develop programs for collecting data using both the hexagonal grid and spiral methods and then convert the data back to the conventional 5° x 5° grid.

Establishment of Manganese Oxide and Lanthanum Oxide as Atomic Layer Deposition Materials for Lanthanum Strontium Manganate (LSM) Electrodes. DAVID HONEGGER (Lewis & Clark College, Portland, OR, 97219) JEFFREY ELAM (Argonne National Laboratory, Argonne, IL, 60439)

Heat-Reflective Paint for Deck Surfaces of Naval Vessels. EMILY OTTENWELLER (University of St. Francis, Fort Wayne, IN, 46808) RICK LOWDEN (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

The new V-22 Osprey aircraft has the capability to vertically take off from and land on the deck of an aircraft carrier. During take off and landing, the hot exhaust from the Osprey aircraft engines impinges directly onto the deck of the ship. The deck surfaces were not designed to handle high temperatures and thus warp from the excess heat. Insulating paints that use special ceramic additives have been developed to improve the energy efficiency of buildings and structures. The decks of naval vessels are coated with paints that include ceramic grit to make them non-skid. It was hypothesized that the insulating additives could be used to replace the non-skid grit and create a paint that could protect the deck from the hot exhaust. Ceramic particles were added to an epoxy-based surface coating to alter the layer’s thermal properties, i.e. to reflect, absorb or conduct heat. The ceramic additives include Bionic Bubbles which are hollow microspheres derived from fly ash, Insuladd particles which are hollow ceramic mircospheres invented by NASA, and silicon carbide platelets. The test specimens were ½ inch thick steel plates to which paints with different additives were applied. The plates were heated using a heat gun to simulate the exhaust of the aircraft and temperature distributions on the backside of the painted specimens were measured. The temperature distributions for the plates coated using paints with additives were compared to results for bare metal, paint with no additive, and the standard non-skid deck coating. The plate with the highest concentration of Bionic Bubbles was the most effective in reducing the temperature of the plate; however, the layer is likely too fragile for the application. The deck coating must not only be insulating but also robust and non-skid. It appears that the ceramic additives will need to be modified to best suit the needs of this application.

High Activity Fuel Cell Catalysts via Mesoporous Nanocomposite Polymers. GREGORY BAKER (Pennsylvania State University, University Park, PA, 16802) ERIC COCHRAN (Ames Laboratory, Ames, IA, 50011)

Hydrogen fuel cells have the potential to improve the way we propel our vehicles. Catalyst particles within cathode catalyst layer (CCL) promote the reaction of protons, electrons, and oxygen, producing water, which must be removed. The current CCL design suffers from poor mass transport properties, limiting the efficiency of the present-day hydrogen fuel cell. The current structure is a combination of different materials put together to achieve these goals but lacks the order needed to achieve the desired efficiency. In this research, we investigated the development of a novel CCL design that will significantly increase the transport of reactants to active catalyst sites. The first step towards this design was the synthesis of a new catalyst support, based on single-wall carbon nanotubes (SWCNTs), that integrates electon and proton conductivity into a single particle. First, pristine SWCNTs were functionalized with an aniline derivative compound using a solvent free technique. Then, azide-terminated polystyrene was “click-coupled” to the alkyne group. This SWCNT-graft-polystyrene was then sulfonated; this created negatively charged regions in the polymer, which facilitated the deposition of platinum nanoparticles through the reduction of platinum salts. After sulfonation the polymer is also proton-conductive. Thermogravimetric analysis analyzed the effectiveness of the grafting reactions. Nuclear magnetic resonance spectroscopy demonstrated that the proper products were prepared during the synthesis of the aniline derivative and also to ensure that azide terminated polystyrene was achieved. Transmission electron microscopy determined the effectiveness of the decoration with platinum.

High Storage Density Capacitors Fabricated Using Atomic Layer Deposition. ANDREA BLUMENTRITT (LeTourneau University, Longview, TX, 75602) JEFFREY ELAM (Argonne National Laboratory, Argonne, IL, 60439)

