Chemical Analysis of Sump Water in Pressurized Water Reactors. JUSTIN KIESER (University of Texas at El Paso El Paso, TX 79968) JONG HEE PARK (Argonne National Laboratory, Argonne, IL, 60439)

During a Loss of Coolant Accident (LOCA) within the containment vessel of a pressurized water reactor (PWR), it possible for the discharged high temperature, high pressure radioactive water stream to displace thermal piping insulation comprised of Calcium Silicate (CalSil). This material then enters the sump water storage tank which contains Tri-Sodium Phosphate (TSP) to maintain a neutral pH. Aside from this actual material accumulating on the sump filtration screens, leached CalSil solution reacting with TSP, 3CaSiO3 + 2Na3PO4 Ca3(PO4)2 + 3Na2SiO3, can form precipitates that may collect on the filtration screens and also accumulate on the inner piping walls, preventing the required amount of sump water from cooling the impaired reactor core. In order to study the reaction and determine an unsafe concentration of TSP, simulations and experiments were performed to study the formations of ions from both reactants, measuring conductivity as a function of time and temperature. A titration was also executed to examine the formation of obstructing precipitates. Based on titration and visual observation, a TSP concentration ranging from 250 ppm to 1000 ppm forms the largest amount and greatest size of Calcium Phosphate Ca3(PO4)2 precipitates reaching 4 mm in diameter which pose the maximum threat for these particles to coalesce and cover a large majority of filter screen surface area. After 1000 ppm concentration is surpassed, Ca3(PO4)2 begins to dissolve while the solutions pH rises to basic level between 8.0 and 8.75. A rise in pH allows for the high iso-electric Ca3(PO4)2 to bond with the inner steel piping walls, causing further precipitate accumulation which reduces sump water flow and increases head loss.

Erosion Resistance of MoCuN Coated Steel. SULAV SINGH (University of Illinois at Urbana Champaign Champaign, IL 60439) JULES ROUBORT (Argonne National Laboratory, Argonne, IL, 60439)

The objective of this research is to characterize and understand erosion behavior of various films deposited under different conditions on stainless steel substrates. Experiments were performed at Argonne National Laboratory to evaluate the erosion resistance of coated substrates using SiC particles having 143 µm diameter, at incidence angles of 20o, 45o, and 90o, and velocities of 30 m/s and 100 m/s. Engineered coatings are very beneficial for machine components to protect them from severe environmental conditions. However, these environmental conditions, often erode, in service, and break down the coatings over time. Thus, there is a need to understand the erosion behavior of these protective coatings in order to prolong and improve their life. The present study was conducted on MoCuN (molybdenum copper nitrite) coating on 304 stainless steel substrates, in order to better understand and characterize the erosion resistance of this coating. To characterize the erosion rate, the ANL particle slinger was used to erode coated substrates. The particle slinger can erode ten samples simultaneously, though for this experiment only three samples were eroded at a time. The particle slinger mechanically accelerates solid particle abrasives onto a sample's surface at a predetermined velocity and angle in a vacuum. Several MoCuN coated steel substrates were eroded at velocities of 30 m/s and 100 m/s and at impact angles of 20o, 45o, and 90o using SiC erodent. The thickness of the coating is between 4 and 5 microns. Following each trial, the eroded substrate was cleaned by applying an air jet onto the sample to remove any unwanted particles. The weight loss of the sample was then measured on a balance with a sensitivity of 0.1 mg. This data was then used in a computer program that calculated erosion rate. In this experiment I ran all the trail runs. Then, I collected data and measured the weight loss of the material. After the weight loss was recorded I inputed the recorded data into the computer program that calculated the erosion rate. When this was completed, I analyzed the results with my supervisor, in order to understand the behavior of the coated substrates erosion characteristics.

Evaluation of Titanium Aluminide and Silicon Nitride Valves Using Elastic Optical Backscattering Techniques. DAVID POTEMPA (Bradley University Peoria, IL 61606) DR. JIANGANG SUN (Argonne National Laboratory, Argonne, IL, 60439)

Silicon nitride and titanium aluminide are advanced materials that exhibit excellent thermal properties, wear resistance, and corrosion resistance. It is because of these characteristics that they are ideal for use as engine valves. In order to assist in bringing these advanced materials into commercial realization, it is our task here at Argonne National Laboratory to provide information on the design, manufacturing, and structural performance of these valves. Using elastic optical backscattering techniques, surface and subsurface defects are detected and analyzed to predict valve fractures or confirm the origins of a fractured valve. Images obtained from newly refinished silicon nitride valves show less surface and subsurface machining damage than previously recorded. Since a primary cause of failure in ceramics is the propagation of a surface crack developed during machining, less surface and subsurface machining damage implies a stronger valve. Titanium aluminide valves, scanned for the first time, provide for excellent images of surface machining damage. Their poor optical translucency prevents deep scans of subsurface defects. Additional tests and subsequent scans will be necessary to determine the structural performance of these valves. These scans are the first in a planned program of alternating scan and rig/engine tests. As the program continues, additional rig/engine tests and subsequent scans will provide more information regarding the structural performance, future manufacturing, and future design of these valves.

