bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of 2D and 3D dynamic image analyzing systems to cell motility
Authors: Soil David R.
Published: June 2020

Most noncilliated and nonflagellated animal cells change their shape in the act of translocation. These shape changes are intimately involved in the process of translocation and represent complex and coordinated cytoskeletal and membrane reorganization. Unfortunately, as microscopists we have too often viewed the motile cell as a static structure, and we have used our information on the static organization of the cytoskeleton to generate models of cellular motility. In 1987, we developed a computer-assisted 2 dimensional dynamic image analysis system (DMS) which dynamically analyzed motion and shape changes accom panying cellular translocation. In the past year, we have developed an advanced system, 2D-DIAS. In this system, videorecordings or live videos of cells are digitized into the 2D-DIAS data file and motion analyzed. The system computes more than 50 parameters of motion and dynamic morphology every thirtieth of a second for up to 50 cells in parallel.
Ultrastructural comparison of pituitary somatotrophs and lactotrophs in mice transgenic for bovine and human growth hormone
Authors: Kovacs K. , Stefaneanu L. , Mayerhofer A. , Wagner T. E. , Bartke A.
Published: June 2020

Acromegaly and gigantism are due to prolonged oversecretion of growth hormone (GH) most often caused by a somatotroph adenoma of the pituitary. Although the morphologic features of various types of somatotroph adenomas have been extensively investigated by electron microscopy, very little information is available on the ultrastructural changes of non-tumorous somatotrophs in cases of protracted GH excess. Transgenic mice with foreign GH gene incorporated into their genome secrete ectopically increased quantities of GH, have elevated serum GH levels and develop gigantism; thus it seemed conceivable that these animals represent a valuable experimental model to investigate the effects of GH excess on the ultrastructure of pituitary somatotrophs and lactotrophs, the two adenohypophysial cell types which are more likely affected by the foreign GH gene.
N-Ac-KDEL induces rapid alterations in endoplasmic reticulum structure
Authors: Wolniak Stephen M. , Larsen Paul M. , Herm Eliot M.
Published: June 2020

KDEL (i.e., Lysine-Aspartate-Glutamate-Leucine) is a tetrapeptide motif that serves as a retention sequence at the carboxy-terminus of proteins which reside within the ER lumen. A specific receptor located in or near the cis-Golgi recognizes proteins bearing carboxyterminal KDEL and mediates their return to the ER. We reasoned that it may be possible to saturate the KDEL receptor with a hapten, thereby competitively inhibiting its function in living cells. We hypothesized that if we blinded the receptor with an excess of hapten then the intermediate compartment should be unable to differentiate between polypeptides containing carboxyterminal KDEL from those that do not. If the receptor could be blinded, then KDEL-polypeptides such as BiP should be secreted.
Application of post-embedding immunogold technique in the diagnostic evaluation of fine-needle aspirates of neuroendocrine tumors
Authors: Diocee M. , Ravinsky E. , Quinonez G.
Published: June 2020

The diagnostic feature of a neuroendocrine tumor by transmission electron microscopy (TEM) is the presence of neurosecretory granules (NSG). However, other electron dense inclusions like lipid droplets and primary lysosomes may mimic NSC. In this study, post-embedding immunogold (PEI) technique using chromogranin A antibody has been used to confirm the ultrastructural impression of neuroendocrine tumor. This technique is contrasted with immunohistochemical results.

Material for this study was obtained from 5 transabdominal fine needle aspirates of multiple hepatic masses of unknown nature, processed for light and electron microscopic examinations and immunohistochemistry. Thin gold sections were cut (Reichart) with a Diatome diamond knife and mounted on 200 mesh nickel grids. A nickel grid with section side down was placed on drops of 11% aqueous sodium metaperiodate for 30 minutes, and was then washed with distilled water. Grids were incubated in 1% albumin for 15 minutes and transferred directly to chromogranin A and incubated for 60 minutes at room temperature.
Temperature Dependence of Dipalmitoyi Phosphatidylcholine/Diheptanoyl Phosphatidylcholine Aqueous Mixtures
Authors: Naranjo E. , Zasadzinski J.A.N.
Published: June 2020

There is great interest in the process of lipid self-assembly, especially the microstructure formed from lipid mixtures. Spontaneous unilamellar vesicles have been reported by Roberts from mixtures of long-chain lecithins and short-chain lecithins. Alone, dipalmitoyi phophatidylcholine (DPPC) forms normal multilamellar phases, a solid Lβ phase up to about 37°C, a Pβ or ripple phase from 37 to 43°C, and a fluid or Lα phase above 43°C. Diheptanoyl phosphatidylcholine (DHPC) by itself generally aggregates as spherical micelles over this temperature range. At temperatures below 40°C the two lipids, DPPC and DHPC, phase separate, leading to the possibility of physical segregation of the two lipid species. As a result of this separation, the DHPC might migrate to the boundaries of the DPPC-rich bilayers where it could stabilize the bilayer edge to allow the formation of bilayer discs, as first described by Fromherz and Rüppel.
Sertoli-germ interactions in iron-administered rats: An ultrastructural study
Authors: Bains H.K. , Kanwar K.C. , Bawa S.R.
Published: June 2020

The antitesticular effect of many heavy metal salts including iron has been reported to cause gonadal atrophy in rats I However, altered ultrastructural events of Sertoli-germ cell interactions following exogenous administration of iron has not been clarified. Present study was undertaken to identify the testicular organelles most affected in ferrous gluconate injected rats.

