bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Ga Implantation during Focused Ion-Beam Milling
Authors: Larson D J , Kvitek R J
Published: July 2020

In recent years, the use of the focused-ion beam (FIB) microscope has become widespread in the areas of materials processing and materials characterizaation. Although initial commercialization of FIB instruments was driven by applications in the semiconductor industry, recently the FIB has emerged as a broad characterization tool capable of imaging, material removal and material deposition. This combination makes it a useful instrument for applications ranging from site-specific sample preparation for transmission electron microscopy1 to thin-film head manufacturing. However, since the interaction of a high-energy ion beam (e.g., 30 keV Ga) with a solid inevitably produces implantation damage and the possibility of other effects such as grain growth, dislocation motion or degradation of magnetic properties, it is important to quantify to what extent the material under examination has been modified. Simple TRIM simulations may provide an estimation of the implantation level and depth to which ions will travel into a solid, but these results may not be accurate because FIB milling is not a static situation.

In order to investigate Ga implantation depth, concentration and possible grain growth effects, three circular regions on a 500 nm thick electroplated Ni-80 at.% Fe film were milled using 30 keV Ga ions at three different beam currents, Fig. 1.
The Effect of Implanted Gallium on the Recrystallization of Amorphous Layers formed during FIB Milling of Silicon
Authors: Rubanov S , Munroe PR
Published: July 2020

The focused ion beam (FIB) miller allows preparation of site-specific transmission electron microscopy (TEM) specimens from a wide range of materials in both cross-sectional and planar configurations [1,2]. However, radiation damage during exposure to the high-energy gallium beam may result in the formation of amorphous regions on thin film specimens. The thickness of such damage layers, on both sides of a TEM specimen, is comparable with the thickness required for lattice imaging. For example, the thickness of an amorphous layer in Si after 30 kV Ga+ FIB processing has been reported in the range from 15 [3] to 28 nm [4]. This problem limits the capabilities of FIB sample fabrication.

The aim of this study was to investigate, in detail, the structure, composition and the thickness of the damage layers in Si specimens after milling with a gallium ion beam. Using a FEI xP200 FIB system, with 30 kV Ga+ ions, a row of trenches on a silicon sample was milled under different beam currents ranging from 150 to 6600 pA. The average size of such trenches was 15×10 μm wide and 1 μm deep. The trenches were then removed from the FIB and sputter coated with a thick Au film to preserve the trench surfaces from further damage during subsequent TEM specimen preparation steps. Cross-sectional TEM specimens of the trench walls were then prepared using standard FIB procedures [5]. Observations were made using a Philips CM 200 Field Emission Gun TEM operating at an accelerating voltage of 200 kV.
Computer-Controlled Transmission Electron Microscopy: Automated Tomography
Authors: van der Krift Theo , Ziese Ulrike , Geerts Willie , Koster Bram
Published: July 2020

The integration of computers and transmission electron microscopes (TEM) in combination with the availability of computer networks evolves in various fields of computer-controlled electron microscopy. Three layers can be discriminated: control of electron-optical elements in the column, automation of specific microscope operation procedures and display of user interfaces. The first layer of development concerns the computer-control of the optical elements of the transmission electron microscope (TEM). Most of the TEM manufacturers have transformed their optical instruments into computer-controlled image capturing devices. Nowadays, the required controls for the currents through lenses and coils of the optical column can be accessed by computer software. The second layer of development is aimed toward further automation of instrument operation. For specific microscope applications, dedicated automated microscope-control procedures are carried out. in this paper, we will discuss our ongoing efforts on this second level towards fully automated electron tomography. The third layer of development concerns virtual- or telemicroscopy. Most telemicroscopy applications duplicate the computer-screen (with accessory controls) at the microscope-site to a computer-screen at another site. This approach allows sharing of equipment, monitoring of instruments by supervisors, as well as collaboration between experts at remote locations.

Electron tomography is a three-dimensional (3D) imaging method with transmission electron microscopy (TEM) that provides high-resolution 3D images of structural arrangements. with electron tomography a series of images is acquired of a sample that is tilted over a large angular range (±70°) with small angular tilt increments.
Newly Automated EPMA with Phase Identification System
Authors: Notoya S , Takahashi H , Okumura T , Nielsen CH
Published: July 2020

We have developed a new Electron Probe Microanalyzer (EPMA), JXA-8100/8200, with improved basic capabilities such as X-ray intensities of wavelength dispersive spectrometers (WDS), imaging functions, automated functions and analysis software. Fig. 1 shows the appearance of JXA-8200, WD/ED combined microanalyzer. in this session, we report mainly on the improved imaging functions, automated functions and analysis software.

The JXA-8100/8200 is the first EPMA in the world to feature 1280 x 1024 pixels high resolution live scanning image display. Regarding scanning image, two or four different signal live images, of course including X-ray images, can be displayed simultaneously. Further, image mixing is also possible to display. On the high resolution image, an operator can choose the probe position or the stage position by mouse clicking. The stage position can also be chosen on the optical microscope (OM) live image. Another new “Swing Mouse” function, which is the seamless movement of mouse pointer between the scanning image display and the computer display, has been developed.

