bluuebunny/crossref_metadata_2025_split huggingface dataset:
The microstructure change of low-carbon electrical steels by residual aluminum
Authors: Hou C.K. , Hu C.T. , Lee Sanboh 
Published: June 2020

The fully processed low-carbon electrical steels are generally fabricated through vacuum degassing to reduce the carbon level and to avoid the need for any further decarburization annealing treatment. This investigation was conducted on eighteen heats of such steels with aluminum content ranging from 0.001% to 0.011% which was believed to come from the addition of ferroalloys.The sizes of all the observed grains are less than 24 μm, and gradually decrease as the content of aluminum is increased from 0.001% to 0.007%. For steels with residual aluminum greater than 0. 007%, the average grain size becomes constant and is about 8.8 μm as shown in Fig. 1. When the aluminum is increased, the observed grains are changed from the uniformly coarse and equiaxial shape to the fine size in the region near surfaces and the elongated shape in the central region. SEM and EDAX analysis of large spherical inclusions in the matrix indicate that silicate is the majority compound when the aluminum propotion is less than 0.003%, then the content of aluminum in compound inclusion increases with that in steel.
Solidification of alternative phases in submicron spheres of pure nickel
Authors: Lin Hong-Ming , Kelly Thomas F. 
Published: June 2020

Alternative phases which are other than the most stable crystalline phase can be formed from highly supercooled liquids. Phase selection occurs during nucleation which is strongly affected by the extent of supercooling. A large supercooling in the liquid is generally needed in order to nucleate alternative phases. Supercooling will increase with suppression of heterogeneous nucleation and with increasing cooling rate. Thus, high cooling rate and isolation of the heterogeneous catalytic sites should be simultaneously reaLized in order to achieve large supercooling. From a practical point of view, production of very small liquid droplets in high vacuum using electrohydrodynamic (EHD) atomization is a very effective way to achieve large liquid supercoolings.Seventeen pure elements have been studied previously by using the electrohydrodynamic (EHD) process. The results show that pure nickel forms an amorphous phase in the smallest (< 10 nm diameter) submicron spheres.
Microstructures of Ni3Al alloys as a function of Cr and Al levels
Authors: Horton J.A. , Liu C.T. 
Published: June 2020

Several alloys based on boron-doped Ni3Al are undergoing alloy development for a wide range of potential uses. The microstructures of several of these alloys were characterized by transmission electron microscopy as a function of the chromium and aluminum levels. The series included alloys with 0 to 10 at. % Cr and with 15.6 to 21% Al, see Table I.In Ni-AI alloys with low aluminum content and in most Ni-Al alloys with chromium additions, a twophase γ’ plus γ structure resulted. The major phase (and matrix) was ordered γ’ and the minor phase disordered γ· Both phases appeared interconnected and were completely epitactic. The ordered phase was aluminum-enriched while the disordered phase was chromium-enriched. Within the disordered phase a reprecipitation of γ’ often occurred, depending on heat treatment, and gave an appearance of a “disordered web”. Typical x-ray energy dispersive spectroscopic (EDS) analyses are listed in Table II.
Dislocations in B2 ordered alloys
Authors: Baker I. 
Published: June 2020

Intermetallic compounds are currently the subject of considerable research effort because of their possible structural applications, particularly at high temperature. The B2 structure, sometimes called L20, ordered body-centered cubic or CsCl-type, is the simplest ordered structure an AB-type compound can adopt. Nevertheless, three different dislocation Burgers’ vectors are found, namely <100>, <110> and <111>, depending on the compound and the temperature of deformation. Only <100> and <111> are normally observed at lower temperatures. For example, figure 1 shows <100> slip in PdIn and <111> slip in FeAl. An important practical difference between <111> and <100> slip is that the latter provides only three independent slip systems and, thus, can lead to only limited general plastic flow in a polycrystal.At low temperature, why <100> or <111> slip occurs is not wholly clear, although there have been several attempts at rationalizing the experimentally observed slip vectors. Rachinger and Cottrell made the first attempts at rationalization when they used a nearest-neighbor model to estimate a critical ordering energy above which <100> slip would operate and below which <111> slip was presumed to occur.
Sectorized crystallization of higher n-alkanes: A high resolution search for oblique chain packing
Authors: Dorset D. L. , Wittmann J. C. , Lotz B. , McConnell C. H. , Fryer J. R. , Zemlin F. 
Published: June 2020