Sexually mature male albino rats weighing 175-180 grams were put on ferrous gluconate for 2 months by intraperitoneal injections at a dose rate of 20 mg/kg body weight/day. Slices of testes were fixed at room temperature in 3% glutaraldehyde in 0.1M phosphate buffer pH 7.4 for 2 hours, postfixed in 1% osmium tetraoxide in 0.1M phosphate buffer. After thorough rinsing of the fixed material with phosphate buffer pH 7.4 samples were dehydrated through graded acetone prior to embedding in Epon-Araldite. Subsequently ultrathin sections were stained with Uranyl acetate and Lead citrate (Reynold's) and examined under Jeol 1200EX electron microscope.
Nano-area analysis by an energy-dispersive x-ray spectrometer mounted on a field-emission transmission electron microscope
Authors: Hashimoto T. , Sato Y. , Ueki Y. , Kamino T. , Isakozawa S. , Ikematsu Y. , Uemori R. , Morikawa H.
Published: June 2020

Hitachi HF-2000 is an analytical electron microscope equipped with a cold field emission electron source which is operable at 200kV. The cold field emission source has an excellent coherency of the beam and an inherent source brightness of about 1,000 times greater than that of the conventional heated sources such as a tungsten hairpin type filament or a LaBs emitter. The HF-2000 is, therefore, advantageous in the following points:

1)

In the TEM imaging, the illumination beam angle is about 1/10 of conventional microscopes. The information limit can be extended to a higher spacial frequency.

2)

In a focused fine probe of about 1 nm in diameter, which is typically used for elemental microanalysis, a high probe current of about 100 times greater than that available with conventional TEMs, is available.

In addition, it is also possible with the HF-2000 to check the analysis area in high resolution TEM image with sufficient image brightness and contrast during the x-ray work. This capability assures high positional accuracy for point analysis.
Development of a new intelligent EPMA with advanced basic performance
Authors: Kawabe K. , Matsuya M. , Arima H. , Fuktida H. , Tajima H. , Nagatsuka Y. , Saito M. , Nielsen C. H. , Nakagawa S.
Published: June 2020

A new electron probe mieroanalyzer (EPMA), the JXA-8800, has been developed with improved basic capabilities such as the specimen stage, wavelength dispersive x-ray spectrometers (WDS), and imaging functions. It can be operated easily like automated office equipment and is expandable owing to the use of the latest microelectronics and computer technology.

The block diagram of the JXA-8800 is shown in Fig. 1. The control devices for the stage, WDSs, and electron optical system (EOS) are all made intelligent as they are each provided with a built-in microcomputer. Each device is connected to a system controller that manages TARGET, by a high-speed network. The system controller is connected to a host computer by GPIB. A 32-bit engineering workstation (EWS) is used as the host computer and UNIX is used as OS. By utilizing the high-speed graphics function of EWS, the operation of the EPMA can be freely carried out from the graphic display on the EWS color monitor, with the mouse or keyboard.
Imaging molecules adsorbed onto electrodes under potential control by scanning probe microscopy
Authors: Tao N.J. , DeRose J.A. , Oden P.I. , Lindsay S.M.
Published: June 2020

Clemmer and Beebe have pointed out that surface structures on graphite substrates can be misinterpreted as biopolymer images in STM experiments. We have been using electrochemical methods to react DNA fragments onto gold electrodes for STM and AFM imaging. The adsorbates produced in this way are only homogeneous in special circumstances. Searching an inhomogeneous substrate for ‘desired’ images limits the value of the data. Here, we report on a reversible method for imaging adsorbates. The molecules can be lifted onto and off the substrate during imaging. This leaves no doubt about the validity or statistical significance of the images. Furthermore, environmental effects (such as changes in electrolyte or surface charge) can be investigated easily.
A two-spring model of the tip-sample interaction using the Scanning Tunneling Microscope in air
Authors: Woodward John T.
Published: June 2020

The scanning tunneling microscope (STM) is capable of imaging surface features of electrically conductive samples with lateral resolution of 2 Angstroms and vertical resolution of 0.1 Angstroms. This is accomplished by rastering a conducting tip just above the sample surface using a piezoelectric drive. The tunneling current between the tip and the sample, which depends on the distance separating the two, is then used to keep the tip a constant distance above the sample and generate a height plot of the surface.

