bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemical twinning in the Ti4C2S2-TiS system
Authors: Hua Mingjian , Garcia C. I. , DeArdo A. J. 
Published: June 2020

Titanium carbosulfide Ti4C2S2 (H phase, P63/mmc, a=0.321 nm and c= 1.120) are TiS (Rm, a=0.3417 nm and c = 2.65) are frequently found to coexist within composite particle in ultra-low carbon interstitial-free (IF) steels. This more suggest that a direct transformation from TiS to Ti4C2S2 may be a major stabilization of C at higher temperatures in these steels. The deduced orient between Ti4C2S2 and TiS is in agreement with a reported crystal structure mode transformation mechanism between these two phases appears to be strongly related structures.At the as-cast condition, most of the S- and C-rich particles in the studied IF step as pure M4C2S2 (M=Ti, Nb). After a re-heating treatment at 1300°C, M4C2S2 discharge and a new phase were observed. This new phase can be indexed as a trigonated with a=0.33 nm and c=5.3 nm (Figure 1). After a second re-heating treatment appeared at the center layer of the multi-phase particles (Figure 2). It should be noted that (i) some planar defects were observed inside the new phase and Ti4C2S2 carbon and 2a).
Hollow-cone analysis of intercalated particles in layered H(Ca2Nan-3NbnO3n+1) materials
Authors: Treacy M. M. J. , Bisher M. E. , Jacobson A. J. 
Published: June 2020

The series of compounds H(Ca2Nan-3NbnO3n+1) form tetragonal perovskite-related layer structures that are strongly bound in two dimensions, but more weakly bound in the third. These materials can be delaminated by intercalating basic surfactant molecules into the layers, which spontaneously exfoliate the structure to form stable dispersions in a polar solvent. On drying a diluted droplet of this dispersion on an amorphous carbon film supported on a TEM specimen grid, all sheets are observed to lie flat on the carbon, with the thin tetragonal c-axis parallel to the optic axis. Typical sheet dimensions are 1 μm × 1 μm × 1.4 nm. Layered materials prepared in this way make fascinating specimens for transmission electron microscopy because the thickness, composition and orientation are known. Depending on the dispersion density, sheets will occasionally overlap with parallel c axes, but with random relationship between the a axes.Layers of exfoliated H(Ca2Nb3O10) material were examined in a Hitachi H9000NAR microscope equipped with a high angle electronic hollow cone unit.
Scanning electron microscopy 1928-1965
Authors: McMullan D. 
Published: June 2020

The beginning of the general use of the scanning electron microscope (SEM) can be accurately dated to 1965 when the Cambridge Instrument Company in the U.K. marketed their Stereoscan 1 SEM (to be followed about 6 months later by JEOL in Japan). But development had been in progress intermittently over the previous 30 years in Germany, the U.S.A., France, and the U.K. where in 1948 work was begun in Charles Oatley’s department at the Cambridge University Engineering Department which led directly to the Stereoscan. The purpose of this paper is to trace the development of the SEM and to show that some of the ideas pul forward by the early workers were well ahead of their time and only became technologically practicable much later.The First proposal for the application of scanning to microscopy was made in 1928 by Synge, an Irish scientific dilettante, who conceived the near-field scanning optical microscope but did not attempt to build one.
In situ high-temperature corrosion with the environmental SEM
Authors: Touryan L. A. , Hobbs L. W. 
Published: June 2020

Electron microscopy has greatly aided in understanding the microstructure and morphological development of corrosion scales formed by high temperature oxidation and sulfidation of metals. However, this knowledge has been limited by the fact that the microstructure and morphological features could only be studied after corrosion had occurred. The recent development of the environmental scanning electron microscope (ESEM) permits actual in-situ observation of the evolution of high temperature corrosion scales at the scale-gas interface, allowing for a better understanding of the detailed mechanisms of scale growth. The objective of this study is to investigate the evolution of oxidation and sulfidation scales on various metals and alloys.R.A. Rapp and associates adapted a conventional SEM for oxidation studies by developing a stage that could be heated in excess of 1000 C. Because of the vacuum restrictions of the SEM, a gas pipe directed at the surface of the samples was utilized in order to increase the local oxygen partial pressure, and this resulted in low (0.2 Torr) but sufficient pressures for oxidation.
Observation of corynebacterium species using Scanning Electron Microscopy
Authors: McWilliams Toya S. , Hammond Ernest C. , Luzarraga Marlene B. 
Published: June 2020

