bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elemental mapping of segregation in stainless steels with an imaging filter
Authors: Bentley J. , Kenik E. A. 
Published: June 2020

Elemental mapping in a TEM equipped with an imaging filter is expected to become an important microanalysis technique in materials science. The efficacy of the technique for studying solute segregation and composition gradients is not as well established as for mapping precipitate distributions. We have therefore undertaken a preliminary investigation of two types of solute segregation in 300-series austenitic stainless steels.Elemental mapping was performed at 200 kV with Gatan Imaging Filters (GIF™) attached to JEM 2010 and Philips CM20 electron microscopes operating with probe currents of > 100 nA. Further work will also use a GIF on a Philips CM30 at ORNL. Images were recorded (exposure times of 15-50 s) with the slow scan CCD camera of the filter for 30- or 40-eV-wide windows before and after ionization edges of interest, including Cr-, Fe-, and Ni-L23 edges (see the spectrum shown in Fig. 1), and were processed with Gatan Digital Micrograph™ software.
Detection of ultrafine particles in the lung macrophages of healthy people
Authors: Hatch V. , Hauser R. , Hayes G. B. , Stearns R. , Christiani D. , Godleski J. J. 
Published: June 2020

Modern environmental air pollution control strategies are designed to reduce airborne particulate mass by reducing the size of effluent particles to less than lOOnm. Recently, Dockery et al have clearly shown that fine-particulate air pollution (<2.5(μm) can be directly related to excess mortality in humans. Although ultrafine metal fumes (<100nm) have been shown to produce adverse effects in occupational settings, little is known of the extent to which they contribute to ambient environmental particulate air pollution. The purpose of this study is to determine to what extent ultrafine particles are present in lung macrophages of healthy human volunteers studied by electron energy loss spectroscopy (EELS) and electron spectroscopic imaging (ESI).Lung macrophages were obtained by bronchoalveolar lavage from 14 current non-smokers, 7 of whom work at an oil-fired power plant but were not considered to have significant occupational exposure, 4 of whom were welders at the power plant with the possibility of metal fume (ultrafine particulate) exposure, and 3 of whom were university employees with no known occupational or environmental exposure.
Progress in biological cryo-SEM
Authors: Hermann R. , Hohenberg H. , Bauer H. H. , Muller M. 
Published: June 2020

Field-emission SEM's of the in-lens type generate electron beam diameters of less than 1 nm at high accelerating voltages and of ca. 3-5 nm at 1 kV. These instruments, combined with a proper understanding of the involved signal generation and detection processes, represent one of the means to investigate biological surfaces with a structural information at the macromolecular level. In order to obtain this information, the biological structures have to be preserved as close as possible to the native state. This can be achieved with cryotechniques, e.g. cryoimmobilization, eventually followed by freeze-drying of the sample, metal coating at low specimen temperatures and lowtemperature observation in the SEM.Thin beam transparent samples can be visualized in this way with a structural resolution of ca. 3 nm. Fig. 1 shows a micrograph of differently polymerized human calcitonin: (a) a single fibril of ca. 8 nm diameter, exhibiting helical windings, and (b) a ribbon-like higher order structure, which is composed of individual fibrils.
Ultra-high-resolution low-voltage imaging of polymers
Authors: Butler J. H. 
Published: June 2020

We have been using an LVSEM with an immersion-type objective lens extensively for the examination of polymers at low (<2 keV) incident beam energies. Because of this instrument's field emission source, the incident probe can be demagnified down to subnanometer dimensions and still provide enough incident beam current to stimulate detectable image forming signals, esp. secondary electrons. Also, the incident beam penetration depth at low voltages is less than the SE escape depth (=200Å) for carbonaceous materials), so the sample/beam interaction volume is correspondingly smaller. The combination of these two factors suggest that the attainable resolution at low voltages for polymeric materials can be significantly higher than that which can be obtained via conventional SEM, all while the beam induced radiation damage is correspondingly reduced.Another reason that higher resolution can be obtained at low voltages is that, for all materials, a surface charge balance situation (wherein the incident beam current is equal to the summed SE and backscattered currents) exists for a particular incident beam energy, E2.
AFM: The art of touching molecules
Authors: Moy V. T. , Hofmann U. G. , Benoit M. , Wagner D. , Ludwig M. , Florin E. L. , Holstein T. , Gaub H. E. 
Published: June 2020