In Situ Measurement of Stresses in Carburized Gears via Neutron Diffraction. BRYAN BOGGS (University of Tennessee at Martin, Martin, TN, 38238) CAMDEN HUBBARD (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Carburized gears are characterized by a very hard outer layer that contains chemistry, phase, and microstructure gradients. X-rays have been used in the past to attain measurements of residual stresses, but X-ray diffraction is limited to near surface stress measurements due to attenuation. X-ray diffraction also has difficulty reaching the critical stress regions of a gear tooth due to beam interference from the complex geometry. This research seeks to develop experimental methods for measuring the stresses/strains in carburized gears at locations unattainable by X-rays and to do this as a function of applied load on the gear tooth. Experiments are being performed to determine if neutron diffraction can be used as an alternative to X-ray diffraction to measure the total stresses. Total stresses consist of both the residual stresses imparted during the carburization process and the load induced stresses resulting from power transmission. The experiments are being performed at the Neutron Residual Stress mapping Facility (NRSF2) at the High Flux Isotope Reactor (HFIR). In neutron diffraction, a powder sample is normally used to determine the unstressed lattice spacing or d₀. In carburized components, d₀ can not be determined from a single powdered sample because of the non-homogeneous material in the carburized region. As an alternative to using a powder sample, a method commonly used in X-ray diffraction known as the sin² method is being studied to determine if it can be used with neutron diffraction to accurately quantify d₀ in the carburized region. If successful, the sin² method will be used to determine d₀ at a number of points in the carburized region. Neutron diffraction methods will then be used to measure the d-space at each of the points for which d₀ was determined. The combination of d-space and d₀ at each point will enable the strains and stresses to be determined at the measurement points. The measurement of the d-space in a loaded gear is being facilitated with a Static Load Application Device (SLAD). This device was designed to statically load the gears as well as be compatible with the equipment at NRSF2. Stress analysis was done on the SLAD to ensure that the device would not exceed strength values found in engineering design standards.

In-Situ Stress Measurement for MOCVD Growth of High Efficiency Lattice-Mismatched Solar Cells. ALEJANDRO LEVANDER (Pennsylvania State University, State College, PA, 16802) JOHN GEISZ (National Renewable Energy Laboratory, Golden, CO, 89401)

Dislocations, formed in order to relieve stress, act as sites for nonradiative electron/hole pair recombination, which reduces the efficiency of photovoltaics. Stress forms as a result of mechanical and thermal mechanisms during the metal-organic chemical vapor deposition growth process. Mechanical stress is the result of depositing lattice-mismatched (LMM) layers on top of one another and thermal stress results from a thermal gradient within the sample and depositing layers with different thermal expansion coefficients on top of one another. To reduce the number of dislocations in the active layer when using LMM materials, compositionally step-graded layers and a buffer layer are placed between the two LMM materials. In order to achieve a better understanding of the effect of stress on the active layer, the buffer composition, and therefore lattice constant, was varied to change the stress on the active layer. The in-situ stress and ex-situ strain were characterized using a multi-beam optical stress sensor and x-ray diffractometry respectively. The quality of the photovoltaic devices was measured using a solar simulator and quantum efficiency instrument. Samples with near zero stress or small amounts of compressive stress in the active layer had the highest open-circuit voltages and efficiencies. Tensile stress in the active layer significantly degraded performance. The biaxial modulus was calculated from a stress v. strain curve, but several sources of error exist. The band gap of the active layer increased with increasing stress, despite the composition remaining constant. Future work will concentrate on the effect of dopant type on stress development and dislocation formation in the graded layer.

Microbiologically Influenced Corrosion in Oil Pipelines: Causes and Effective Treatments. BRENDEN VAN SLYKE (State University of New York at Stony Brook, Stony Brook, NY, 11794) BRENDEN VAN SLYKE (Brookhaven National Laboratory, Upton, NY, 11973)

