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Study of Kinetics of Oxide Scale Formation in air on Nicrofer-6025HT for Clean Coal Energy Delivery and other High Temperature Applications using XPS
Project Lead: Jens Darsell
Project Lead Institution: Pacific Northwest National Laboratory
Abstract
Oxygen separation membranes for clean coal energy delivery in advanced coal based power plants rely on use of solid state electronic and ionic conductors which operate at temperatures in the range 700-900oC. Nicrofer-6025HT is a nickel based alloy which shows compatibility with such a system and can be used as a manifold material to transport the hot gases into the oxygen separation membranes. The main aim of the project is to develop a braze filler composition which hermetically seals the two materials with sufficient mechanical strength at the said operating temperatures. Brazing relies on surface composition of the two mating surfaces and thus a detailed investigation of the oxide scales on the surface of the Nicrofer is necessary.
This proposal calls for studying the oxide scales on Nicrofer in air at different temperatures and for several periods of time using X-ray photoelectron spectroscopy (XPS) electron spectroscopy for chemical analysis (ESCA). XPS sputter depth profiling would help us understand the oxide scales composition and bonding mechanism along with the kinetics of oxide scale growth. The information gained from this study is need for optimization of the Nicrofer oxide scale and engineering the braze alloy compositions necessary for joining Nicrofer to the oxygen separation membrane.
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EFFECT OF STRUCTURE AND SURFACE CHEMISTRY ON ELECTRODE REACTIONS IN SOLID OXIDE FUEL CELLS
Project Lead: Srikanth Gopalan
Project Lead Institution: Boston University
Abstract
One of the most intriguing questions about solid oxide fuel cells is the relative importance of gas-solid interfaces including three-phase boundaries between electrode, electrolyte and gas with respect to redox reactions and the role of the electrode surface structure and surface chemistry on the kinetics of the electrode reactions. We plan to use a suite of thin film deposition tools and characterization tools available at the EMSL to study such reactions.
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Exploring the Radiation Damage Resistance of Nanoscale Interfaces
Project Lead: Richard Kurtz
Project Lead Institution: Pacific Northwest National Laboratory
Abstract
The objective of this research is to rigorously test the hypothesis that internal interfaces can be manipulated at the nanoscale to enhance recombination of radiation-produced defects to dramatically reduce radiation damage without compromising other physical and mechanical properties. This hypothesis has never been rigorously tested and there has never been a fundamental study of radiation damage at interfaces that encompasses the wide range of interface types and structures proposed here. In this project we seek to 1) understand defect absorption at interfaces as a function of interface character and properties, 2) determine interface ability to adsorb and delocalize defects to promote recombination, and 3) determine interface stability and evolution under irradiation, including the saturation limit for defect absorption. This proposal is aligned with two of the principal focus areas within the Materials Sciences and Engineering Division of BES; including exploration of approaches to improve materials performance through interfacial design, and investigation of radiation effects on the mechanical and physical behavior of materials. The work consists of integrated experiments and modeling of a wide range of interface types to determine how variation in interface properties can affect defect absorption and recombination. Precisely tailored interfaces as well as nanostructured polycrystalline thin films will be studied in order to explore the full range of interface types relevant to the materials found in advanced nuclear energy systems. Reaching these objectives will demonstrate the stated hypothesis by determining interface stability under irradiation and will enable design of higher performance nuclear energy systems with attendant economic, safety and environmental benefits.