When an STM is used in air, a small liquid bridge can be formed between the scanning tip and the sample as shown in Fig. 1, This bridge results from any fluid contamination on the surfaces along with condensation of primarily water from the air. For most applications of the STM, this liquid bridge has little effect on the image. However if the sample is somewhat flexible or only weakly bound on the STM base, as is the case for freeze fracture replicas, the forces exerted by the liquid bridge on the sample as the tip scans the surface can significantly alter measured heights from their actual values.
3D microscopic analysis of molecular distributions in vivo: Modulation of hexokinase localization
Authors: Lynch R.M. , Carrington W. , Fogarty K.E. , Fay F.S.
Published: June 2020

Several enzymes involved in cell metabolism appear to associate with subcellular structures in a dynamic fashion; i.e., their binding is modulated during changes in metabolic rate. Our current focus of investigation is on the modulation of binding of hexokinase isozyme I (HKI) to mitochondria in vivo. Binding of HKI to the mitochondrial outer membrane is proposed to provide kinetic advantages to the enzyme, thereby elevating turnover rate. Moreover, binding of the enzyme may be modulated, and therefore, is suggested to be involved in regulating glycolysis. Recently, we have used quantitative confocal microscopy to demonstrate that HKI is localized to mitochondria in astrocytes even though fractionation studies of these cells indicate that most HKI is not bound. In order to understand the dynamics of association of HKI with mitochondria under different metabolic conditions, we have used 3D microscopic imaging techniques to acquire information regarding the distribution of fluorophore labeled HKI and quantitative image analysis to monitor changes in this distribution over time in living cells.
Multi-color laser scanning confocal microscopy with a krypton/argon ion laser
Authors: Clark Brelje T. , Sorenson Robert L.
Published: June 2020

Fluorescence is presently the most important imaging mode in biological confocal microscopy. The optical properties of laser scanning confocal microscopy (LSCM) are particularly favorable for fluorescence microscopy since the generally high signal-to-background ratio is enhanced by LSCM by rejecting out-of-focus fluorescent emissions. In addition, this improved imaging capability along the optical (z-)axis allows the optical sectioning of specimens by adjusting the plane of focus. This removes one of the most severe limitations of convential fluorescence microscopy, the necessity to examine monolayers of cells or thin sections of tissues.

However, the advantages of LSCM for multi-color fluorscence microscopy are critically dependent on the availability of suitable light sources and fluorophores. By far the most commonly used light source is a small, air-cooled argon ion laser with emission wavelengths at 488 and 514 nm. Although the most frequently used fluorophores, fluorescein (FITC) and tetramethylrhodamine, can be excited by these wavelengths, it is impossible to specifically excite each fluorophore in the presence of the other fluorophore.
Measurements in 3D images
Authors: Russ John C.
Published: June 2020

Three-dimensional (3D) images consisting of arrays of voxels can now be routinely obtained from several different types of microscopes. These include both the transmission and emission modes of the confocal scanning laser microscope (but not its most common reflection mode), the secondary ion mass spectrometer, and computed tomography using electrons, X-rays or other signals. Compared to the traditional use of serial sectioning (which includes sequential polishing of hard materials), these newer techniques eliminate difficulties of alignment of slices, and maintain uniform resolution in the depth direction. However, the resolution in the z-direction may be different from that within each image plane, which makes the voxels non-cubic and creates some difficulties for subsequent analysis.
Fulfilling the needs of physical and biological scientists in intermediate and HVEM
Authors: Kersker Michael M.
Published: June 2020

There are three (therefore 4 or 5) reasons that high voltage microscopes have remained viable tools for applications in both biological and materials science. Higher voltage means higher penetration with lessened effect from image degrading mechanisms, higher resolution due to decreased electron wavelength, and more (or less) damage to structure due to irradiation effects (more) or to decreased ionization cross section (less). Of the 47 high voltage instruments (V > 500kV) installed worldwide, many remain operational for at least one of these three reasons.

Few existing instruments are capable of delivering all three advantages. Earlier microscopes were primarily focussed on providing increased penetration and more or less damage since the high voltage stability and objective lens designs were not optimized to provide high resolution imaging as well. Though the past requirements for fulfilling the needs of physical and biological scientists have not changed for now nor are they likely to change in the future, many of the requirements fulfilled by high voltage microscopes are now achievable using lower kV intermediate voltage instruments, and in some cases, even more ubiquitous lower kV ones.
What HVEM tomographic reconstruction methods tell us about biological ultrastructure: Present and future developments
Authors: McEwen B. F. , Frank J.
Published: June 2020

For biological specimens, the primary application of high-voltage electron microscopy (HVEM) has been to enhance three-dimensional (3D) structural investigations. The chief advantage of higher accelerating voltages is that they enable imaging of thicker specimens which are correspondingly richer in 3D information. In order to realize this advantage, however, the specimen must be viewed from more than one direction so that features from different depths superimposed in a single projection may be separated. The simplest application of this approach is stereo viewing, which uses a pair of images viewed from directions separated by a relatively small angle. Due to its simpicity, stereo viewing is widely used but it has the disadvantages of being qualitative, subjective and limited in the amount of 3D information that can be revealed. These limitations can be overcome by electron tomography where several views of the specimen are collected over a wide angular range (up to 180°), entered into a computer, and a 3D image computed from these views according to well-established mathematical principles.
The many faces of STEM in materials science
Authors: Silcox John
Published: June 2020

Determination of the microstructure and microchemistry of small features often provides the insight needed for the understanding of processes in real materials. In many cases, it is not adequate to use microscopy alone. Microdiffraction and microspectroscopic information such as EELS, X-ray microprobe analysis and Auger spectroscopy can all contribute vital parts of the picture. For a number of reasons, dedicated STEM offers considerable promise as a quantitative instrument. In this paper, we review progress towards effective quantitative use of STEM with illustrations drawn from studies of high Tc superconductors, compound semiconductors and metallization of H-terminated silicon.