Microbiologically Influenced Corrosion (MIC) is a serious problem in the oil industry. During oil extraction, especially secondary recovery, water may become mixed with the oil. This water can harbor microorganisms, that when not controlled can cause serious corrosion due to their metabolic processes. Two particularly damaging and widespread forms of bacteria involved in MIC are sulfate reducing bacteria (SRB) and acid producing bacteria (APB). The initial phase of this project was literature research into the causes and mechanisms for MIC. Then this information was applied to examining photographs and replicas of a pipeline suffering from possible MIC. Based on this examination, information on different treatment options were researched. The literature research aspects of the project were undertaken using electronic media such as the Internet and online journals, correspondence with industry officials and scientific researchers, and printed material. Literature research into the causes of MIC led to two distinct areas of interest. The first of these was the human factor, which dealt with poor maintenance and improper use of biocides allowing bacteria to proliferate in the system. On the bacteria side, the SRB and APB formed colonies with themselves and other non-corrosive bacteria. The bacteria can influence corrosion by the production of corrosive metabolites, hydrogen sulfide in the case of SRB and organic acids with APB present. SRB also can stimulate the development of iron sulfide deposits, which increase corrosion by enlarging the cathode. Furthermore, , acids produced by APB can also complex with metal ions at the anode, removing them and accelerating the corrosion reaction. The replica casting were made from actual corroded oil pipe using Struers Repliset kits. These were then sputter coated using an Anatech Hummer VII to show more contrast. After examining the photographic evidence and replicas three types of corrosion were suspected. Two cases of MIC, one each by SRB and APB, were determined. One sample showed inorganic carbon dioxide corrosion and a fourth section exhibited an undetermined form of corrosion. The most important factor in limiting MIC is keeping oil pipelines clean and as water free as possible. Biocides containing glutaraldehyde as the active agent and quaternary ammonium compounds to break up biofilms are suggested. This project is part of a larger investigation into oil pipeline corrosion, which is ongoing.

Model Based Illumination Optimization for a 003-Numerical Aperture Extreme Ultraviolet Lithography Tool. JONATHAN NATION (University of Arizona, Tucson, Tucson, AZ, 85701) PATRICK NAULLEAU (Lawrence Berkeley National Laboratory, Berkley, CA, 94720)

There have been many recent advances in high numerical aperture (NA) extreme ultraviolet (EUV) lithography systems. The 0.3-NA Micro Exposure Tool (MET) at the Advanced Light Source (ALS) currently utilizes a programmable coherence illuminator system with the capability of creating different pupil fills. It is well known that illumination settings can be tailored to optimize printing performance for particular features. The optimal illumination settings, however, depend not only on the feature type but also on the specifics of the pupil function, including phase (or aberrations) and amplitude (or pupil obscurations). In order to maximize the productivity of the MET, the best possible pupil fill should be chosen for the feature type being imaged in each experiment. In this research, aerial image modeling software is used to study the optimal illumination conditions for the SEMATECH Berkeley MET tool as a function of feature size and type taking into consideration the known pupil function of the optic. The metrics of maximum contrast over a 50 nm focus range and depth of focus with contrast greater than 0.5 are used to gauge the performance of each pupil fill tested. We will present the best annular, dipole, and monopole pupil fills for each feature type as well as for each individual feature size. Experiments relying on only one feature size will obtain the greatest improvement in contrast and depth of focus by using the presented pupil fills, at the possible expense of losing quality of other feature sizes. The results are also directly compared to the default annular 0.35-0.55 setting used in the commercial implementations of the MET tool. Initial results for annular pupil fills reveal that improvements of up to 12% in each metric can be obtained.

Optimization of Spray-Coated Organic Photovoltaics. RENEE GREEN (University of Pittsburgh, Pittsburgh, PA, 15261) GARRY RUMBLES (National Renewable Energy Laboratory, Golden, CO, 89401)

Organic photovoltaic devices, traditionally spin-coated, were made via an airbrush spray-deposition technique from a 1:1 poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C₆₁ butyric acid methyl ester (PCBM) blend in dilute (1mg/ml each) solution. Devices were tested for dependence on solvent boiling point and annealing temperature. Working devices resulted from solutions prepared in chloroform, toluene, chlorobenzene, and para-xylene, with an initial maximum power conversion efficiency of over 2% (average 1.787%) from a p-xylene solution. Chlorobenzene was selected for use in further studies due to its small statistical spread of device efficiencies, high-quality smooth films, and comparable (1.15%) efficiency values. Annealing the device active layer at 120°C resulted in the highest power conversion efficiency among annealing temperatures ranging from 90°C to 200°C. Spray-coating is ideal for its ability to deposit highly dilute solutions, create multilayer organic devices, and expand the range of available analysis techniques by permitting the creation of high-quality thick films.