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The Role of Interfacial Processes on Mineral Transformations in Wet Supercritical CO2
Project Lead: Andrew Felmy
Project Lead Institution: Environmental Molecular Sciences Laboratory
Abstract
We propose a comprehensive experimental and theoretical investigation of the role of interfacial water and CO2 on the energies, mechanisms, and rates of reactivity of a series of orthosilicate and phyllosilicate minerals in contact with supercritical-CO2 (scCO2) containing variable H2O. The molecular mechanisms for carbonation reactions, as well as the distribution of H2O between scCO2 and mineral surfaces, will be followed using molecular simulations and surface spectroscopy as a function of T, P, mineral composition and structure, and aH2O. The dynamics of water reactivity will be simulated using newly developed molecular dynamics models and reaction barriers will be calculated using density functional and molecular orbital theory electronic structure methods. The theoretical studies will be coupled with high-resolution spectroscopic measurements (e.g., IR/FTIR, NMR) to investigate the formation and structure of water layers at mineral surfaces and in the interlayer region of phyllosilicates, and identify potential interfacial carbonate and silicate species. The macroscopic reactivity of the orthosilicates and the changes in interlayer water structure and reactivity of the phyllosilicates will be determined experimentally using high pressure cells. The proposed research will provide new insights into mineral transformations under extreme conditions and help establish a basis for assessing the effectiveness of CO2 sequestration in geologic disposal sites.
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The role of U(V) during heterogeneous reduction of aqueous U(VI) to U(IV).
Project Lead: Eugene Ilton
Project Lead Institution: Pacific Northwest National Laboratory
Abstract
This proposal is being submitted in response to the Science theme call: Biogeochemistry and Subsurface Science, understanding the chemistry of radionuclides in the subsurface. It directly relates to the EMSL mission to provide resources for discovery and technological innovation in the environmental molecular sciences. The results of the proposed work will support the needs of the DOE and nation in managing uranium waste resulting from weapons production and the nuclear fuel cycle. We request standard access and the work is non-proprietary.
We are proposing to study the role of the intermediate pentavalent oxidation state of uranium during heterogeneous reduction of U6+ to U4+ on mineral surfaces exposed to uranyl-bearing aqueous solutions. We will build on our previous work that showed that U5+ had measurable residence times on annite surfaces. The primary question is whether U4+ is formed by two sequential one electron transfers from the mineral to sorbed uranyl, or by disproportionation of sorbed U5+. We intend to probe the redox mechanism by monitoring the residence time of sorbed U5+ after the surface has been rendered redox inert and by varying the free energy of the reduction reaction, Gr. We will vary Gr by working with different minerals that span geochemically relevant redox potentials and by tuning the chemical potential of aqueous uranium (e.g., introduce carbonate). We also plan to investigate U5+ surface speciation. We will use a variety of microscopic and spectroscopic methods to interrogate our samples, including HRTEM (+EELS) and high resolution cryogenic XPS that are available at the EMSL. Additional characterization with XANES and EXAFS will be performed at the APS. We also propose to develop a quick and accessible method to quantify sorbed U5+ concentrations that only involves wet chemistry and optical spectroscopy. This method would make it possible for most geochemistry programs to identify U5+ without traveling to a synchrotron or having a high energy resolution XPS. We note that U5+ has significance for contaminated DOE sites in three primary ways: 1.) the U5+ to U4+ transformation is likely the rate determining step for reduction of uranyl to UO2; consequently U5+ could provide critical information on reduction rates and mechanisms, 2.) U5+ is easily mistaken for either U6+ or U4+ without careful analysis which could lead to false estimates of U transport behavior in the subsurface, and 3.) identifying and eventually quantifying U5+ will provide more accurate estimates for total energy balance during bioreduction of uranyl.
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In-Situ/Liquid Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) for Environmental Interfaces
Project Lead: James Cowin
Project Lead Institution: Pacific Northwest National Laboratory
Abstract
Chemistry of liquid interfaces is extremely important in environmental and industrial processes but is poorly understood. Liquid layers coat nearly all real-world systems from the oceans to atmospheric particles, and include surface "brines" that coat rocks and soils, and ice, selective membranes for energy storage and production, important industrial catalysts, and even us. New tools are needed to study these inherently inhomogeneous systems, under realistic conditions of humidity and in the presence of trace and reactive gases. We propose an In-Situ/Liquids Time-of-Flight Secondary Ion Mass Spectrometer (ISL-TOFSIMS) system, that will for the first time allow a comprehensive molecular-specific understanding of chemistry at liquid and liquid/solid interfaces. Major recent developments in TOFSIMS (cluster beams) and novel micro-scale chemistry methods make this revolutionary advance possible and timely. The proposed system can measure molecular and ion concentrations, microsecond reaction kinetics with high spatial resolution (120 nm laterally, 1 nm vertically) and 3D mapping capability, and has a unique "in operation" sensitivity calibration. These features will enable exploring pressing issues in interface-specific photochemistry, surface segregation and transport at liquid, brine, ice and mineral surfaces, and transport across aqueous-based membranes and adherent films, all under relevant gaseous conditions.
