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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Direct Fabrication of Atomically Defined Pores in MXenes Using Feedback-Driven STEM

Controlled fabrication of nanopores in 2D materials offer the means to create robust membranes needed for ion transport and nanofiltration. Techniques for creating nanopores have relied upon either plasma etching or direct irradiation; however, aberration-corrected scanning transmission electron microscopy (STEM) offers the advantage of combining a sub-Å sized electron beam for atomic manipulation along with atomic resolution imaging. Here, for this work, a method for automated nanopore fabrication is utilized with real-time atomic visualization to enhance the mechanistic understanding of beam-induced transformations. Additionally, an electron beam simulation technique, Electron-Beam Simulator (E-BeamSim) is developed to observe the atomic movements and interactions resulting from electron beam irradiation. Using the MXene Ti 3 C 2 T x , the influence of temperature on nanopore fabrication is explored by tracking atomic transformations and find that at room temperature the electron beam irradiation induces random displacement and results in titanium pileups at the nanopore edge, which is confirmed by E-BeamSim. At elevated temperatures, after removal of the surface functional groups and with the increased mobility of atoms results in atomic transformations that lead to the selective removal of atoms layer by layer. This work can lead to the development of defect engineering techniques within functionalized MXene layers and other 2D materials.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Phase Transformations among TiO2 Polymorphs

Polymorphs widely exist in nature and synthetic systems and are well known to determine material properties. Understanding phase transformation mechanisms among polymorphs enables the design of structures and tuning of phases to tailor material properties. However, current understanding is limited due to the lack of direct observations that track the processes and the structural evolution is not known at atomic scale. Here, integrating (semi) in situ transmission electron microscopy and density functional theory, we report atomic structural evolutions of phase transformation from anatase (A) to rutile (R), brookite (B), R-phase, and TiO. Besides the consistent paths with previous reports, we discover several unreported paths, including a [001] direction and (020) plane of anatase to [100]A and (011)R of rutile, respectively, ( , ) and , . Density functional theory analysis elucidates atomic structural evolution during the processes and over 16% of Ti-O bonds break and reform during the processes with energy barriers of ~0.7-1.0 eV per TiO2 formula unit. Under electron-beam irradiation, anatase particles transform into TiO2-R phase or TiO at high or room temperature, respectively. We also reveal the anisotropic nature of electron-beam effect, which is seldom discussed: dependence of crystallographic orientation with respect to electron-beam irradiation direction. Understanding the atomic structural evolution sheds light on interpreting and controlling TiO2 polymorphs and interface structures for various applications. The revealed electron-beam effects in our work provide guidance for in situ transmission electron microscopy studies.

Song, Miao↗
DOE OSTI2022

An e-beam irradiation beamline at Jefferson Lab for 1,4-dioxane and per- and polyfluoroalkyl substances (PFAS) remediation in wastewater

The Upgraded Injector Test Facility (UITF) at Jefferson Lab, providing a beam energy up to 10 MeV, is suitable for wastewater remediation research. To investigate the degradation of 1,4-dioxane and per- and polyfluoroalkyl substances (PFAS), widespread in wastewater and potential to be regulated in near future, a beamline for electron-beam irradiation has been designed, installed and successfully commissioned at the UITF. A solenoid with a peak axial magnetic field of up to 0.28 T and a raster were used to obtain a Gaussian beam profile with a transverse standard deviation of 15 mm. It was applied to irradiate 1,4-dioxane sample filled in the target cell that was designed to let the entire sample receive significant irradiation doses. The dose distribution and absorbed dose, few studied in the current publications, are necessary measures for the degradation mechanism investigation and have been innovatively achieved in this work using simulations which were calibrated with opti-chromic dosimeter rods directly exposed to the electron beam. This approach provides an important way for investigating the environmental remediation impact of electron-beam irradiation.

