bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microstructural Development in Nb-Ti Multifilamentary Superconductors During Processing
Authors: West A. W. 
Published: June 2020

The influence of the filament microstructure on the critical current density values, Jc, of Nb-Ti multifilamentary superconducting composites has been well documented. However the development of these microstructures during composite processing is still under investigation.During manufacture, the multifilamentary composite is given several heat treatments interspersed in the wire-drawing schedule. Typically, these heat treatments are for 5 to 80 hours at temperatures between 523 and 573K. A short heat treatment of approximately 3 hours at 573K is usually given to the wire at final size. Originally this heat treatment was given to soften the copper matrix, but recent work has shown that it can markedly change both the Jc value and microstructure of the composite.
Surface Plasmons: a Sensitive Diagnostic Tool for Characterizing Interfaces
Authors: Scheinfein M. R. 
Published: June 2020

There has been considerable interest in characterizing the electronic and chemical properties of interfaces and grain boundries at high spatial resolution. This abstract describes a technique which utilizes the energy dispersion of surface plasmons in the transmission electron energy loss spectrum to evaluate the local dielectric constant variation across interfaces. This technique is shown to yield extremely high spatial resolution.We have been conducting studies of interfaces in a VG HB-5 STEM located at NRRFSS which is equipped with a high resolution electron energy loss analyzer. In STEM, using small probes, a typical surface plasmon excited by 100 keV electrons (Al for example) reaches its asymptotic energy value at a scattering angle between.3 and.4 mr. Since we are convoluting the incident angular distribution with the surface plasmon intensities integrated over a collection aperture, the surface plasmon excitation energies are given by their asymptotic (in k-space) energy values. These asymptotic energy excitations are very sensitive functions of the thickness and dielectric constant [eg, 2-5] of the surrounding medium.
Analytical Electron Microscopy of Surface-Modified Ceramics
Authors: Sklad P. S. 
Published: June 2020

Over the past several years, it has become increasingly evident that materials for proposed advanced energy systems will be required to operate at high temperatures and in aggressive environments. These constraints make structural ceramics attractive materials for these systems. However it is well known that the condition of the specimen surface of ceramic materials is often critical in controlling properties such as fracture toughness, oxidation resistance, and wear resistance. Ion implantation techniques offer the potential of overcoming some of the surface related limitations.While the effects of implantation on surface sensitive properties may be measured indpendently, it is important to understand the microstructural evolution leading to these changes. Analytical electron microscopy provides a useful tool for characterizing the microstructures produced in terms of solute concentration profiles, second phase formation, lattice damage, crystallinity of the implanted layer, and annealing behavior. Such analyses allow correlations to be made with theoretical models, property measurements, and results of complimentary techniques.
Hardness and Microstructure Change During Annealing Process of a Modified Inconel-718
Authors: Hu Chen-Ti , Syu Yau-Tsurng 
Published: June 2020

A modified Inconel 718 alloy with a higher content of Mo and lower was prepared from metals of electrolytic grade purity with a L-H IS 8/III vacuum induction melting furnace. The results of chemical analysis were shown in Table 1. After about 80 pet reduction in thickness with hot forging, material was then subjected to 1200°C solution treatment for one hour, air cool and 720°C ageing treatment for 16 hour, air cool. An uniformly dispersed γ’ and γ” precipitates was obtained.Material was plastically deformed to 70 pet reduction in thickness by cold rolling treatment. Then all specimens were divided into four groups and annealed in salt baths with temperatures of 750°C, 850°C, 920°C and 1060°C, respectively. 850°C was chosen to conduct a complete investigation of interior microstructures of different time periods: (1) 2 sec (2) 5 sec (3) 10 sec (4) 30 sec (5) 1 min (6) 5 min (7) 10 min (8) 20 min (9) 35 min (10) 1 hr (11) 2hr. Hardness of all thermomechanically treated specimens were examined with a Rockwell Hardness machine, using RC and RB scales.
Dislocations Motion in Alloys with Periodic Antiphase Boundaries
Authors: Vanderschaeve G. , Faress A. 
Published: June 2020

