bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth and morphology of NaCl-type crystals prepared by various methods
Authors: Saito Yoshio , Kaito Chihiro , Maeda Shigeo 
Published: June 2020

NaCl type crystals generally grow a cube. NaCl-type crystals with rhombic prism shape have been found among the cube crystals. No convincing interpretation for the rhombic prism crystals has been given. The growth mechanisms of some crystals have been clarified by means of potetial energy calculations in previous papers. In the present paper, free energy of NaCl type crystals having various shapes have been calculated in order to make clear the origin of the appearing of the rhombic prism crystals. The growth mechanism is discussed on the basis of the free energy.NaCl crystals were grown from aqueous solution in a glass made growth cell thermostated with circulating water(±l⋅C). The NaCl crystals were grown at temperature of 50°C which is equivalent to the supersaturation of 2%. The grown crystals were mounted on a net and were dried with a filter paper as quickly as possible. The specimens were examined by a microscope. PbS crystals are prepared by the two-heater method which have been developed to produce ultrafine particles of low melting materials. The detail of the preparation has been shown in a previous paper. The grown crystals collected on a carbon film supported by an electron microscope grid were observed with a Hitachi H-9000 electron microscope.
EM studies of long-lived fiber gels complemented by solid state 2H-NMR spectroscopy
Authors: Svenson Sönke 
Published: June 2020

Aqueous gels (1%) consisting of the amphiphilic N-octyl-D- gluconamide (D-Glu-8) usually crystallize within a few hours.They remain stable for more than five months if 0.4% of sodium dodecylsulfate (SDS) is added. It was shown by electron microscopy that the gels are formed by helical fibers of at least bimolecular thickness (4 nm) and of several micrometers length. Randomly dispersed particles with a mean diameter of 5 nm, which are assumed as micelles, were also observed on micrographs (Fig.1).To provide evidence for this assumption and to rule out the possibility of artefacts introduced by the preparative method, we applied an additional technique, namely solid state 2H-NMR spectroscopy. The spectra point out the temperature dependent equilibrium between “solid” fibers and micelles, as represented by the Pake powder spectrum and the isotropic central singlet (Fig.2). The micellar part of the equilibrium is strongly enhanced in the presence of detergents such as SDS. High concentrations of SDS micelles extend the gel’s lifetime, presumably because these micelles dissolve the crystallization nuclei of D-Glu-8 and thus, prevent further crystal growth.
Characterising scale-breakdown mechanisms during high-temperature oxidation using EM
Authors: Rowley P .N. , Brydson R. , Little J. A. , Saunders S. R. J. 
Published: June 2020

The microstructure and chemical composition of oxide films formed during the initial stages of high temperature oxidation have long been recognised as having a major effect on subsequent scaling behaviour. For example, the development of thick (>lμm) duplex scales on Fe-Cr alloys is assumed to occur via a mechanism of pore and fissure formation in the initial oxide (Atkinson, Tomlinson and Cory.) However, this process has rarely been observed using electron microscopy.The investigation of the oxidation behaviour of Fe-9Cr alloys in high temperature steam gives an insight into these scale breakdown processes. Within 3 minutes of the onset of oxidation, significant breakdown of the initially formed thin film occurs due to the development of readily visible fissures and pores at oxide grain boundaries (figure 1). This leads to the ready ingress of oxidant and the rapid development of a thick duplex Fe3O4/(Fe,Cr)3O4 oxide with a thin outer layer of α-Fe2O3 (figure 2). The extremely porous nature of this scale allows further inward diffusion of molecular oxidant, thereby instituting the continued growth of (Fe,Cr)3O4 at the scale/metal interface.
The crystallography characteristic of (Mn,Fe)S single crystal
Authors: Xishan Jiang 
Published: June 2020

This paper reports the growth step pattern and morphology at equilibrium and growth states of (Mn,Fe)S single crystal on the wall of micro-voids in ZG25 cast steel by using scanning electron microscope. Seldom report was presented on the growth morphology and steppattern of (Mn,Fe)S single crystal.Fig.1 shows the front half of the polyhedron of(Mn,Fe)S single crystal,its central area being the square crystal plane,the two pairs of hexagons symmetrically located in the high and low, the left and right with a certain, angle to the square crystal plane.According to the symmetrical relationship of crystal, it was defined that the (Mn,Fe)S single crystal at equilibrium state is tetrakaidecahedron consisted of eight hexagonal crystal planes and six square crystal planes. The macroscopic symmetry elements of the tetrakaidecahedron correpond to Oh—n3m symmetry class of fcc structure,in which the hexagonal crystal planes are the { 111 } crystal planes group,square crystal plaits are the { 100 } crystal planes group. This new discovery of the (Mn,Fe)S single crystal provides a typical example of the point group of Oh—n3m.
TEM study on fine carbide precipitates and dislocation cell structure
Authors: Chen Mengzhe , Wang Siqin , Ke Jun 
Published: June 2020