Li, Xi↗
DOE OSTI2022

Beamline for E-beam processing at UITF

Electron beam irradiation is a method that has shown a good potential to reduce several pollutants in wastewater. One of the main challenges towards wider adoption of this method is the need for compact, reliable, cost-effective, high-power accelerators. Jefferson Lab is working on the design and prototyping of accelerator components, based on superconducting radio-frequency (SRF) technology, aiming at accelerators for industrial applications. The LDRD project aimed at designing, procuring, installing, and commissioning a beamline at the Upgraded Injector Test Facility (UITF) accelerator to allow electron-beam irradiation studies of different materials, beginning with wastewater. The availability of such beamline allows exploring the ability of electron-beam radiation to reduce or eliminate so-called “forever chemicals” that can be found in wastewater or industrial sites. After successful commissioning, the beamline was used to irradiate wastewater samples with different concentrations of 1,4-dioxane, in collaboration with Hampton Roads Sanitation District (HRSD).

42 ENGINEERING↗
DOE OSTI2026

Freeze It or Leave It? Evaluating the Role of Cryo-Electron Microscopy in Battery Research

Cryogenic electron microscopy (cryo-EM) continues to gain prominence in materials science, particularly in battery research where it has enabled high-resolution, multimodal characterization of electrode materials and interfaces that otherwise degrade quickly under electron beam irradiation. But as anyone who has attempted cryo-EM techniques knows, freezing comes at a cost; cryo-EM experiments are time-consuming, highly sensitive, and carry an increased risk of artifacts due to issues such as frost contamination. Thus, when planning new characterization of battery materials or other beam-sensitive samples, it is critical to consider whether (and which) cryo-EM techniques are appropriate, based on study goals and an understanding of electron beam-sample interactions. Here we review such considerations for battery materials to elucidate the questions of when, why, and how to freeze to achieve high-quality characterization.

25 ENERGY STORAGE↗
DOE OSTI2022

Probing Electron Beam Induced Transformations on a Single-Defect Level via Automated Scanning Transmission Electron Microscopy

A robust approach for real-time analysis of the scanning transmission electron microscopy (STEM) data streams, based on ensemble learning and iterative training (ELIT) of deep convolutional neural networks, is implemented on an operational microscope, enabling the exploration of the dynamics of specific atomic configurations under electron beam irradiation via an automated experiment in STEM. Combined with beam control, this approach allows studying beam effects on selected atomic groups and chemical bonds in a fully automated mode. Here, in this study, we demonstrate atomically precise engineering of single vacancy lines in transition metal dichalcogenides and the creation and identification of topological defects in graphene. The ELIT-based approach facilitates direct on-the-fly analysis of the STEM data and engenders real-time feedback schemes for probing electron beam chemistry, atomic manipulation, and atom by atom assembly.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Compact, high-power superconducting radio-frequency accelerators for environmental applications

Electron-beam irradiation has been proven to destructively reduce or eliminate a wide variety of organic chemicals, viruses and bacteria from wastewater, as well as reducing sulfur and nitrous oxides emission from coal-fired power plants. It is estimated that there are approximately 30,000 such particle accelerators in use worldwide for industrial processes including surface and bulk processing of material, medical sterilization, and environmental remediation. Maximum beam power from accelerators used in these applications is currently limited to less than 500 kW, and a higher beam power is needed to reduce treatment costs. The market availability of continuous-wave (CW) electron-beam accelerators with power of the order of ~100 kW is also very limited. Superconducting radio-frequency (SRF) linear accelerators (linacs) are commonly used at basic research laboratories throughout the world due to their exceptionally high efficiency as compared to current industrial varieties. Recent advances in cryogenics, SRF thin films and high-power magnetrons allow for the design of increasingly compact and efficient CW SRF electron linacs in the energy range 1-10 MeV, with up to 1 MW of beam power. A new class of compact, high-efficiency electron-beam accelerators may provide cost-effective solutions for a range of industrial and environmental remediation applications, particularly with respect to tackling one such class of contaminants so-called “forever chemicals”, including per- and polyfluoroalkyl substances (PFASs), which are ubiquitous in a wide range of products and for which there is currently no effective destruction technology. We have recently demonstrated the key technologies required for such accelerators by: 1) operating a Nb3Sn SRF accelerating cavity cooled by commercial cryocoolers up to an accelerating gradient of 12.4 MV/m and 2) demonstrating the phase-locking as well as a high-efficiency power combining scheme for industrial magnetron transmitters. In this presentation, we will introduce the principles and benefits of MW-class SRF linacs, based on the conduction-cooled SRF technology that we have demonstrated for environmental remediation. We propose the development of a 4 MeV, 20 kW prototype to be built at Jefferson Lab as a first accelerator demonstrator unit. We will also present the results from samples study on the effect of electron-beam irradiation on so-called “forever chemicals” such as 1,4-dioxane and PFAS, using an existing multi-purpose 10 MeV, low-power, CW SRF linac at Jefferson Lab.