Plastic deformation of L12 ordered alloys (Cu3Au type) occurs by slip of dislocation pairs. In alloys with periodic APB's however, dislocations moving through the crystal are continually crossing APB's and mechanical properties of these alloys are affected by conditions governing the propagation of dislocations through them.This paper describes some peculiarities of the interaction of moving dislocations with periodic APB's in a Cu 20.3at%Pd alloy, where the average distance between periodic APB's is Ma∼7.6a. The frequently observed configuration (Fig. 1) consisting of dislocation pairs followed by alternatively widely extended and unsplit unit dislocations can be understood if one analyzes the effective surface tension acting on each Shockley partial.
Energetic Cluster Ion Impacts on Carbon and Gold/Carbon Films
Authors: Ledbetter M.C. , Matthew M.W. , R.J. Beuhler  , Friedman L. 
Published: June 2020

Mass analyzed beams of accelerated cluster ions have been used to study energy transfer processes on impact with solid surfaces. Singly-charged water molecule clusters containing between 20 and 150 water molecules and one proton have been accelerated to kinetic energies as high as 300 kV and collided with 10 nm films of carbon or carbon covered with 2 μg/cm2 evaporated gold. Alterations in the structure of these films have been studied by transmission electron microscopy.Carbon films bombarded with water clusters of 25 and 100 molecules accelerated to 300 kV are shown in Fig. 1. The use of 100 water molecules produced craters about 7-8 nm in diameter and even 50 molecules produced craters about 1.5-2 nm in diameter; however, 25 molecules failed to produce any detectable alterations in the film. The bombardment of a gold-covered film by similar clusters is shown in Fig. 2. In these cases, gold grains were removed to form voids about 10-20 nm in diameter, even by the clusters as small as 25 molecules, which produced no craters in pure carbon.
Contrast Enhancement of Spermatozoa in Seminal Stains
Authors: Ward Dennis C. , Hall Robert W. 
Published: June 2020

The localization and visualization of intact spermatozoa in dried stains confirms the presence of semen in cases of suspected rape. Even though the average human male ejaculate contains over 240 million spermatozoa, current searching methods are often inefficient and tedious. These methods include the light microscopic search for spermatozoa following either: extraction of the stain components in aqueous buffer, destruction of the stain substrate, or the in situ staining of the suspected area.The extraction technique is most commonly employed even though it is inefficient in cell recovery. Spermatozoa apparently bind tenaciously to the support medium during the drying of the seminal plasma. The extraction process often fails in extracting complete cells. The number of spermatozoa collected from a stain may be further reduced by dilution of the semen with other body fluids, dilution of stain components with extraction medium, limited stain size, or a low sperm count due to physiological and/or elective (vasectomy) reasons.
Freeze-Fracture Imaging of Solutions of Ordered Rigid Rods
Authors: Zasadzinski J. A. N. , Sammon M. J. , Meyer R. B. 
Published: June 2020

Solutions of rigid rods display orientational and/or positional order at appropriate concentrations. Model systems of rigid rods are formed by Tobacco Mosaic Virus (TMV) in water or dilute salt solutions. In pure water, TMV particles are strongly negatively charged and electrostatic repulsion orders the virus into three-dimensional crystals with both orientational and positional order. When salt is added to the system, electrostatic repulsion is screened and the TMV particles lose much of their positional order, but retain their orientational order and form a nematic liquid crystal phase.The long and short-range order of TMV solutions is best studied using freeze- fracture replication TEM. Each virus, which is the equivalent of a single molecule in a normal crystal or liquid crystal, is easily visualized as a discrete particle (TMV are approximately 300 nm long and 18 nm in diameter).
Hepatic Glycogen Synthesis in Adrenalectomized Rats After Short- and Longterm Stimulation by Dexamethasone Observed by Light and Electron Microscopic Radioautography
Authors: Michaels J.E. , Garfield S.A. , Smith S.S. , Hung J.T. , Cardell R.R. 
Published: June 2020