Advanced automated functions, such as autofocus, auto astigmatism and auto contrast brightness, are effective to optimize the scanning image.
Appreciating Massive Data Sets from Tiny Specimens
Authors: Mohler William A
Published: July 2020

Continuing improvements on laser scanning microscopy now allow easy acquisition of multi-gigabyte-sized data sets from single living specimens. These multi-dimensional data comprise stacks of serial optical sections (3D) collected repeatedly over time (4D), often recording separate signal channels simultaneously (5D). in our work imaging developmental and cell biological processes in living embryos, we try to take advantage of the full scope of spatial and temporal detail that microscopes can now accumulate. Aside from the obvious difficulties of data management and archival, we still struggle to visually appreciate both the holistic view of the specimen and the smaller dynamic details that we know are captured within these recordings. Ideally, the multi-dimensional microscopist should view and analyze the specimen as the full set of tens of thousands of images. Although strides have been made, visualization software and computer hardware for browsing and analyzing multi-dimensional data are not yet up to the task of giving the microscopist full kinesthetic access to the thriving subject that the microscope hardware and software have captured. Several pieces of software allow the viewer to fluidly browse the original optical sections through space and over time. Moving beyond the constraints of the raw image plane by rendering, re-slicing, digitally dissecting, and animating the time-varying volumes is the task that is currently so demanding that all approaches are only partially satisfactory.
Cytokine Production and Cellular Localization in a Murine Model of Brain Inflammation
Authors: Cavallo J S , Wu Q , Szczepanik AM , Ying X , Ringheim GE
Published: July 2020

Brain inflammation is typically involved in the pathogenesis of acute conditions such as stroke and brain trauma and in chronic neurodegenerative diseases, for instance, Alzheimer’s disease. Accordingly, a well-characterized in vivo model of brain inflammation can be a useful tool to evaluate specific drug effects focused on various inflammation targets in the pharmaceutical drug discovery process. A model of brain inflammation was induced by the injection of β-amyloid peptide (αβ) or the bacterial endotoxin lipopolysaccharide (LPS) into the lateral ventricles of CD-I mice. The time course and dose response kinetics of cytokine and chemokine production were characterized. Levels of the pro-inflammatory cytokines IL-1α, IL-1β, IL-6 and the chemokine MCP-1 were significantly increased with respect to both time and dose in the cortex and hippocampus as determined by ELISA. Immunohistochemical assays were developed to detect IL-1β to determine cellular localization of this cytokine to microglia and astrocytes. Astrocytes were labeled with antibodies to glial fibrillary acidic protein (GFAP) and microglia were labeled with F4/80 antibodies. IL-1β was localized to cell type in frozen sections using double immunofluorescence (IMF) tags and were visualized with traditional fluorescence and confocal imaging.
Confocal Imaging of Scale Development on Butterfly Wings
Authors: Paddock Stephen W
Published: July 2020

Both surfaces of the butterfly wing are covered with thousands of colored scales that are arranged in precise linear arrays. Each scale contributes a single color to the overall pattern, which is usually different on the upper and lower surface of the wing. Moreover, the scales have a characteristic surface substructure that is visible using confocal autofluorescence (fig. 1). The ridges on the surface of all of the scales function to control the flow of air across the wing surface during gliding flight, and they contribute to the interference colors in a subset of the scales.

The fruit fly Drosophila melanogaster is the closest relative of butterflies for which detailed developmental, genetic and confocal imaging protocols have been established. Specimen preparation techniques for butterfly imaginal discs were largely developed from those for Drosophila tissues. The various stages of butterfly wing development have presented new challenges for confocal imaging. For example, butterfly fifth instar wing imaginal discs are much larger and thicker than those of the fruit fly.
Platelet-Derived Growth Factor (PDGF) Stimulates Embryonic Cardiac Growth and Myofibrillogenesis
Authors: Haley Stephen , Price Robert L , Bullard Tara A , Terracio Louis
Published: July 2020

Congenital heart disease is a leading cause of death in children with about 40,000 babies born in America each year with congenital heart disease. Common problems include atrial septal defects, patent ductus arteriosus and ventricular septal defects. However, very little is known about the underlying causes of congenital heart disease or the embryonic origin of cardiac malformation. The goal of our recent research has been to examine the role that specific growth factors and their receptors play in the development of the contractile apparatus of the heart and the experiments reported here further define the role of PDGF-AA and the PDGF alpha-receptor (PDGFR-α) during early heart growth and morphogenesis.

The PDGF ligand and receptor system consists of two well-characterized ligands, PDGF-A and B, and a third recently identified ligand, PDGF-C. The active forms of PDGFA and B exist as either AA or BB homodimers or an AB heterodimer. The PDGFR-α binds all of the dimers with high affinity while the PDGFR-β binds only the PDGF-BB homodimer with high affinity.
The Feasibility of High Resolution, Multiple Labeling using Colloidal Particles of Similar Size but Different Shapes and Elemental Compositions
Authors: Meyer DA , Albrecht RM
Published: July 2020