Ciovati, Gianluigi↗
DOE OSTI2025

Towards Mitigating Electron Beam-Induced Damage in MOFs Using Low Dose Electron Microscopy for In-Situ Room-Temperature Measurements

Metal-Organic Frameworks (MOFs) have emerged as a versatile class of materials with applications in gas storage and separation, catalysis, and drug delivery [1]. Understanding their damage mechanisms in under various environmental conditions is crucial for optimizing performance and stability [2]. This study employs a combination of Length Structural Coherence (LSC) analysis in electron scattering and Electron Energy Loss Spectroscopy (EELS) to elucidate the damage mechanisms in two representative MOFs. MIL101(Fe), and MIL101(Cr). Here, the primary objective is to reveal structural and chemical changes that occur under electron beam irradiation in Scanning Transmission Electron Microscopy (STEM), both in the pristine state and during in-situ CO and CO 2 adsorption. By combining LSC in Radial Distribution Function (RDF) analysis with EELS, comprehensive insights into the nanoscale alterations are obtained and correlated to the electron dose rate.

dos Santos, Gabriel T. [Northwestern University, E↗
DOE OSTI2023

Mending cracks atom-by-atom in rutile TiO2 with electron beam radiolysis

Abstract Rich electron-matter interactions fundamentally enable electron probe studies of materials such as scanning transmission electron microscopy (STEM). Inelastic interactions often result in structural modifications of the material, ultimately limiting the quality of electron probe measurements. However, atomistic mechanisms of inelastic-scattering-driven transformations are difficult to characterize. Here, we report direct visualization of radiolysis-driven restructuring of rutile TiO 2 under electron beam irradiation. Using annular dark field imaging and electron energy-loss spectroscopy signals, STEM probes revealed the progressive filling of atomically sharp nanometer-wide cracks with striking atomic resolution detail. STEM probes of varying beam energy and precisely controlled electron dose were found to constructively restructure rutile TiO 2 according to a quantified radiolytic mechanism. Based on direct experimental observation, a “two-step rolling” model of mobile octahedral building blocks enabling radiolysis-driven atomic migration is introduced. Such controlled electron beam-induced radiolytic restructuring can be used to engineer novel nanostructures atom-by-atom.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Atomic-scale e-beam sculptor

A system and method (referred to as the system) fabricates controllable atomic assemblies in two and three dimensions. The systems identify by a non-invasive imager, a local atomic structure, distribution of vacancies, and dopant atoms and modify, by a microscopic modifier, the local atomic structure, via electron beam irradiation. The systems store, by a knowledge base, cause-and-effect relationships based on a non-invasive imaging and electron scans. The systems detect, by detectors, changes in the local atomic structure induced by the electron irradiation; and fabricate, a modified atomic structure by a beam control software and feedback.

Kalinin, Sergei V.↗
DOE OSTI2023

Atomic-scale in situ observation of electron beam and heat induced crystallization of Ge nanoparticles and transformation of Ag@Ge core-shell nanocrystals