The effects on glycogen synthesis of short- and long-term stimulation with dexamethasone (DEX) were studied in adrenalectomized, overnight-fasted rats by light (LM) and electron microscopic (EM) radioautography (RAG). Rats were injected with DEX 3 hr (short-term) or 14 hr (long-term) prior to labeling by intravenous injection of 2 mCi 3H-galactose, a glycogen precursor. Liver was prepared for LM and EM RAG by routine procedures.Short-term rats were sacrificed 1, 6 and 12 hr after labeling. One hr after injection of label (Fig. 1) equal percentages (44%) of heavily (> 10 grains/100 μm2 hepatocyte cytoplasm) and lightly (<10 grains/100 μm2 cytoplasm) labeled hepatocytes were evident. Six hr after labeling, heavily labeled cells increased slightly as labeled and unlabeled glycogen became evident. The appearance of unlabeled glycogen was evidence that glycogen synthesis continued between 1 and 6 hr, as circulating label fell to a level below that necessary for radioautographic labeling to occur. Twelve hr after labeling (Fig. 2) the percentage of heavily labeled hepatocytes (31%) decreased to less than at one hour as unlabeled glycogen increased. These results indicated that although glycogen synthesis had continued, some loss of label had occurred.
Blood/Material Interactions on Silicone Rubber-Hydrogels
Authors: Greer R. T. , Schwen K. , Cyr M. , McAllister P. , D. T. Zhang  
Published: June 2020

The composition and structure of a polymer surface in contact with flowing blood are major factors determining the extent of thrombus and embolus formation. Use of scanning electron microscopy (SEM) provides temporal information on morphology of thrombi and cells on polymer surfaces exposed to blood, and associated Fourier transform infrared/attenuated total reflectance (FT-IR/ATR) measurements aid in characterizing protein buildup.Medical grade silicone rubber-filler formulations (0,2,12 and 24 weight percent cristobalite filler contents; source material Silastic 382) were polymerized to form substrates. These were subsequently coated with five different hydrogels by radiation grafting (y-rays) to provide samples with a range of hydrophilicity characteristics.
Fluorescent and Immuno-Electron Microscopy of Detergent Extracted Cytoskeletal and Associated Antigens
Authors: Basgall E.J. , Soong M.M. , Tompkins W.A.F. 
Published: June 2020

Triton X-100 detergent extraction has been shown to be a relatively simple method for revealing the internal architecture of cultured cells. This method has proven valuable in studies of cytoskeleton-associated proteins and their functions in regulating cell activities. Exposed cytoskeletal elements can be examined using either transmission or high-resolution scanning electron microscopy. Immunochemical studies at the electron microscopic level have been simplified by the availability of Protein A-colloidal gold as a high affinity marker for immunoglobulins, specifically IgG.Several investigators have reported an association between the cytoskeleton and viral antigens. Evidence has indicated that, in some systems, the cytoskeleton plays a significant role in virus infection. Immunofluorescent studies on canine distemper virus infected, extracted cells have revealed altered cytoskeletal staining patterns, as compared to non-infected controls. In our laboratory, immuno-electronmicroscopy studies of extracted NIH/3T3 cells infected with Maloney-murine leukemia virus have indicated an association between cytoskeletal actin and the viral antigens gp70 and pl5E.
Ultrastructural Observations on Microspore Development in Rice Anther Culture
Authors: Ren S. S. , Chen J. C. , Chen Y. R. 
Published: June 2020

The plants produced from rice anther culture varied in ploidy level. Genetic analysis of anther-derived plants indicated genome multiplication occurred in microspore development in vitro. Cytological studies on early roicrospore division suggested endoreduplication and nuclear fusion may be related to the production of nonhaploid plants. In the present study, fine structures of callus ontogeny in anther culture were emphasized.Anthers of rice(Oryza sativa L. c. v. Hsinchu 4, 2n=24) containing mid-uninucleate microspores were excised and cultured in Ng liquid medium, supplimented with 60 g/l sucrose, 1 mg/l kinetin and 2 mg/l naphthalenacetic acid. Cultured anthers were collected at 2 days intervals for 20 days and fixed in 2.5% glutaraldehyde in 0.1M cacodylate buffer(pH=7.0), postfixed in osmium tetraoxide, and then embedded in Spurr's resin. Thin sections were stained with uranyl acetate and lead citrate, observed under Hitachi H-600 at 75 KV.
Defect structures of Nb1+αS2 sulfidation scales
Authors: Zhou Chuxin , Hobbs L. W. 
Published: June 2020

