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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Applications of analytical electron microscopy to guide the design of boron carbide

Compositional analysis of boron carbide on nanometer length scales to examine or interpret atomic mechanisms, for example, solid-state amorphization or grain-boundary segregation, is challenging. This work reviews advancements in high-resolution microanalysis to characterize multiple generations of boron carbide. First, ζ-factor microanalysis will be introduced as a powerful (scanning) transmission electron microscopy ((S)TEM) analytical framework to accurately characterize boron carbide. Three case studies involving the application of ζ-factor microanalysis will then be presented: (1) accurate stoichiometry determination of B-doped boron carbide using ζ-factor microanalysis and electron energy loss spectroscopy, (2) normalized quantification of silicon grain-boundary segregation in Si-doped boron carbide, and (3) calibration of a scanning electron microscope X-ray energy-dispersive spectroscopy (XEDS) system to measure compositional homogeneity differences of B/Si-doped arc-melted boron carbides in the as-melted and annealed conditions. Overall, the improvement and application of advanced analytical tools have helped better understand processing–microstructure–property relationships and successfully manufacture high-performance ceramics.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Mitigating e-beam-induced hydrocarbon deposition on graphene for atomic-scale scanning transmission electron microscopy studies

Chemical vapor deposition (CVD) grown graphene used in (scanning) transmission electron microscopy [(S)TEM] studies must undergo a careful transfer of the one-atom-thick membrane from the growth surface (typically a Cu foil) to the TEM grid. During this transfer process, the graphene invariably becomes contaminated with foreign materials. This contamination proves to be very problematic in the (S)TEM because often >95% of the graphene is obscured, and imaging of the pristine areas results in e-beam-induced hydrocarbon deposition which further acts to obscure the desired imaging area. In this article, the authors examine two cleaning techniques for CVD grown graphene that mitigate both aspects of the contamination problem: visible contamination covering the graphene, and “invisible” contamination that deposits onto the graphene under e-beam irradiation. Furthermore, the visible contamination may be removed quickly by a rapid thermal annealing to 1200 °C in situ and the invisible e-beam-deposited contamination may be removed through an Ar/O 2 annealing procedure prior to imaging in the (S)TEM.

36 MATERIALS SCIENCE↗
DOE OSTI2023

In situ plasmonic tip preparation and validation techniques for scanning tunneling microscopy

Among the many parts constituting a scanning tunneling microscope, the metallic tip is the component that directly interacts with the specimen and plays a critical role in visualizing the physical quantity of interest. While tip materials such as W and Pt–Ir are commonly used for topographic imaging and their preparation is well-documented, the preparation of plasmonic materials such as Ag for tip-enhanced Raman spectroscopy is relatively less standardized. Furthermore, we present several in situ Ag tip preparation and validation techniques for the microscopist to use depending on their intended application, including atomic resolution imaging, scanning tunneling spectroscopy (STM), and tip-enhanced Raman spectro-microscopy in ultrahigh vacuum. Besides optical applications, these methods are not limited to Ag but also applicable to other STM tip materials.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Combining molecular beam epitaxy and low-energy electron microscopy with in situ magnetic susceptibility measurements within an integrated ultrahigh vacuum system

Quantum two-dimensional materials, including ultrathin superconducting films, are of great current research interest. These films are typically fabricated under ultra-high vacuum (UHV) conditions and are sensitive to the environment—prone to oxidation and contamination when exposed to the atmosphere. This hampers the study of their intrinsic properties by standard ex situ techniques. Here, we present a variable-temperature mutual inductance probe system integrated under UHV with molecular beam epitaxy (MBE) synthesis and low-energy electron microscopy, enabling nondestructive in situ characterization of superconducting thin films. The system employs a reflection-type configuration and reaches a low temperature (∼4 K) using a high-cooling-power, vibration-isolated cryocooler. In conclusion, we demonstrate the system performance by measuring the superconducting critical temperature in a copper-oxide thin film.