Crystallization of amorphous materials by thermal annealing has been investigated for numerous applications in the fields of nanotechnology, such as thin-film transistors and thermoelectric devices. The phase transition and shape evolution of amorphous germanium (Ge) and Ag@Ge core–shell nanoparticles with average diameters of 10 and 12 nm, respectively, were investigated by high-energy electron beam irradiation and in situ heating within a transmission electron microscope. The transition of a single Ge amorphous nanoparticle to the crystalline diamond cubic structure at the atomic scale was clearly demonstrated. Depending on the heating temperature, a hollow Ge structure can be maintained or transformed into a solid Ge nanocrystal through a diffusive process during the amorphous to crystalline phase transition. Selected area diffraction patterns were obtained to confirm the crystallization process. In addition, the thermal stability of Ag@Ge core–shell nanoparticles with an average core of 7.4 and a 2.1 nm Ge shell was studied by applying the same beam conditions and temperatures. The results show that at a moderate temperature (e.g., 385 °C), the amorphous Ge shell can completely crystallize while maintaining the well-defined core–shell structure, while at a high temperature (e.g., 545 °C), the high thermal energy enables a freely diffusive process of both Ag and Ge atoms on the carbon support film and leads to transformation into a phase segregated Ag–Ge Janus nanoparticle with a clear interface between the Ag and Ge domains. In conclusion, this study provides a protocol as well as insight into the thermal stability and strain relief mechanism of complex nanostructures at the single nanoparticle level with atomic resolution.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Morphological Ordering of the Organic Layer for High-Performance Hybrid Thermoelectrics

Inorganic-organic hybrids, such as Te-PEDOT:PSS core/shell nanowires, have emerged as a class of promising thermoelectric materials with combined attributes of mechanical flexibility and low cost. However, the poorly understood structure-property relationship calls for further investigation for performance enhancement. Here, through precise treatments of focused electron beam irradiation and thermal annealing on individual Te-PEDOT:PSS nanowires, new, nonchemical mechanisms are introduced to specifically engineer the organic phase, and the measured results provide an unprecedented piece of evidence, confirming the dominant role of organic shell in charge transport. Paired with the Kang-Snyder model and molecular dynamics simulations, this work provides mechanistic insights in terms of heating-enabled morphological ordering of the polymer chains. The measured results show that thermal annealing on the 42 nm nanowire results in a ZT value of 0.78 at 450 K. In conclusion, through leveraging the interfacial self-assembly of the organic phase to construct a high electrical conductivity domain, this work lays out a clear framework for the development of next-generation soft thermoelectrics.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Redox Mediated Control of Electrochemical Potential in Liquid Cell Electron Microscopy

Liquid cell electron microscopy enables the study of nanoscale transformations in solvents with high spatial and temporal resolution, but for the technique to achieve its potential requires a new level of control over the reactivity caused by radical generation under electron beam irradiation. An understanding of how to control electron-solvent interactions is needed to further advance the study of structural dynamics for complex materials at the nanoscale. Additionally, we developed an approach that scavenges radicals with redox species that form well-defined redox couples and control the electrochemical potential in situ . This approach enables the observation of electrochemical structural dynamics at near-atomic resolution with precise control of the liquid environment. Analysis of nanocrystal etching trajectories indicates that this approach can be generalized to several chemical systems. The ability to simultaneously observe heterogeneous reactions at near-atomic resolution and precisely control the electrochemical potential enables the fundamental study of complex nanoscale dynamics with unprecedented detail.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

CHARACTERIZATION OF RADIATION DAMAGES TO POSITRON SOURCE MATERIALS

The secondary beam production target at future positron sources at the Continuous Electron Beam Accelerator Facility (CEBAF), the International Linear Collider (ILC) or the Future Circular Collider (FCC), features unprecedented mechanical and thermal stresses which may compromise sustainable and reliable operation. Candidate materials are required to possess high melting temperature together with excellent thermal conductivity, elasticity and radiation hardness properties. In order to substantiate the material choice for the CEBAF and ILC positron sources, the response of candidate materials such as titanium alloys, tungsten, and tantalum to electron beam irradiation was experimentally investigated. CEBAF and ILC expected operating conditions were mimicked using the 3.5 MeV electron beam of the MAMI facility injector. The material degradations were precisely analyzed via high energy X-ray diffraction at the HEMS beamline operated by the Helmholtz-Zentrum Hereon at the PETRA III synchrotron facility. This work reports the results of these measurements and their interpretation.