Intrinsically, STEM is a quantitative instrument. Images are acquired directly by detectors in serial mode which is particularly convenient for digital image acquisition, control and display. The VG HB501A at Cornell has been installed in a particularly stable electromagnetic, vibration and acoustic environment. Care has been paid to achieving UHV conditions (i.e., 10-10 Torr). Finally, it has been interfaced with a VAX 3200 work station by Kirkland. This permits, for example, the acquisition of bright field (or energy loss) images and dark field images simultaneously as quantitative arrays in perfect registration.
In situ evaporation in a high-resolution TEM
Authors: Krakow William
Published: June 2020

In recent years there has been a growing interest in the structure and stability of small particles at the atomic resolution level. In a number of cases, metal clusters were prepared ex situ and placed in a HREM which allowed significant contamination to be present. The one successful application to in situ work has been achieved by Takayanagi and his associates who have used a narrow gap pole piece 200 kV microscope modified to UHV conditions which achieves pressures in the 10-9Torr range. Studies with this microscope have shown small gold clusters of a few tens of atoms extending over edges of graphite surfaces and small clusters 20-30Å in lateral extent.
In situ TEM studies of irradiation effects for materials improvement
Authors: Allen Charles W.
Published: June 2020

Irradiation effects studies employing TEMs as analytical tools have been conducted for almost as many years as materials people have done TEM, motivated largely by materials needs for nuclear reactor development. Such studies have focussed on the behavior both of nuclear fuels and of materials for other reactor components which are subjected to radiation-induced degradation. Especially in the 1950s and 60s, post-irradiation TEM analysis may have been coupled to in situ (in reactor or in pile) experiments (e.g., irradiation-induced creep experiments of austenitic stainless steels). Although necessary from a technological point of view, such experiments are difficult to instrument (measure strain dynamically, e.g.) and control (temperature, e.g.) and require months or even years to perform in a nuclear reactor or in a spallation neutron source. Consequently, methods were sought for simulation of neutroninduced radiation damage of materials, the simulations employing other forms of radiation; in the case of metals and alloys, high energy electrons and high energy ions.
Image resolution in conventional transmission electron microscopy
Authors: Sarikaya Mehmet , Howe James M.
Published: June 2020

The image resolution in bright-field (BF) and dark-field (DF) conventional transmission electron microscopy (TEM) is given by: r = 0.66 CS¼¾¾, where Csand ¾ are the spherical aberration coefficient of the objective lens and electron wavelength, respectively. Based on this formula, it should be possible to resolve single atoms or clusters of atoms by phase contrast imaging with a highly coherent electron beam and a properly defocused objective lens; this has been demonstrated for both BF and DF imaging. However, for most situations encountered in conventional TEM, the type of information that can be obtained about the specimen is the most important, rather than the instrumental resolution. Atomicresolution microscopy of crystalline specimens relies on phase contrast produced when two or more beams interfere to form an image and this is discussed elsewhere in this symposium. This paper discusses the contrast and resolution when either a single beam or diffuse scattering is used to form an image.
Spreadsheet program for calculating secondary electron trajectories in electrostatic fields
Authors: Bradley Grady F. , Joy David C.
Published: June 2020

With the increasing importance of Low Voltage Scanning Electron Microscopy, the problem of describing the influence exerted by Secondary electron detectors on the path of primary electrons as well as its effects on the trajectories followed by secondary electrons become increasingly important. In situations where uncoated, insulating specimens are studied in an SEM, the additional problem of sample charging also has to be considered. Characterizing these interactions can be very difficult by conventional programming methods. The large number of points and the interdependence of the potentials at all of the points make the “bookkeeping” very difficult to manage. Spreadsheet programs with macroinstruction languages, however, can make these calculations much easier to perform. Not only can spreadsheets be used to calculate the potential field within a microscope column, macro programming can be used to calculate trajectories throughout that field. For the computations described in this paper, Microsoft Excel for the Macintosh was the spreadsheet chosen because of its effective use of the graphics capabilities of the Macintosh.
On the structural characterization of precipitates in boron microalloyed steels
Authors: Perez R. , Juarez-Islas J.A. , Campillo B. , Albarran J.L. , Martinez L.
Published: June 2020

Boron alloying has been recognized in the past as a very attractive method for improving the properties of high strength low alloy (HSLA) steels. Small additions of this element have pronounced effects on the hardenability of the steels. Partial explanations on this effect are based on theoretical models which suggest segregation of boron in particular areas of the microstructure such as grain boundaries or precipitates. The detection of boron in steels has so far proved to be difficult due to the small amounts of boron involved and also to the fact of being a light element and therefore difficult to be detected by X-ray microanalysis and transmision electron microscopy.
Transmission Electron Microscopy studies of texture of Cr underlayer of magnetic recording hard disk
Authors: Tang L. , Thomas G. , Khan M. R. , Duan S. L.
Published: June 2020