During recent years the atomic force microscopy (AFM) has evolved into an extremely useful instrument in life sciences. Particularly the option of this novel technique to operate under quasi physiological conditions and in real time has initiated a broad spectrum of new experiments. As a result, structural and micro-mechanical properties of supramolecular arrangements like molecular films and protein complexes were elucidated. Dynamic processes in live cells were recorded at unparalleled resolution and molecular interactions were investigated. Selected examples of such aspects will be the topic of this lecture.The AFM has improved drastically the understanding of the molecular structure of Langmuir-Blodgett films. LB films have in turn evolved into standards for the improvement of the understanding of the fundamental imaging mechanisms because of several reasons: they may be formed from a broad variety of substances and their molecular packing can be varied and controlled to a large degree at the air water interface prior to transfer, allowing the intelligent design of certain surface properties like roughness and charge density or micro-mechanical properties.
Using STM to characterize interactions at metal-ceramic interfaces
Authors: Bonnell D. , Liang Y. , Carroll D. 
Published: June 2020

The atomic interactions at metal/ceramic interfaces are often the limiting factor in mechanical and electrical properties. As such, much attention has been devoted to the issue. Experimental approaches include high resolution transmission electron microscopy, Auger electron spectroscopy, low energy electron diffraction, photoemission, etc. Scanning probe microscopies have yielded considerable insight into similar studies concerning semiconductors. Here we demonstrate how the spatial localization of scanning tunneling microscopy (STM) and tunneling spectroscopy (STS) can be exploited to elucidate atomic interactions at initial stages of metal/ceramic interface formation.A SrTiO3 single crystal is doped with 0.1% niobium so that the oxide will be conductive even when fully oxidized. The (001) surface was prepared with standard polishing techniques, then annealed at 1000 C in a UVH chamber backfilled with oxygen. This treatment results in a surface that consists of terraces 50-100 nm wide and several 100 nm long. The steps separating the terraces are 0.4 - 0.8 nm, i.e. one or two unit cells in height.
Scanning-probe microscope analysis of optical thin films: A new analytical tool in a manufacturing environment
Authors: Sapers S. P. , Clark R. , Somerville P. 
Published: June 2020

OCLI is a leading manufacturer of thin films for optical and thermal control applications. The determination of thin film and substrate topography can be a powerful way to obtain information for deposition process design and control, and about the final thin film device properties. At OCLI we use a scanning probe microscope (SPM) in the analytical lab to obtain qualitative and quantitative data about thin film and substrate surfaces for applications in production and research and development. This manufacturing environment requires a rapid response, and a large degree of flexibility, which poses special challenges for this emerging technology. The types of information the SPM provides can be broken into three categories:(1)Imaging of surface topography for visualization purposes, especially for samples that are not SEM compatible due to size or material constraints;(2)Examination of sample surface features to make physical measurements such as surface roughness, lateral feature spacing, grain size, and surface area;(3)Determination of physical properties such as surface compliance, i.e. “hardness”, surface frictional forces, surface electrical properties.
Quasi-epitaxial orientations of grains and structure of grain boundaries in YBa2Cu3O7−x thin films
Authors: Shin D. H. , Silcox J. , Russek S. E. , Lathrop D. K. , Moeckly B. , Buhrman R. A. 
Published: June 2020

When a thin film is grown on a substrate with a large difference in lattice constants, the interface energy as a function of relative orientation shows several cusped minima. If the lattice mismatch is small, or if the growth temperature is high and the deposition rate is slow, most of the nucleated islands assume the orientation corresponding to the minimum interface energy, and a nearly single crystalline film is obtained. If the growth conditions are not so favorable, a polycrystalline film is obtained in which each of the grains may take a variety of orientations corresponding to local minima of interface energy. These relative orientations between the film and substrate determine the tilt angles at the grain boundaries.YBCO films grown on MgO at high temperatures or on SrTiO3 where the lattice mismatch is minimal are found to be nearly single crystal.
A study of twinning in YBa2Cu3O7−x by large-angle convergent-beam electron diffraction
Authors: Midgley P.A. , Vincent R. , Cherns D. 
Published: June 2020