Although it was once thought that a major distinction between paraffin and polyethylene lozenge crystals was the sectorization of the latter due to polarization of chain fold surfaces, a recent study has shown that n-paraffins longer than C44H90, but with unfolded chains, also crystallize as sectorized lozenges (Fig. 1) with bright field fringes running along <130> compared to the <130> direction in polyethylene. High resolution electron microscopy and microdiffraction of corrugated polyethylene lozenges, furthermore, have shown that, for the infinite chain folded polymer, these fringes correspond to local oblique chain packings. Although shadowing with C-Pt indicates that the sectorized paraffin lozenges are not corrugated like polyethylene, it was thought that chain obliquity, nevertheless, should also be the cause of the Bragg fringe contrast in Fig. 1.An attempt was made to visualize the detail directly using the SULEIKA cryomicroscope at the Fritz Haber Institute in Berlin, given our previous success in obtaining 2.5Å resolution images of the C44H90 chain packing.
A remarkable property of the angular distribution of plural inelastic scattering, with benign consequences for the deconvolution of electron energy-loss spectra
Authors: Egerton R.F. , Liou S.-H. 
Published: June 2020

Electrons which have been inelastically scattered two or more times during passage through a thin specimen are known to be distributed more broadly in angle than those which are scattered only once. However, the literature contains no simple guide or analytical formula for the plural-scattering angular distribution. We decided to calculate this distribution by two-dimensional self-convolution of the single-scattering angular distribution, taking the latter to be a Lorentzian function: with characteristic angle ΘE and with an abrupt cut-off of the intensity at scattering angle Θ = Θc.The results are given in Fig. 1 in integral form: Fn(β) is the fraction of the electrons (which have been scattered n times) collected by an on-axis aperture of semi-angle β. Also shown in Fig. 1 are dashed curves representing the square and cube of F1. The close correspondence between the calculated points (F2 and F3) and the dashed curves is noteworthy. Similar agreement was obtained for cut-off angles in the range 50ΘE to 200ΘE, typical of most materials.
TEM observation of cylindrite
Authors: Wang Su 
Published: June 2020

Cylindrite, approximately FePb3Sn4Sb2S14, contains two different types of layers, pseudo-tetragonal(t-lattice) with PbS structure and pseudo-hexagonal (h-lattice) with SnS2 structure. The two kinds of layers are superimposed in the order of htht.., and the repeat periodicity is a. In the past only the composite SAED pattern corresponding to the b*c* plane of the two lattices was obtained as shown in Fig. 1a. Now we have succeeded, by careful tilting, in taking separate SAED patterns and HREM images of these two lattices(Figs. 2 and 3). The CBED pattern containing two [100] zone axes indicates: , as shown in Fig. lb.In the SAED patterns shown in Figs. 2, 3 and 4, each main reflection is accompanied by a row of satellite spots caused by the common structural modulation of the two lattices shown by the dark bands inthe HREM images. The rows of satellites, defined by q, in general donot parallel to any axes defined by the main reflections. In the q direction, the additional long-range periodicity corresponding to the satellites and the basic periodicity of both lattices are incommensurate.
A Transmission Electron Microscopic study of the densification of 10:90 colloidal silica: Alkali silicate sol-gels
Authors: Kerch H. M. , Gerhardt R. A. , Grazul J. L. 
Published: June 2020