Cr thin films are often used as underlayers for Co alloy magnetic thin films, such as Co1, CoNi2, and CoNiCr3, for high density longitudinal magnetic recording. It is belived that the role of the Cr underlayer is to control the growth and texture of the Co alloy magnetic thin films, and, then, to increase the in plane coercivity of the films. Although many epitaxial relationship between the Cr underlayer and the magnetic films, such as ﹛1010﹜Co/ {110﹜Cr4, ﹛2110﹜Co/ ﹛001﹜Cr5, ﹛0002﹜Co/﹛110﹜Cr6, have been suggested and appear to be related to the Cr thickness, the texture of the Cr underlayer itself is still not understood very well. In this study, the texture of a 2000 Å thick Cr underlayer on Nip/Al substrate for thin films of (Co75Ni25)1-xTix dc-sputtered with - 200 V substrate bias is investigated by electron microscopy.
TEM in situ straining of polycrystalline stoichiometric NiAl
Authors: Nagpal P. , Baker I.
Published: June 2020

The purpose of this paper is to present a comparison of the dislocation structures that are present in polycrystalline samples of the B2 (ordered body-centered cubic) compound NiAI after straining in bulk and after in-situ straining of thin foils in the TEM.

A dumbell-shaped tensile specimen (gauge length ∼ 10mm; diameter ∼ 3mm) of ∼15μm grain-sized stoichiometric NiAl which had a low initial dislocation density was strained to fracture under tension. The fracture strain was ∼ 2%. Discs were cut from the gauge and thin foils were prepared as described elsewhere. (Processing conditions to obtain this fine-grained material are also described elsewhere.) TEM in-situ straining samples (7mm long; 3 mm wide; 0.25 mm thick, with 1mm diameter loading holes located 1.5mm from the ends, see reference 4 for details) were prepared from the same material and strained in a modified JEOL straining holder. Both sets of samples were viewed in a JEOL 2000FX operated at 200 KeV. For the in-situ experiments images were recorded either on film after a given strain increment or dynamically during straining using a Gatan camera, an image intensifier and a VCR.
Microstructures in rapidly solidified Ni4Mo alloy
Authors: Cao Siqi
Published: June 2020

The alloy of Ni-20 at pet Mo has a single phase structure with an order-disorder transition at 868°C. A short-range ordered fee structure (α) exists above 868°c, which shows a diffuse (1,1/2,0) diffraction feature. The intensity of the (1,1/2,0) diffraction becomes weak as the temperature increases, but may exist to the melting point. Below 868°C, long-range ordered bet structure (β) occurs by rearrangement of atoms from a. The short-range ordered a can be retained by water quenching from above 868°C. The purpose of this paper is to determine the effect of rapid solidification on the microstructures and the suppression of ordering.
Bulk defects as domain boundaries in surface reconstructions
Authors: Dunn D.N. , Ai R. , Savage T.S. , Marks L.D. , Merkle K.L.
Published: June 2020

Much of the study of reconstructed surfaces has been done with surface sensitive techniques that rarely allow the investigator to probe both the bulk and surface properties. As a result, not much has been written about the possiblity of bulk defects influencing the shape and position of domains on a reconstructed surface. With the recent advent of UHV microscopes with attendent surface science chambers connected, it has become possible to examine both the bulk and surface of a given sample and obtain a more complete picture of the surface reconstruction process. We have found in several investigations of Au (001) and Si (111) surfaces that bulk defects such as dislocations and stacking faults near the surface can act as boundaries for domains of a reconstructed surface.
RHEED investigation of oxygen-annealed sapphire surfaces
Authors: Liu J. , Cowley J. M.
Published: June 2020

Reflection high energy electron diffraction (RHEED) has been widely used to study surface reconstructions, surface morphology and crystal growth. In a transmission electron microscope RHEED can be combined with reflection electron microscopy (REM) to study the structures of surfaces with high spatial resolution. In this paper we report some preliminary results of RHEED investigation of the reconstruction of the oxygen annealed sapphire surfaces.

The optically polished sapphire samples were obtained from Saphikon Inc. The specimens were cut, cleaned and chemically etched in boiling phosphoric acid before annealing in pure oxygen. Details of the sample preparation procedure was reported elsewhere. Oxygen annealing prevented change of surface stoichiometry and surface reactions with elements other than oxygen. The RHEED experiments were conducted in a Philips 400T transmission electron microscope operated at 120 kV with a vacuum pressure about 10-7 Torr and equipped with cold and hot stages.
Interfacial structure and interfacial reactions at the MgO/Al2O3 interface
Authors: Li D. X. , Pirouz P. , Heuer A. H. , Yadavalli S. , Flynn C. P.
Published: June 2020

MgO films were deposited on the (sample A), (0001)Al2O3 (sample B), and the (sample C) planes of sapphire by Molecular Beam Epitaxy (MBE). Cross-sectional UREM specimens were prepared using standard techniques and examined in a top-entry JEOL 4000FX high resolution electron microscope. Image simulations were performed using the SHRLI programs developed by O'Keefe.
Quantification of metallic aluminum profiles in Al+ implanted MgAL2O4 spinel by EELS
Authors: Evans N. D. , Zinkle S. J. , Bentley J. , Kenik E. A.
Published: June 2020