Oxidation Characterization of Chromium Tungsten Niobium Superalloys. AMANDA BASTIDOS (University of Texas at El Paso, El Paso, TX, 79901) DR. KEN NATESAN (Argonne National Laboratory, Argonne, IL, 60439)

Photovoltaic properties of epitaxially grown Bismuth Ferrite. SOURAV BASU (University of California at Berkeley, Berkeley, CA, 94704) RAMAMOORTHY RAMESH (Lawrence Berkeley National Laboratory, Berkley, CA, 94720)

Photovoltaic properties of epitaxially grown (111) BiFeO₃ (a ferroelectric material) were investigated under a 100 mW/cm² solar simulator light source and tunable halogen source. Photo-excited carriers were extracted through transparent Indium Tin Oxide (ITO) top electrodes. Carrier migration was through-film, in the direction of intrinsic polarization. Current densities observed under solar spectrum at no applied field exceeded 1 mA/cm² for certain samples, much higher than previously observed in photovoltaic ferroelectric materials. All films were grown by Pulsed Laser Deposition (PLD). Annealing of samples in varying partial pressures of oxygen was conducted post-deposition to introduce oxygen vacancies and consequently improve the conductivity of the BiFeO₃ films. The magnitude of the photocurrent was observed to be directly proportional to the conductivity of the migration pathway. Traditionally, photovoltaic ferroelectric materials have been prevented from being used in energy conversion primarily because of their low current density output. By observing current densities in excess of 1 mA/cm² (on the order of magnitude of current densities produced by many photovoltaic semiconductors), we demonstrate the possibility for the use of BiFeO₃ in direct energy conversion. In addition, preliminary results involving wavelength dependence of photocurrent indicate the presence of the absorption edge near a wavelength corresponding to BiFeO₃’s theoretically predicted bandgap. In addition, future research involving the multiferroic properties of BiFeO₃ could present the possibility of optically controlled magnetization.

Production of Pure Phase Multiferroic Materials by High Oxygen Pressure Annealing Processes. MATTHEW CROMWELL (Brigham Young University-Idaho, Rexburg, Idaho, 83460) DR. R. W. MCCALLUM (Ames Laboratory, Ames, IA, 50011)

This study aims to form multiferroic materials from Rare Earth compounds and Manganese oxides. The desired composition is RMn₂O₅ (R = Rare Earth). Multiferroic materials import stems from simultaneous ferromagnetic and ferroelectric characteristics. Because of their dual nature, multiferroic materials could be utilized in various technologies. Understanding the properties and behavior of their crystal systems is critical to the eventual application of such materials, yet producing a pure single phase is still problematic. This must be done by reacting highly stable R₂O₃ with Mn-O, which remain stable in air to 1200 ºC. Existing phase diagrams for the given system indicate that increasing partial pressure of Oxygen (P_O2) greatly improves the kinetics of the phase transition. However, at such temperatures and pressure, standard materials soften and fail. Oxygen also presents a problem, being highly corrosive in nature. A furnace chamber maintaining up to 1000 ºC with 10 bar P_O2 was built from Hainesalloy-230, a high-nickel superalloy. This pressurized system was installed and various safety considerations and procedures were negotiated in bringing this into operation. A series of experiments varying annealing conditions were then performed to study the effect of changing P_O2. Two sets of samples were made from the same mixture and run at 900 ºC and 1000 ºC for twenty hours. Within each set, four pressures (in bar) were applied- 9.3, 3, 1 and 0.2. Results were examined by X-Ray Diffraction (XRD) to determine composition. XRD showed the content of desired phase increased significantly at higher temperature and also with increasing P_O2. Increasing temperature by 100 ºC produced double the desired phase over the 20 hour test. Still significant was the increase due to P_O2 which lifted the desired phase from 60% to 72%. This affirms the importance of P_O2 in this phase system. In further study, the effect of P_O2 over greater time intervals and elevated temperatures may be instructive in obtaining pure phase materials.

Quasielectrostatic Carbon Orientation for Lithium-Ion Battery Applications. CLIFF MCCOLD (Vanderbilt University, Nashville, TN, 37235) JANE Y. HOWE (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