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Proposal for Development of Mass Closure via PNNL PESA for Continuous Fine, Very fine, and Ultra-fine Aerosol Sampling for Health Impact Studies
Project Lead: Thomas Cahill
Project Lead Institution: University of California, Davis
Abstract
"One of the most urgent needs for future progress in reducing the substantial impacts of ambient air particulate matter (PM) on human health is to determine which of the components are having the greatest effect.... Furthermore, because of cost considerations, there is virtually no prospect of collecting the data needed by health researchers for more definite analyses as long as there is continued reliance on current FRM (EPA filter based) sampling and analysis methodologies." (Lippmann, M, 2009). Further, ultra fine particles (< 0.1 micrometer diameter) are heavily implicated in 4 of the 6 main potential causal reasons for death and morbidity due to aerosols (Devlin, EPA, 2003).
It is clear that no amount of tinkering with filter based samplers can resolve the problem. A radically new approach is needed, based on focused energy beams.
For these reasons, the DELTA Group has in the past decade developed methods to economically generate such data, all of which require directed energy beams for their implementation (optical spectrometry and soft beta rays at Davis, polarized x-rays S-XRF at the ALS, LBNL.) We have designed and validated an enhancement of the well tested UC Davis DELTA Group 8 stage DRUM impactor (3 hr resolution) to allow both integrated (2 week) and continuous (3 hr) collection and analysis of ultrafine (<0.09 micrometer) particulate matter.
However, full analysis of these samples requires capabilities not available at Davis or LBNL that are available at EMSL, PNNL. This is especially true for the analysis of the organic surrogate hydrogen by proton elastic scattering analysis (PESA) with proton beams. Without this capability, we can not achieve mass closure. The second is Proton Induced X-ray Emission (PIXE) that serves as both a key quality assurance and operational backup to the S-XRF system and a better way to get very light elements (and some heavy metals) poorly seen by S-XRF.
These capabilities will be evaluated this summer at a major test in Cleveland, funded by the US EPA, with UC Davis sole source of particle collection and analysis. We wish to have EMSL a partner in this effort that could and should lead to an entirely new way of collection and analyzing US aerosols and an essential link to human health impacts.
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A Systems Biology Approach to Infectious Diseases Research
Project Lead: Joshua Adkins
Project Lead Institution: Pacific Northwest National Laboratory
Abstract
We describe an integrated program for coupling advanced capabilities in high-throughput transcriptomics, proteomics, and metabolomics with a comprehensive informatics infrastructure and a sophisticated approach to computational reconstruction and modeling of metabolic and gene regulatory networks. These powerful tools will be directed at delineating the mechanisms by which two related pathogens, Salmonella and Yersinia, adapt to the intracellular environment upon infecting macrophages and then manipulate that environment to facilitate their own survival and replication. The insights derived from modeling these behaviors may lead to the identification of novel therapeutic targets. The overall objectives are to: 1) Develop genome-scale metabolic and regulatory network reconstructions for Salmonella and Yersinia to provide the computational foundation for our systems biology approach; 2) Develop and disseminate 'sample matched' global datasets for Salmonella and Yersinia using transcriptomics, proteomics, and metabolomics technologies to provide the experimental foundation for our systems biology approach; 3) Produce and characterize knock-out mutations in regulatory genes predicted to be essential for systemic infection in mouse models for Salmonella enterica and Yersinia pestis; and 4) Use the network reconstructions, omics results, and phenotype changes in knock-out mutants to refine computational models of pathogenesis for Salmonella and Yersinia.
EMSL world class capabilities in proteomics, NMR for structure and metabolomics, and advanced computation are well recognized. While all of these areas are included in the proposal the real benefit of using EMSL's capabilities is the team oriented nature of the operations; the project described above requires multiple-disciplines and multiple-strategies. These capabilities with the high quality team are why we request to perform this research in collaboration with EMSL.