Magnesium aluminate spinel (MgAl2O4) is being considered as an insulator material within fusion reactors because of its favorable damage characteristics. The microstructure of material implanted at 650°C with 2 MeV Al+ ions is shown in cross-section in Fig. 1. Little damage occurs near the surface, whereas at greater depths (0.5 - 1.0 μm) dislocation loops are formed on {110} and {111} planes. Small features thought to be metallic aluminum colloids were observed in the implanted volume near end-of-range. Phase identification by electron diffraction is complicated because the lattice parameter of spinel (0.8083 nm) is almost exactly twice that of aluminum (0.4049 nm). However, the spinel <222> reflection is weak but the aluminum <111> reflection is intense. In <222>sp<111>Al dark-field images of the implanted volume near end-of-range (Fig. 2) the bright 5-10nm diameter features were presumed to be metallic aluminum colloids.
Transmission Electron Microscopy of oriented Co84Cr14Ta2 thin films for longitudinal magnetic recording
Authors: Nolan T. P.
Published: June 2020

Thin film magnetic media are being used as low cost, high density forms of information storage. The development of this technology requires the study, at the sub-micron level, of morphological, crystallographic, and magnetic properties, throughout the depth of the deposited films. As the microstructure becomes increasingly fine, widi grain sizes approaching 100Å, the unique characterization capabilities of transmission electron microscopy (TEM) have become indispensable to the analysis of such thin film magnetic media.

Films were deposited at 225°C, on two NiP plated Al substrates, one polished, and one circumferentially textured with a mean roughness of 55Å. Three layers, a 750Å chromium underlayer, a 600Å layer of magnetic alloy of composition Co84Cr14Ta2, and a 300Å amorphous carbon overcoat were then sputter deposited using a dc magnetron system at a power of 1kW, in a chamber evacuated below 10-6 torr and filled to 12μm Ar pressure. The textured medium is presently used in industry owing to its high coercivity, Hc, and relatively low noise. One important feature is that the coercivity in the circumferential read/write direction is significandy higher than that in the radial direction.
Microstructural characterization of CoPtCr/Cr thin film disks by cross-section TEM and elongated probe micro-diffraction
Authors: Parker M.A. , Johnson K.E. , Hwang C. , Bermea A.
Published: June 2020

We have reported the dependence of the magnetic and recording properties of CoPtCr recording media on the thickness of the Cr underlayer. It was inferred from XRD data that grain-to-grain epitaxy of the Cr with the CoPtCr was responsible for the interaction observed between these layers. However, no cross-sectional TEM (XTEM) work was performed to confirm this inference. In this paper, we report the application of new techniques for preparing XTEM specimens from actual magnetic recording disks, and for layer-by-layer micro-diffraction with an electron probe elongated parallel to the surface of the deposited structure which elucidate the effect of the crystallographic structure of the Cr on that of the CoPtCr.

XTEM specimens were prepared from magnetic recording disks by modifying a technique used to prepare semiconductor specimens. After 3mm disks were prepared per the standard XTEM procedure, these disks were then lapped using a tripod polishing device. A grid with a single 1mmx2mm hole was then glued with M-bond 610 to the polished side of the disk.
HREM contributions to microstructural investigations of magnetic thin films and ultrathin multilayers
Authors: Li Z.G. , Smith David J. , Parkin S.S.P.
Published: June 2020

Magnetic thin films and ultrathin multilayers(ML) have been developed which are of great fundamental and technological interest Since their physical properties depend strongly upon growth conditions, it requires microstructural investigations to establish and understand their interrelationship. The required information about thin films includes, for example, layer-layer and layer-substrate interfaces, crystallinity, crystal type, columnar growth, crystal orientations and so on, all of which could influence or even totally change the macrobehavior. Unlike other commonly used structural determination techniques which average over comparatively large volumes, HREM provides real-space information on the atomic scale. It has been demonstrated to be an ideal method for investigating thin film microstructure, especially for ultrathin ML with bilayer thicknesses on the nanometer scale. A limitation of electron microscopy is that the information is obtained from twodimensional projections of the sample. However, thin films and ML can be prepared in both cross-section and plan-view. It is thus usually possible to obtain quasi-3D information and answer important structural questions about crystalline, polycrystalline and amorphous-like thin films.
HREM Observations of Mg2Si-Based Multilayers for Soft X-Ray Optics
Authors: Modak A. R. , Smith David J. , Li Z. G. , Boher P. , Houdy Ph.
Published: June 2020

Multilayers fabricated with alternating materials having significant differences in X-ray scattering powers are being investigated for applications in soft X-ray optics. Multilayers consisting of combinations of W, Rh, Fe, Si3N4, SiO2 and Si, C, B4C have been studied in the past. Mg2Si based multilayer structures are theoretically efficient reflectors of wavelengths above the Mg-Kα line (9.89 Å) and the Mg-Lα line (251.5 Å) because of their low absorption in the respective wavelength regimes due to the presence of magnesium. In the present study, Mg2Si based multilayers fabricated on silicon substrates by ultra high vacuum rf sputtering have been characterized by HREM. W, Si, and Mg2Si targets in conjunction with the introduction of nitrogen were employed to deposit alternate Mg2Si and W or Si3N4 layers. We report here our preliminary observations of a characteristic short period W/Mg2Si layered structure used above the Mg-Kα line and two long period multilayers based on W/Mg2Si and Si3N4/Mg2Si used above the Mg-Lα line.
Deviations from Ideal Decagonal Symmetry in Electron Diffraction Patterns of the “Decagonal” Phase in the Al-Co-Cu Alloy System
Authors: Ramani Atul S. , Ryba Earle R. , Howell Paul R.
Published: June 2020

