The National Research Council sponsors a 2-year fellowship to work at NIST. Quick facts about the fellowship:
Detailed information on application procedures and materials along with supporting documents are available here.
Nanoscale Structure in Nanomaterials
Accurate knowledge of atomic arrangements and internal substructure in nanomaterials is a key to understanding their properties. Despite the availability of techniques for probing local atomic order, finding a comprehensive structural solution for nanostructured materials remains a formidable challenge. This opportunity seeks to address this measurement problem by integrating theoretical analyses and several critical experimental techniques including total x ray and neutron scattering for extracting atomic pair distribution functions, small-angle scattering, and extended absorption fine structure measurements. Surface structure of nanoparticles and nanotubes is of particular interest. NIST’s Ceramics Division has access to state-of-the-art synchrotron and neutron radiation facilities for these measurements. Opportunities exist to investigate nanomaterials and nanodevices for a myriad of applications such as biomedical devices, catalytic converters, and batteries.
Ceramic Additive/Advanced Manufacturing
Additive manufacturing (AM) is a rapidly growing technology, but its commercial adaptation to ceramic-based materials lags behind the metals and polymers sectors. Innovations that improve the availability of reliable, custom, on-demand ceramic parts will benefit a range of structural, thermal management, medical, and electronic applications. These applications often call for multi-material or composite parts that require ceramics to be integrated with less-refractory materials. The ceramic AM field will progress with innovations that combine experience from traditional ceramic processing with recent breakthroughs in densification of ceramics, like cold sintering or ultra-fast high-temperature sintering. Our effort at NIST focuses on developing predictive tools for ceramic AM by combining computational and experimental approaches to study fundamental material processes during direct-ink writing and post-processing of ceramic parts. We are interested in postdoc candidates with prior experience in any of the following areas: ceramic processing, nano-particle synthesis, colloidal chemistry (i.e., rheological testing, zeta-potential), advanced characterization (ultrasound, x-ray scattering, IR imaging), and experimental equipment design (CAD, controls (i.e., LabView, Python, Arduino, G-code), image/video processing (i.e., ImageJ).
Modeling and Simulation in Ceramic Additive Manufacturing
Additive manufacturing (AM) is a rapidly growing technology, but its commercial adaptation to ceramic-based materials lags behind the metals and polymers sectors. Innovations that improve the availability of reliable, custom, on-demand ceramic parts will benefit a range of structural, thermal management, medical, and electronic applications. These applications often call for multi-material or composite parts that require ceramics to be integrated with less-refractory materials. The ceramic AM field will progress with innovations that combine experience from traditional ceramic processing with recent breakthroughs in densification of ceramics.
Our effort at NIST focuses on developing predictive tools for ceramic AM by combining computational and experimental approaches to study fundamental material processes during direct-ink writing and post-processing of ceramic parts. Successful candidate will perform modeling and simulation of direct ink writing and processing of ceramic parts and test-structures. This is an excellent opportunity for a theoretical / computational scientist to work in equal partnership with experimentalists including collaborative experimental design and data analysis. (See related NRC opportunity Ceramic Additive/Advanced Manufacturing).
Current modeling methods include multi-phase Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM). The successful candidate will have experience in these methods, a strong background in computational model development and implementation, or an innovative proposal.
Towards Understanding the Structure and Microstructure Evolution Kinetics of Additive Manufactured Alloys
Additive manufacturing (AM) of metals represents a suite of emerging technologies that manufactures three-dimensional objects directly from digital models through an additive process. AM allows rapid manufacturing of complex objects with few constraints, little lead time and assembly, which makes it an attractive option for fabrications of customized, high value-added parts in industries ranging from aerospace, oil and gas, healthcare, and defense.
While recent development of AM has clearly demonstrated its potential as a new paradigm for advanced manufacturing, major technical challenges still exist. Many of these challenges are rooted in the extreme material processing conditions during the AM build process, where repeated rapid heating and cooling (with rates up to 10^6 K/s) leads to materials with high level of residual stress, heterogeneous metastable microstructures, and nonequilibrium elemental compositions or phase distributions. The microstructure evolutions during the build process and the post-build heat treatment are often poorly understood, making it difficult to construct the critical structure-process-performance relationship of the industrially important AM alloys.
To overcome these measurement challenges, this NRC postdoctoral research opportunity extends ongoing efforts at the Materials Measurement Science Division of National Institute of Standards and Technology and seeks to understand the structure and microstructure evolution of AM alloys through rigorous in situ and ex situ high-energy synchrotron X-ray scattering, diffraction, and imaging experiments. Essential to this opportunity is the design and execution of experiments to optimize processing pathway, validate predictive modeling, and enable further development of AM technologies, with emphasis on AM materials structures. This research is expected to be conducted through internal and external collaboration, which provides access to a full range of materials characterization and modeling capabilities.
Carbon (CO2) Capture, Selective Gas Sorbent Materials, and Carbon Sequestration
Many industrial processes generate carbon dioxide as a by-product, which is released to the atmosphere and contributes to global warming. To address the increasing urgency of mitigating global warming, clean, low-carbon-dioxide emission technologies must be complemented with more aggressive carbon capture technologies, including those for the direct air capture (DAC) of carbon dioxide, and its permanent mineralization or sequestration through appropriate carbonation processes. Development of these technologies is critical to meet U.S. energy and manufacturing needs in an environmentally sustainable manner. Low carbon emission and direct carbon capture technologies depend on transient gas/solid material interactions. Such interactions cannot be inferred from initial or final state materials property measurements such as sorbent microstructure, but must be measured in situ during the sorption or release process. This project focuses on the design, construction, and application of a suite of in situ measurement platforms for use with NIST’s state-of-the-art neutron and synchrotron X-ray scattering facilities, capable of interrogating critical carbon capture properties across the range of candidate carbon dioxide sorbent solid materials, as well as candidate materials, both natural and fabricated, for final mineralization or sequestration of carbon dioxide through carbonation. Measurements will focus on in situ determination of changes in structure, microstructure, atomic bonding, and dynamics in sorbent materials during the sorption and release of carbon dioxide under controlled conditions of temperature, pressure, humidity, and atmosphere, or in the case of mineralization as a function of carbonation reaction. Where possible, X-ray or neutron diffraction and scattering analysis and thermogravimetric analysis will be carried out in situ with samples that are simultaneously undergoing evolved gas analysis. The experimental measurements will be complemented by computer model simulations using available capabilities based on methods such as density functional theory (DFT).
Microstructure of Structural and Functional Ceramics for Additive Manufacturing, Energy Conversion, and Storage
Control of microstructure, internal dynamics, materials physics and chemistry is of primary importance in determining the processing, performance and viability of advanced ceramic components such as relevant to solid oxide or hydrogen fuel cells, carbon capture materials (including direct air capture and carbon mineralization), and other systems that advance the hydrogen economy, promote US energy independence, or support advanced manufacturing methods such as additive manufacturing (AM) and post-process densification. The operative scale range for the void and phase microstructures of relevance extends from the micrometer scale down to the sub-nanometer scale regime. Our goal is to leverage our access to state-of-art X-ray and neutron facilities to develop and apply operando measurement methods that can quantify full three-dimensional void and phase microstructures and dynamics in technological ceramic materials, including changes during service life and dependence on processing conditions. Such characterization addresses issues relevant to (e.g.) the electrodes and electrolyte of SOFCs, component phases and interfaces in fuel-reforming, hydrogen storage or carbon dioxide capture materials. In these cases, the microstructure frequently must be related to the reaction site kinetics and to changes in site chemical reactivity during service life. Equally, these characterization methods interrogate physics-based phenomena relevant to many aspects of ceramic advanced manufacturing such as found in direct-ink write ceramic extrusion AM and in novel post-process densification methods such as cold sintering of AM ceramic green bodies. This opportunity will address these interconnected issues by utilizing unique instrumentation, developed by NIST and its collaborators, and located at the Advanced Photon Source, the National Synchrotron Light Source II, and the NIST Center for Neutron Research. In summary, the opportunity exists for investigating fundamental processes relevant to novel energy materials and devices including structural and electronic ceramics, batteries, solid oxide fuel cells, energy harvesting devices, photovoltaics, carbon capture materials, as well as phenomena relevant to additive manufacturing of ceramics and their post-process densification. Complementary computational model simulation capabilities are also available.
Atomic-Resolution Chemical Imaging of Individual Nanostructures in an Aberration-Corrected STEM/TEM
Electron scattering is uniquely suited to the atomic-scale characterization of individual nanostructures because electrons have small (nm-scale) elastic and inelastic mean free paths and because electromagnetic fields can be used as electron optical lens elements for image formation. Recent breakthroughs in electron optical design and fabrication have allowed the correction of performance-limiting lens aberrations. Our group houses a state-of-the-art (scanning) transmission electron microscope (STEM/TEM) equipped with a monochromator and aberration-corrected electron energy-loss spectroscopy (EELS) imaging energy filter (for sub-0.3 eV spectral resolution) and aberration corrector (sub-0.1 nm spatial resolution), suitable for atomic-resolution chemical imaging of nanoscale structures with single-atom sensitivity. The instrument is also equipped with a specialized data acquisition module that allows STEM high-angle annular dark field (HAADF) and X-ray energy-dispersive spectroscopy (XEDS) spectral images integrated over thousands of frames with "on the fly" drift correction. We seek a creative researcher to work with us to develop and apply various methods of electron scattering for atomic- and nanometer (nm)-scale characterization of individual nanostructures, including techniques for ascertaining the coordinates and elemental identities of all atoms in nanostructures comprised of tens to thousands of atoms (e.g., catalyst particles). Experience in STEM/TEM imaging and microanalysis is preferred but is not a requirement.
Four-Dimensional (4D) Scanning Transmission Electron Microscopy
New developments in detector technology have made possible the acquisition of the full electron scattering distribution at each pixel in a scanning transmission electron microscope (STEM) image. This is a fundamental transformation from the existing image acquisition paradigm and could enable new types of nano- and atomic-scale metrology. The Material Measurement Laboratory has an active effort in the development of electron microscopy methods for high spatial resolution materials characterization and has recently upgraded its aberration-corrected STEM with a high-speed, pixelated detection system. Taking full advantage of this cutting edge technology will require the development of new methods for collecting, processing, and interpreting the large amounts of data we now have access to. Qualified candidates will have a background in electron microscopy or a relevant branch of computer science.
Nano- and Atomic-Resolution Electron Microscopy of Three-Dimensional Structures
The modern transmission electron microscope (TEM) is capable of atomic-resolution structural and chemical imaging. However, such data typically only represents a two-dimensional (2-D) projection of the underlying physical or chemical structure. To characterize the three-dimensional (3-D) makeup of a specimen, electron tomography is often employed. This involves the computational determination of 3-D features of a specimen from a series of their 2-D projections. By carefully preparing the specimen, designing the experimental acquisition, and subsequent data processing, semi- and fully-quantitative 3-D characterization should be possible. The successful candidate should possess a strong foundation in TEM characterization. Experience with aberration-corrected electron optics and/or tomographic reconstruction techniques would be ideal, but not a prerequisite.
Precision Cryo-electron Microscopy for Biopharmaceutical Structures
Research opportunities are available that focus on the development of precision cryo-electron microscopy (cryo-EM) measurements and analysis tools to enable robust high-resolution (better than 0.3 nm) structural characterization of flexible, protein-based drugs (i.e., protein biopharmaceuticals or biologics) that are below a molecular weight limit of ~ 200 kDa. To address current limitations of low contrast and the challenges with alignment and averaging of small, flexible biomolecules, we are simultaneously pursuing two strategies for bioengineering sample platforms for cryo-EM measurements. One approach will be to tag the protein of interest with gold nanoclusters, determine the gold-gold distances, and use this information to perform the alignment. The other will be to anchor the mAb to a large, well-characterized macromolecular system (e.g., a virus particle) to increase the apparent molecular weight of the analyte. In each case, we are utilizing the NIST mAb (RM8670) as a model system for the proposed measurements since it has been extensively characterized by multiple analytical, biophysical and structural methods. Both strategies will require the development of new data analysis and mathematical modeling tools to enable quantification of the inherent uncertainty in the various features of the calculated structures.
Computational Studies of Nanoporous Solids
Nanoporous solids such as zeolites and metal-organic frameworks have wide applications in gas separation and storage, and have recently received attention as possible materials for efficient carbon dioxide capture. This class of materials exhibits a wide variety of pore sizes, geometries, and connectivities, as well as a range of exposed chemical species and ligands that may bind a given adsorbate more or less favorably. These variations allow enormous potential for optimizing physical properties, such as the selective adsorption of one species over another. Density functional theory (DFT) calculations assist in the rational design of new materials by providing quantitative results on the stability of the framework and the binding energies of adsorbate species. Research opportunities are available to use DFT methods on problems in nanoporous solids, including, but not limited to: (1) the thermodynamics and phase transitions of flexible nanoporous materials, (2) the preferred binding sites of adsorbate species in nanoporous solids and predicted experimental signals (e.g., infrared spectra), and (3) the development of DFT-based force field models for the high-throughput simulation of adsorption isotherms in nanoporous solids.
Computational Studies of Functional Oxide Materials and Devices
Certain functional materials, especially those with perovskite or related structures, exhibit remarkable physical properties, such as large dielectric constants, large piezoelectric coefficients, and colossal magnetoresistance. Materials with optimal properties are generally solid solutions, often involving four or more different metal ions. Research opportunities exist in the systematic development of advanced models for the prediction of the above physical properties in such solid solutions. We use first-principles density functional theory calculations to uncover the microscopic physics responsible for the observed properties. The results obtained are then used to develop models that can be used to simulate systems with up to hundreds of thousands of atoms. Monte Carlo and molecular dynamics simulations allow the temperature dependence of the physical properties to be simulated, as well as the transition temperatures for ferroelectric and related structural phase transitions. The effects of external electric fields and pressure are incorporated into the models. The results of simulations based on these models will be used to explain experimental measurements, predict the properties of new materials, and determine the nanoscopic chemical clustering that can be used to optimize the physical properties.