Bacteria of the genus Corynebacterium are considered part of the bacterial flora of skin and mucosa. Even C. diphtheriae, a long recognized pathogen, may be isolated from the throat of healthy individuals. Recent evidence indicates that other Corynebacteria are associated with opportunistic conjunctival infections in aging laboratory mice.Our goal of using scanning electron microscopy was to expand previous studies and to observe the association of the bacteria with the conjunctival surface of aged mice. To accomplish this, we needed a point of reference for identification of the corynebacteria which were frequently present in the company of other bacteria. We studied cultures of known corynebacteria of ocular origin during the exponential growth phase. These cultures contained pleomorphic cells that were round, ovoid and rod shaped, clustered together and surrounded by a biofilm. Several of the cylindrical rods appeared as V-shaped pairs, classic features of the genus Corynebacterium. The V-shape arrangement is accomplished by a snapping postfission movement.
Crystalline nanostructures in porous silicon and their relation to optical and electronic properties
Authors: Cullis Anthony G 
Published: June 2020

Although Si normally emits only extremely weak infrared photoluminescence (PL) due to its relatively small and indirect band gap, light-emitting devices based upon Si would find many applications in both VLSI and display technologies. Therefore, there has been much interest in the recent demonstration of very efficient visible light emission from highly porous, electrochemically etched Si. Although it was originally proposed that the efficient PL was due to recombination of quantum-confined carriers in pore walls, evidence for this was only indirect and transmission electron microscopy (TEM) studies have been required to provide a detailed understanding of the light emission mechanism.Porous Si samples are generally prepared by anodization in HF solution and porosities as high as ∼80% are required for efficient PL emission. Typical PL spectra from highly porous Si are shown in Fig. 1 where it is evident that emission is usually in the red and near infra-red regions of the spectrum.
TEM study of chemically converted SiC thin film on nanometer curved Si surface
Authors: Stepanova A. N. , Liu J. , Christensen K. N. , Son U. T. , Bachmann K. J. , Givargizov E. I. , Hren J. J. 
Published: June 2020

Silicon whiskers with nanometer curvature have a variety of applications such as probes in STM and AFM, or field emission cathodes for vacuum microelectronic devices. For these and other applications it is essential to stabilize the sharply curved silicon surface during usage. Carburization of the silicon surface seems to be a very suitable solution to this problem, since SiC crystals have excellent physical properties and are chemically quite inert. There have been a number of reports of the carburization of flat surface silicon wafers by chemical reaction using both CVD and MBE methods. However, to carburize while maintaining a very sharp silicon tip is extremely difficult. It is also desirable to carburize only a very thin layer, so as to avoid excessive mechanical strain arising from the large difference (∼20%) in lattice parameters.Our carburizations were carried out in a turbo-pumped ultra-high vacuum system. The silicon specimens were oxidation sharpened and cleaned in a buffered HF solution.
HREM of epitaxially grown Fe/TiO2 and Cu/TiO2 interfaces
Authors: Lu P. , Cosandey F. 
Published: June 2020

High-resolution electron microscopy (HREM) has been used to provide information on atomic structures of metal/oxide interfaces, which are of both scientific and technological interest. In this report, we present results of a study on Fe/TiO2 and Cu/TiO2 interfaces by HREM. The Fe/TiO2 and Cu/TiO2 interfaces were formed by vapor deposition of Fe and Cu on TiO2 (110) surface, respectively, in a UHV chamber with a base pressure of ∽1x10−10 torr. Cross sectional HREM specimens were prepared using standard techniques involving mechanical polishing, dimpling and ion-milling. The samples were examined in an Topcon-002B high-resolution electron microscope. HREM simulations were performed using the EMS program.Figs, 1a and 1b show a HREM micrograph and a select area diffraction pattern of Fe/TiO2 interface, respectively, taken along the TiO2 [001] direction. From Fig.la and Fig.1b, the following orientation relationship is obtained: [001]Fe//[001]TiO2 and (100)Fe//(110)TiO2. With this orientation, there is about 12.6% lattice misfitt along the TiO2 [10] direction.
Scanning-probe microscopy of polymers
Authors: Reneker Darrell H. , Patil Rajkumari , Kim Seog J. , Tsukruk Vladimir 
Published: June 2020