The sintering behavior of a low density 10:90 wt% colloidal silica: potassium silicate sol-gel is being investigated. This material is of technological interest because of its ease of processing, high purity and relatively low sintering temperature. Porous structures are most frequently characterized by mercury penetration porosimetry and B.E.T. sorption technique. The underlying theory of both these procedures assume a priori knowledge of the pore geometry. Conversely, microscopic analysis allows direct observation of the pore network provided sample preparation does not alter the structure. To this end, the techniques of ultramicrotomy and Pt/C replication were adopted.Specimen preparation for ultramicrotomy is described elsewhere. All thin-sectioning was performed with a D.D.K. diamond knife using a distilled water media. The replicas were produced by a Balzers 301 freeze etch apparatus at a vacuum of 1 X 10-7 Torr. Platinum was evaporated at a thickness of 2.5 nm at 45° followed by a 15 nm layer of carbon deposited at 90°. The replicas were retrieved by immersing the gel in HF with a distilled water rinse. Both ultramicrotomed sections and replicas were collected onto carbon coated 400 mesh grids. All micrographs were taken on a JEOL 100CX in bright field mode.
Transmission Electron Microscopy of Epitaxial silicides grown by ultra high vacuum deposition
Authors: Loretto D. , Gibson J. M. , Yalisove S. M. 
Published: June 2020

The silicides CoSi2 and NiSi2 are both metallic with the fee flourite structure and lattice constants which are close to silicon (1.2% and 0.6% smaller at room temperature respectively) Consequently epitaxial cobalt and nickel disilicide can be grown on silicon. If these layers are formed by ultra high vacuum (UHV) deposition (also known as molecular beam epitaxy or MBE) their thickness can be controlled to within a few monolayers. Such ultrathin metal/silicon systems have many potential applications: for example electronic devices based on ballistic transport. They also provide a model system to study the properties of heterointerfaces. In this work we will discuss results obtained using in situ and ex situ transmission electron microscopy (TEM).In situ TEM is suited to the study of MBE growth for several reasons. It offers high spatial resolution and the ability to penetrate many monolayers of material. This is in contrast to the techniques which are usually employed for in situ measurements in MBE, for example low energy electron diffraction (LEED) and reflection high energy electron diffraction (RHEED), which are both sensitive to only a few monolayers at the surface.
A generalized Kambe approximation for transmission electron diffraction
Authors: Zuo J. M. 
Published: June 2020

The methods used by Kambe to treat nonsystematic three-beam interaction have been extended to a more general case, in which there are two groups of reflections, gi (i = 1..n) and hi (i = 1..m). Each reflection has strong interactions with reflections in its own group and weak interactions with reflections in another group. ThusPractical cases of interest are (i) parallel rows of reflections in the ZOLZ and (ii) HOLZ and ZOLZ groups. In the following we will develop an approximate intensity expression for reflections, hi, with weak coupling to the incident beam. We assign g1 = 0 as the incident beam. This intensity expression can be used to describe the intensity distribution in CBED disks of nonsystematic reflections for cases (i) and (ii) above.Many-beam dynamical electron diffraction in RHEED with reflections gi and hi is described by
Reflection Electron Microscopy (REM) observation of () planes of α-Al2O3 single crystals
Authors: Kim Yootaek , Hsu Tung 
Published: June 2020

The surfaces of α-Al2O3(R-Surfaces) which are used as substrates for the growth of SOS (Silicon on Sapphire) were investigated with the REM technique. Most of the studies using TEM and SEM have been centered on SOS interfaces but only limited studies have been conducted on surfaces of sapphire before the growth of Si. The purpose of this paper is to show that surfaces have different distributions of steps and facets as compared to the (0001) and surfaces which are characterized by large atomically flat areas separated by steps that are several atomis high.Specimens were obtained from Sapphikon Inc., NH. Polished and cleaned faces were observed before and after annealing at 1400°C for 24 hrs in air. All observations were carried out using a JEOL-JEM 200CX microscope at 100kV.
Phase identification and defect structures in II-IV-V2 heteroepitaxial semiconductor thin films grown on III-V substrates
Authors: Posthill J.B. , Xing G.C. , Solomon G.S. , Bachmann K.J. , Timmons M.L. 
Published: June 2020

The ternary chalcopyrite-structure compound semiconductors (space group , Fig. 1) offer several promising materials properties that may be useful in electronic and optoelectronic devices. These compounds have a wide range of direct and pseudodirect band gaps, and they generally lattice match well to available substrates for heteroepitaxial growth. However, before the properties of this class of materials can be fully exploited, specific issues pertaining to the crystal growth (both bulk and epitaxial) must be understood and optimized. This contribution briefly describes some of our microstructural studies of heteroepitaxial ZnGeAs2-on-GaAs(100) and ZnGeP2-on-GaP(100) grown by organometallic chemical vapor deposition (OMCVD).The details of OMCVD growth of these materials are described in detail elsewhere. Cross-section [110] samples for transmission electron microscopy (TEM) were held at reduced temperature using a liquid nitrogen cooled stage to minimize the deleterious effects of Ar+ ion bombardment during final thinning. Diffraction contrast and phase contrast (HRTEM) imaging was accomplished at 200 kV.
HREM at orthogonal projections of GaAs islands on silicon
Authors: Ponce F. A. , Hetherington C. J. D. 
Published: June 2020

HREM studies typically examine only one projection of a structure and information in the electron beam direction is lost. In most cases, the structure in this direction is uniform and already known, but in others a second projection needs to be observed. This could involve preparing a second specimen sectioned at right angles to the first, or as described here, tilting a specimen through ±45° and observing the same volume in orthogonal projections. The specimen used here was of GaAs islands on <001> silicon, examined in the Atomic Resolution Microscope at LBL.In the effort to grow defect-free GaAs films on silicon substrates, understanding of the early stages of growth is required. For this experiment we chose a specimen of ultra-thin GaAs grown on silicon substrate by metal-organic chemical vapor deposition (MOCVD). The GaAs was grown at 550°C for a nominal thickness of20nm from trimethyl gallium and arsine sources.The growth conditions lead to three-dimensional growth of islands bound by {111}A planes, terminated on Ga layers.
A computer-control program for TEM in situ fatigue experiments
Authors: Vecchio Kenneth S. , Hunt John A. 
Published: June 2020

In-situ experiments conducted within a transmission electron microscope provide the operator a unique opportunity to directly observe microstructural phenomena, such as phase transformations and dislocation-precipitate interactions, “as they happen”. However, in-situ experiments usually require a tremendous amount of experimental preparation beforehand, as well as, during the actual experiment. In most cases the researcher must operate and control several pieces of equipment simultaneously. For example, in in-situ deformation experiments, the researcher may have to not only operate the TEM, but also control the straining holder and possibly some recording system such as a video tape machine. When it comes to in-situ fatigue deformation, the experiments became even more complicated with having to control numerous loading cycles while following the slow crack growth. In this paper we will describe a new method for conducting in-situ fatigue experiments using a camputer-controlled tensile straining holder.The tensile straining holder used with computer-control system was manufactured by Philips for the Philips 300 series microscopes. It was necessary to modify the specimen stage area of this holder to work in the Philips 400 series microscopes because the distance between the optic axis and holder airlock is different than in the Philips 300 series microscopes. However, the program and interfacing can easily be modified to work with any goniometer type straining holder which uses a penrmanent magnet motor.
Studies of phase transformation of Fe1-xS by in Situ TEM
Authors: Nguyen Thao A. , Hobbs Linn W. 
Published: June 2020

The transformation from Fe1-xS (IC) phase to a mixture of FeS (2C) and iron poor Fe1-xS (IC) phases has been investigated by a series of in-situ heating experiments. The purpose of this study is to resolve the controversy over the mechanism of phase transformation (spinodal decomposition versus nucleation and growth) and to explain the different microstructures observed in the two phase mixture of FeS and Fe1-xS (Figure 1).In-situ heating experiments were carried out using a JEOL JEM EM-SHTH double tilt heating holder. Synthetic “single” Fe0.97S crystals were cut into 3 mm disks, mechanically and ion thinned to electron transparency. In all cooling experiments, the sample was first held at 390 K, a temperature above the transition temperature in order to generate an initial single phase material; then, the temperature was quickly reduced to the temperature of interest.Figure 2a shows the development of a lamellar type microstructure after the sample's temperature was reduced from 390 K to 363 K and then held at this temperature for ten minutes. At 363 K, the undercooling is 27 K. The troilite FeS (2C) phase heterogeneously nucleates and grows along the edge of the sample. Diffraction analysis shows that the FeS (2C) phase is embedded in the iron-poor Fe1-x,S matrix with a rod-like structure.
Radiation-induced amorphization of intermetallic compounds
Authors: Okamoto P. R. 
Published: June 2020