A series of investigations have been conducted into the nature and origin of the dislocation cell structure. R.J.Klassen calculated that the dislocation cell limiting size in pure ferrite matrix is about 0.4 μm. M.N.Bassion estimated the size of dislocation cell in deformed ferrite of HSLA steels to be of the same order.In this paper, TEM observation has been concentrated on the interaction of fine carbide precipitates with dislocation cell structure in deformed Fe-C-V (0.05%C, 0.13% and 0.57%V) and Fe-C-Nb (0.07 %C and 0.04%Nb) alloys and compared with that in Fe-C (0.05%). Specimens were austenitized at 1500 “C/20 min and followed by isothermal treatment at 750 °C and 800 “C for 20, 40 and 120 minutes . The carbide particle sizes in these steels are from 9 to 86nm measured from carbon extraction replicas. Specimens for TEM were cut from differently deformed areas of tensile specimens deformed at room temperture. The thin foils were jet electropolished at -20 C in a solution of 10% perchloric acid and 90% ethanol. The TEM observation was carried out in JEM 100CX , EM420 at 100kv and JEM 2000FX at 200kv.
Devitrification products of rapidly solidified Ni-Nb amorphous alloys.
Authors: Bertero G. A. , Hofmeister W.H. , Evans N.D. , Wittig J.E. , Bayuzick R.J. 
Published: June 2020

Rapid solidification of Ni-Nb alloys promotes the formation of amorphous structure. Preliminary results indicate promising elastic properties and high fracture strength for the metallic glass. Knowledge of the thermal stability of the amorphus alloy and the changes in properties with temperature is therefore of prime importance. In this work rapidly solidified Ni-Nb alloys were analyzed with transmission electron microscopy (TEM) during in-situ heating experiments and after isothermal annealing of bulk samples. Differential thermal analysis (DTA), scanning electron microscopy (SEM) and x-ray diffraction (XRD) techniques were also used to characterize both the solidification and devitrification sequences.Samples of Ni-44 at.% Nb were electromagnetically levitated, melted, and rapidly solidified by splatquenching between two copper chill plates. The resulting samples were 100 to 200 μm thick discs of 2 to 3 cm diameter. TEM specimens were either ion-milled or alternatively electropolished in a methanol-10% sulphuric acid solution at 20 V and −40°C.
Deformation and fracture behavior of an Al-Li-Cu-Mg-Zr alloy 8090
Authors: Jiang D.M. , Hong B.D. 
Published: June 2020

Aluminum-lithium alloys have been recently got strong interests especially in the aircraft industry. Compared to conventional high strength aluminum alloys of the 2000 or 7000 series it is anticipated that these alloys offer a 10% increase in the stiffness and a 10% decrease in density, thus making them rather competitive to new up-coming non-metallic materials like carbon fiber reinforced composites.The object of the present paper is to evaluate the inluence of various microstructural features on the monotonic and cyclic deformation and fracture behaviors of Al-Li based alloy. The material used was 8090 alloy. After solution treated and waster quenched, the alloy was underaged (190°Clh), peak-aged (190°C24h) and overaged (150°C4h+230°C16h). The alloy in different aging condition was tensile and fatigue tested, the resultant fractures were observed in SEM. The deformation behavior was studied in TEM.
Domain structures in rapidly solidified Mn76Fe4Si20 alloys
Authors: Zhou D. S. , Cao W. , Jin Z.X. , Ye H.Q. 
Published: June 2020

In the study course of microstructures of the rapidly quenched Mn-Si alloy, 45° rotation twins showing striking eightfold symmetry in the electron diffraction pattern have been reported. These previous investigations interpreted the domain structures in terms of the β-Mn phase. The aim of this work is to show the similar domain structure having pseudo-eightfold symmetry in the reciprocal space in the Mn-Fe-Si system and to ascertain a new structure in the domain structure.The main phase in this alloy is the β-Mn phase with primitive cubic and a=0.63 nm. Fig.l gives the [001] HR image of the β-Mn phase where a square unit cell has been outlined. A planar fault showing projected rectangle network was also seen.The short edge of the rectangle remains to be the same as the a axis of the p-Mn phase, while its long side is equal to . The planar fault could appear repeatedly and form domain structure as shown in Fig.2.
TEM of twinning in alpha and beta phase plutonium
Authors: Zocco T. G. , Sheldon R. I. , Rizzo H. F. 
Published: June 2020