High resolution, quantitative cell labeling analysis for electron microscopy is typically accomplished using colloidal gold (cAu) particles which have a uniform diameter such that each particle conjugates no more than one ligand with monovalent specificity, such as an Fab antibody fragment. in this way, one particle labels exactly one target molecule. The corresponding particle size which satisfies this requirement, in the case of the Fab fragment, is 3-5nm. Under these constraints, multiple labeling cannot be performed using the standard cAu technology in which particles of various diameters are used such that each size corresponds to a unique label. Particles larger than 5nm may conjugate multiple Fab fragments, and thus a single particle may lable multiple target sites. Conversely, several particles smaller than 3nm may bind to a single Fab fragment so that several particles may label a single target molecule. Recent work in our lab has focused on the development of a labeling system which maintains the advantages of the standard cAu labeling technology, namely the use of electron-dense particles with excellent secondary and backscattered electron emission properties which make them readily detectable by both TEM and SEM, while at the same time offering greater versatility by permitting multiple labeling for high resolution, quantitative analysis. This novel labeling system makes use of colloidal particles which have unique and distinctive shapes, and composed of a variety of different metals including Au, Ag, Pt, Pd, Rh, and Ru. These elements all form stable aqueous colloidal suspensions, and the particles have surface charge properties similar to those of Au, permitting the adsorption of proteins and other ligands to them by the same conjugation techniques used with cAu (fig. 1).
Molecular Bioengineering of Multifuctional Markers for Energy Filtering Transmission Electron Microscopy (EFTEM) Correlative with Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI)
Authors: Malecki Marek , Sun Angel , Wohlwend Lynn , Hsu Annie
Published: July 2020

Molecular immunolabeling allows us to recognize location of molecules within complex biomolecular assemblies, cells, and organs. This technology helps us to facilitate correlations of the data available from biochemistry, molecular biology, pathology, and molecular imaging laboratories concerned with the gene expression as well as location and functions of its products. in this sense, molecular imaging serves as an integrative factor for life sciences endeavors (Albrecht et al. 1992, Bazett-Jones et al. 1996, Hainfeld and Powell 2000, Malecki et al. 1998, Robinson et al. 2000, Malecki 2000). Nevertheless, the essential requirement for pursuit of those projects is availability of molecular markers, which are detectable with various imaging instruments (Malecki 1996). Correlations between positron emission tomography (PET) providing metabolic information, magnetic resonance imaging (MRI) delineating precise anatomical location, and energy filtering transmission electron microscopy (EFTEM) expanding insights into the molecular level are particularly powerful. We have designed three main strategies for pursuit of this project: (a) expression of fusion proteins containing amplified metal binding sites (Malecki et al. 1998), (b) expression of recombinant single chain variable fragment (scFv) antibodies containing elemental recipient (Malecki et al. 2000), and (c) covalent coupling of IgG and Fab with organometallic clusters (Malecki 1996). Herewith, we report the results obtained through imaging of organometallic clusters inserted into the recombinant single chain variable fragment (scFv) antibodies.
Identification of Left-Handed RNA in the Cells of the Meridional Rows of the Normal Adult Mammalian Ocular Lens
Authors: Gagna CE , Kuo H-R , Turley J , Spencer J , Rescinti N , Lambert WC
Published: July 2020

The purpose of this research project was to characterize the distribution of left-handed Z-RNA sequences within the epithelial cells of the adult noncataractous crystalline dog lens: the meridional rows (MR). This was achieved by using anti-Z-RNA IgG polyclonal antibody probes. Both light microscopy (LM) and electron microscopy (EM) were used to analyze the tissue binding of the anti- Z-RNA antibodies. Nucleic acids can adopt many different helical conformations (1), such as Z-DNA (Fig. 1) and Z-RNA (2,3). The lens is made up of a single cell type, which is a monolayer of undifferentiated epithelial cells covering its anterior surface (Fig. 2). At the equator of the lens, these cells elongate and form concentric layers of the secondary (nucleated) fiber cells, which undergo cell death-terminal differentiation (denucleation). The epithelial monolayer consists of several cell types, each of which has unique characteristics.

The production of anti-Z-RNA polyclonal antibody probes was achieved using four
Designing, Building and Operating a Microcalorimeter Eds Outside a Cryogenic Research Facility
Authors: Howard J , Hammermeister D , McCarthy J
Published: July 2020

In 1999 Thermo NORAN completed licensing agreements with NIST for the microcalorimeter x-ray spectrometer technology developed by Martinis, Irwin, Hilton and Wollman.Steady progress has been made to commercialize this technology.

Briefly, the NIST microcalorimeter consists of a Transition Edge Sensor (TES) which measures the temperature rise in an absorber due to an incident photon. The sensor must be operated at temperatures below 100 milliKelvin, which is provided by an Adiabatic Demagnetization Refrigerator (ADR), coupled with a traditional liquid helium cryostat. Additional enabling technology includes a Superconducting Quantum Interference Device (SQUID) and a SQUID Array for device readout and low temperature signal amplification. All of this technology has been widely used in cryogenic research facilities for many years, but is not readily available for commercial purchase and use.

