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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Application of Weak-Beam Dark-Field STEM for Dislocation Loop Analysis

Nanoscale dislocation loops formed by irradiation can significantly contribute to both irradiation hardening and embrittlement of materials when subjected to extreme nuclear reactor environments. Here, this study explores the application of weak-beam dark-field (WBDF) scanning transmission electron microscopy (STEM) methods for quantitative irradiation-induced defect analysis in crystalline materials, with a specific focus on dislocation loop imaging and analysis. A high-purity Fe-5 wt% Cr model alloy was irradiated with 8 MeV Fe 2+ ions at 450°C to a fluence of 8.8 × 10 19 m -2 , inducing dislocation loops for analysis. While transmission electron microscopy (TEM) has traditionally been the primary tool for dislocation imaging, recent advancements in STEM technology have reignited interest in using STEM for defect imaging. This study introduces and compares three WBDF STEM methods, demonstrating their effectiveness in suppressing background contrasts, isolating defect information for dislocation loop type classification, providing finer dislocation line images for small loop analysis, and presenting inside–outside contrast for identifying loop nature. Experimental findings indicate that WBDF STEM methods surpass traditional TEM approaches, yielding clearer and more detailed images of dislocation loops. The study concludes by discussing the potential applications of WBDF STEM techniques in defect analysis, emphasizing their adaptability across various material systems beyond nuclear materials.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Radiation Tolerance of Nanoporous Gadolinium Titanate

Defect sinks play a crucial role in reducing radiation-induced damage accumulation, but their effectiveness varies. This study directly compares the efficacy of grain boundaries and pores (free surfaces) in gadolinium titanate (Gd 2 Ti 2 O 7 ) using in situ ion irradiation transmission electron microscopy (TEM). A unique sample configuration is developed, where each of the three distinct regions, each containing only one primary sink of interest, is in the same TEM lamella for simultaneous irradiation. Regular assessments of crystallinity in each region via nanobeam electron diffraction show that, at both room temperature and 600°C, free surface (pore) defect sinks are more effective than grain boundaries in capturing radiation-induced defects and delaying the onset of amorphization. These findings have significant implications for further microstructural engineering and the design of radiation-resistant microstructures.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Exploring dynamic surface processes during silicate mineral (wollastonite) dissolution with liquid cell

Most liquid cell transmission electron microscopy (LC TEM) studies focus on nanoparticles or nanowires, in large part because the preparation and study of materials in this size range is straightforward. By contrast, this is not true for samples in the micrometre size range, in large part because of the difficulties associated with sample preparation starting from a ‘bulk’ material. There are also many advantages inherent to the study of micrometre-sized samples compared to their nanometre-sized counterparts. Here, we present a liquid cell transmission electron study that employed an innovative sample preparation technique using focused ion beam (FIB) milling to fabricate micrometre-sized electron transparent lamellae that were then welded to the liquid cell substrate. This technique, for which we have described in detail all of the fabrication steps, allows for samples having dimensions of several square micrometres to be observed by TEM in situ in a liquid. We applied this technique to test whether we could observe and measure in situ dissolution of a crystalline material called wollastonite, a calcium silicate mineral. More specifically, this study was used to observe and record surface dynamics associated with step and terrace edge movement, which are ultimately linked to the overall rate of dissolution. The wollastonite lamella underwent chemical reactions in pure deionized water at ambient temperature in a liquid cell with a 5-math formulam-spacer thickness. The movement of surface steps and terraces was measured periodically over a period of almost 5 h. Quite unexpectedly, the one-dimensional rates of retreat of these surface features were not constant, but changed over time. In addition, there were noticeable quantitative differences in retreat rates as a function crystallographic orientation, indicating that surface retreat is anisotropic. Several bulk rates of dissolution were also determined (1.6–4.2 • 10 -7 mol m -2 s -1 ) using the rates of retreat of representative terraces and steps, and were found to be within one order of magnitude of dissolution rates in the literature based on aqueous chemistry data.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Multimodal and In-Situ Chemical Imaging of Critical Surfaces and Interfaces in Li Batteries

Interfaces play a critical role in the properties and lifetime of current generation and advanced batteries. However, detailed characterization of the critical interfaces during battery operation which can enable performance improvements and improved design has been a significant challenge requiring innovative technique development and creative experiments. This paper describes ways that information from a range of microscopy, spectroscopy, and spectrometry tools can be used to address important challenges associated with energy storage science and technology, in particular the development of advanced batteries for consumer use, transportation, , and renewable storage. Expanding the types of measurements that can be made on operational model batteries has significantly expanded the type and quality of information that can be obtained. This paper first shows examples of approaches being used to collect in situ transmission electron microscopy (TEM), secondary ion mass spectrometry (SIMS) and x-ray photoelectron spectroscopy data. The final section of the paper briefly shows two examples: the use of in situ XPS to examine SEI layers and a variety of methods including scanning TEM, atom probe tomography, scanning transmission x-ray microscopy (STXM), and x-ray adsorption near edge spectroscopy to understanding improve the performance of layered lithium transition metal oxide (LTMO) cathodes .

interface analysis, batteries in situ method, batt↗
DOE OSTI2020

Chemical and bonding analysis of liquids using liquid cell electron microscopy

Liquid cell transmission electron microscopy (TEM) has become an essential tool for studying the structure and properties of both hard and soft condensed-matter samples, as well as liquids themselves. Liquid cell sample holders, often consisting of two thin window layers separating the liquid sample from the high vacuum of the microscope column, have been designed to control in situ conditions, including temperature, voltage/current, or flow through the window region. While high-resolution and time-resolved TEM imaging probes the structure, shape, and dynamics of liquid cell samples, information about the chemical composition and spatially resolved bonding is often difficult to obtain due to the liquid thickness, the window layers, the holder configuration, or beam-induced radiolysis. Here, we review different approaches to quantitative liquid cell electron microscopy, including recent developments to perform energy-dispersive x-ray and electron energy-loss spectroscopy experiments on samples in a liquid environment or the liquid itself. We also cover graphene liquid cells and other ultrathin window layer holders.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Insights into solar nebula formation of pyrrhotite from nanoscale disequilibrium phases produced by H 2 S sulfidation of Fe metal

Lauretta (2005) produced sulfide in the laboratory by exposing canonical nebular metal analogs to H 2 S gas under temperatures and pressures relevant to the formation of the Solar System. The resulting reactions produced a suite of sulfides and nanophase materials not visible at the microprobe scale, but which we have now analyzed by TEM for comparison with interplanetary dust samples and comet Wild 2 samples returned by the Stardust mission. In this paper, we find the unexpected result that disequilibrium formation favors pyrrhotite over troilite and also produces minority schreibersite, daubréelite, barringerite, taenite, oldhamite, and perryite at the metal-sulfide interface. TEM identification of nanophases and analysis of pyrrhotite superlattice reflections illuminate the formation pathway of disequilibrium sulfide. Finally, we discuss the conditions under which such disequilibrium can occur, and implications for formation of sulfide found in extraterrestrial materials.

58 GEOSCIENCES↗
DOE OSTI2021

IVEM Contributions to CINR Penn State MT17-12797: In situ Ion Irradiation to Add Irradiation Assisted Grain Growth to the MARMOT Tool

In-situ TEM experiments were performed at the IVEM-Tandem Facility in Argonne National Laboratory to study the irradiation-induced grain growth of nanocrystalline UO 2 and CeO 2 thin films using 1 MeV Kr ions at various temperatures from 50K to 1073K. The grain growth kinetics was studied under both irradiation and thermal annealing conditions. Bright field and dark field TEM images and diffraction patterns were systematically recorded as a function of temperature, irradiation dose and annealing time. A comprehensive grain growth data of UO 2 was collected for further analysis and for the implementation to the MARMOT tool.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Dielectrics Under Extreme Electric Fields: In Situ Studies on Nanoscale Mechanisms (Final Technical Report)

The lack of materials that can function reliably under extreme electric fields is a critical roadblock to achieving higher energy efficiency and extended service lifetime of devices in electricity generation, transmission, and consumption. Materials typically fail at two or three orders of magnitude below their theoretical dielectric breakdown strength. Identifying the origins of premature dielectric breakdown using state-of-the-art characterization tools will, therefore, enable the design and discovery of transformational materials capable of approaching their intrinsic limits. The vast improvement in the resolution power of imaging tools, combined with the recently developed in situ electric biasing technique, has made high resolution observations of dielectric breakdown as it happens possible. The overall goal of the project is to directly image the dynamic processes of defect formation, accumulation, and interaction with preexisting defects (e.g., dislocations, domain walls, and grain boundaries in crystalline dielectric films) under electric fields up to 1,000 MV/m with a temporal resolution better than 5 microseconds. Using the newly acquired, custom-made Hysitron PI95 transmission electron microscopy (TEM) specimen holder, in situ TEM observations of breakdown at the sub nanometer resolution will be made on representative dielectric compounds with progressive complexities: the linear dielectric SiO 2 , CuO, and TiO 2 , the ferroelectric BaTiO 3 nanocrystals and nanocubes. Through direct observation of the breakdown event at high spatial and temporal resolutions, the nanoscale mechanisms for the failure of dielectrics under intense electric fields will be identified. The results of the project will be applied to the design and processing of new dielectric materials with higher efficiency, improved reliability, and a prolonged lifetime. Such new dielectrics are urgently needed for modernizing energy infrastructures.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2023

Multi-Scale Characterization of Porosity and Cracks in Silicon Carbide Cladding after Transient Reactor Test Facility Irradiation

Silicon carbide (SiC) ceramic matrix composite (CMC) cladding is currently being pursued as one of the leading candidates for accident-tolerant fuel (ATF) cladding for light water reactor applications. The morphology of fabrication defects, including the size and shape of voids, is one of the key challenges that impacts cladding performance and guarantees reactor safety. Therefore, quantification of defects’ size, location, distribution, and leak paths is critical to determining SiC CMC in-core performance. This research aims to provide quantitative insight into the defect’s distribution under multi-scale characterization at different length scales before and after different Transient Reactor Test Facility (TREAT) irradiation tests. A non-destructive multi-scale evaluation of irradiated SiC will help to assess critical microstructural defects from production and/or experimental testing to better understand and predict overall cladding performance. X-ray computed tomography (XCT), a non-destructive, data-rich characterization technique, is combined with lower length scale electronic microscopic characterization, which provides microscale morphology and structural characterization. This paper discusses a fully automatic workflow to detect and analyze SiC-SiC defects using image processing techniques on 3D X-ray images. Following the XCT data analysis, advanced characterizations from focused ion beam (FIB) and transmission electron microscopy (TEM) were conducted to verify the findings from the XCT data, especially quantitative results from local nano-scale TEM 3D tomography data, which were utilized to complement the 3D XCT results. In this work, three SiC samples (two irradiated and one unirradiated) provided by General Atomics are investigated. The irradiated samples were irradiated in a way that was expected to induce cracking, and indeed, the automated workflow developed in this work was able to successfully identify and characterize the defects formation in the irradiated samples while detecting no observed cracking in the unirradiated sample. These results demonstrate the value of automated XCT tools to better understand the damage and damage propagation in SiC-SiC structures for nuclear applications.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2024

An Investigation of Oxides of Tantalum Produced by Pulsed Laser Ablation and Continuous Wave Laser Heating

Recent progress has seen multiple Ta 2 O 5 polymorphs generated by different synthesis techniques. However, discrepancies arise when these polymorphs are produced in widely varying thermodynamic conditions and characterized using different techniques. This work aimed to characterize and compare Ta 2 O 5 particles formed at high and low temperatures using nanosecond pulsed laser ablation (PLA) and continuous wave (CW) laser heating of a local area of tantalum in either air or an 18 O 2 atmosphere. Scanning electron microscopy (SEM) and Raman spectroscopy of the micrometer-sized particles generated by PLA were consistent with either a localized amorphous Ta 2 O 5 phase or a similar, but not identical, crystalline β-Ta 2 O 5 phase. The Raman spectrum of the material formed at the point of CW laser impingement was in good agreement with the previously established ceramic “H-Ta 2 O 5 ” phase. TEM and electron diffraction analysis of these particles indicated the phase structure matched an oxygen-vacated superstructure of monoclinic H-Ta 2 O 5 . Further from the point of laser impingement, CW heating produced particles with a Raman spectrum that matched β-Ta 2 O 5 . We confirmed that the high-temperature ceramic phase characterized in previous work by Raman spectroscopy was the same monoclinic phase characterized in different work by TEM and could be produced by direct laser heating of metal in air.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Revealing the Latent Atomic World Through Data-Driven Microscopy

Many emerging technologies depend on the precise design of materials structure, chemistry, and defects. As devices shrink, manufacturing tolerances tighten, and performance envelopes improve, we must increasingly measure and manipulate materials at or near the single atom level. Here we describe how transmission electron microscopy (TEM) underpins our ability to see and direct the latent atomic world. We review a selection of our recent high-resolution TEM studies of the synthesis of oxide-based nanomaterials and their evolution in extreme environments. We then discuss powerful new artificial intelligence (AI) and machine learning (ML) approaches we have developed for rich, reproducible, and scalable experimentation. Furthermore, we conclude by discussing future developments that will enable new materials for breakthrough technologies.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2026

Thermoreflectance Detection of Point Defects Resulting from Focused Ion Beam Milling

Focused ion beam (FIB) milling is a commonly used tool for nanoscale material processing, such as for transmission electron microscopy (TEM) sample preparation, or the creation of fiducial markers prior to other processes and measurements. During milling, a high energy ion beam is used to remove material via sputtering. The expelled target material may return to the sample surface however, affecting subsequent measurements. Beam spreading or irradiation due to neutral gallium may also irradiate a larger area than intended. Extensive research has explored the effects of FIB milling on the prepared TEM sample, but few have looked at the effects of milling on the properties of the sample surrounding the milled region. We use multiple pump-probe laser-based techniques (time domain thermoreflectance and steady-state thermoreflectance) to measure the spatial extent of FIB-induced surface/subsurface changes on a series of silicon wafers milled at multiple currents and doses. We supplement these measurements with high-resolution scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, stylus profilometry, and time-of-flight secondary ion mass spectroscopy. We find a sample surface affected by the FIB up to 1 mm from where milling occurred, with a notable dependence on the ion beam current. We also note remarkably high sensitivity to surface defects using the thermoreflectance metrologies, including detection where other measurements failed.

defects↗
DOE OSTI2024

Precision Calcination Mechanism of CaCO 3 to High-Porosity Nanoscale CaO CO 2 Sorbent Revealed by Direct In Situ Observations

Deploying energy storage and carbon capture at scale is hindered by the substantial endothermic penalty of decomposing CaCO 3 to CaO and CO 2 , and the rapid loss of CO 2 absorption capacity by CaO sorbent particles due to sintering at the high requisite decomposition temperatures. The decomposition reaction mechanism underlying sorbent deactivation remains unclear at the atomic level and nanoscale due to past reliance on postmortem characterization methods with insufficient spatial and temporal resolution. Thus, elucidating the important CaCO 3 decomposition reaction pathway requires direct observation by time-resolved (sub-)nanoscale methods. Here, chemical and structural dynamics during the decomposition of CaCO 3 nanoparticles to nanoporous CaO particles comprising high-surface-area CaO nanocrystallites are examined. Comparing in situ transmission electron microscopy (TEM) and synchrotron X-ray diffraction experiments gives key insights into the dynamics of nanoparticle calcination, involving anisotropic CaCO 3 thermal distortion before conversion to thermally dilated energetically stable CaO crystallites. Time-resolved TEM uncovered a novel CaO formation mechanism involving heterogeneous nucleation at extended CaCO 3 defects followed by sweeping reaction front motion across the initial CaCO 3 particle. These observations clarify longstanding, yet incomplete, reaction mechanisms and kinetic models lacking accurate information about (sub-)nanoscale dynamics, while also demonstrating calcination of CaCO 3 without sintering through rapid heating and precise temperature control.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Direct Quantification of Heat Generation Due to Inelastic Scattering of Electrons Using a Nanocalorimeter

Transmission electron microscopy (TEM) is arguably the most important tool for atomic-scale material characterization. A significant portion of the energy of transmitted electrons is transferred to the material under study through inelastic scattering, causing inadvertent damage via ionization, radiolysis, and heating. In particular, heat generation complicates TEM observations as the local temperature can affect material properties. Here, the heat generation due to electron irradiation is quantified using both top-down and bottom-up approaches: direct temperature measurements using nanowatt calorimeters as well as the quantification of energy loss due to inelastic scattering events using electron energy loss spectroscopy. Combining both techniques, a microscopic model is developed for beam-induced heating and to identify the primary electron-to-heat conversion mechanism to be associated with valence electrons. Building on these results, the model provides guidelines to estimate temperature rise for general materials with reasonable accuracy. This study extends the ability to quantify thermal impact on materials down to the atomic scale.

42 ENGINEERING↗
DOE OSTI2018

Design Rules for Self-Assembly of 2D Nanocrystal/Metal–Organic Framework Superstructures

Here, we demonstrate the guiding principles behind simple two dimensional self-assembly of MOF nanoparticles (NPs) and oleic acid capped iron oxide (Fe 3 O 4 ) NCs into a uniform two-dimensional bi-layered superstructure. This self-assembly process can be controlled by the energy of ligand–ligand interactions between surface ligands on Fe 3 O 4 NCs and Zr 6 O 4 (OH) 4 (fumarate) 6 MOF NPs. Scanning transmission electron microscopy (TEM)/energy-dispersive X-ray spectroscopy and TEM tomography confirm the hierarchical co-assembly of Fe 3 O 4 NCs with MOF NPs as ligand energies are manipulated to promote facile diffusion of the smaller NCs. First-principles calculations and event-driven molecular dynamics simulations indicate that the observed patterns are dictated by combination of ligand–surface and ligand–ligand interactions. This study opens a new avenue for design and self-assembly of MOFs and NCs into high surface area assemblies, mimicking the structure of supported catalyst architectures, and provides a thorough fundamental understanding of the self-assembly process, which could be a guide for designing functional materials with desired structure.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2018

Design Rules for Self-Assembly of 2D Nanocrystal/Metal-Organic Framework Superstructures

Here we demonstrate the guiding principles behind simple two dimensional self-assembly of MOF nanoparticles (NPs) and oleic acid capped iron oxide (Fe 3 O 4 ) NCs into a uniform two-dimensional bi-layered superstructure. This self-assembly process can be controlled by the energy of ligand–ligand interactions between surface ligands on Fe 3 O 4 NCs and Zr 6 O 4 (OH) 4 (fumarate) 6 MOF NPs. Scanning transmission electron microscopy (TEM)/energy-dispersive X-ray spectroscopy and TEM tomography confirm the hierarchical co-assembly of Fe 3 O 4 NCs with MOF NPs as ligand energies are manipulated to promote facile diffusion of the smaller NCs. First-principles calculations and event-driven molecular dynamics simulations indicate that the observed patterns are dictated by combination of ligand–surface and ligand–ligand interactions. This study opens a new avenue for design and self-assembly of MOFs and NCs into high surface area assemblies, mimicking the structure of supported catalyst architectures, and provides a thorough fundamental understanding of the self-assembly process, which could be a guide for designing functional materials with desired structure.

36 MATERIALS SCIENCE↗