One of the major purposes in the present work is to study the high temperature sulfidation properties of Nb in severe sulfidizing environments. Kinetically, the sulfidation rate of Nb is satisfactorily slow, but the microstructures and non-stoichiometry of Nb1+αS2 challenge conventional oxidation/sulfidation theory and defect models of non-stoichiometric compounds. This challenge reflects our limited knowledge of the dependence of kinetics and atomic migration processes in solid state materials on their defect structures.Figure 1 shows a high resolution image of a platelet from the middle portion of the Nb1+αS2 scale. A thin lamellar heterogeneity (about 5nm) is observed. From X-ray diffraction results, we have shown that Nb1+αS2 scale is principally rhombohedral structure, but 2H-NbS2 can result locally due to stacking faults, because the only difference between these 2H and 3R phases is variation in the stacking sequence along the c axis. Following an ABC notation, we use capital letters A, B and C to represent the sulfur layer, and lower case letters a, b and c to refer to Nb layers. For example, the stacking sequence of 2H phase is AbACbCA, which is a ∼12Å period along the c axis; the stacking sequence of 3R phase is AbABcBCaCA to form an ∼18Å period along the c axis. Intergrowth of these two phases can take place at stacking faults or by a shear in the basal plane normal to the c axis.
Structures and defects identified by dark-field HREM
Authors: Zhang J.P. 
Published: June 2020

The tilted illumination dark field high resolution imaging technique was applied to structures and defects of semiconductors and superconductors. We used a Hitachi-H9000 top entry microscope with a high resolution pole-piece of Cs=0.9 mm, operated at 300 Kv. Proper apertures, tilting angle and imaging conditions were chosen to minimize the phase shift due to aberrations. Since the transmitted beam was moved outside the aperture, the noise ratio was greatly reduced, which resulted in a significant enhancement of image contrast and apparent resolution. Images are not difficult to interpret if they have a clear correspondence to structure - information from image simulations in bright field mode can be used to assist in dark field image interpretation.An example in a semiconductor, GaAs/Ga0.49In0.51P2 superlattice imaged along [110] direction is shown in Figure 1. In this dark field image the GaAs and GaInP layers can be easily distinguished by their different contrast, and the difference in quality between both sides of interfaces is clear. An enlarged image in Figure 1 shows the defective area on the rough side of interface. Since this image shows the same pattern as the [110] projection of an fee structure, the major structural information about {111}, {200}, {220} planes can be obtained from this zone. Note that in bright field mode, [110] is not a good zone for imaging such multilayers.
Use of EDS mapping to characterize thermochemical stability of fibers in intermetallic matrix composites
Authors: Porter John R. 
Published: June 2020

New ceramic fibers, currently in various stages of commercial development, have been consolidated in intermetallic matrices such as γ-TiAl and FeAl. Fiber types include SiC, TiB2 and polycrystalline and single crystal Al2O3. This work required the development of techniques to characterize the thermochemical stability of these fibers in different matrices.SEM/EDS elemental mapping was used for this work. To obtain qualitative compositional/spatial information, the best realistically achievable counting statistics were required. We established that 128 × 128 maps, acquired with a 20 KeV accelerating voltage, 3 sec. live time per pixel (total mapping time, 18 h) and with beam current adjusted to give 30% dead time, provided adequate image quality at a magnification of 800X. The maps were acquired, with backgrounds subtracted, using a Noran TN 5500 EDS system. The images and maps were transferred to a Macintosh and converted into TIFF files using either TIFF Maker, or TNtolMAGE, a Microsoft QuickBASIC program developed at the Science Center. From TIFF files, images and maps were opened in either NIH Image or Adobe Photoshop for processing and analysis and printed from Microsoft Powerpoint on a Kodak XL7700 dye transfer image printer.
The microstructure of an oxidized γ-TiAl+Cr alloy
Authors: Sutliff J.A. , Huang S.C. , McKee D.W. 
Published: June 2020