Initial work focused on adapting the NIST design to a modern FESEM. The available ports in an FESEM required scaling the heat shields, and cold extension diameters by 68%.
Progress Towards Arrays of Microcalorimeter X-Ray Detectors
Authors: Nam SW , Wollman DA , E. Newbury Dale , Hilton GC , Irwin KD , Rudman DA , S.Deiker  , Bergren NF , M. Martinis John
Published: July 2020

The high performance of single-pixel microcalorimeter EDS (μ,cal EDS) has been shown to be very useful for a variety of microanalysis cases. The primary advantage of jxcal EDS over conventional EDS is the factor of 25 improvement in energy resolution (∽3 eV in real-time). This level of energy resolution is particularly important for applications such as nanoscale contaminant analysis where it is necessary to resolve peak overlaps at low x-ray energies. Because μcal EDS offers practical solutions to many microanalysis problems, several companies are proceeding with commercialization of single-pixel μal EDS technology. Two drawbacks limiting the application of uxal EDS are its low count rate (∽500 s−1) and small area (∽0.04 mm for a bare single pixel, ∽5 mm2 with a polycapillary optic). We are developing a 32x32 pixel array with a total area of 40 mm2 and with a total count rate between 105 s−1 and 106 s−1.
A New Methodology for Element Imaging in the Scanning Electron Microscope
Authors: Smith Paul , Gannon John , Eggert Frank
Published: July 2020

The analysis of samples with a scanning electron microscope often requires element distribution images. Until recently, element mapping was strongly limited by the count rate that could be processed with conventional EDS systems using Si(Li) or Ge crystal diode detectors. The enhancement of secondary and backscattered SEM images can now be achieved through the addition of rapid color imaging. Using a new methodology for color enhancement, features as small as 1 micrometer can be colored and easily distinguished. The addition of color to SEM images enables easy visualization of element distributions and allows the microstructural features and compositional variations of different materials to be more readily identified. Persons unfamiliar with electron microscopy can more readily interpret color images than black and white or gray scale images. This new technology for imaging elements has great potential to revolutionize electron microscopy.

The detector technology behind this new methodology is the silicon drift diode (SDD).
A Microcalorimeter for High Resolution EDS Microanalysis in Low Voltage SEM Applications
Authors: Redfern Del , Nicolosi Joe , Hess Uwe , Höhne Jens
Published: July 2020

As scientists look to determine elemental composition of smaller and smaller particles using a scanning electron microscope, the usefulness of conventional EDS detectors (Si(Li)) becomes limited. to obtain analytical information from the SEM on extremely small particles the analyst can reduce the excitation energy of the electron beam; excitation energies of around 3kV are regularly used for the analysis of these particles. with only low energies (up 3keV) to work with, the scientists have to use L, or in some cases M, spectra to determine the chemical composition of the particle. A standard Si (Li) with a resolution of ≈100eV @3keV (130eV at 6keV) will be unable to adequately resolve spectra for confident characterization work to be carried out for these low energy lines. A new generation of EDS detectors for microanalysis is required to fulfill the scientists requirements for fast, simultaneous chemical determination of these small particles.
Catalyst Characterization with the Hitachi Hd-2000 STEM
Authors: Blom DA , Allard LF , Gates BC , Park PW
Published: July 2020

New EPA regulations limiting the emissions of NOx from diesel engines will require a reduction by 70% in the amount of NOx leaving the tailpipe of diesel powered vehicles by the year 2004. Some form of exhaust aftertreatment will need to be applied to diesel engines to meet the new stricter requirements. One option is to develop a “lean-NOx” catalyst that uses a hydrocarbon reductant (e.g. diesel fuel) to convert NOx into N2 and O2. Two of many constraints on such a catalyst are that it achieve a high degree of conversion over a fairly broad temperature range and that the amount of reductant necessary to reach the 70% goal is sufficiently small as to be cost effective. A number of promising systems comprise either platinum group metals or base metals on oxide supports. Such catalyst systems typically involve near-atomic dispersions, or ultra-fine clusters, of the heavy metal species on the oxide support.
Electron Energy Loss Spectroscopy Study of ZSM-5 Zeolite and MCM-41 Mesoporous Materials
Authors: Paraguay D F , Miki-Yoshida M , Espinosa-Magaña F , Terrés E , Dominguez JM
Published: July 2020

Zeolites are crystalline aluminosilicates possessing a regular microporous channel network. Unique properties of zeolites such as the presence of framework cations, acid sites, and their well-defined porous structure-with pore sizes similar to those of small molecules-account for their traditional utilization in ion exchange, catalysis, and separation. in addition, zeolites are being investigated for novel emerging applications in a diversity of areas including optoelectronic devices and reactive membranes because they provide for discrimination, recognition, and organization of molecules with a precision of less 1 Å. However, their applications are limited by the relatively small pore openings; therefore, pore enlargement was one of the main aspects in zeolite chemistry. A new class of porous materials, which contain large uniform spaces in the mesopore size regimen (15-100 Å), was reported. These so-called mesoporous materials have two different characters, disorder at the atomic scale but long range order at the atomic scale but long range order at the mesoscopic scale.
Sintering of Pd Automotive Catalysts
Authors: Xu Q , Kharas KCC , Datye AK
Published: July 2020

The focus of this work is on processes that lead to loss of active metal surface area during high temperature operation of automotive catalysts. As under-floor catalytic converters are moved closer to the engine to achieve faster light off, the catalyst is subjected to higher operating temperatures during the normal driving cycle. Sintering of the active metal phase leading to loss of surface area represents one of the most important factors limiting the long-term durability of automotive catalysts. Despite its obvious technological importance, fundamental understanding of sintering is still lacking.