The “decagonal” phase in the Al-Co-Cu system of nominal composition Al65CO15Cu20 first discovered by He et al. is especially suitable as a topic of investigation since it has been claimed that it is thermodynamically stable and is reported to be periodic in the dimension perpendicular to the plane of quasiperiodic 10-fold symmetry. It can thus be expected that it is an important link between fully periodic and fully quasiperiodic phases. In the present paper, we report important findings of our transmission electron microscope (TEM) study that concern deviations from ideal decagonal symmetry of selected area diffraction patterns (SADPs) obtained from several “decagonal” phase crystals and also observation of a lattice of main reflections on the 10-fold and 2-fold SADPs that implies complete 3-dimensional lattice periodicity and the fundamentally incommensurate nature of the “decagonal” phase. We also present diffraction evidence for a new transition phase that can be classified as being one-dimensionally quasiperiodic if the lattice of main reflections is ignored.
Creep Damage Mechanisms in Ceramic Composites
Authors: Nutt S. R. , Lipetzky P.
Published: June 2020

Whisker-reinforced ceramics show improvements in a variety of mechanical properties, and because of the inherent thermal and chemical stability of ceramics, it is natural to consider issues related to mechanical behavior at high temperatures. Implementation of ceramic materials in high-temperature structural applications is often limited by creep, and recent studies on Al2O3-SiCw have shown that creep resistance of ceramics can be enhanced by whisker reinforcement. These studies demonstrated that creep response is strongly affected by the presence of the reinforcing phase and the properties of the whisker-matrix interface, in addition, oxidation reactions that occurred during creep degraded interface properties, facilitated microstructural damage, and accelerated creep. The objective of the present study was to determine the effects of test ambients on creep damage mechanisms in Al2O3-SiCw composites and to correlate these observations with compressive creep response under different stress-temperature conditions.
Effects of Additives on the Interfacial Microstructure of SiC Fiber/Li2O-Al2O3-6SiO2 Glass-Ceramic Composites
Authors: Hsu J.Y. , Berta Y. , Speyer R.F.
Published: June 2020

SiC fiber reinforced lithia-alumina-silica glass-ceramic composites have exhibited superior mechanical properties at room and elevated temperatures. The flexural strength of these composites is 3 to 4 times larger than that of monolithic glass-ceramics. The high flexural strength of these composites is due to the transfer of the applied load from the matrix to the stronger and stiffer SiC fiber reinforcement. These composites also have demonstrated very high fracture toughness, KIC (critical stress intersity factor) values of ∼ 17 MPa m1/2, which is attributed to an amorphous carbon-rich interfacial layer between the fiber and matrix. Nb2O2 has been added to the matrix composition in order to develop a NbC layer outside the amorphous C-rich layer after thermal processing, thereby buffering the fiber/matrix reactivity (avoid carbon forming CO gas which would deteriorate the matrix).
Tensile creep of Y-Si3N4: I. Microstructure
Authors: Hockey B. J. , Wiederhorn S. M.
Published: June 2020

The tensile creep behavior of three different silicon nitrides has been investigated. Two of these materials were hot-pressed with yttria (6w/o) and alumina (1.5 w/o) as sintering aids; one, W/YAS, was reinforced with SiC whiskers (30 v/o) while the other, YAS, was not. The third material, (YS), was HIP ed with yttria (4.0 w/o) as the sole sintering aid. In this paper (Part I), microstructural analysis by ATEM is used to describe and discuss the effect of microstructure on the creep of these materials. Particular emphasis is placed on describing the time dependent changes that occur within the intergranular phase, since these changes alter the interfacial properties that effectively govern creep deformation and rupture. A companion paper, Part II, describes the cavitation processes, which are ultimately responsible for creep rupture.
Hierarchical Twin Structures in the Nacre of Red Abalone Shell
Authors: Liu Jun , Sarikaya Mehmet , Aksay Ilhan A.
Published: June 2020

The nacre structure of red abalone (Haliotis rufescens) shell has a higher strength and fracture toughness at room temperature compared to some monolithic ceramics. The unusual mechanical properties may be attributed to the unique microarchitecture that can be described as a laminated composite of about 95% CaCO3 and 5% organic matter (a combination of proteins, chiten, and other macromolecules). It is desirable to form synthetic materials having a microarchitecture similar to the nacre through a biomimetic approach to obtain improved mechanical properties. In order to achieve this goal, it is necessary to have a better understanding of the microstructure of the nacre at different length scales. The purpose of this work was to examine the structure of nacre in more detail. It has been found that the structure is actually composed of twins which are hierarchical from the nanometer to sub-millimeter scale.
Microstructural and Microchemical Characterization of Nickel Sulfide Inclusions in Plate Glass
Authors: Cooper J. , Popoola O. , Kriven W. M.
Published: June 2020