Lengler, T.↗
DOE OSTI2022

Effects of X-Rays, Electron Beam, and Gamma Irradiation on Chemical and Physical Properties of EVA Multilayer Films

Gamma-ray irradiation, using the cobalt-60 isotope, is the most common radiation modality used for medical device and biopharmaceutical products sterilization. Although X-ray and electron-beam (e-beam) sterilization technologies are mature and have been in use for decades, impediments remain to switching to these sterilization modalities because of lack of data on the resulting radiation effects for the associated polymers, as well as a lack of education for manufacturers and regulators on the viability of these sterilization alternatives. For this study, the compatibility of ethylene vinyl acetate (EVA) multilayer films with different ionizing radiation sterilization (X-ray, e-beam, and gamma irradiation) is determined by measuring chemical and physical film properties using high performance liquid chromatography, differential scanning calorimetry, Fourier-Transform InfraRed spectroscopy (FTIR), surface energy measurement, and electron spin resonance techniques. The results indicate that the three irradiation modalities induce no differences in thermal properties in the investigated dose range. Gamma and X-Ray irradiations generate the same level of reactive species in the EVA multilayer film, whereas e-beam generates a reduced quantity of reactive species.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Nonadiabatic Effects on Defect Diffusion in Silicon-Doped Nanographenes

Single atom impurities in graphene, substitutional silicon defects in particular, have been observed to diffuse under electron beam irradiation. However, the relative importance of elastic and inelastic scattering in facilitating their mobility remains unclear. Here, we employ excited-state electronic structure calculations to explore potential inelastic effects, and find an electronically nonadiabatic excited-state silicon diffusion pathway involving “softened” Si–C bonding that presents an ~2 eV lower diffusion barrier than the ground-state pathway. Beam-induced transition rates to this state indicate that the excited-state pathway is accessible through irradiation of the defect site. However, even in the limit of fully elastic scattering, upward nonadiabatic transitions are also possible along the diffusion coordinate, increasing the diffusion barrier and further demonstrating the potential for electronic nonadiabaticity to influence beam-induced atomic transformations in materials. Additionally, we also propose some experimentally testable signatures of such excited-state pathways.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

Atomic-Scale Dynamic Mechanisms of Embedded MoS 2 Wires

Nanowires composed of a 1:1 stoichiometry of transition metals and chalcogen ions can be fabricated from two-dimensional transition metal dichalcogenides (TMDs) by using electron beam irradiation. Wires fabricated through in situ experiments can be geometrically connected to TMD sheets in various ways, and their physical properties can vary accordingly. Understanding the structural transformation caused by electron beams is critical for designing wire-sheet structures for nanoelectronics. In this study, we report the behavior of nanowires formed inside a monolayer MoS 2 sheet by combining phase-contrast images and large-scale atomistic modeling. Here we investigate the effect of vacancies on the dynamic evolution of wires, such as rotations with different edge structures and breaking, by considering the interactions between MoS wires and MoS 2 nanosheets. The obtained insights can be applied to other monolayer TMDs to guide the behavior of TMD wires and fabricate favorable geometries for various applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Impacts of Ionizing Radiation on Sulfur Chloride Compounds for Advanced Fuel Cladding Decontamination Processes

Tripling the nation’s nuclear energy capacity is a critical component for significantly increasing energy production and reducing energy costs for American families and businesses. Achieving this vision requires fuel cycle technologies that maximize resource utilization while minimizing radioactive waste generation. Advanced sulfur chloride–based chlorination technologies are being developed to enable efficient recycling of fuel cladding materials, which account for a significant fraction of used nuclear fuel. However, the impacts of ionizing radiation on the longevity and performance of these sulfur chloride compounds are not well established. Here, we will explore the effects of gamma and electron-beam irradiation on the chemical composition of select sulfur chloride reagents, specifically sulfur monochloride (S2Cl2) and thionyl chloride (SOCl2), and the impacts of pre-irradiation on the chlorination yield/chemical dissolution of surrogate aluminum alloy 6061 (AA6061-T6) materials.

38 - RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCL↗