Fabrication of Anodic Aluminum Oxide Membranes for Catalytic Coating Using Atomic Layer Deposition. KURTIS BLOHM (Hope College Holland, MI 49423) GREGORY KRUMDICK (Argonne National Laboratory, Argonne, IL, 60439)

Anodic aluminum oxide (AAO) has recently gained importance in many frontiers of nanoscience due to the nearly perfect hexagonal array of closely packed alumina nanopores that are generated in an aluminum sample. The purpose of this project is to use AAO membranes as a substrate for the formation of nano separation membranes and catalytic membranes when coated with a catalyst using atomic layer deposition (ALD). By varying parameters of the AAO synthesis procedure such as electrolyte, voltage, temperature, anodization time, etching time and number of anodizations, a membrane with ideal pore dimensions for ALD coating can be obtained. The barrier layer inevitably formed by this process can be removed by chemical etching after successive anodizations, resulting in a permeable "wafer." To minimize grain boundaries, the Al is degreased and annealed to produce an ordered microstructure as well as electropolished to remove any impurities and dislocations on the surface that may produce an uneven charge distribution. The laboratory has been designed to provide flexibility in the fabrication of AAO membranes. Analysis of the dimensions and ordering of the AAO membranes will be conducted with SEM (Scanning Electron Microscopy) and AFM (Atomic Force Microscopy). After analysis, the membranes will be coated using ALD to adjust pore size down to the atomic level and to apply catalytic materials for the production of catalytic membranes.

High Temperature Steam Electrolyzer Materials Development. TODD BOGE (Iowa State University Ames, IA 50013) JENNIFER MAWDSLEY (Argonne National Laboratory, Argonne, IL, 60439)

Due to the increasing interest in hydrogen as a fuel, research is needed to make the production, storage, and transportation of hydrogen more efficient and economical. One of these hydrogen production processes is water electrolysis at high temperatures using heat from a nuclear reactor, known as high temperature steam electrolysis (HTSE). HTSE utilizes solid oxide electrolysis cells, which are based on the current solid oxide fuel cell (SOFC) technology, to split steam into hydrogen and oxygen. Previous studies at ANL have shown that La_0.7Sr_0.2FeO₃ (LSF-ns), Pr_0.5Sr_0.5CoO₃ (PSC), and La_0.8Sr_0.2CoO₃ (LSC) are better air electrodes at temperatures below 900 C than the current SOFC benchmark material, La_0.8Sr_0.2MnO₃. The current study focused on improving the performance of LSF-ns, PSC, and/or LSC using two different strategies. The first strategy was to increase the triple-phase boundary area between oxygen-bearing gas, the oxygen electrode, and the electrolyte by mixing the LSF-ns and LSC powders with an electrolyte material, either gadolinium-doped ceria or yttria-stabilized zirconia (YSZ) powder. The second strategy was to grade the grain size and density of the LSF-ns and PSC, using a gel precursor to create a denser, smaller-grained thin layer on the electrolyte followed by a thicker layer made from larger grained powders. Half-cells of the materials were evaluated using electrochemical impedance spectroscopy (EIS) at temperatures between 800 and 900 C. After analyzing the EIS data, it was found that the PSC with graded density made using the gel precursor had area specific resistances lower than any material previously tested. Work was also done to improve the hydrogen/steam electrode because the current SOFC hydrogen/steam electrode (a nickel-YSZ cermet) oxidizes under the high steam conditions of HTSE. Ten single-phase, non-metallic materials were identified as having the properties needed for an improved hydrogen electrode. These materials were synthesized and are currently in the process of testing alternative materials for the hydrogen/steam electrode via EIS.