In Quasielectrostatic Carbon Orientation (QCO) processing, carbon precursor materials are thermally treated while subject to an alternating current (AC) electric field with the goal of producing carbon materials with oriented graphene sheets. To provide proof-of-principle, QCO-treated samples are characterized to determine if conductive graphene sheets composed of bonded carbon atoms can be aligned in the direction of the electric field. Carbons with oriented graphene sheets could potentially be used in lithium-ion battery anodes, permitting higher charge rates, greater maximum current, and higher power density. A tube furnace was used to raise the temperature of the precursor material in an inert argon atmosphere. The material was held in a rig between top and bottom capacitor plates at different voltages, which applied the field during the entire 24-hour thermal processing. Variables included precursor materials (Mitsubishi AR mesophase pitch, phenolic resin), highest temperature (280°C, 650°C), AC field frequency (200Hz, 10kHz, 700kHz), and electric field strength (no field, 2.4kV/cm, 6.0kV/cm). Created samples underwent x-ray diffraction and impedance spectrometry to determine if desired graphene sheet orientation was achieved. Results indicated that AR mesophase pitch does not respond to QCO processing at softening temperature (280°C). Severe foaming of AR mesophase pitch under numerous run conditions up to carbonization temperature (650°C) excluded carbonized samples from both characterization techniques. Phenolic resin samples showed QCO treatment-dependant results at carbonization temperature, but data was from too small a sample population to see clearly defined trends. Future work includes extensive sample creation under various QCO field frequencies. The ability to apply a stronger field (6.0kV/cm and higher) was only recently developed by minimizing capacitor plate separation, and many samples remain to be created using stronger field conditions. Isotropic pitch and cellulose are potential future precursor materials. Created samples must be analyzed using the x-ray diffraction and impedance spectrometry, and scanning electron microscopy will also be used for future analysis. Once a clear trend in data is observed, the appropriate precursor material and run conditions will be used to create samples for direct lithium-ion battery anode testing.

Redox Reactions wiith Single-Walled Carbon Nanotubes. SOFIANE BOUKHALFA (University of Illinois at Urbana-Champaign, Urbana, IL, 61801) STEPHEN DOORN (Los Alamos National Laboratory, Los Alamos, NM, 87545)

Single Walled Carbon Nanotubes (SWNT) have been under close scrutiny by the scientific community since their discovery in 1992 due to their surprising material properties. SWNT synthesis can be achieved in numerous ways. However, these methods result in a wide spectrum of chiralities of nanotubes. In order to more efficiently use these novel materials, individual chiralities must be isolated. To achieve this, a reduction-oxidation chemistry approach is used. Redox reagents of different electro-chemical potentials were added to solutions of SWNT in surfactant. Spectroscopy (absorbance and fluorescence) measurements were taken in order to monitor the effects of electron transfer between the SWNTs and the salts. Once chiral-specific doping can be achieved, isolation of these individual chiralities of SWNTs is planned through the use of ultracentrifugation. 20µL of each redox reagent was added to 3mL SWNT in surfactant solution while spectroscopy measurements were taken every 7 seconds in order to map out chiralities. Using a Fermi level map of the chiralities as a model, it was determined that the electro-chemical potential of the reagents directly affected the chiralities which were quenched during the experiments. Interaction between the salt and the surfactants is characterized by aggregation of the SWNTs; in the current redox reactions such aggregation, which broadens the spectroscopic signals, is not observed. Thus, a direct correlation was determined between the electro-chemical potential of the redox reagent and its effects on the nanotube solutions. This work establishes a future guideline for new work in the isolation of individual chiralities of nanotubes.

Safety Barrier Program to Protect Experimenters in the Event of Pressure Cell Explosion. RACHEL MORRIS (Maryville College, Maryville, TN, 37804) LAKEISHA WALKER AND LOUIS SANTODONATO (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

In neutron scattering research, high pressure experimentation with pressure cells is becoming more prevalent. Although this particular type of experimentation can provide a plethora of information regarding solutions to geophysical issues as well as hydrogen storage designs, material analysis at high pressure can be very dangerous. For this reason, scientists need to take precaution for ensuring their safety when using pressure cells under extreme conditions. Since pressure cell fragments can be projected if the cell ruptures or explodes, a safety barrier should be constructed to contain the hazard. Therefore, I have written a program in Visual Basic for Applications using a Microsoft Excel spreadsheet interface to help determine an appropriate and cost-efficient safety barrier. The logic of the program is not only based on calculations derived from the equations of motion in physics for radial distance and velocity, but it is also based on equations of acceleration involving the thickness and density of the cell initially and the amount of pressure used in the experiment. These calculations are the basis for determining how fast an infinitesimal fragment (in the worst case-the entire cell) will be traveling at any given distance from the initial starting position of the cell. The primary purpose of the program is to use a model of velocity versus distance to aid in determining the dimensions for a safety barrier that will be impenetrable for the largest fragment traveling at the highest velocity. Although any cell can be modeled with this program (provided the user supplies certain values for variables), the Titanium Zirconium (TiZr) alloy cell is exampled in this paper, which has a pressure equivalent to 200x10⁶ Pa, a density of 5230 kg/m³, a thickness of 0.0039751 m, and an initial radius of 0.003175 m. The TiZr cell was modeled for 35 steps for 0.000036 s, until the radial distance of the fragment reached 0.123 m and the velocity reached 195 m/s. Thus, the projected and desired results were achieved using the program, and the construction of the barrier will occur in fall 2007.