The oxygenation of YBa2Cu3O7−x (YBCO) leads to an orthorhombic distortion of the unit cell to accommodate the extra oxygen atom. This makes the formation of twins energetically favourable with CuO4 planar unit chains running alternately along the a and b axes of the parent tetragonal structure. The geometry of this twinning is such that four possible twin variants may co-exist with the twin boundaries lying in the (110) or (110) planes of the deformed structure. The traces of these planes are not mutually perpendicular and thus the crystal is strained to allow for the mismatch. It is to the nature of this strain field that this work has been addressed.Sintered samples were prepared by crushing and dispersing the resultant powder onto a very fine Cu mesh grid. Single crystals were chemically thinned to perforation. No discernible artefacts were seen and similar results were obtained with either method.
Processing and characterization of YBa2Cu3O7−x/Ag composites
Authors: Javadpour Jafar , Thiel Bradley L. , Mehmet Sarikaya , Aksay Ilhan A. 
Published: June 2020

Practical applications of bulk YBa2Cu3O7−x materials have been limited because of their inadequate critical current density (jc) and poor mechanical properties. Several recent reports have indicated that the addition of Ag to the YBa2Cu3O7−x system is beneficial in improving both mechanical and superconducting properties. However, detailed studies concerning the effect of Ag on the microstructural development of the cermet system have been lacking. Here, we present some observations on the microstructural evolution in the YBa2Cu3O7−x/Ag composite system.The composite samples were prepared by mixing various amounts (2.5 - 50 wt%) AgNO3 in the YBa2Cu3O7−x nitrate precursor solution. These solutions were then spray dried and the resulting powders were either cold pressed or tape cast. The microstructures of the sintered samples were analyzed using SEM (Philips 515) and an analytical TEM (Philips 430T).The SEM micrographs of the compacts with 2.5 and 50 wt% Ag addition sintered at 915°C (below the melting point of Ag) for 1 h in air are displayed in Figs. 1 and 2, respectively.
Transmission Electron Microscopy study of Bi-based superconducting phases
Authors: Wen J.G. , Fung K.K. 
Published: June 2020

Bi-based superconducting phases have been found to be members of a structural series represented by Bi2Sr2Can−1Cun−1On+4, n=1,2,3, and are referred to as 2201, 2212, 2223 phases. All these phases are incommensurate modulated structures. The super space groups are P2/b, NBbmb 2201, 2212 phases respectively. Pb-doped ceramic samples and single crystals and Y-doped single crystals have been studied by transmission electron microscopy.Modulated structures of all Bi-based superconducting phases are in b-c plane, therefore, it is the best way to determine modulated structure and c parameter in diffraction pattern. FIG. 1,2,3 show diffraction patterns of three kinds of modulations in Pb-doped ceramic samples. Energy dispersive X-ray analysis (EDAX) confirms the presence of Pb in the three modulated structures. Parameters c are 3 0.06, 38.29, 30.24Å, ie 2212, 2223, 2212 phases for FIG. 1,2,3 respectively. Their average space groups are all Bbmb.
Imaging of BaCuO2 impurity in solution-grown YBa2Cu3O7−δ
Authors: Dufner D. C. , Mohan Ram R.A. , Clearfield A. 
Published: June 2020

Solid state reactions are the most commonly employed processes for the preparation of high-Tc superconducting ceramic oxides. However, there has been considerable effort expended to prepare the YBa2Cu3O7−δ (1-2-3) superconductor by low-temperature methods in order to obtain a more homogeneous oxide mixture resulting in products with superior superconducting properties. In our investigations, TEM was used to characterize the microstructure of these materials as a function of various processing parameters.The precursors for the (1-2-3) superconductors were prepared by precipitating hydroxides of Y, Ba, and Cu and heating the precipitates at various temperatures in the 750-930°C range for 12-60 hours in flowing O2. Crystals for electron microscopy were crushed, suspended in acetone, and dispersed onto holey carbon grids. TEM characterization was carried out on the Philips 400T operating at 120kV or on the JEOL 2000FX at the Texas Center for Superconductivity at the University of Houston.In this work, one of the impurity phases was observed and identified as BaCuO2.
Investigation of the atomic structure of crystal/amorphous interfaces in Pd80Si20 Alloy by HRTEM and image simulations
Authors: Shieh P.C. , Howe J.M. 
Published: June 2020

Determining the atomic structures of solid/liquid interfaces is important for understanding mechanisms of solidification of crystalline materials. To date, research in this area has largely been theoretical in nature because of the difficulty of determining the atomic structure of a solid/liquid interface experimentally. This study has employed HRTEM and image simulations to investigate the atomic structure of crystalline/amorphous interfaces in directionally crystallized Pd80Si20 amorphous ribbons. The crystalline/amorphous interface is similar to a solid/liquid interface in many respects. The HRTEM analyses of directionally crystallized samples have shown that the amorphous Pd80Si20 alloy crystallizes into a lamellar mixture of faceted Pd3Si and nonfaceted Pd9Si2. Interpretation of the HRTEM images requires knowledge of the visibility of ordered structures imbedded in amorphous surroundings. This paper reports the results of a computer simulation study undertaken to determine this visibility.Computer simulations were performed in two parts: 1) construction of a model atomic structure, and 2) simulation of HRTEM images of the model structure. The atomic model was started with a crystalline seed of Pd3Si several unit-cells thick and new atoms were deposited on to the seed according to the dense random packing model for metal-metalloid systems. A unit cell of appropriate size was cut from the resulting composite structure and sliced into layers for input into the image simulations. The HRTEM images were calculated using the TEMPAS multislice program with the following parameters for a JEOL 4000EX: 400kV accelerating potential, 1.0 mm spherical aberration coefficient, 5.0 nm half-width of Gaussian spread of defocus, 0.5 mrad semi-angle of beam convergence, 6.5 nm−1 objective aperture radius, −50.0 nm defocus (near Scherzer defocus) and diffracted beams out to 4.0 nm−1
Electron diffraction investigation of the incommensurate modulation in Ba1−xKxBiO3
Authors: Verwerft M. , Van Tendeloo G. , Hinks D.G. , Dabrowski B. , Richards D.R. , Mitchell A.W. , Marx D.T. , Pei Shiyou , Jorgensen J.D. 
Published: June 2020

The perovskite system Ba1−xKxBiO3 has been studied by different techniques since the discovery of superconductivity at an onset temperature of ≈ 30 K for the compound Ba6K4BiO3. Structural phase transitions (between commensurate structures) occur as function of both composition and temperature. Electron diffraction and high resolution experiments revealed an extra modulation induced by electron beam irradiation (fig. 1 and fig.2) of which the wavevector varies with composition and irradiation amount. For this modulation, different models have been proposed: ordering of oxygen / vacancies, of Ba/K or of Bi3+/Bi5+, but direct evidence for any of these models has not been found yet.In order to determine the symmetry and nature of this modulation, electron diffraction tilting experiments were performed (fig. 2) on the Ba.75K.25BiO3 sample. Extinction of the satellite reflections is observed for reflections (hkl) with 1 = n+1/2 (n = integer).In order to obtain the symmetry restrictions on the modulation, these diffraction results are interpreted using the superspace concept.
Continuous transformation of decagonal quasicrystal to a related crystalline phase
Authors: Kuo K.H. , Zhang H. 
Published: June 2020

Decagonal quasicrystal is a two-dimensional one with a periodicity of about 1.2 or 1.6 nm along its tenfold rotation axis. It is known to exist in rapidly solidified Al-rich Al-Mn-Si and Al-Cr-Si alloys, sometimes coexisting with the bcc α-AlMnSi or cubic Al13Cr4Si4 phase. Both these two crystalline phases are known to have many icosahedral units in them. The structural similarity between the decagonal phase and the related bcc α-AlMnSi has been studied extensively lately.However, recently we have found a new base-centered orthorhombic phase with a=1.24, b=3.79, and c=1.23 nm coexisting with the decagonal phase to these alloys. Moreover, evidence of a continuous transformation from the latter to the former has been found by selected area electron diffraction. Fig. la is the tenfold electron diffraction pattern (EDP) of the decagonal quasicrystal with strong spots forming a series of concentric decagons. However, in the region close to the boundary to the crystal, the circle on which the inner 10 strong spots lie becomes an ellipse with its long axis in the arrowed direction (Fig. 1b). The closer to the boundary, the more the distortion of this decagon (Fig. 1c) and finally the EDP changes almost to a 2D crossgrid pattern of a base-centered crystal (a reciprocal unit cell is outlined in Fig. 1d).
HREM images of phason-defected quasicrystals
Authors: Li F.H. , Yokota Y. , Pan G.Z. , Hashimoto H. 
Published: June 2020