Scanning probe microscopy techniques, particularly atomic force microscopy (AFM) and scanning tunneling microscopy (STM) are finding a rapidly growing number of applications to both synthetic and biological polymers. Segments of individual polymer molecules can often be observed with atom scale resolution. Observation of polymeric objects as large as 100 microns with nanometer resolution is possible with contemporary AFM, although features caused by the convolution of the shape of the sample and the shape of the tip must be recognized and properly interpreted. The vertical resolution of the atomic force microscope readily provides precise data about the heights of molecules, crystals, and other objects.Lamellar crystals of polyethylene are well characterized objects with many features which can be observed with scanning probe microscopes. Figure 1 shows the fold surface near a fold domain boundary of a lamellar crystal of polyethylene, as observed with an AFM. The folded chain crystal is about 15 nm thick.
Morphological study of structured latex particles by Transmission Electron Microscopy
Authors: Segall Iris , Shaffer Olga L. , Dimonie Victoria L. , El-Aasser Mohamed S. 
Published: June 2020

Transmission electron microscopy plays an important role in the study of the influence polymerization conditions have on the morphology of structured latex particles and thus in the understanding of the morphological effect of such particles on the structure-property relationships of polymeric end products.Structured latex particles are prepared by seeded emulsion polymerization, where the first stage is a polymerization of ”the core” poly(n-butyl acrylate) (PBA), followed by a second stage polymerization of ”the shell” poly(benzyl methacrylate/styrene) (P(BM/St)) at various ratios. The changes in polymerization conditions include such variables as the polymerization mode (batch vs. semicontinuous), core/shell ratio, shell thickness, and shell composition. Morphology studies of the structured latex particles are performed by transmission electron microscopy on preferentially stained samples. In a small vial, a few drops of latex sample are combined with a few drops of uranyl acetate (UAc) 2% solution. The uranyl acetate serves as a negative staining to better delineate the particles edges.
Evaluation of matrix and interface properties in SiC/SiC composites
Authors: Surrett A.D. , More K.L. , Lowden R.A. 
Published: June 2020

It has become increasingly important to characterize composite matrix materials in terms of processing-microstructure-property relationships. The characteristics of composite matrices can differ significantly from monolithic materials processed using more conventional techniques such as hot-pressing or sintering. Knowledge of the mechanical and thermophysical properties of the matrix as a function of processing parameters is necessary for the modeling and design of composite materials. In this study, the microstucture and mechanical properties of the matrix in the Nicalon/SiC composite system have been characterized as a function of processing temperature.The composites were fabricated by stacking multiple layers of plain-weave Nicalon fabric rotated in a 30°-60°-90° sequence within the cavity of a graphite holder. The preforms were then coated with carbon at 1375 K and 3 kPa. The coated preforms were densified using a forced chemical vapor infiltration (FCVI) technique developed at ORNL. The SiC matrix was produced by the decomposition of methyltrichlorosilane carried in hydrogen at temperatures of 1000, 1100, 1200, 1300, and 1400°C in order to reveal the effect of temperature on the properties of the composite and matrix.
Application of SEM to the study of multi-phase ceramic composites
Authors: Chan Helen M. , Harmer Martin P. , Miller Gary A. 
Published: June 2020

Recent on-going research at Lehigh has focussed on the tailoring of multi-phase ceramic composite structures for enhanced mechanical behavior. Results have shown that by suitable control of the morphology and nature of the phases present, improvements may be obtained in properties such as microstructural stability, flaw tolerance, and strength. What follows is a brief discussion of examples illustrating applications of scanning electron microscopy (SEM) to this type of study for several specific systems.Work by French et al. revealed that relative to single phase materials, duplex structures (which consist of ∼ 50:50 vol.% mixtures of mutually insoluble phases) show significantly enhanced resistance to grain coarsening. It was postulated that the slower grain growth rate in the duplex material resulted from the necessity for long-range diffusion. To test this hypothesis, the grain growth behavior of two duplex Al2O3:ZrO2 materials was compared, the difference being that a grain boundary glassy phase was deliberately incorporated into one of the structures.
Phase transformations in ceramics
Authors: Kriven W. M. 
Published: June 2020