2D materials↗
DOE OSTI2018

Adaptation of microscopy with ultraviolet surface excitation for enhancing STEM and undergraduate education

Microscopy with ultraviolet surface excitation (MUSE) is investigated as a means to enhance curricula and education in the life sciences based on simplicity of use, the incorporation of inexpensive hardware, and the simplest methods of tissue preparation. Ultraviolet excitation in effect replaces tissue sectioning because it penetrates only a few micrometers below the tissue surface at the single cell level, preventing the generation of out-of-focus light. Although tissue autofluorescence may be used, image quality and content can be enhanced by a brief immersion in a solution of nontoxic fluorescent dyes that selectively highlight different cellular compartments. Safe mixed-dye powder combinations have been developed to provide students who have minimal lab proficiencies with a one-step tissue staining process for rapid tissue preparation.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Optical manipulation of magnetic vortices visualized in situ by Lorentz electron microscopy

By understanding the fundamental dynamics of topological vortex and antivortex naturally formed in microscale/nanoscale ferromagnetic building blocks under external perturbations is crucial to magnetic vortex–based information processing and spintronic devices. All previous studies have focused on magnetic vortex–core switching via external magnetic fields, spin-polarized currents, or spin waves, which have largely prohibited the investigation of novel spin configurations that could emerge from the ground states in ferromagnetic disks and their underlying dynamics. We report in situ visualization of femtosecond laser quenching–induced magnetic vortex changes in various symmetric ferromagnetic Permalloy disks by using Lorentz phase imaging of four-dimensional electron microscopy that enables in situ laser excitation. Besides the switching of magnetic vortex chirality and polarity, we observed with distinct occurrence frequencies a plenitude of complex magnetic structures that have never been observed by magnetic field– or current-assisted switching. These complex magnetic structures consist of a number of newly created topological magnetic defects (vortex and antivortex) strictly conserving the topological winding number, demonstrating the direct impact of topological invariants on magnetization dynamics in ferromagnetic disks. Their spin configurations show mirror or rotation symmetry due to the geometrical confinement of the disks. Combined micromagnetic simulations with the experimental observations reveal the underlying magnetization dynamics and formation mechanism of the optical quenching–induced complex magnetic structures. Their distinct occurrence rates are pertinent to their formation-growth energetics and pinning effects at the disk edge. On the basis of these findings, we propose a paradigm of optical quenching–assisted fast switching of vortex cores for the control of magnetic vortex–based information recording and spintronic devices.

4D electron microscopy↗
DOE OSTI2017

Determination of Particle Size Distribution of Zirconium Dioxide Powders by Static Laser Scattering and Optical Microscopy

Dispersing conditions of powdered zirconium dioxide with addition of 3 mol % yttrium oxide are determined. The particle size distribution of the powders is determined by static laser scattering and optical microscopy. The zeta potential of suspension of zirconium dioxide particles as a function of pH of medium is measured by electrophoresis with titration. The influence of acidity on suspension stability during measurements is studied. It is demonstrated that a stable suspension can be obtained by shift of pH to both the acid and alkaline regions as well as by addition of surfactants, such as Dolapix CE 64.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Electron microscopy study of an Old Russian (XII century) encolpion cross with black inlay

The phase compositions of the basic material (alloy) of a pre-Mongolian Old Russian encolpion cross found near Suzdal and its black inlay have been investigated by methods of scanning and transmission electron microscopy and energy-dispersive X-ray microanalysis. The cross material is lead–zinc–tin α-bronze, and the black is copper sulfide with lead inclusions. As a result of the corrosion, tin and copper oxides and zinc sulfides, which made the cross dark gray, were formed on its surface. It is shown that the corrosion depth is as large as 50 μm; thus, laps must be prepared to accurately determine the morphology and phase composition of the corrosion layer. Decoration with black was apparently performed by pouring with copper sulfide melt or melting a powder preliminarily placed in grooves forming an image on the surface.

36 MATERIALS SCIENCE↗
DOE OSTI2017

New method of automated statistical analysis of polymer-stabilized metal nanoparticles in electron microscopy images

The efficiency of the synthesis and application of metal/nonmetal particles several nanometers in size, prepared in solutions and stabilized with polymers, can be increased by applying a reliable statistical analysis and determining particle-size distributions for different systems. A new method for processing electron microscopy images of nanoparticles ≤10 nm in size and the program Analyzer of Nanoparticles designed for rapid recognition and measurements are presented. The program combines two approaches: threshold image processing for particle recognition and fitting the model of the particles with neighborhood background to the real experimental images.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2017

Study of magnetic metal periodic structures by X-Ray and electron microscopy methods

Complex studies of magnetic periodic metallic systems based on Dy/Gd layers have been carried out by X-ray diffraction, resonance X-ray reflectometry, transmission electronic microscopy, and energydispersve microanalysis. The application of these methods and joint analysis of their results provide an effective approach to study of the structure and determination of the parameters of individual layers and interfaces and their structural quality with a high degree of reliability.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Nanohematite from Ferruginous Quartzites of Kursk Magnetic Anomaly According to Transmission Electron Microscopy Data