Ionogel-Templated Synthesis of Cadmium Sulfide Nanoparticles. GISSELLE BENITEZ (University of Puerto Rico at Mayaguez Mayaguez, PR 00681) MILICENT FIRESTONE (Argonne National Laboratory, Argonne, IL, 60439)

Nanoparticles have been studied for many years mostly because of their physicochemical properties such as optoelectronic and photovoltaic devices. Previous work in the Firestone lab has focused on ionogel templated synthesis of gold nanoparticles. 1-Decyl-3-methylimidazolium chloride was combined with an aqueous gold solution yielding a 2-D hexagonally ordered mesostructural gel. Upon irradiation of this composite, anisotropic gold (Au) nanoparticles were obtained. In this report we describe two extensions of this prior work: 1) Development of a covalent (polymerized) ionogel as a template of scaffold for the in-situ formation; aggregation of gold nanoparticles. 2) The synthesis of semi-conducting nanoparticles within an Ionogel was also explored. Gold nanoparticles were grown combining 1-decyl-3-vinylimidazolium chloride with an aqueous gold solution. Using photochemical irradiation, the polymerized ionic liquid and the aqueous gold solution was reduced to create gold nanoparticles. Cadmium sulfide nanoparticles were created by adding 1-decyl-3-methylimidazolium chloride to an aqueous cadmium chloride solution and exposing it to hydrogen sulfide gas. These nanoparticles were formed and studies using UV-Vis, SAXS, and POM.

Magnetic States of a 50% La_2-2xSr_1+2xMn₂O₇ Bilayered Manganite Sample. ALEXANDER TUMMINELLI (Cornell University Ithaca, NY 14850) KEN GRAY (Argonne National Laboratory, Argonne, IL, 60439)

Layered Manganites are proving to be useful in the study of electron spin and the magnetic field that it induces. Recently, we've been able to isolate a sample with x close enough to 50% so that the chemical formula is essentially La1Sr2Mn2O7. While this sample's conductivity states are not dominated by magnetic ordering, the data was sufficient enough to allow us to study further states that are dominated by charge ordering and orbital ordering. The data needed to be collected between temperatures of 5 and 300 Kelvin, so liquid helium and liquid nitrogen were both used in a cryogenic system to cool the sample to appropriate temperatures. It was also required that data be collected with different amounts of current running through the sample at different places on the sample, so a wide array of electrical connections needed to be attached to the sample. Data collection was completed using a combination of LabView programs, temperature controllers, voltmeters and a current source. The data we collected very clearly shows that a high current running through the sample will alter the states that the sample experiences. While these states appear to be dominated solely by charge and orbital ordering, they could prove useful in studying the magnetic ordering of other samples by allowing us to understand more fully the basics behind charge and orbital ordering. Studying this sample is only a part of a larger project directed at determining the magnetic properties of layered manganites as a whole, including other percentages of Lanthanum and Strontium.

Magneto-Optic Imaging studies of Diluted Magnetic Semiconductor and Exchange Bias systems. ZACHARY WEBER (Kenyon College Gambier, OH 43022) ULRICH WELP (Argonne National Laboratory, Argonne, IL, 60439)

The Magneto-Optical Imaging (MOI) technique relies on the Faraday rotation of polarized light to make magnetic domains visible. The MOI is adaptable to a wide variety of systems; in this study, MOI was used to examine films of a diluted magnetic semiconductor, Ga_1-xMn_xAs, and an exchange coupled magnetic metal multilayer system, Co/FeF₂. Both of these systems are of interest in the development of spintronics devices, such as nonvolatile memory. In this study, MOI and magnetization measurements of Ga_1-xMn_xAs indicated that both as-grown and annealed samples had biaxial easy magnetization along the [100] and [010] directions. As temperature increased, the easy magnetization axis turned to the [110] direction and became uniaxial. The rotation of the easy magnetization axis orientation is due to the competing, temperature dependent anisotropy energies from the tetragonal structure of Ga_1-xMn_xAs (biaxial easy magnetization) and layer-by-layer surface reconstruction (uniaxial easy magnetization). The annealed sample demonstrated greater magnetic inhomogeneity, possibly indicating the presence of increased Mn clusters or interstitials. The Co/FeF₂ sample demonstrated a unidirectional field bias after cooling at high fields perpendicular to the c-axis. The same sample also seems to demonstrate separate regions with exchange bias in opposite directions after cooling at high fields parallel to the c-axis. These results support the notion that magnetic domains in the antiferromagnet give rise to the exchange bias.