Many ordered intermetallic compounds become amorphous when irradiated at low temperatures with energetic particles. There is still no fundamental understanding of why some compounds but not others are susceptible to amorphization. However, recent studies indicate that a progressive loss of chemical long-range order (LRO) is a necessary, though not a sufficient condition for the crystal-to-glass transformation. To shed further light on the role of chemical disordering, our work has focused on correlating the structural effects of chemical disorder on the shear modulus of a number of LI2, B2, and A-15 type intermetallic compounds under irradiation conditions where some become amorphous and others remain crystalline.The Brillouin scattering technique was used to measure the change in the velocity of sound (Vs) relative to that of the unirradiated state (Vos) in Zr3Al, FeAl, FeTi, NiAl, and Nb3Ir during irradiation at 298 K with 1-MeV Kr+ ions. The corresponding changes in the Bragg-Williams LRO parameter (S/So), and lattice expansion (Δa/ao) were measured by means of electron diffracting during in-situ irradiation with 1-MeV Kr in the ANL high voltage electron microscope.
Utilization of a high-speed x-ray analysis system with a SEM
Authors: Sandborg A. O. , Anderhalt R. W. 
Published: June 2020

A high speed x-ray analysis system has been developed using a scanning electron microscope(SEM) with an energy dispersive spectrometer(EDS). In this system digital beam control is combined with other microscope control from the EDS system. The EDS system has specially designed software to allow a full quantitative analysis to be performed in fractions of a second. This allows several novel forms of analysis, such as fully quantitative x-ray maps and analysis of non-homogeneous specimens. Due to the high speed of the software, conventional intensity x-ray maps are made into quantitative maps, during the process of acquiring them. Non-homogeneous samples are analysed by randomly positioning the beam on the sample, doing a full analysis, then moving the beam to a new point. When this procedure is repeated many times, the specimen is sampled in a way to produce a true average analysis.Background and peak overlap corrections must be applied to obtain net elemental intensities from the EDS spectrum. It is impractical to store a full spectrum at each analysis location of the map, so the corrections must be made “on the fly”. Normally it requires tens of seconds to obtain net elemental intensities and to convert these to concentrations with a ZAF technique. In this work these times have been reduced to 100 milliseconds by the use of optimized programming of the various correction procedures.
Direct measurement of electron-diffraction-pattern intensities using an energy loss spectrometer
Authors: Jackson A. G. , Rowe M. 
Published: June 2020

Diffraction intensities from intermetallic compounds are, in the kinematic approximation, proportional to the scattering amplitude from the element doing the scattering. More detailed calculations have shown that site symmetry and occupation by various atom species also affects the intensity in a diffracted beam. [1] Hence, by measuring the intensities of beams, or their ratios, the occupancy can be estimated. Measurement of the intensity values also allows structure calculations to be made to determine the spatial distribution of the potentials doing the scattering. Thermal effects are also present as a background contribution. Inelastic effects such as loss or absorption/excitation complicate the intensity behavior, and dynamical theory is required to estimate the intensity value.The dynamic range of currents in diffracted beams can be 104or 105:1. Hence, detection of such information requires a means for collecting the intensity over a signal-to-noise range beyond that obtainable with a single film plate, which has a S/N of about 103:1. Although such a collection system is not available currently, a simple system consisting of instrumentation on an existing STEM can be used as a proof of concept which has a S/N of about 255:1, limited by the 8 bit pixel attributes used in the electronics. Use of 24 bit pixel attributes would easily allowthe desired noise range to be attained in the processing instrumentation. The S/N of the scintillator used by the photoelectron sensor is about 106 to 1, well beyond the S/N goal. The trade-off that must be made is the time for acquiring the signal, since the pattern can be obtained in seconds using film plates, compared to 10 to 20 minutes for a pattern to be acquired using the digital scan. Parallel acquisition would, of course, speed up this process immensely.