Transmission electron microscopy study of ferruginous quartzite (jaspilites) from the Lebedinsky field of Kursk magnetic anomaly has revealed for the first time hematite nanoformations (about 10 nm in size), sp. gr. R3̅, which coexist with hematite, sp. gr. R3̅c, in the same crystallographic orientation or manifest themselves as individual nanoinclusions in the substrate of poorly crystallized magnetite. On the assumption that, in correspondence with the energy-dispersive X-ray analysis data, octahedral sites in the hematite structure can be occupied by only Fe cations, several structural models are proposed explain the hematite symmetry lowering to R3̅.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Study of the Ancient Crimean Ceramics by Electron Microscopy Methods

Fragments of ancient amphorae and tiles dated to the IVth to IInd centuries BC, which were found on the Crimean peninsula, have been investigated by methods of scanning and transmission/scanning electron microscopy, combined with energy-dispersive X-ray microanalysis. The revealed differences in the compositions of the clay core and inclusions (leaners) are associated with the differences in the periods of time when items were made and the sites of their origin.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Low-Voltage Scanning Electron Microscopy and Energy-Dispersive X-Ray Microanalysis of the Interface of Multilayer Polymer Composite

The morphology of the layer of polyelectrolyte complex, which is formed in the composite based on chitosan and sulfoethyl cellulose during the contact of a solution of one of them with a gel film of the other one, has been investigated by the low-voltage (≤3 kV) scanning electron microscopy. A technique for eliminating the effects related to charge accumulation on the dielectric film surface is proposed.

36 MATERIALS SCIENCE↗
DOE OSTI2018

A Study of Iron Phthalocyanine Pyrolyzate with Mössbauer Spectroscopy and Transmission Electron Microscopy

A pyrolyzate of iron phthalocyanine is studied by Mössbauer spectroscopy and transmission electron microscopy. The phase composition and magnetic state were found for pyrolysis products (α-Fe, γ-Fe, Fe{sub 3}C, and magnetite). Morphological features of carbon and iron-containing phases (metal particles of various shapes and sizes, as well as carbon nanotubes, carbon hollow nanopolihedra, and nongraphitized carbon) are determined. The morphology and structure of iron phthalocyanine pyrolyzates and diphthalocyanines of rare-earth elements are analyzed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Magnetization Reversal of Permalloy Microparticles with the Configuration Anisotropy by Magnetic-Force Microscopy

Abstract—Magnetic force microscopy has been used to study the distribution of the magnetization in permalloy microparticles with a configurational anisotropy. The triangular particles with different degrees of concavity of the lateral sides have been studied. An analysis of the results enables us to state that the particles can be in several quasi-homogeneous stable states. It is shown that the particle magnetization reversal can occur both stepwise and also via an intermediate state in the dependence on the particle orientation. It is demonstrated that the quasi-homogeneous magnetization orientation in a particle can be changed by a magnetic-force microscope probe.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Microstructure of Si Crystals Subjected to Irradiation with High-Energy H{sup +} Ions and Heat Treatment by High-Resolution Three-Crystal X-Ray Diffraction and Transmission Electron Microscopy

The structural features of the formation of radiation defects in proton-implanted layers of silicon plates during their heat treatment have been studied. New data on the nature, the characteristics, and the microdefect concentration in Si crystals irradiated with protons with energies 100 + 200 + 300 keV with the total dose 2 × 10{sup 16} cm{sup –2} and the evolution of the defect structure during heat treatment have been obtained by high-resolution three-crystal X-ray diffraction and transmission electron microscopy over wide temperature range from 200 to 1100°C.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Determination of the Thicknesses and Visualization of Ion-Exchange Waveguides in Glasses by Scanning Electron Microscopy

The formation of a surface layer with silver and sodium concentration gradients in K8-grade glasses as a result of ion exchange is demonstrated by scanning electron microscopy (SEM) and electron probe X-ray microanalysis. The silver ions enriched layers with different thicknesses, depending on the duration of the ion exchange from the silver melt, are visualized in the secondary electrons mode. SEM data on the thickness of the silver enriched layer are in good agreement with the results of calculation from the diffusion equation for silver in glass. The dependence of the silver concentration on the diffusion depth is obtained using elemental composition mapping over the glass cross section. The presence of a layer with a silver concentration gradient leads to formation of a gradient waveguide. Discrete peaks in silver concentration profiles, caused by specific features of mutual diffusion of sodium and silver ions in glasses, are found.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