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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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Characterization of Natural Gas Methane Hydrate Rich Sediment
Project Lead: Herbert Schaef
Project Lead Institution: Pacific Northwest National Laboratory
Abstract
Synthetic and natural gas hydrate samples (NGHP-01, Mt Elbert) will be characterized by FIB-SEM equipped with a cryo stage and residual gas analyzer. Gas hydrate dissociation profiles collected on different samples will be compared along with the gas chemistry. Synthetic gas hydrate samples containing different amounts of NaCl will also be characterized to determine the pore water salinity effects on gas hydrate dissociation. These measurements will be obtained with the FIB-SEM housed in the Environmental Molecular Sciences Laboratory at PNNL. The FIB-SEM is equipped with a cryostage, and several attachments including elemental scanning by EDXS and Electron Backscatter Diffraction (EBSD). We intend to explore in situ sectioning of naturally-occurring and synthesized gas hydrate crystals formed in the pore spaces of sediment samples using the Ga ion beam available in the FIB-SEM. The EBSD will be used to determine the crystal structure of these individual crystals. Post-processing will be used to provide the first in situ 3D reconstruction of the microstructure of gas hydrate crystals formed in pore spaces.
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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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Fundamental understanding of atomic force microscope-induced
nanoscale interfacial reactions through nanostructure characterization
Project Lead: Marco Rolandi
Project Lead Institution: University of Washington
Abstract
The proposed research focuses on the fundamental understanding of the chemical reactions occurring at the nanoscale tip-sample interface during atomic force microscope (AFM) lithography. This understanding requires a detailed characterization of the nanostructures manufactured using different lithography conditions and parameters. In particular, we will focus on features produced with either high field liquid precursor direct write or local anodic oxidation. The proposed research at EMSL would focus on (1) compositional characterization, (2) bonding characterization, and (3) nanostructural characterization. The goal of this research is to understand the mechanisms involved in the fabrication of features within this complex multi-interfacial environment and to enable careful tailoring of processing parameters. This will afford the facile manufacturing of a broad range of nanostructures with several potential applications such as: nanotransistors, multiplexed chemical and biological sensors, nanoscale waveguides, and memory devices. Because of the very small size of the features deposited via AFM lithography (2-3 nm height, 10-50 nm width per line), we must look outside our home institution to the EMSL facility for the instrumentation required for nanoscale characterization.
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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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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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WSU Tricities Electron Microscopy COurse
Project Lead: Edgar Buck
Project Lead Institution: Pacific Northwest National Laboratory
Abstract
Electron Microscopy (EM) has long been an important experimental tool in materials science, biological sciences, and geosciences. At PNNL, electron microscopes, both SEM and TEM, are used in nearly every aspect of research, from applied research on classified nuclear materials to the study of cellular processes. Furthermore, electron microscopy is not just high magnification images; electron microscopes exploit the complete range electron beam interactions to probe material's properties. Access to the EMSL microscopy labs is requested as this will provide an essential introduction to this graduate level course and complements on-going classroom studies.
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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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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.