Self-Assembly of Au Nanorods. ERIC PETERSEN (Harvard University, Cambridge, MA, 2138) JIN WANG (Argonne National Laboratory, Argonne, IL, 60439)

Single Component Variation of Low Activity Tank Waste to Determine Chemical and Physical Behavior on Molten Ionic Salt. SHAELAH EASTERDAY (Gonzaga University, Spokane, WA, 99258) MICHAEL SCHWEIGER (Pacific Northwest National Laboratory, Richland, WA, 99352)

Bulk vitrification is a process used to safely contain Low Activity Waste (LAW) on the Hanford Site into a vitreous waste form. This is done by heating the LAW mixed with glass-forming minerals in a large melting container lined with Castable Refractory Block (CRB). At temperatures above 275325°C, sodium nitrate and sodium nitrite (NO₃+NO₂) in the LAW form Molten Ionic Salt (MIS) that penetrates the CRB. When this occurs, the MIS may be able to leach from the CRB into the environment. Feeds were prepared by drying a liquid LAW simulant with glass-forming minerals. The LAW composition was varied, one component at a time. Feeds were placed in silica crucibles of a similar porosity as the CRB, and heated to 500°C at 5°C/minute and held for 30 minutes. The feed was removed, and the crucibles were heated from 650°C to 1000°C at 7°C/minute and held at 1000°C for 60 minutes. To determine MIS penetration, the crucibles were weighed before and after each heat treatment. It was found that by replacing NO₃+NO₂ with any component, but sulfate, MIS migration decreased. Replacing NO₃+NO₂ with sulfate had no effect on MIS migration. Acetate and chromate decreased MIS migration more than other components. This project provides important data for the Bulk Vitrification of LAW on the Hanford Site by allowing to asses the response of MIS migration in melter feeds to composition variations of the waste.

Slag Penetration in Coal Gasifier Refractories. BRENT HICKS (Brigham Young University, Provo, UT, 84604) S.K. SUNDARAM (Pacific Northwest National Laboratory, Richland, WA, 99352)

Coal gasification is a process used to convert coal in the presence of water, elevated temperature, high pressure, and a reducing atmosphere into high-value chemicals and fuels. A gasifier refractory lining protects the stainless steel shell of the gasifier from elevated temperatures and corrosive coal slag. Refractories composed primarily of Cr₂O₃ have been found the most resistant to slag corrosion, but they still fail to meet their targeted operational lifetime of three years. Experimental data on the slag-refractory interaction is necessary to develop models to 1) identify critical conditions at which refractory corrosion sharply increases 2) predict the service life of a gasifier refractory, and 3) discover processes/techniques to protect the refractories for extended life. Laboratory tests were conducted to determine the penetration depth of three slags representative of a wide variety of coals in the United States into five high-chrome refractories. The slags were pressed into pellets, placed inside a core-drilled refractory sample, and heat-treated in a controlled atmosphere furnace. Variables tested were refractory-slag combinations, different maximum temperatures and partial pressures of O₂, and thermal cycling between temperature extremes found in commercial gasifiers. Slag penetration depths were measured from spliced optical images of each refractory. Samples heated to 1470°C for 2 hrs had average penetration depths ranging from 1.99±0.15 mm to approximately 27 mm; compare to 1.53±0.26 mm to 8.47±0.34 mm for samples heat-treated at 1310°C for 2 hrs and 8.55±0.55 mm to approximately 26.2 mm for samples thermally cycled three times between 1150°C and 1550°C. AUREX 95P, a high-chrome refractory containing 3.3wt% P₂O₅, showed the least slag penetration of all studied conditions. P₂O₅ likely reacts with the slags to increase their viscosity and restrict molten slag penetration. Results indicate that lower temperatures correspond to less slag penetration; the slag is less fluid at 1310°C than at 1470°C. Scanning electron microscopy will be used to verify slag penetration depths for AUREX 95P because it was difficult to distinguish slag from P₂O₅ with optical microscopy.