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Role of Microenvironments and Transition Zones in Subsurface Reactive Contaminant Transport
Project Lead: James Mckinley
Project Lead Institution: Pacific Northwest National Laboratory
Abstract
The PNNL Scientific Focus Area (SFA) will resolve critical Hanford and basic subsurface science issues through integrated, multi-disciplinary, science-theme focused research on the role of microenvironments and transition zones in the reactive transport of technetium (Tc), uranium (U), and plutonium (Pu). Microenvironments are small domains within larger ones that exert a disproportionate influence on subsurface contaminant migration. They may be internal fractures or microbiologic niches within porous media lithic fragments; grain coatings, bio-films, or micro-colonies on larger mineral particles; or compact silt/clay stringers in gravel-dominated subsurface sediments. Transition zones are field scale features where chemical, physical, or microbiologic properties change dramatically over relatively short distances (e.g., 1 m). They exhibit steep, transport-controlled gradients of system controlling chemical species such as O2, H+, or organic carbon. Microenvironments and transition zones frequently dominate subsurface contaminant reactivity, with strong effects resulting from the coupling of chemical reaction, physical transport (advection, diffusion), and microbiologic processes. Past EMSP and NABIR research has documented the importance of these zones at the Hanford site.
The overall ten-year goals of the SFA are to develop: i.) an integrated conceptual model for microbial ecology in the Hanford subsurface and its influence on contaminant migration, ii.) a fundamental understanding of chemical reaction, biotransformation, and physical transport processes in microenvironments and transition zones, and iii.) quantitative biogeochemical reactive transport models for Tc, U, and Pu that integrate multi-process coupling at different spatial scales for field-scale application. Targeted contaminant chemical reaction and biotransformation processes include heterogeneous/biologic electron transfer, precipitation and dissolution, and surface complexation. The SFA will emphasize lab-based, coupled computational and experimental research using relevant physical/biologic models, and sediments and microbial isolates from various Hanford settings to explore
molecular, microscopic, and macroscopic processes underlying field-scale contaminant migration. It will also pursue the refinement of geophysical techniques to define, characterize, and map spatial structures and reactive transport properties of microenvironments and transition zones in the field. The SFA will partner with the PNNL Environmental Molecular Sciences Laboratory (EMSL) to develop molecular understandings of key processes, and the Hanford Integrated Field Challenge (IFC) for access to, and samples from subsurface environments where these zones exist and are important.
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Exploring the processes that control uranyl reduction by magnetite and the growth of nanoparticulate surface precipitates by X-ray scattering and X-ray absorption spectroscopy
Project Lead: Glenn Waychunas
Project Lead Institution: Lawrence Berkeley National Laboratory, University of California, Berkeley
Abstract
Uranium (U) has been released into the environment through mining operations, nuclear testing, and accidental spills, and is a contaminant in soils, sediments and groundwater at 70% of the Department of Energy (DOE) facilities. Developing accurate predictive models of subsurface U transport in contaminated environments is a major goal of the DOE Environmental Remediation Sciences Program (ERSP). Understanding the fundamental processes by which U can be sequestered into an immobile phase (including adsorption, precipitation, and reduction) is critically important in attaining this goal. In particular, it is unclear what the role calcium (Ca) has in U(VI) adsorption and reduction at mineral surfaces, such as magnetite. This project aims to determine the size, structure, composition, and morphology of U(VI)-surface complexes and U(VI)-bearing nanoprecipitates. This study will use a suite of complimentary techniques including transmission electron and scanning probe microscopy and counterpart synchrotron-based X-ray scattering and X-ray absorption spectroscopy using magnetite thin films and single crystals. These techniques will provide information to accurately describe sorption complexes and surface precipitates from the initial exposure of magnetite to aqueous U solution species, and the transformations that occur during nucleation and particle growth. Understanding the geochemical controls on these processes from the molecular scale and up is critical to better predict the long-term potential for U retention or migration.