In this research, we have prepared a series of Pd metal catalysts on a θ alumina support. The metal loading was varied from 1.1 wt% to 7 wt%. The catalysts were subjected to sintering at 900 °C for up to 192 hours. To ensure relevance to automotive catalysts, the sintering was performed in a gas atmosphere that contained 10 mol % H2O in flowing N2 or in air.
Characterization of Antimony-Doped TIN Oxide Catalysts
Authors: Sun K , Liu J , Browning ND
Published: July 2020

Antimony-doped tin oxide (ATO) catalysts are used for the oxidation of propylene to acrolein, the ammoxidation of propylene to acrylonitrile and the oxidative dehydrogenation of butanes to 1,3- butadiene. The distribution and valence states of Sb in ATOs are key in determining their catalytic activities. While these materials have been subjects of intensive studies for more than 20 years, X-ray photoelectron spectroscopy, Mössbauer spectrometry, and X-ray absorption spectroscopy4 have so far provided only indirect data for the distribution of Sb and its valence states. in particular, while has been hypothesized that the tin (IV) oxide contains Sb (V) within the bulk lattice and Sb (III) located at surface sites, no direct experimental evidence for this has been provided.

Here we use electron energy loss spectroscopy (EELS) combined with Z-contrast imaging in a JEOL 2010F field emission STEM/TEM operating at 200 KV to analyze ATO catalysts.
Structure Changes in Transition Metal Oxides Induced During Electron Microscopy
Authors: Su DS , Zeitler E , Schlögl R
Published: July 2020

Many catalytic materials, especially the maximum valence transition metal oxides, are particularly susceptible to electron beam irradiation and thus undergo structural changes. Hence knowledge about the behaviour of catalytic materials under the electron beam is of importance for all TEM investigations of such materials. On the other hand, this effect can be utilised for an in-situ study of the reductive property, phase transition and/or phase stability of various transition metal oxides in an inert, simple ambient high-vacuum. The knowledge so obtained is needed for understanding the reduction mechanism of catalysts in more complicated chemical environments. in the present work, we study the electron beam induced change in MoO3 and TiO2 (anatase) by means of electron energy-loss spectroscopy (EELS), electron diffraction and high-resolution electron microscopy (HREM).

Molybdenum trioxide, MoO3, important as catalyst in the selective oxidation of hydrocarbons, forms an orthorhombic crystal layer structure. Fig. 1 shows oxygen AT-edges recorded at various irradiation periods in a Philips 200 FEG electron microscope.
Characterizing Industrial Catalysts: Challenges and Opportunities
Authors: Liu Jingyue
Published: July 2020

Industrial catalysts are often chemically and physically complex systems resulting from many years of technology, science, and art. Successful development of commercial catalysts requires talents of many disciplines including chemistry, chemical engineering, surface science, materials science, and physics. A better understanding of the relationship between catalyst structure and activity can provide a scientific prediction of catalytic properties. The insight gained from catalyst characterization can provide guidance for designing and synthesizing better commercial catalysts. Characterization of industrial catalysts is challenging and expensive; however, it can be highly rewarding in developing commercial catalysts used for manufacturing multibillion-dollar products.

The ultimate goal of catalyst characterization is to correlate the physical, chemical, mechanical, and electronic properties of a catalyst to its activity, selectivity, and stability. in industrial practice, however, because of the complexity of the catalysts, the time limit, and the available resources, the goal of characterizing industrial catalysts is often to elucidate the key performance indicators of a catalyst; these key performance indicators, such as the size and spatial distribution and the composition of the active components and promoters, can then be used to provide guidance for manufacturing better catalysts with desired properties.
Structural Insights of Supported Nanoparticles By Z-Contrast and High Resolution Electron Microscopy
Authors: Yang Judith C , Devlin Erin , Rhodes William , Bradley Steven
Published: July 2020

A vital component to nanoparticle science will be the three dimensional (3-D) characterization of both structure and chemistry of these nanoparticles on their supports at the nanometer scale and below. to achieve this goal, quantitative Z-contrast and atomic resolution will provide essential information about their structure. Z-contrast imaging is ideal for imaging these large Z nanoparticles on low Z supports. in this proceedings, we present a quantitative Z-contrast method to determine number of atoms and a few examples of a combination of electron microscopy methods to gain structural insights into supported nanoparticle, such as Pt on different support materials, PtRu5 on C and Pt-Sn on SiO2.

A relatively new and powerful method is to determine the number of atoms in a nanoparticle, by very high angle annular dark-field (HAADF) imaging or Z-contrast technique [1, 2]. We have shown that quantification of the absolute image intensity from very HAADF microscopy will provide the number of atoms in very small particles of high atomic number to ±2 atoms for Re6 nanoparticles supported on carbon [3].
Nanoscale Imaging of Topotactic Redox Reactions of Antimony Single Crystals
Authors: Germinario Louis T
Published: July 2020

Antimony compounds play a major role in commercial polyester catalysis. Antimony complexes are used in ppm quantities, not only to catalyze melt-phase reactions in which oligomers are converted to high molecular weight polymers, such as poly(ethyleneterephthalate) (PET), but to further increase chain length through a high temperature solidphase polymerization process. During the course of the melt-phase reaction the initial, clear and colorless, Sb+3 compounds are transformed to a gray product that has been linked with the reduction of Sb+3 complexes to metallic antimony (Sb°). The presence of oxygen during the solid-phase process also increases clarity and reduces color of gray polymers. to further our understanding of antimony catalysis, a field emission-based scanning electron microscope (FEGSEM) was used to study antimony transformations during melt-phase polymerization and after treatments at high temperature in oxidizing and reducing environments.