The study of phase transformations in ceramic has received limited coverage in ceramic text books, other than for example, ferroelectric transformations, (e.g., in barium titanate), zirconia and amorphous to crystalline transformations in glass. While Newnham has comprehensively reviewed the crystal chemistry of “ferroic” (ferroelectric, ferroelastic or ferromagnetic) ceramics, the success of “transformation toughening” as a mechanism for reducing the brittleness of ceramics has stimulated the search for other potential transformation tougheners alternative to zirconia.While phase transformations have been widely studied in metals over the past 50 years, caution needs to be exercized in transplanting conventional wisdom from metals to ceramics. The differences in bonding in ceramics ((mixed covalent and ionic ), can lead to profound differences in crystal structures and transformation mechanisms. An alternative approach which has been particularly helpful in our work is that of Hyde et al., which empasizes cation arrangements, into the interstices of which, the anions are inserted, rather than the inverse perspective of putting cations into a packed anion array.
Spherical aberration-free observation of reconstructed Au(011)2 × 1 surface by HRTEM using defocus-modulation image processing
Authors: Takai Yoshizo , Taniguchi Yoshifumi , Ikuta Takashi , Shimizu Ryuichi 
Published: June 2020

The surface profile imaging technique by HRTEM has a good potential for observing surface reconstructions. It also has possibilities for measuring with high accuracy the displacement of atoms in the direction perpendicular to the surface. However, surface profile images have been strongly influenced by imaging parameters such as defocus and spherical aberration. Therefore atom images generally appear to be appreciably displaced from their actual positions in crystal. In order to correct the spherical aberration in the image, the authors have recently developed a novel approach based on defocus-modulation image processing and experimentally confirmed that spherical aberration can be corrected very well by this method, as shown in a symmetric Thon diagram reproduced from amorphous carbon images,In the present paper, a reconstructed (011) gold surface has been observed by HRTEM (HF-2000) with a field emission gun at an accelerating voltage of 200kV. processing system, which records through focus images by changing the objective lens current while controlling image shift coils to compensate image drift.
Towards 1-Ångstrom-resolution STEM
Authors: von Harrach H.S. , Jesson D.E. , Pennycook S.J. 
Published: June 2020

Phase contrast TEM has been the leading technique for high resolution imaging of materials for many years, whilst STEM has been the principal method for high-resolution microanalysis. However, it was demonstrated many years ago that low angle dark-field STEM imaging is a priori capable of almost 50% higher point resolution than coherent bright-field imaging (i.e. phase contrast TEM or STEM). This advantage was not exploited until Pennycook developed the high-angle annular dark-field (ADF) technique which can provide an incoherent image showing both high image resolution and atomic number contrast.This paper describes the design and first results of a 300kV field-emission STEM (VG Microscopes HB603U) which has improved ADF STEM image resolution towards the 1 angstrom target. The instrument uses a cold field-emission gun, generating a 300 kV beam of up to 1 μA from an 11-stage accelerator. The beam is focussed on to the specimen by two condensers and a condenser-objective lens with a spherical aberration coefficient of 1.0 mm.
In situ studies of heterogeneous reactions using surface electron microscopies LEEM, MEM, and PEEM
Authors: Engel W. , Rausenberger B. , Swiech W. , Rastomjee C. S. , Bradshaw A. M. , Zeitler E. 
Published: June 2020

The preferred imaging techniques for the observation of physical and chemical processes at solid surfaces with high temporal and spatial resolution are low-energy electron microscopy (LEEM), mirror electron microscopy (MEM) and photoemission electron microscopy (PEEM). In these techniques the energy transfer to the surface during the imaging process itself is small so that surface processes such as adsorption, diffusion, chemical reactions etc. remain largely undisturbed.LEEM, MEM and PEEM, which all can be performed in an ultra-high-vacuum surface microscope of the Bauer/Telieps type, have been applied to the study of CO/O reaction-diffusion fronts on a Pt(100) surface saturated with CO. These fronts develop after admission of oxygen to the surface (10-6 mbar) at surface defects which provide adsorption sites for oxygen and thus initiate the autocatalytic oxidation process. The formed CO2 is instantaneously desorbed, freeing adsorption sites which are then occupied by oxygen from the gas phase. The front propagates over the whole surface, leaving behind an oxygen-covered region.
Materials science aspects in designing giant magnetoresistance in heterogeneous Cu1-xCox thin films
Authors: Hütten Andreas , Thomas Gareth 
Published: June 2020