Twinning in α and β phase Pu has been studied by Transmission Electron Microscopy (TEM) to experimentally determine active twinning systems in this complex metal. Twinning in alpha phase Pu was studied in 2 specimens including a triode sputter deposited film, and a partially transformed (α+δ phase) Pu nominally lwt% Ga alloy. A thick film of metastable beta phase was also obtained by triode sputter deposition. Phase identification of all samples was determined from x-ray diffraction patterns. Alpha phase has a monoclinic crystal structure with 16 atoms per unit cell and a P21/m space group. Beta phase has a body-centered monoclinic crystal structure with 34 atoms per unit cell and an I2/m space group.Parent/twin orientation relationships were determined by electron diffraction pattern analysis, stereographic projection analysis and fundamental crystallographic calculations.A computer program was also developed to search for all possible twinning systems in α Pu.
Microstructural study of dispersed phase ceramic Bn-AlN composite coatings by chemical vapor deposition
Authors: Freeman G. B. , Lee W. Y. , Lackey W. J. 
Published: June 2020

Dispersed phase ceramic composites have recently received much attention because of their superior mechanical properties including fracture toughness, strength, hardness, resistance to wear and erosion. Chemical vapor deposition (CVD) offers one avenue of preparing ceramic composites by simultaneous deposition of multiple phases, i.e. codeposition. The major advantage of preparing dispersed phase ceramic composites by CVD is that mechanical as well as chemical, electrical, optical, and thermal properties of the composites can be favorably tailored by controlling the composites’ composition and microstructure via variation and optimization of CVD process variables such as temperature, pressure, reagent concentration, substrate type, reactor geometry, etc.In this study, the codeposition of boron nitride (BN) and aluminum nitride (AlN) was explored because the BN+AlN composite system (as a deposited coating) offers the promise of tailoring properties such as friction coefficient, hardness, and resistance to wear and erosion for possible radome, electromagnetic window and tribological applications.
Direct observation of microstructural changes in ion-beam modified ceramics
Authors: Grant Norton M. , Fleischer Elizabeth L. , Hertl William , Mayer James W. , Barry Carter C. 
Published: June 2020

A technique for the direct observation of microstructural changes in ceramics following ion- implantation is presented. Ion-implantation produces modifications to the mechanical properties of ceramic surfaces. These modifications have been investigated as a means of improving the hardness and wear of such materials. Examples of these changes will be presented for single-crystal specimens of MgO which have been implanted with Xe+ ions. The resultant microstructural changes are a function of ion fluence and are related to structural modifications at or near the surface.Transmission electron microscopy (TEM) is a powerful technique for examination of microstructure on a nanometer scale. A problem often encountered when conventional methods of specimen preparation, for TEM analysis, are used is the possibility of ion-beam induced damage. Ion-beam damage can be a serious problem especially in the preparation of MgO specimens. In the present study damage resulting from ion-milling can be entirely avoided by ion-implantation directly into an electron-transparent thin-foil specimen.
An electron diffraction study of the tetragonal— monoclinic transformation in 12 mole% ceria-zirconia
Authors: Hugo G.R. , Muddle B.C. , Hannink R.H.J. 
Published: June 2020

The tetragonal (t) ↔ monoclinic (m) transformation occurring in 12 mole% CeO2-ZrO2 is a source of significant transformation plasticity and transformation toughening in this ceramic material. The t↔m transformation is martensitic in nature and a quantitative understanding of the transformation plasticity and transformation toughening requires that the crystallography of this martensitic transformation be understood in detail. Crystallographic characteristics of a martensitic phase transformation are:1. the existence of a unique lattice correspondence between the phases, which specifies the directions in the product crystal lattice into which any given directions in the parent crystal lattice are transformed,
2. a fixed orientation relationship preserved between parent and product phases, and
3. the orientation of the habit plane or interface plane between the parent and product phases.For the t↔m transformation occurring in ceria-zirconia, three possible lattice correspondences are plausible.
TEM studies of tweed microstructures in annealed amelia albite
Authors: Kim Y. J. , Henderson D. M. 
Published: June 2020