Spallation Neutron Source (SNS). YAN-JIUN CHEN (National Taiwan University, Taipei, N/A, 104) ROBERT W. SHAW (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

The Spallation Neutron Source (SNS) uses a Multi-Turn Charge-Exchange Injection to form short pulses of protons in its accumulator ring. Carbon stripper foils are used in this process for removing electrons from the incoming H- Linac beam. Testing at various facilities has shown diamond stripper foils have an expected lifetime of more than 100 hours, five times that of evaporated carbon ones. Longer lifetimes can reduce beam downtime for replacement. This project involves producing diamond foils for the SNS and other accelerators. Diamond foils are grown via microwave plasma enhanced Chemical Vapor Deposition (CVD) on patterned silicon substrates. Substrates are patterned using photolithography, and etched chemically to produce corrugations 5~7 µm deep around the edges for mechanical stability of films. To enhance nucleation, the substrate surface is abraded with diamond powder slurry in an ultrasonic bath. Subsequently, 1~2 µm thick nano-crystalline diamond films are grown on the substrates under 1000 W of microwave power and 130 torr with a gas mixture of 2% CH4, 8% H2, and 90% Ar. The substrate is then partially removed with a 1:1:1 mixture of hydrofluoric acid, acetic acid, and nitric acid, leaving a silicon edge for support of the foil. The main focus of the project is to optimize the performance of these diamond foils. Recently, foil areas have been increased by 57% to minimize beam loss, and foil thickness has been increased to maximize efficiency. Scanning electron microscopy (SEM) of the foils has revealed imperfections in the films, including black spots and pits. Black spots have not been proven to affect performance. Nevertheless, they can be successfully removed by etching away the surface of the film in a pure H2 plasma. They are also suppressed with a lower growth pressure. Pits, ranging from 1 µm~10 µm wide, are suspected to cause loss of stripping efficiency and may result in holes or weak spots in foils. These pits are mainly caused by dust particles during the patterning of the substrates. Special attention is now paid to the preparation of substrates to minimize these occurrences. A cloudy visual appearance signifies uneven nucleation densities and/or substrate roughness. As a result, adjustments to the duration of ultrasonic abrasion are being made. Further testing in the SNS will reveal whether these measures lead to greater efficiency and longer lifetimes of foils.

Synthesis and Characterization of Nickel Oxide and Vanadium Oxide Nanostructures. AMANDA TIANO (University of Tennessee, Knoxville, TN, 37996) DR. STANISLAUS S. WONG (Brookhaven National Laboratory, Upton, NY, 11973)

In the field of nanotechnology, transition metals have attracted research interest because of their electronic and magnetic capabilities. Nickel(II) oxide (NiO), an antiferromagnetic material and p-type semiconductor, has been a large focus in research due to its diverse applications, such as catalysis, electrochromic devices, gas sensors, and magnetic films, making it an attractive material for the fabrication of nanodevices. Vanadium oxide (VO₂), like NiO, has also appealed to researchers because it undergoes a semiconductor-to-metal transition, known as a Mott transition, at 68°C. Below this temperature, VO₂ maintains monoclinic (M) phase and above converts to the metallic (R) phase. Since the Mott transition is also associated with reversible changes in optical, magnetic, and electrical properties as well as structure, VO₂ is also appealing for a variety of applications from energy storage to catalysis. NiO nanocrystals formed with and without the presence of a surfactant via thermal decomposition at 830°C in molten NaCl of two different precursors: nickel(III) oxide (Ni₂O₃) and nickel oxalate (NiC₂O₄•2H₂O). These precursors formed quasi-circular particles measured as 283 ± 135 nm and 287 ± 100 nm in size, respectively. NiO nanosheets, 355 ± 166 nm in diameter and 44 ± 12 nm in thickness, were also formed by hydrothermal treatment of nickel acetate, Ni(CH₃COO)₂•4H₂O, to generate nickel hydroxide with subsequent thermal decomposition at 400°C. Monoclinic VO₂ (B) nanorods, (width: 185± 37 nm, length: 1.4 ± 0.4 µm) were synthesized by hydrothermal treatment of V₂O₅. Subsequent thermal decomposition at 340°C in air produced V₂O₅ nanoparticles (107 ± 26 nm) while heating at 500°C in a flowing argon atmosphere produced larger monoclinic VO₂ (M) rod-like particles (width: 0.98 ± 0.38 µm, length: 6.8 ± 2.2 µm). The products were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and a magnetic property measurement system (MPMS). We have confirmed the presence of nickel oxide and vanadium oxides with XRD and determined size, shape and morphology with SEM. We have begun analysis with the MPMS but the current signal intensity associated with our samples has thus far been too weak for adequate interpretation. Through characterization, we can conclude the successful synthesis of nickel oxides and several forms vanadium oxide nanostructures by both molten salt and hydrothermal methods.