Nickel sulfide inclusions have been implicated in the spontaneous fracture of large windows of tempered plate glass. Two alternative explanations for the fracture-initiating behaviour of these inclusions have been proposed: (1) the volume increase which accompanies the α to β phase transformation in stoichiometric NiS, and (2) the thermal expansion mismatch between the nickel sulfide phases and the glass matrix. The microstructure and microchemistry of the small inclusions (80 to 250 μm spheres), needed to determine the cause of fracture, have not been well characterized hitherto. The aim of this communication is to report a detailed TEM and EDS study of the inclusions.
EELS Equipment: A Brief Survey
Authors: Batson P.E. , Egerton R.F.
Published: June 2020

By far the most commonly used electron spectrometer is the 90° magnetic sector. As summarized in Figure 1, this device uses a uniform magnetic field to deflect high energy electrons through part of a circle. Since the radius of the circle depends on the electron velocity, a small slit can be used to select a particular energy. Modern devices have shaped pole piece edges to allow 2nd order focussing of electrons, producing an energy dispersed image of a source point at the final detection slits. This arrangement gives a good energy resolution (≈0.5 eV in 100KeV) and is easily mounted below the camera chamber of typical TFM columns. Commercial versions arc available. A disadvantage of the design is the lack of a straight optical axis, making it difficult to place the spectrometer within the column of an already existing microscope for energy filtering of images.
High-Resolution Electron Microscopy of C60 Clusters
Authors: Disko M. M. , Behal S. K. , Sherwood R. D. , Cosandey F. , Lu P. , Creegan K. M. , Tindell P. , Cox D. M.
Published: June 2020

Methods for the preparation of significant quantities of C60 clusters separated from carbon soot were recently reported by Krätschmer and co-workers. Evidence that these clusters have the “Buckminsterfullerene” structure with five-fold and six-fold carbon rings on the surface of a sphere (soccer-ball structure) has been provided by several techniques. NMR shows a single type of carbon bonding, and IR peaks consistent with modes characteristic of this system have been identified. Since C60 can be isolated and has stable “graphitic” bonding, it represents a unique opportunity to observe individual stable carbon molecules with transmission electron microscopy in order to test the morphology deduced from other techniques. Also, the study of packing sequences and defect structures in C60 crystals found by x-ray diffraction to have an FCC lattice constant of 1.41 nm provides important new information on variations of crystallization with conditions such as solvent type and crystallization rate.
Profile TEM observations of small UHV-grown palladium particles
Authors: Neiman D.L. , Fuchs G. , Poppa H.R.
Published: June 2020

Projectional Transmission Electron Microscopy (TEM) of vapor-grown metal clusters on oxide supports is an extensively-used technique. An important limitation to this technique is the difficulty in determining the particle shape parallel to the electron beam. Use of submicron-sized “micro-supports” such as microcubes (MgO) and microspheres (TiO2 and Al2O3) allows the metal particles to be seen directly in profile. This has been shown for nonreactive deposits such Au, but few results for reactive metals have been published (notably Pd/MgO2 and Rh/TiO2). We present results for the system Pd/Al2O3, which show limitations to the use of profile TEM in the study of reactive metal deposits.

Plasma-grown microspheres of A12O3 were supended in cthanol and then applied to commercial holey carbon grids. The grid were inserted into an ultrahigh vacuum (p<2x10-7 Pa) system for Pd deposition. Palladium was deposited from a heated-wire source at a rate R = 0.03nm/min. Sample temperature during deposition was 573K.
The role of surface characteristics in low-voltage SEM of polymers
Authors: Krause S J. , Adams W.W.
Published: June 2020

It has been shown that there are numerous advantages in imaging both coated and uncoated polymers in scanning electron microscopy (SEM) at low voltages (LV) from 0.5 to 2.0 keV compared to imaging at conventional voltages of 10 to 20 keV. In imaging metal coated polymers in LVSEM beam damage is reduced, contrast is improved, and charging from irregularly shaped features is reduced or eliminated. Imaging uncoated polymers in LVSEM allows observation of the surface with little or no charging and with no alterations of surface features from the metal coating process required for higher voltage imaging. This is particularly important for high resolution studies where it is desired to image features 1 to 10 nm in size. At low voltages the sample-beam interaction volume resides closer to the surface which increases the ratio or exiting current to that of the primary beam current.
Silver staining of fluorocarbon copolymer membranes for contrast enhancement
Authors: Garrison C.C. , Garcia-Meitin E.I.
Published: June 2020

Fluorocarbon copolymer membranes will replace conventional diaphragms in new generation chlorine cell designs. One design of such membranes is a bilayer material consisting of barrier (carboxylic) and support (sulfonic) layers which allow transport of sodium ions and inhibit transfer of other species. While the two layers can be distinguished without staining in the transmission electron microscope (TEM), resolution at the interface is typically 50 nanometers. Resolution can be improved to 5 nanometers after staining the membranes with silver ions.

Previous work on staining sulfonic copolymers has been published. Xue et al. obtained excellent staining with vapor phase ruthenium tetraoxide. However, our lab was unsuccessful in applying this technique in the current study. Chryssikos et al. obtained good results using silver ions to stain by ion exchange. Since the membrane is designed to transport sodium ions, similarities between silver ions and sodium ions (+1 charge, similar ionic radii) point toward silver as a good choice. Staining experiments were carried out using silver ions, zinc ions, and ruthenium tetraoxide vapor.