Antimony metal powder from Fisher Scientific was used in redox studies.
Nanoscale Structural and Chemical Segregation in Pt50Ru50 Electrocatalysts
Authors: Stroud Rhonda M , Long Jeffrey W , Swider-Lyons Karen E , Rolison Debra R
Published: July 2020

To address how the chemical and structural heterogeneity of Pt50Ru50 nanoparticles affects methanol oxidation activity, we have employed an arsenal of transmission electron microscopy techniques (conventional bright field-imaging, selected area diffraction, atomic-resolution lattice imaging, electron-energy loss spectroscopy, and energy-dispersive x-ray spectroscopy) to characterize 2.5-nm particles in differing oxidation and hydration states. Our studies demonstrate that electrocatalysts containing a high fraction of Ru-rich hydrous oxide, as apposed to the anhydrous PtRu bimetallic alloy, have as much as 250x higher methanol oxidation activity

The nominally 2.5-nm Pt50Ru50 particles were studied in as-received, reduced and reoxidized forms. The reducing treatment consisted of 2 h at 100 °C in flowing 10% PL/argon mixture. For re-oxidation, the reduced particles were heated for 20 h at 100 °C in an H2O-saturated oxygen atmosphere. The particles were suspended in methanol, and pipetted onto holey-carboncoated Cu grids for TEM studies.
Scanning Electron Microscopic Analysis on the Deformation Mechanisms in NACRE
Authors: Wang RZ , Suo Z , Evans AG , Yao N , Aksay IA
Published: July 2020

Princeton Materials Institute, Princeton University, Princeton, New Jersey 08544 Some biological materials exhibit structural robustness, despite the brittle nature of their constituents.Nacre (mother-of-pearl), the pearly internal layer of many mollusc shells, is addressed in this study. This material comprises about 95% aragonite tablets (a mineral form of CaC03), The polygonal tablets were glued with only a few percent of biological macromolecules into layered structure. The goal of the present study is to elucidate the basic inelastic deformation mechanisms.

Typical stress /strain curves in tension and compression are plotted in Fig. 1. All tensile curves exhibited extensive inelastic deformation. After testing, the samples were initially examined using a stereo microscope (Leica MZ8) and a metallurgical microscope (Leica MEF4M) followed by analysis of the structural details using scanning electron microscopy (Philip XL-30). Optical imaging provided a visualization of the inelastic zone, manifest as white tension lines.
TEM Studies of Shear Bands in a Bulk Metallic Glass Based Composite
Authors: Pekarskaya E , Kim CP , Johnson WL
Published: July 2020

In 1980’s the discovery of multicomponent systems with exceptional glass forming ability enabled the synthesis of metallic glasses at relatively low cooling rates, 10−1 — 102 K/s and at a larger thicknesses. Bulk metallic glasses normally have very high yield stress, σy = 0.02 · Y (Y is Young’s modulus), high elastic limit of about 2%, but fail with very little global plasticity, typically along a localized shear band at a 45 degree angle with respect to the applied stress.

The material studied in the present work is a two-phase Zr56.3Ti13.8Cu6.9Ni5.6Nb5.0Be12.5 alloy,prepared by in-situ processing. The alloy consists of amorphous and crystalline phases. In-situ TEM straining (tensile) experiments were performed at room temperature in JEOL 4000EX operating at 300kV. The experiments were carried out in the Center for Microanalysis of Materials in the University of Illinois at Urbana-Champaign. The goal of the study was to understand the deformation mechanisms of such composite material.
Scanning Electron Microscopy Investigation of Deformation in the Vicinity of a Mode II Crack Tip in Unidirectional Toughened Epoxy Composites
Authors: Iarve EV , Ragland W
Published: July 2020

Delamination related research in fiber-reinforced composites has attracted considerable interest due to its significant practical importance. Significant difference in deformation patterns in the crack tip vicinity were observed for Mode I and Mode II delaminations and reported by several authors including [1-3]. A sequence of 45° (with respect to the crack plane) microcracks is believed to form beyond the Mode II crack tip in polymer composites. The propagation of a Mode II crack is believed to be a result of rupture and coalescence of these tension microcracks.

A Philips XL30 ESEM scanning electron microscope was used for testing. A three-point bend stage was designed to perform in situ end notch flexure tests on a pre-cracked miniature (1.4” long and 0.25” wide) 24-ply unidirectional specimen. The material system utilized in the experiment was a toughened carbon epoxy unidirectional composite, IM7/977-3. The miniature specimen was cut out of a standard size (8” long, 1” wide) specimen after a shear crack formed in the course of ENF testing.
Microstructures in Pressureless Sintered AIN-SiC Ceramics
Authors: Yu YD , Tangen I-L , Einarsrud M-A , Høier R , Grande T , Solberg JK
Published: July 2020

Aluminum nitride (AlN) is known to have a high thermal conductivity and is one of the valid candidates as substrate material for integrated circuits. The material also has a potential in metal production and handling. However, AlN has only a moderate flexural strength and fracture toughness. It has been reported that SiCA1N composites (SiC/AIN ratio ≥ 50%) can be manufactured by means of pressureless sintering. Furthermore, it is possible to fabricate self-reinforced SiC-based materials with whisker-like crystals in composite ceramics by choosing appropriate sintering additive and condition. in the present study, we investigated the possibility to prepare in-situ formed SiC-whisker reinforced AlN-materials and studied the microstructure of the composite.

An AlN-SiC composite ceramic sample (20 vol% SiC) was prepared for the investigation. The AlN-SiC composite was processed from a mixture of the starting powders with 2.5 wt% Al2O3-Y2O3 as a sintering additive.
Compositional Mapping with Energy Filtering TEM: The Present Status
Authors: Hofer Ferdinand , Kothleitner Gerald , Warbichler Peter
Published: July 2020

Energy filtering transmission electron microscopy (EFTEM) has matured into an important nanoanalytical technique in both materials and life sciences. One of the technique′s main advantages stems from the possibility to quickly form images that contain two-dimensional elemental information for most elements (Li to Pu) from relatively large specimen areas with nanometer resolution. Over the last years numerous and wide-ranging applications have demonstrated its almost unrivalled power for assessing typical materials science questions.

Both in-column or post-column filter microscopes have reached a high performance level, but future improvements are still desirable, in particular with respect to increased transmissivity, improved isochromaticity and higher detection efficiency. Current instruments allow to acquire elemental maps with 1-5 nm spatial resolution limited mainly by the aberrations of the microscope and by the quality of the specimen. As recently shown 0.4 nm resolution is feasible.

One major practical problem of EFTEM compositional mapping is the poor signal-to-noise ratio, which means that experimental parameters have to be chosen very carefully in order to optimize this ratio.
Elemental Mapping of Co-Based Magnetic Recording Media: EFTEM and STEM Spectrum Imaging
Authors: Bentley J , Wittig JE , Al-Sharab JF , Evans ND
Published: July 2020

The optimized performance of Co(CrTaPt) thin-film longitudinal magnetic recording media (for computer hard discs) depends critically on the grain size distribution and on intergranular Cr segregation that magnetically isolates the grains. These microstructural aspects of both model and commercial media have been extensively investigated at ∽1 nm resolution with quantitative elemental mapping by energy-filtered transmission electron microscopy (EFTEM) of Cr, Co, and O, but not Ta and Pt which unfortunately are not amenable to quantitative elemental mapping by EFTEM. Procedures for data acquisition and processing have been refined in order to provide robust methods for measuring intergranular compositions for statistically significant numbers of grains. Figure 1 shows results obtained with a Gatan imaging filter (GIF) interfaced to a LaB6 Philips CM30 for a carbon-capped 25-nm-thick film of Co80Cr16Ta4 grown on a Cr underlayer. Typical acquisition parameters have been described previously. to avoid the Cr underlayer, foil thicknesses t<0.2X are used, including the carbon overlayer (λ = inelastic mean free path ≌100 nm).
ELNES in Hexagonal and Cubic Boron Nitrides Evaluated with DV-Xα Method
Authors: He LL , Ye HQ , Oikawa T , Murakami Y , Shindo D
Published: July 2020

The hexagonal boron nitride (h-BN) exhibits a phase transformation to the cubic one (c-BN), the latter of which is well known as the second hardest material so far, under high pressure. This transformation is accompanied not only by the geometrical change in the crystal structure, e.g. stacking sequence of the close-packed planes, but also change in the chemical bonding from sp2 to sp3 characters. Electron energy-loss spectroscopy (EELS) is a hopeful way to characterize the state of bonding around the phase boundaries etc., and will provide rich information on the transformation mechanism. However, the energy-loss near-edge structure (ELNES) is rather sensitive to the orientation of specimens, if the structure is anisotropic as in the case of h-BN. This is sometimes obstructive to evaluations of ELNES, whereas a detailed investigation on this peculiar effect is needed. in the present work, the angular dependence of ELNES in h-BN was extensively studied by both calculations with DV-Xα (Discrete Variational X α cluster) method and experiments, beside investigations of the c-BN.
Dielectric Properties of ZrC by Electron Energy Loss Spectroscopy
Authors: Espinosa-Magaña F , Duarte-Moller A , Martínez-Sánchez R , Paraguay-Delgado F
Published: July 2020

Zirconium carbide belongs to the group of refractory compounds having NaCl structure with high chemical inertness and melting point, characteristics that have made these materials to play a prominent role as hard coatings and these properties are closely related to their electronic structure. The electronic configuration of ZrC is: (Xe) 5d2 6s2, one s electron being able to be promoted to a d orbital forming four equivalent sd3 hybrid orbitals, favoring covalent bonds maintaining, however, a percentage in ionic character of about 30%.