Synthesis and Integration of Carbon Nanofibers for Nanobiological Applications. PATRICIA REYNOLDS (University of Toledo, Toledo, OH, 43606) MICHAEL L. SIMPSON (Oak Ridge National Laboratory, Oak Ridge, TN, 37831)

Recent advances in the controlled synthesis of nanomaterials are enabling new approaches for probing biological system functionality at the nanoscale. Several CNMS projects incorporate one such nanomaterial, carbon nanofibers, as functional elements. Applications include the use of carbon nanofibers as nanoelectrodes, as means for gene delivery, and as the principle component of biomimetic membranes. Current efforts make use of vertically aligned carbon nanofibers (VACNF) as suspension supports for lipid bilayers (LBL). There are two main purposes; one is to develop techniques to form LBL structures and secondly to use them as a platform to study integral membrane proteins and their interactions using neutron scattering. Carbon nanofibers are synthesized in a plasma enhanced chemical vapor deposition process from metal (nickel) catalyst, and the vertical alignment results from the applied electric field during synthesis. The growth process allows for controlled synthesis as the parameters (e.g., length, diameter, shape, position, and chemical composition) of individual nanofibers can be selected by definition of catalyst properties and growth conditions. LBLs are composed of phospholipid head groups which are hydrophilic and hydrocarbon centers which are hydrophobic. To fabricate hybrid structures composed of VACNF arrays with deposited LBLs, small unilamellar lipid vesicles were generated through the sonication of LBLs, deposited on VACNF arrays, and heated to 35 degrees C for 30 minutes to encourage layer development. Atomic Force Microscopy was used to map the VACNF array surface both before and after LBL deposition, and encouraging initial results were acquired to show a change in surface topography that is indicative of the formation of a LBL on the nanofibers. The next step in this work is to image these hybrid structures with neutron scattering to validate the presence of a suspended LBL on the surface of carbon nanofibers.

Synthesis of Calix[4]cyclohexanol to Serve as an Electron Trap. BENJAMIN ZALISKO (Elmhurst College, Elmhurst, IL, 60126) JOHN A. SCHLUETER (Argonne National Laboratory, Argonne, IL, 60439)

Synthesis of leucite nanocrystals through glass hydration and sol-gel method. ELISA SANCHEZ (San Antonio Community College, San Antonio, TX, 78247) PAVEL HRMA (Pacific Northwest National Laboratory, Richland, WA, 99352)

Leucite (KAlSi2O6), a potassium alumino-silicate, has been widely used as a principal component in porcelain-fused-to-metal restorations to match the thermal expansion coefficient (CTE) of dental porcelain with the CTE of the metal. The combination of porcelain and metal creates a strong and durable restoration that is highly biocompatible and wear-resistant but lacks the natural translucency of enamel. The low strength and fracture toughness of natural looking all-ceramic restorations have restricted their widespread use in aesthetic dentistry. The introduction of nanoleucite porcelain might make the all-ceramic restorations possible. It was found that the fracture toughness and flexural strength of the leucite porcelain can be significantly increased by controlling the amount, particle size, and distribution of the leucite crystals in the porcelain matrix. The objective of this study was to synthesize nanocrystals of leucite via glass hydration and sol-gel method where the silica sol was mixed either with potassium aluminate for a basic synthesis or with potassium nitrate and aluminum nitrate for an acidic synthesis. The synthesized powders were analyzed with X-ray diffraction (XRD) to determine the concentration of leucite, and with scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS) to determine the crystal size of leucite. Differential thermal analyses and thermogravimetric analyses were used to study the phase changes in amorphous gels leading to the formation of leucite. Preliminary results of XRD analyses of the glass hydration samples show crystal formation. The concentration of leucite increases with temperature, time, and added volume of water. Average crystal size as determined by SEM was approximately 1 µm. At the time of this report, sol-gel data collection is ongoing, but nearing completion. Preliminary results of this study suggest a promising trend toward synthesis of nano-sized particles of leucite using both tested methods.

Synthesis of Microporous Materials Using Amino Triazoles. LAURA ENGERER (Valparaiso University, Valparaisp, IN, 46383) DR. JOHN SCHLUETER (Argonne National Laboratory, Argonne, IL, 60439)

Materials Sciences Abstracts: