bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dislocation structures in titanium aluminides deformed at 815°C
Authors: Donlon W.T. , Dowling W.E. , Allison J.E. 
Published: June 2020

Ordered (L10) intermetallic γ-TiAl alloys are candidates for high temperature structural applications in the automobile industry because of their low density and high strength at elevated temperature. The major drawback of these materials is their low ductility at ambient temperature. Improvements in low temperature ductility may be achieved without sacrificing the desired high temperature performance by optimizing the microstructure through thermomechanical processing. This investigation measured the tensile and fatigue properties of an “as-cast” and cast plus heat treated Ti-48A1-1V-0.2C (at%) alloy at 25 and 815°C.The microstructure of both samples consisted of primary γ grains with an average intercept size of 100 μm, and regions of a γ matrix with α2 lathes. The vol% of the primary γgrains was 40% and 85% in the “as-cast” and cast plus heat treated samples, respectively. Figure 1 shows the microstructure of the “as-cast” material.
Intergranular phase in Nd-Fe-B permanent magnets
Authors: Chu Tsung-Yao , Rabenburg L. K. 
Published: June 2020

Even though the significance of the intergranular phase in the Nd-Fe-B magnets in terms of sintering aid and domain wall pinping has now been recognized, its exact nature has not yet been conclusively determined. This is so because the Nd-rich intergranular phase has been reported to stabilize in a variety of structures instead of the equilibrium hexagonal α-Nd structure as the ternary phase diagram suggests. This study is directed toward obtaining detailed crystal structure of the intergranular phase by means of transmission electron microscopy.Magnet ribbons with a starting composition of Nd13.5Fe80B6.5 were prepared by melt-spinning; the ribbons were subsequently hot pressed into fully dense magnets. Electron transparent samples, prepared from the hot-pressed magnets by mechanical grinding and ion beam milling, were examined in a JEOL 1200EX scanning transmission electron microscope.
Microstructural characterization of CaO-doped AlN substrate material
Authors: Bischoff E. , Ruckmich S. , Kranzmann A. E. 
Published: June 2020

AIN ceramics are candidates for substrate materials in electronic circuits. In spite they are insulators they exhibit a very high thermal conductivity. Impurities and the unavoidable sintering additives usually degrade the thermal conductivity. With a special heat treatment it was possible to improve the thermal properties. Microstructural characterization with analytical transmission electron microscopy (TEM) on sintered and purified AIN samples was conducted to understand the reason for this behavior.AIN powder contaminated with 1 wt% oxygen and doped with 1.4 wt% CaO was pressureless sintered in a N-atmosphere to more than 98.1 % relative density. Additional annealing at 2100 K yielded a translucent product with a high thermal conductivity. With annealing for less than 24 h in a reducing or non reducing atmosphere thermal conductivity increased slowly from 41 Wm-1K-1 to 75 Wm-1K-1. This could be attributed to microstructural changes like grain growth and change in fractal dimension via SEM. A drastic increase was achieved after 44 h in a reducing atmosphere, where a thermal conductivity of 219 Wm-1K-1 was reached, approaching that of pure aluminum. Thin specimen for TEM were prepared in the usual manner from a 23.5 and 44 h annealed sample and examined in a Jeol 2000 FX. Analytical work was done with a Tracor Northern energy dispersive x-ray system (EDS) and a Gatan serial electron energy loss spectrometer (EELS).
Observing the relaxation of molecular orientation in sheared liquid crystalline polymer solutions
Authors: Putnam Wendy , Viney Christopher 
Published: June 2020

Liquid crystalline polymers (solutions or melts) can be spun into fibers and films that have a higher axial strength and stiffness than conventionally processed polymers. These superior properties are due to the spontaneous molecular extension and alignment that is characteristic of liquid crystalline phases. Much of the effort in processing conventional polymers goes into extending and aligning the chains, while, in liquid crystalline polymer processing, the primary microstructural rearrangement involves converting local molecular alignment into global molecular alignment. Unfortunately, the global alignment introduced by processing relaxes quickly upon cessation of shear, and the molecular orientation develops a periodic misalignment relative to the shear direction. The axial strength and stiffness are reduced by this relaxation.Clearly there is a need to solidify the liquid crystalline state (i.e. remove heat or solvent) before significant relaxation occurs. Several researchers have observed this relaxation, mainly in solutions of hydroxypropyl cellulose (HPC) because they are lyotropic under ambient conditions.
Study of silver-bearing filler metal diffusion in copper metal base by SEM and EDXA, in the brazing
Authors: Traveria A. , Tura J.M. , Camps X. , de Castellar M.D. , Saulό J. 
Published: June 2020

The brazing is a joint process between two or more metallic parts, by using a nonferrous filler metal, having a melting point below that of the Base Metal. The filler metal is distributed between the closely fitted surface of the joint by wettability and capillarity attraction.In the present work the filler metal (FM) was DIN 8513: L-Ag30Cd and the base metal (BM) was electrolytic Cu (Figure 1). In the rod of the filler metal the following phases were identified: αZn(Cu), ordered β’(CuZn) and brittle β(Cu2Cd). The larger part of the matrix was composed by βCd(Ag). In this research two brazed structures were studied, obtained in the same experimental conditions, with the single exception of the post-brazing cooling cycle. Probe I suffered a slow solidification process at room temperature. Probe II was rapidly cooled by immersion in cold water.Probe I. In order to estimate the thickness of the diffusion zone in the braze-metal interfaces the specimen was arranged with its joint clearance not completely refilled ( Fig.2). As it may be observed one clear gap between the affected zone and the unaltered base metal appears.
The Structure of Thin Gold Films at the Early Stage of Continuous Film Growth
Authors: Krakow William 
Published: June 2020

The use of a transmission electron microscope to observe surface structure of thin films has been demonstrated in recent years by diffraction contrast imaging to ∼ 10Å resolution using the forbidden reflections of [111] Au and at atomic resolution using bright-field phase contrast on both [001] and [111] oriented Au films. It has also been possible to demonstrate that beyond a minimum thickness, these films can be free standing and viewed in the microscope without significant modification due to the incident electron beam generating sputtering events at high beam currents. It is therefore now possible to obtain free standing [001] Au films which exhibit various types of surface topography. These films were obtained by varying the growth parameters with a microprocessor controller attached to a UHV deposition system. The deposition of Au was precisely controlled onto a thick Ag substrate which was initially deposited upon NaCl single crystals.Fig. 1 shows a low magnification image ∼ 40Å thick [001] Au film grown at a vacuum level of 5 × 10-9 Torr, 50° substrate temperature and a deposition rate of ∼ 1/20 ML/sec. Clearly defined atomic step regions are visible as demonstrated by the terrace-like contrast variations over extended regions i.e. a step-ledge growth regime. Regions between these terrace areas represent coalescence of individual grains which were not attached at an earlier stage of growth. These regions exhibit finer scale terraces and ledges which follow either <100> or <110> directions as evidenced by comparing their directions to stacking faults and twins occasionally observed in the field of view. Small holes are also present which have crystallographic edge facets and anomalous contrast bands also occur which represent the lack of tracking of the upper surface layer growth to steps which exist at the lower surface. Fig. 1 was obtained by diffraction contrast from the direct beam alone. It was not necessary to use the forbidden reflections here since they produced too drastic a contrast change.
Interpretation of the Contrast of High-Resolution Electron Microscopy Images of Ni4Mo by Means of Simulated Image Maps
Authors: Thust A. , Urban K. 
Published: June 2020

The alloy of composition Ni4Mo develops, at temperatures below 860 °C, an ordered Dla-structure which is based on the fcc-lattice. This alloy has been widely investigated with respect to its physical properties and its ordering behaviour. High resolution studies are rare and concentrated mainly on its short-range order structure. The aim of the present work was to develop a detailed understanding of image contrast and to apply the results to antiphase-boundary studies in ordered Ni4Mo by means of a JEOL 4000 EX electron microscope.In high-resolution electron microscopy, depending on defocus and foil thickness, a large variety of different images is obtained. Only a few of these allow a direct interpretation concerning the location and the type of the atoms. By computing a through-focus/through-thickness map (TFTT map) before starting experimental work it is possible to determine the proper conditions at which images can be obtained which are closely related to the projected potential.
Algorithms for Composition Determination from HREM Images of Substitutional Alloys
Authors: de Jong A.F. , Van Dyck D. 
Published: June 2020

In a substitutional alloy the positions of the lattice sites are fixed, but they may be randomly occupied by two or more different atom types. An example is the semiconductor Alx Ga1-x As, which has the group III sites arranged in columns at a (projected) distance of 0.28 nm when imaged in the [100] direction. The determination of compositions at atomic resolution would enable the study of roughness and interdiffusion at epitaxial interfaces such as GaAs/Alx Ga1-x . With high-resolution electron microscopy (HREM) it is possible to image the different columns, but it is difficult to image differences in composition. One method has been proposed so far to measure compositions from HREM images. We derive a linear relationship between deviations in composition and image contrast, and propose and test two new image processing algorithms to measure compositions in atomic columns.Consider a substitutional alloy with one atomic position occupied by either type A or type B atoms, and assume that the z -dependence of the potential can be disregarded. For the average composition an average potential V0 (dependence on (x,y ) implicit) results in an average electron wavefunction ϕo (z ) at the exit plane of the sample. Locally (e.g. in one atomic column) the composition may deviate from the average by y , causing a small deviation from the average potential of y(VA – VB ). VA and VB are the potentials when the crystal would contain only type A or type B atoms, respectively. The wavefunction can be calculated using perturbation theory, yielding formally to first order:
HREM Studies of Some Phases in the ZrO2-Nb2O5 System
Authors: Sundberg Margareta , Marinder Bengt-Olov 
Published: June 2020

High resolution electron microscopy and x ray powder diffraction techniques were used to study samples of various compositions in the Nb2O5-rich part of the ZrO2-Nb2O5 system at 1500°C. A large number of fragments were also characterized by electron diffraction in combination with EDS analysis. Some HREM results concerning block structures formed in the above region have previously been reported.The x ray powder pattern of a ZrO2.9Nb2O5 sample indicated a phase isotypic with T-Nb2O5. The micrograph in Fig. 1, of a thin crystal fragment from that sample, illustrates a phase related to the UVO5 (m=2) structure type. The electron diffraction patterns showed an ordered commensurate phase (m=8) with unit cell dimensions similar to those reported for T-Nb2O5 and Ta30W2O81. The structure models of these two compounds are rather similar and differ mainly in the oxygen content.
Structure Determination at Atomic Resolution by Electron Crystallography
Authors: Zou Xiaodong , Hovmöller Sven 
Published: June 2020

Structure determination by electron microscopy is emerging as a serious competitor to the classical methods of X-ray diffraction. The main advantage of EM is that the phase information is restored in the image, whereas with X-ray diffraction it is lost.The structure determination of an inorganic crystal by electron microscopy would be trivial if the micrograph was just a magnified image of the electron density in the crystal. Unfortunately it is not. A limited number of non-linear effects distort the image. These effects can be divided into two parts; those arising already in the crystal and those that are due to optical distortions. For a crystal one unit cell thick the wave front at the exit surface of the crystal is a linear function of the electron density within the unit cell. As the crystals become thicker more and more of the diffracted electrons will have been doubly diffracted, making the image no longer a linear function of the electron density. For crystals thinner than half the mean free path for electrons most of the scattered electrons are still scattered only once, making the image interpretable.
Characterization of Modulated Structure Through Structure Images and their Computer Simulation
Authors: Nakai Kiyomichi , Isobe Yusuke , Kinoshita Chiken , Shinohara Kazutoshi 
Published: June 2020

Induced spinodal decomposition under electron irradiation in a Ni-Au alloy has been investigated with respect to its basic mechanism and confirmed to be caused by the relaxation of coherent strain associated with modulated structure. Modulation of white-dots on structure images of modulated structure due to high-resolution electron microscopy is reduced with irradiation. In this paper the atom arrangement of the modulated structure is confirmed with computer simulation on the structure images, and the relaxation of the coherent strain is concluded to be due to the reduction of phase-modulation.Structure images of three-dimensional modulated structure along <100> were taken with the JEM-4000EX high-resolution electron microscope at the HVEM Laboratory, Kyushu University. The transmitted beam and four 200 reflections with their satellites from the modulated structure in an fee Ni-30.0at%Au alloy under illumination of 400keV electrons were used for the structure images under a condition of the spherical aberration constant of the objective lens, Cs = 1mm, the divergence of the beam, α = 3 × 10-4 rad, underfocus, Δf ≃ -50nm and specimen thickness, t ≃ 15nm. The CIHRTEM code was used for the simulation of the structure image.
Electron Microscopy/Diffraction Study of the Ternary Mn-Er-S System
Authors: Landa Canovas A. R. , Otero Diaz L.C. , White T. , Hyde B.G. 
Published: June 2020

X-Ray diffraction revealed two intermediate phases in the system MnS+Er2S3,:MnEr2S4= MnS.Er2S3, and MnEr4S7= MnS.2Er2S3. Their structures may be described as NaCl type, chemically twinned at the unit cell level, and isostructural with CaTi2O4, and Y5S7 respectively; i.e. {l13} NaCl twin band widths are (4,4) and (4,3).The present study was to search for structurally-related (twinned B.) structures and or possible disorder, using the more sensitive and appropiate technigue of electron microscopy/diffraction.A sample with nominal composition MnEr2S4 was made by heating Mn3O4 and Er2O3 in a graphite crucible and a 5% H2S in Ar gas flow at 1500°C for 4 hours. A small amount of this material was thenannealed, in an alumina crucible, contained in sealed evacuated silica tube, for 24 days at 1100°C. Both samples were studied by X-ray powder diffraction, and in JEOL 2000 FX and 4000 EX microscopes.
Staphylococcus aureus α-Toxin Crystals on Lipid Layers: Effects of Trypsin Treatment
Authors: Olofsson Anders , Hebert Hans , Kavéus Urban , Thelestam Monica 
Published: June 2020

α-toxin is a lethal, dermonecrotic, cytotoxic, and hemolytic protein which is secreted by most strains of Staphylococcus aureus . The biological effects are brought about by pertubation of membrane structures making them permeable to ions and small molecules. The structural basis for the mode of action is not known in detail. One hypothesis is that an oligomeric form of the toxin, observed both biochemically and by electron microscopy, circumscribe a hydrophilic pore through which transport can occur. Recent functional studies have demonstrated that oligomerization is a necessary but not a sufficient criterion for permeabilization. For example, trypsin treated α-toxin was, despite its lack of membrane damaging activity, able to form 200 kDa aggregates on mouse adrenocortical (Yl) tumor cells. In this work we have compared the structure of trypsin treated α-toxin with that of the intact toxin.α-toxin was purified from S. aureus strain wood 46 by isoelectric focussing and gel filtration. Tryptic toxin fragments (18 and 17 kD as determined by SDS-PAGE) were generated by digestion of native α-toxin (1 mg in 1.5 ml Tris buffered saline) with 30μg trypsin for 4 h at 37°C, pH 8.0. The reaction was terminated by the addition of 30μg lima beam trypsin inhibitor. Toxin specimens were applied to lipid layers pre-formed on carbon support films. Electron microscopy was performed after negative staining either with 1% Na-PTA (pH 7.0) or with a mixture of Na-PTA and glucose. Subsequent image processing of large coherent crystalline arrays produced correlation averaged projection maps. A three-dimensional model was obtained by collecting and combining data from tilted views.
Design of a 400KV Ultrahigh-Resolution Analytical TEM
Authors: Tsuno H. , Honda T. , Kokubo Y. 
Published: June 2020

The condenser-objective (C/O) lens proposed by Riecke, which has a very short gap length and small spherical aberration, was utilized for a commercial 200 kV ultrahigh resolution analytical TEM by Yanaka and Kaneyama. Fig. 1 shows the relation between theoretical resolution and objective lens (OL) spherical aberration coefficient (Cs) at accelerating voltages 200-1250 kV. It was reported that the Cs of a 400kV high resolution TEM is 1.0 mm and its resolution is 0.167 nm. The Cs of 400kV analytical TEM is 1.8 mm and the pre-field spherical aberration coefficient (Csp) is 1.8 mm. Fig. 2 (A), (B) show beam broading in specimens against the thickness when a 200kV and a 400kV electron beam transmit the specimen (C-Au), respectively. The broading of 400kV electron beam is about half of 200kV one. Then it is expected that spacial resolution of x-ray analysis improve. The above-captioned 400kV ultrahigh resolution analytical TEM is designed by applying a new technology which is adopted for a 200kV ultrahigh resolution analytical electron microscope, JEM-2010.Its fundamental construction is the same as the 400kV analytical electron microscope JEM-4000FX, except the 0L. The goniometer is a modified JEM-2010 goniometer, because it is too small for 400kV EM. Although it was expected that the focus ampere turn increases because of its short gap length, the objective lens coil used by JEM-4000EX/FX is adopted, because it has enough capacity. The shapes of the upper yoke and objective polepiece were calculated by the finite element method (55×110 Meshes) under the following condition: (1) maximum tilting-angle 10° (2) x-ray take-off angle 17.5° and solid angle 0.068 strad (3) minimized Cs.
Development of an Autofocus System in Tem
Authors: Ito T. , Kondo Y. , Mori S. , Watabe T. , Arai Y. 
Published: June 2020

An autofocus system has been developed by combination of a high-sensitivity TV camera, a 32-bit CPU with a frame memory, and TEM image wobbler function. Center-crossing line profiles of images, instead of 2D images, have been used for autofocusing, thus ensuring high speed autofocusing within 8∽24 seconds for the medium magnification range, × 2000 ∽ 50000.The image wobbler is a well-known function for a standard commercial TEM, and widely used for biological specimens. For autofocusing by using an image wobbler, the 2D image matching technique is extremely important, and some papers have been published. However, in image matching, image data has to be considered as large as 512×512×8 bits, thus requiring a long computation time. A new type of matching, line profile matching instead of image matching, can save much time and computer memory.
A New Computer Control System for the EM 910 Transmission Electron Microscope
Authors: Benner Gerd , Prinz Manfred , Bihr Johannes , Frey Josef 
Published: June 2020

Modern analytical electron microscopes must provide a multitude of illumination and imaging modes, a user-friendly operation and a high degree of flexibility. In addition a large number of monitoring and control functions must be performed. In the new Zeiss EM 910 this is achieved by a complete digitization of the instrument control system. The computer network comprises an AT-compatible system computer, 4 microprocessor-controlled subsystems and a flexible data and program memory. Two control panels and an interactive control monitor are used for operation of the instrument. A keyboard is integrated for data input.Fig. 1 shows a block diagram of the computer control of the EM 910. The integrated system computer with an 80286 processor and a clock frequency of 12 MHz controls and monitors the electron optics (lenses, deflection systems, stigmators). Specially developed interrupt-controlled parallel interfaces ensure rapid communication between the system computer and the 4 autonomous Z80 microprocessor-controlled subsystems. The subsystems are:1. gun subsystem which controls and monitors the high-voltage system;2. goniometer subsystem for control and operation of the motorized 4-axis eucentric goniometer;3. camera subsystem which controls the sheet film camera and the components required for exposure such as automatic screens and the shutter;4. vacuum subsystem for control of the vacuum system and monitoring the compressed air and water supply.
<310> Single-Crystal LaB6 as Thermal Field Emitter for Electron Microscope
Authors: Harada Ken , Nagata Haruto , Shimizu Ryuichi , Tanji Takayoshi , Yada Keiji 
Published: June 2020

Thermal field emission (T.F.E.) properties of single crystal LaB6 -tips has been investigated by observing emission patterns. Applying field evaporation technique we succeeded to get the clean pattern consisting of <310> spots with very good reproducibility. This investigation has led to conclusion;, the <310> spot is promising electron source of high brightness provided that the tip is operated at tip temperature∽ 1000-1050°C in vacuum of 10−9 Torr region.As a preliminary experiment of brightness-measurement, we mounted the <310> LaB6-tip in a commercial type TEM, JEM-100CX-FEG, attached with an electron gun system for T.F.E. of <100> W-tip, being operated at 10−9 Torr region without Schottky shield electrode. The LaB6-tip, however, can not be operated without the Schottky shield because thermionic emission (T.E.) from the LaB6-tip is considerably high even though the tip is operated at lower than ∽1000 °C. In the present experiment, therefore, we manufactured a Schottky shield electrode as shown in Fig.l and performed the measurement of brightness by setting the Schottky shield electrode, applied the same voltage as the tip since the electron gun system has no extra feed-throughs for bias-voltage.