Polymer Ionogel-Templated Synthesis of Gold Nanoparticles. LEGNA VARELA (University of Puerto Rico at Mayaguez Mayaguez, PR 00680) MILICENT FIRESTONE (Argonne National Laboratory, Argonne, IL, 60439)

Nanoparticles have been studied for many years mostly because of their physicochemical properties such as optoelectronic and photovoltaic devices. Previous work in the Firestone lab has focused on ionogel templated synthesis of gold nanoparticles. 1-Decyl-3-methylimidazolium chloride was combined with an aqueous gold solution yielding a 2-D hexagonally ordered mesostructural gel. Upon irradiation of this composite, anisotropic gold (Au) nanoparticles were obtained. In this report we describe two extensions of this prior work: 1) Development of a covalent (polymerized) ionogel as a template of scaffold for the in-situ formation; aggregation of gold nanoparticles. 2) The synthesis of semi-conducting nanoparticles within an Ionogel was also explored. Gold nanoparticles were grown combining 1-decyl-3-vinylimidazolium chloride with an aqueous gold solution. Using photochemical irradiation, the polymerized ionic liquid and the aqueous gold solution was reduced to create gold nanoparticles. Cadmium sulfide nanoparticles were created by adding 1-decyl-3-methylimidazolium chloride to an aqueous cadmium chloride solution and exposing it to hydrogen sulfide gas. These nanoparticles were formed and studies using UV-Vis, SAXS, and POM.

Radiation Damage in Structural Stainless Steels. DAVID RIVERA (University of Texas at El Paso El Paso, TX 79968) OMESH K. CHOPRA (Argonne National Laboratory, Argonne, IL, 60439)

Austenitic stainless steels (SS's) are widely used in nuclear reactor cores around the world. Their superior fracture toughness, durability, and relatively high strength make these materials a prime candidate for use in reactor core internal components. However it has been shown that extended periods of neutron irradiation can have a severe detrimental effect on such materials, namely a marked reduction in ductility and fracture toughness coupled with a drastic increase in material yield strength. Slow strain rate tests (SSRT's) were conducted on several irradiated SS tensile specimens in simulated boiling water reactor (BWR) conditions. All tests were conducted with a strain rate of 1.65 x 10^-7 s^-1 and a pressure of 1300-1450psi at 289 C. After failure, the specimen fracture surfaces were examined using a scanning electron microscope in order to asses the extent of intergranular and transgranular fracture. The results of the SSRT's reveal the characteristic increase in yield stress and reduction in ductility experienced by samples subjected to irradiation. Nearly all the 304 and 316 SS alloys followed a similar trend in work hardening behavior in that each individual alloy experienced a tendency to work harden at the same rate regardless of irradiation dosage. This leads to the possibility of a unique critical true stress existing for every austenitic SS alloy. Changes in yield strength as a function of displacements per atom (dpa) were plotted and showed to correlate reasonably with the previous model proposed by Oddeta & Lucas. These changes in yield strength and ductility are brought about by the creation of many small defects within the material consisting of a vacancy and a self interstitial atom (SIA). Such defects have a tendency to group together and form dislocation loops, which in turn inhibit other dislocations from moving thus increasing yield strength and decreasing ductility and fracture toughness. Reduction of fracture toughness leaves the material susceptible to irradiation assisted stress corrosion cracking (IASCC). The depletion of Cr at the grain boundaries (GB's) is believed to be the primary cause of IASCC, such a reduction in Cr at the GB's leads to the preferential attack of corrosion at these sites. This investigation is part of a much larger research effort focused on studying the effects of radiation on austenitic SS's in order to increase the life expectancy and efficiency of current and future nuclear reactors.

Salt Flux Experiments for Secondary Aluminum Processing. JONATHAN HAVENGA (Iowa State University Ames, IA 50011) GREGORY K. KRUMDICK (Argonne National Laboratory, Argonne, IL, 60439)

The aluminum industry consists of two basic components: primary and secondary aluminum production. Primary aluminum production involves the reduction of alumina (Al₂O₃) into aluminum using the Hall-Héroult process. Secondary processing is the remelting of aluminum scrap to produce 'new' aluminum or alloys, rather than using alumina as the source of the raw material. This process is much more energy efficient than primary aluminum production. Current secondary aluminum processing requires various methods used to improve recovery of aluminum by minimizing oxidation and metal melt loss. One method utilizes a salt flux; the most commonly used mixtures are approximately equal portions of NaCl and KCl with small amounts of a fluoride compound. Other fluxes offer potential advantages over this mixture, yet have not been proven for possible industrial use. This experiment seeks to determine if the advantages of using a new flux are great enough to motivate research on a larger scale. To do this, different mixtures of the salt flux will be melted with aluminum chips, stirred, and then analyzed after cooling. The analysis will evaluate how well the different fluxes improve aluminum recovery by determining how much oxidation takes place, if the flux contaminates the metal, and the flux composition and oxide content after melting. The experiments are currently being performed.