The recent discovery of giant magnetoresistance (GMR) in heterogeneous Cu1-xCox thin films has brought new insights in the phenomenon of GMR, which was previously believed to be restricted to multilayered structures only. Subsequent theoretical analyses of GMR in this new materials class have shown that GMR is mainly controlled by the mean radius and the volume fraction of single domain ferromagnetic particles. In addition to these parameters, the mean free path for electron in the non-magnetic matrix as well as coherency between particles and matrix are influencing the amplitude of GMR. Clearly, the key to increase the amplitude of GMR is to determine the decomposition kinetics and from which to optimize the single domain ferromagnetic Co particle size distribution in heterogeneous Cu1-xCox thin films.Cu81Col9 films, 50 nm in thickness, have been deposited by dc magnetron sputtering from separate Cu and Co targets onto 30 nm thick silicon nitride electron transparent grids.
Microstructural analysis of cobalt alloy single and multilayer longitudinal recording media
Authors: Kuwabara M. , Visokay M.R. 
Published: June 2020

Co-based alloys have been successfully used as sputtered thin film media for hard disk drives. Media with higher recording density and lower media noise are required for the future hard disk drives. The magnetic properties can be controlled by processing and alloy composition. However, the origin of the magnetic properties, such as film coercivity and transition noise, are not fully understood yet. In this paper the analysis of the magnetic properties versus microstructure of Co-based alloy single and multilayer media is reported.Co-alloy media were prepared by DC magnetron sputtering of Cr, Co-alloy (CoCrNi and CoCrPt) and overcoat materials(C and Zr) on Ultra Densified Amorphous Carbon (UDAC) substrates. The sputtering pressure and deposition temperature were 3-5 mTorr and between 30°C and 300°C, respectively.The coercivity of CoCrNi and CoCrPt media increases with the deposition temperature in the range between room temperature and a few hundred degree Celsius. Figure 1 shows cross-section TEM(XTEM) images of CoCrPt media.
Magnetic-domain imaging techniques
Authors: McFadyen Ian R. 
Published: June 2020

The concept of domains in ferromagnets was introduced by Weiss in 1906. However, they were not observed until 1931 when Bitter showed that domain boundaries could be observed by decorating them with fine magnetic particles. Since then the field of magnetic domain imaging has expanded enormously.The original Bitter technique involved the decoration of a magnetic sample with a colloidal suspension of fine magnetic particles (usually magnetite) and observation by dark field optical microscopy. This is still a commonly used method and has been extended to finer particles, which include clusters directly deposited on the magnetic sample from a chemical vapor and observation of the clusters in the SEM or TEM at magnifications in excess of 20,000x.Another very popular means of observing magnetic domains employs the magneto-optic Kerr effect. Both polar and longitudinal Kerr techniques has been utilized. In the polar Kerr technique a magnetic sample is illuminated by a beam of plane polarized light normal to the sample surface.
Application of electron holography to material science studies on magnetic domain states of small particles
Authors: Hirayama T. , Ru Q. , Tanji T. , Tonomura A. 
Published: June 2020

The observation of small magnetic materials is one of the most important applications of electron holography to material science, because interferometry by means of electron holography can directly visualize magnetic flux lines in a very small area. To observe magnetic structures by transmission electron microscopy it is important to control the magnetic field applied to the specimen in order to prevent it from changing its magnetic state. The easiest method is tuming off the objective lens current and focusing with the first intermediate lens. The other method is using a low magnetic-field lens, where the specimen is set above the lens gap.Figure 1 shows an interference micrograph of an isolated particle of barium ferrite on a thin carbon film observed from approximately [111]. A hologram of this particle was recorded by the transmission electron microscope, Hitachi HF-2000, equipped with an electron biprism. The phase distribution of the object electron wave was reconstructed digitally by the Fourier transform method and converted to the interference micrograph Fig 1.