The firstly published electron diffraction patterns(EDPs) of icosahedral(I) quasicrystal in Al-Mn alloy show a perfect I symmetry. The high resolution electron microscope images of I quasicrystals are in agreement with the Penrose tiling. However, in most cases the quasicrystals have a special kind of defect caused by the quenched phason strain so that the I symmetry breaks down. It was demonstrated that a special linear phason strain makes the Al-Cu-Mg and Al-Cu-Li quasicrystals distorted such that they turn into some intermediate states between I phase and body centered cubic(bcc) phase. In this abstract three images of quasicrystals with phason strain of different strength are shown.Fig.1 is an image of Al-Cu-Fe quasicrystal taken along the five-fold axis with an EM-4000 electron microscope equipped with the side entry goniometer. The lower part shows a more or less perfect five-fold symmetry, and the arrangement of all points having equivalent enviroment obeys the golden ratio.
TEM study on the diffraction streaks caused by initial phase disorder in a displacive modulation structure
Authors: Wu X. J. , Horiuchi S. 
Published: June 2020

Recently it was found in some electron diffraction patterns from one-dimensional displacive modulation structure that some streaks pass through the satellite spots. Fig.1 taken from a mineral Ankangite shows that the streaks always appear when the crystal was tilted along b*. This means than in this crystal there must be some reflection planes parallel to (a*, b*) plane in the reciprocal space. The similar EDPs are also observed in a crystal (Sr, Ca)3Cu5Ox. The streaks always pass through the satellite spots, which is quite different from the case where streaks are caused by conventional lattice defects like a stacking fault. It implies that in this kind of crystal the streaks must be produced by a new diffraction mechanism.An initial phase disorder model has been proposed to explain this diffraction phenomenon. So-called initial phase disorder means that the modulation wave is not a plane wave.
TEM study of order, structure and defects of β and martensite in Cu-Al-Mn shape memory alloys
Authors: Guilemany J.M. , Peregrin F. 
Published: June 2020

The shape memory effect (SME) shown by Cu-Al-Mn alloys stems from the thermoelastic martensitic transformation occuring between a β (L2,) metastable phase and a martensitic phase. The TEM study of both phases in single and polycrystalline Cu-Al-Mn alloys give us greater knowledge of the structure, order and defects.The alloys were obtained by vacuum melting of Cu, Al and Mn and single crystals were obtained from polycrystalline alloys using a modified Bridgman method. Four different alloys were used with (e/a) ranging from 1.41 to 1.46 . Two different heat treatments were used and the alloys also underwent thermal cycling throughout their characteristic temperature range -Ms, Mf, As, Af-. The specimens were cut using a low speed diamond saw and discs were mechanically thinned to 100 μm and then ion milled to perforation at 4 kV. Some thin foils were also prepared by twin-jet electropolishing, using a (1:10:50:50) urea: isopropyl alcohol: orthophosphoric acid: ethanol solution at 20°C. The foils were examinated on a TEM operated at 200 kV.
Observations on the structure at the transformation interface of pearlite in steel
Authors: Khalid F. A. , Edmonds D. V. 
Published: June 2020

The austenite/pearlite growth interface in a model alloy steel (Fe-1 lMn-0.8C nominal wt%) is being investigated. In this particular alloy pearlite nodules can be grown isothermally in austenite that remains stable at room temperature, thus facilitating examination of the transformation interfaces. This study presents preliminary results of thin foil TEM of the austenite/pearlite interface, as part of a programme of aimed at studying alloy carbide precipitation reactions at this interface which can result in significant strengthening of microalloyed low- and medium- carbon steels L Similar studies of interface structure, made on a partially decomposed high- Mn austenitic alloy, have been reported recently.The experimental alloys were made as 50 g argon arc melts using high purity materials and homogenised. Samples were hot- rolled, swaged and machined to 3mm diameter rod, solution treated at 1300 °C for 1 hr and WQ. Specimens were then solutionised between 1250 °C and 1000 °C and isothermally transformed between 610 °C and 550 °C for 10-18 hr and WQ.