Synthetic Approaches to Develop Electrochemically Active Metal Based Mesoporous Structures. ANTHONY CRISCI (University of Illinois at Urbana Champaign Champaign, IL 61820) MILLIE FIRESTONE (Argonne National Laboratory, Argonne, IL, 60439)

Mesoporous silicas are structured materials that possess an ordered 2D hexagonal array of parallel cylindrical channels with tunable pore diameters (e.g., 30-70 ). Mesoporous silicas such as MCM-41 and SBA-15 have been used primarily as passive frameworks in which active guests (e.g., catalysts) are housed. Less work has been performed on preparing active mesoporous materials that could be used to control the functionality of the intercalated guest. In this report, we describe several synthetic approaches used to develop an electrochemically active ordered mesoporous structure composed of gold. An aqueous gold salt is mixed with a surfactant-based template which is ordered by thermal treatment. Photochemical or chemical reduction is applied to reduce the gold ions (Au 3+) to Au0 which initiates the formation of interconnecting gold bonds encompassing the template. The surfactant-based template is removed through washing with water. Analysis of a surfactant-free sample by small angle x-ray scattering (SAXS) indicates a highly ordered, autonomous structure remained after washing. A Nitrogen adsorption study is scheduled to determine the surface area and aperture diameters of the gold mesopore product. The current focus is on the development of an efficient standard synthesis protocol for metallic mesoporous materials (e.g. gold); to enable the production of functionalized mesopores.

The Solubility of Magnesia in Molten Lanthanum Chloride-Magnesium Chloride Mixtures. TIMOTHY SCARPINATO (Syracuse University Syracuse, NY 13244) GREGORY KRUMDICK (Argonne National Laboratory, Argonne, IL, 60439)

In response to the ongoing pursuit for a better fuel economy, more viable methods for producing primary magnesium are being examined. With its superior strength-to-weight ratio and low density, magnesium has the potential to significantly reduce vehicle mass and be utilized in a variety of other applications. Previous research has suggested that the LaCl3-MgCl2 (lanthanum chloride-magnesium chloride) electrolyte system is a strong candidate for magnesium production through MgO (magnesia) electrolysis. While an earlier study has suggested that magnesia is highly soluble in this system, no details of the measurements were given. The results of our study do not support this, indicating a much lower solubility. However, the solubility did increase with increased molar percentage of LaCl3 in the system, as reported in literature. To study the solubility, the LaCl3-MgCl2 mixture was placed and sealed in a graphite crucible and heated in a crucible furnace to the desired temperature. Samples were taken before adding the magnesia crystals and at successive time increments after the magnesia addition. The experiments were run between 4 and 7 hours and agitated throughout to ensure complete saturation. According to the results, the system is saturated rather quickly, supporting its use in magnesia electrolysis. An investigation on the discrepancies between this study and previous work should be conducted. Future efforts will focus on exploring the level of solubility needed for this system to be an acceptable electrolyte and optimizing the electrolyte based on the solubility curve.

The TuffCell. JONATHAN KIDD (Iowa State University Ames, IA 50014) JOHN DAVID CARTER (Argonne National Laboratory, Argonne, IL, 60439)

Solid Oxide Fuel Cells (SOFC) have been in the developmental stages for quite a few years. SOFC's are high temperature fuel cells that operate between 650 and 1000 C with an efficiency of 50 to 60%. SOFC provide an electrochemical reaction that produces electricity, with the total cell reaction being the oxidation of hydrogen or hydrocarbon fuels. Argonne National Laboratory is developing a new design concept for the SOFC called the TuffCell-a metallic bi-polar plate supported design. The goal with the TuffCell is to create a fuel cell that is rugged, compact, and simple to produce. The TuffCell is currently produced through tape casting methods paired with a stainless steel support system. This paper focuses on the sintering process that involves a high temperature hydrogen furnace and electrode gel, and their application for SOFC's and testing purposes. It examines the problems that were encountered in both the sintering profiles and the testing of the electrode gels. SOFC have the potential to provide a cleaner energy source, a reduced dependence on outside nations, and a wide variety of professional and personal applications.

Tuff Cell Solid Oxide Fuel Cell Design and Fabrication. ERIC ANDERS (Iowa State University Ames, IA 50011) DR. JOHN DAVID CARTER (Argonne National Laboratory, Argonne, IL, 60439)

The Solid Oxide Fuel Cell (SOFC) has the capacity to change the face of energy consumption in our society. There are, however, a few obstacles still in the way. For example, typical SOFCs are expensive and brittle. The Tuff Cell SOFC, developed at Argonne National Laboratory, was designed to counter these problems. Metal cell supports act as a fuel flow field and provides the cell with superior support and strength. The electrolyte and anode are comprised of multi-layered tape castings of both zirconia and nickel oxide ceramics. We report on advances in the fabrication process that have increased the yield rate of functioning cells, and the development of techniques for repairing defective cells.