Microscopy Related User Projects

• 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.
• 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.
• Fuel-Neutral Studies of Particulate Matter Transportation Emissions
  Project Lead: David Foster
  Project Lead Institution: University of Wisconsin, Madison
  Abstract
  Customers and governments are demanding greater fuel efficiency in light duty engine applications. Since the majority of light duty engines in North America are fueled by gasoline, gasoline engine technology must be targeted in order to achieve a dramatic and immediate impact on fuel savings in our region. Efforts to curb carbon dioxide emissions, which have been implicated in global climate change, have added new urgency to the drive towards higher fuel efficiency standards. It is also recognized, however, that higher fuel efficiencies must also be accompanied by reductions in other potentially harmful emissions, including particulates. To this end, novel engine modes and various fuel blends are being examined and re-examined. Spark ignition direct injection (SIDI) gasoline engines are one example of a possible technology for dramatically increasing fuel efficiency in light duty vehicles through combustion modes which are more similar to those found in current diesel engines. One concern, however, is that SIDI engines may just like diesel engines generate more particulate matter (PM) than port fuel injection (PFI) gasoline engines. Diesel particulate filters (DPF)s are considered necessary to meet new particulate emissions limits for diesel engines in Europe, Japan, and North America. Similar measures may also be necessary for gasoline engines employing new combustion technologies such as SIDI. Even if the particulate matter counted on a mass basis is much less than that observed with diesel engines, on a number counted basis the distinction may not be so clear, since the combustion of shorter chain fuels can generally be expected to lead to more and smaller soot particles. In addition to engine operation modes, new flexible engines operated on a variety of fuels are being examined, adding more uncertainty to the nature and quantity of particulate emissions. A study designed to elucidate the effect of engine mode and fuel blend on PM generated in a fuel-neutral engine would therefore be of considerable value in the drive toward future high efficiency transportation in the light duty arena. Understanding the nature of the particulate matter derived from an energy efficient fuel-neutral engine will then enable a pathway to optimal particulate filter technology for this particular application. To meet these challenges, a new initiative comprising Pacific Northwest National Laboratory, GM Research and the University of Wisconsin will examine the properties of particulates derived from a fuel-neutral engine, and then subsequently explore filtration and oxidation strategies for effective mitigation.
• 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.
• Deployment of EMSL Instruments during the 2010 Carbonaceous Aerosol and Radiative Effects Study (CARES)
  Project Lead: Rahul Zaveri
  Project Lead Institution: Pacific Northwest National Laboratory
  Abstract
  The Carbonaceous Aerosol and Radiative Effects Study (CARES) will be conducted during summer 2010 in order to investigate the evolution of carbonaceous aerosols of different types and their optical and hygroscopic properties. CARES will be conducted in central California, with a focus on the Sacramento urban plume. A suite of EMSL instruments are requested to complement an extensive set of measurements planned for this field campaign, which is being organized by the DOE ARM Climate Research Facility (ACRF). Both the instrumentation and expertise of the scientists at EMSL are critical to the successful completion of the CARES objectives described in this proposal. During summer, the Sacramento urban plume transport is controlled by highly consistent winds that draw polluted air to the northeast over the oak and pine trees in the Blodgett Forest area. The Sacramento-Blodgett Forest corridor therefore effectively serves as a mesoscale (~100 km) daytime flow reactor in which the urban aerosols undergo significant aging due to coagulation, condensation, and photochemical processes. The CARES campaign observation strategy will therefore consist of the DOE G-1 aircraft sampling upwind, within, and outside of the evolving Sacramento urban plume in the morning and again in the afternoon. The aircraft measurements will be complemented by a well-instrumented ground site within the Sacramento urban source area (â??T0") and a ~60 km downwind receptor site ("T1") near Cool, CA, to characterize the diurnal evolution of meteorological variables, trace gases/aerosol precursors, and aerosol composition and properties in freshly polluted and aged urban air. EMSL instruments are requested for deployment on the G-1 and at both the T0 and T1 sites. These include measurements of trace gas mixing ratios, aerosol size distribution and composition, and aerosol optical and CCN activation properties.
• 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.
• 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.
• 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.
• 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.
• 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.