Some attention has been paid in the last two decades in studying the optical properties of transition metal carbides and nitrides by electron energy loss spectroscopy (EELS), being TiC and TiN the most extensively reported.

In this work the optical constants of commercial powder ZrC were obtained using a Gatan Parallel Detection Electron spectrometer (model 766) attached to the CM-200 transmission electron microscope (TEM).
Applications of Multi-Variate Statistical Analysis of Spectrum Images to Microelectronic Devices
Authors: Bruley J
Published: July 2020

It is not uncommon for an electrical failure in a microelectronic device to be traced back to an individual resistive contact, such as a W contact lined by TiN to the underlying metal silicide [1]. Identifying the root cause of the defective cell then requires the capability of extracting interfacial chemistry and microstructure with near atomic resolution, which is achieved by recording EELS and EDX data either along 1-d lines or from 2-d arrays. EELS data are characterized by intrinsically low signal-to-background ratios and plural inelastic-scattering effects, which presents a challenge to the reliability of the methods used to extract quantitative information from a spectrum image. Commercially available software packages by Emispec and Gatan currently provide routines for power-law or polynomial background fits and allow the net counts under peaks or edges to be determined from each pixel. in both cases each spectrum in the series is processed in the same manner.
Analysis of Biological Structures by Electron Energy Loss Spectroscopy and Imaging
Authors: Leapman RD , Andrews SB
Published: July 2020

As techniques for electron energy-loss spectroscopy (EELS) reach a higher degree of optimization, detection limits for analyzing biological structures are approaching those predicted by theory. in favorable specimens, single atom detection is predicted for elemental maps acquired by means of the scanning transmission electron microscope (STEM) equipped with a field emission source, paralleldetection EELS and a spectrum-imaging system. to obtain such results, the electron detector should have a detective quantum efficiency close to unity and a well behaved point-spread function; such design features are now available with a cooled charge-couple device (CCD) array. The energy-filtering transmission electron microscope (EFTEM) provides a complementary approach to mapping elements occurring at higher concentrations but distributed over larger regions of the specimen. Use of an optimized CCD detector in the EFTEM now enables accurate quantitation in addition to high analytical sensitivity, albeit not at the single atom level.
Advances in C. elegans Specimen Preparation for TEM Using Microwave and Fast Freeze Techniques
Authors: Hall DH , Starich T , Shaw J , Gobel V , Fleming J , Norris C , Huang C-c
Published: July 2020

The nematode C. elegans is a simple model for genetic studies of cell and tissue development. There is a need to improve the preservation of embryonic and early larval stages, during which nematode tissues elaborate and separate. However, these stages are particularly resistant to fixation and embedment due an impenetrable eggshell and larval cuticle. Their small size at these ages precludes mechanical cutting, which has been used successfully for immersion fixation of older stages. Here we compare the quality of preservation under three rather different regimes: using laserholes to permeabilize the eggshell during the primary fixation step, using microwave energy to enhance the first fixation step, or using fast freezing and freeze substitution to circumvent the standard immersion procedure. Vancoppenolle et al (2000) have recently demonstrated very good results through enzymatic weakening of the eggshell prior to immersion fixation. Their data are comparable to what we achieve by either the laserhole or microwave methods.
Light and Electron Microscope Immunocytochemistry in Freeze-Substituted Plant and Fungal Cells
Authors: Czymmek KJ , Bourett TM , Howard RJ
Published: July 2020

In efforts to better understand the cell biology of fungi and their pathogenic interactions with plants, we have pursued the use of cryo-preparative techniques for specimen preservation and immunocytochemistry at the light and electron microscope level. The chemically diverse composition of plant and fungal walls has proven very challenging for immunofluorescence using confocal microscopy. Typically, to allow probe access in these organisms, immunolabeling has required sectioning or enzymatic digestion of cell walls. The ideal method would preserve the spatial fidelity and antigenicity of the target molecule as well as maintain the integrity of the surrounding tissue. Our early work using methacrylate de-embedment, as described for sectioned plant material, was very effective for freeze-substituted fungi. Further improvements, using a combination of slow freezing and freeze-substitution followed by methacrylate de-embedment, permitted whole mount fluorescence antibody labeling of a variety of phylogenetically diverse fungi without enzymatic digestion or sectioning (Fig.l).
Cryo-Fixation and Gene Product Localization in Fungi
Authors: Bourett TM , Duncan KE , Czymmek KJ , Sweigard JA , Dezwaan TM , Howard RJ
Published: July 2020

There are many strategies for documenting the distribution of gene products or other molecules within cells or tissues. Depending on the required information, techniques can range from cell fractionation to methods that employ electron microscopy: some preclude examination of living cells, and thus can not provide dynamic temporal information. Time sequence data are paramount when gene expression is transient, as is often the case during fungal-pathogen plant-host interactions. Fluorescent dyes and protein tags (e.g., green fluorescent protein, GFP) allow monitoring of specific molecules, organelles or cells over time, for simultaneous recording of both spatial and temporal information. in addition, fluorescent markers are amenable to powerful 3-D analysis using confocal or multi-photon imaging methods. We have achieved good expression of fluorescent proteins in the fungal blast pathogen Magnaporthe grisea, and have generated a functional fusion protein between GFP and P-tubulin (Figs. 1,2).