Alloys based on the intermetallic phase γ-TiAl are considered good candidates for some high temperature aircraft engine applications. While a tremendous effort has been made to understand the mechanical properties of γ-TiAl, relatively little effort has been made to understand its oxidation behavior. Two of the authors have studied oxidation of several γ-TiAl alloys containing ternary and quaternary additions including Cr, Mn, Nb, Ta, and W. In this paper, we present some of the microstructural observations on an oxidized γ-TiAl alloy.An oxidized γ-TiAl alloy with a nominal composition of 50 at% Al and 2 at% Cr was examined using analytical electron microscopy. Oxidation of polished pieces occurred in air at 850°C for 6 hours. The pieces were ground from the unpolished side to a thickness of ∼75 μm and 3 mm disks were punched. The disks were electropolished in a perchloric/methanol solution. Electropolishing was done from the metal side only until “perforation” of the metal substrate. This resulted in a sample with an oxide ‘window’. The samples were further thinned by ion beam milling (5kV/500μA Ar+) from the oxide surface toward the oxide/metal interface. The sample was examined in a Philips EM430 TEM operated at 300 kV and x-ray spectra collected with an EDAX energy dispersive x-ray spectrometer having a windowless Si(Li) detector.
Microstructure and properties of Al-Cu-Li-Ag-Mg-Zr alloy
Authors: Kim M.J. , Lee C.S. , Catalano M. , Shin K.S. 
Published: June 2020

Weldalite™ 049 is an ultrahigh strength weldable Al-Cu-Li based alloy containing minor amounts of Ag, Mg and Zr, developed at Martin Marietta. Additions of Ag and Mg seem to stimulate precipitation in this alloy, but the exact role of these elements in promoting the precipitation of strengthening phases is as yet unclear. In this paper, we report the characteristic microstructure of the Weldalite™ 049 alloy in the near peak aged T8 temper condition and its effect on the measured tensile properties of this alloy.The alloy used in this study was prepared by the Reynolds Metals Company. Measured alloy composition was Al-4.36 Cu-1.25 Li-0.39 Mg-0.35 Ag-0.14 Zr (wt.%). Tensile tests were performed at both room and cryogenic temperatures. The samples for TEM observations were cut from the mechanical testing specimens and then thinned to electron transparency by polishing and ion milling. Liquid nitrogen cooled specimen holder was used for ion milling to avoid local specimen heating. Diffraction contrast and tilting experiments were performed at 200kV in a JEM-2000FX. HREM was done in an ISI-002B at 200kV, with an interpretable resolution limit of 0.18 nm.
Off-axis electron holography applied to the study of interfaces
Authors: Weiss J.K. , Gajdardziska-Josifovska M. , McCartney M. R. , Smith David J. 
Published: June 2020

Interfacial structure is a controlling parameter in the behavior of many materials. Electron microscopy methods are widely used for characterizing such features as interface abruptness and chemical segregation at interfaces. The problem for high resolution microscopy is to establish optimum imaging conditions for extracting this information. We have found that off-axis electron holography can provide useful information for the study of interfaces that is not easily obtained by other techniques.Electron holography permits the recovery of both the amplitude and the phase of the image wave. Recent studies have applied the information obtained from electron holograms to characterizing magnetic and electric fields in materials and also to atomic-scale resolution enhancement. The phase of an electron wave passing through a specimen is shifted by an amount which is proportional to the product of the specimen thickness and the projected electrostatic potential (ignoring magnetic fields and diffraction effects). If atomic-scale variations are ignored, the potential in the specimen is described by the mean inner potential, a bulk property sensitive to both composition and structure. For the study of interfaces, the specimen thickness is assumed to be approximately constant across the interface, so that the phase of the image wave will give a picture of mean inner potential across the interface.
HREM study in Ti/6H-SiC interface
Authors: Bow J.S. , Spellman L.M. , Kim M.J. , Carpenter R.W. , Davis R.F. 
Published: June 2020

A semiconductor of Ti/6H-SiC with rectifying characteristics was reported recendy. That its electrical properties were degraded for 20 min. anneal at 700°C but improved again with subsequent 20 min. and longer anneal was considered to be caused by phase transformation during annealing. The purpose of this study is to identify those phases formed in the annealing process, and to identify those responsible for changing the electrical properties.A 100 nm Ti thin film was deposited on 6H-SiC by electron beam evaporation in UHV, and subsequent annealing was also done in UHV at 700°C. Cross section TEM specimens were prepared by bonding wafers with Ti-films face to face, grinding, polishing, and then ion milling in a Gatan 600. All TEM observations were performed in an ISI 002B with a 0.18nm resolution at 200KV. HREM images were analyzed by using die SEMPER program.