Natural Amelia albite (Ab99.3An0.1Or0.6) annealed at 1073° and 924°C for various periods up to 140 days has been studied by NMR. TEM studies of the same sample revealed a distinct tweed microstructure in some samples annealed at both 1073°C and 924°C. On the whole, the quasi-regular tweed has a periodicity of 100 - 200 Å in both directions, one nearly normal to b* and the other approximately parallel to b*, which gives rise to two-directional streaking in SADP’s (Fig. 1 and 2). However, there are some differences in the tweed structure developed on annealing at 1073°C and at 924°C in albite.Albite samples annealed at 1073° show a systematic trend in their development of tweed structures: the regularity, periodicity, and frequency of occurrence increase with annealing time during the first 3 days, and then decrease gradually until no tweed microstructures are seen in samples annealed for more than 15 days. The tweed structure proceeds locally to form one-directional twin-like microstructures.
Characterization of grain boundary phases in Si3N4 sintered using Y-Si-Al-O-N additives
Authors: Koehler C. , Thomas G. 
Published: June 2020

The usefulness of silicon nitride as a high temperature ceramic can be limited by the presence of amorphous phases at the grain boundaries. Dense silicon nitride ceramics are produced using pressureless sintering of Si3N4 with Y-Si-Al-O-N additives. When these additives are left as a glassy phase at the grain boundaries and triple grain junctions, the mechanical properties at elevated temperatures are weakened due to these low viscous glasses. Post-sintering heat treatments and close compositional control can be effective in transforming the glass into crystalline phases at the grain boundaries thereby increasing the refractoriness.To optimize high temperature mechanical properties, processing must be controlled not only to fully crystallize the grain boundaries but also to avoid certain unstable secondary phases whose oxidation leads to large molar volume changes which causes possible cracking. Transmisssion electron microscopy and x-ray microanalysis (EDS) are significant methods to characterize the amorphous grain boundary pockets and to identify the crystalline grain boundary phases.
Contributions of Electron Microscopy to Environmental Science
Authors: Fisher Robert. M. 
Published: June 2020

Heightened concern about the environment, and particularly the increasing rate of dispersion of toxic substances and irritants has placed severe demands on analytical techniques to define the nature and occurrence of potentially hazardous constituents and devise control technologies as well as to determine the risk to human life. In many cases, environmental contamination involves the presence of very fine particulates, which may pose some health risk in their own right or may simply serve as carriers for hazardous chemicals that fall within the respirable range, i.e. 10 microns or less in major dimension. Electron microscopy, widely used to observe and identify fine particulates in the atmosphere, has already contributed significantly to environmental science but advances in instrumentation are needed to overcome technical and economic limitations to its use.Sources of Environmental ParticulatesAtmosphere particulates, popularly considered to originate primarily from heavy industrial operations such as mining, primary metal production or power generation, can also come from natural sources such as volcanoes, forest fires, silt residue from flooding, and botanical emissions (spores, pollen). Paniculate pollutants also derive from smoking, debris from road wear of automobile and truck tires, fragmentation of asbestos-containing insulation and building materials, food processing, earth moving operations, open burning of agricultural residues and waste dumps and unfiltered emissions from incinerators.
Atomic-Resolution Imaging in the STEM
Authors: Liu J. 
Published: June 2020

Scanning transmission electron microscopy (STEM) instruments offer a variety of important imaging and diffraction techniques for characterizing materials and for investigating electron beam specimen interactions. Microdiffraction patterns and electron energy loss spectra can be obtained with a probe size about 1-1.5 nm in diameter. Secondary electron images with a resolution approaching the probe size ( 0.5 nm) can be obtained in STEM instruments. Atomic resolution images can also be obtained with bright-field (BF) imaging mode by phase contrast or with high-angle annular dark-field (HAADF) imaging mode by atomic number contrast. We report here some recent results on high resolution imaging of crystal structures in the STEM.Phase contrast BF STEM lattice fringes can be obtained by placing a detector at any position of the Ronchigram fringe patterns (shown in figure 1a), formed in the diffraction plane with large convergence of the electron beam incident along a principle zone axis of a single crystal. The image interpretation is similar, due to the reciprocity theorem, to that of the conventional HRTEM images. The image contrast depends on defocus, sample thickness and lens aberrations. Figure 1b shows a BF STEM structural image of a GaAs/InAlAs/InGaAs multiple-quantum-well (MQW) crystal projected along the [110] zone axis. This image reveals the interfaces with weak contrast. Although some information about the interfacial structures can be obtained (e.g., interfaces indicated by arrow A seem abrupt while that indicated by B seems diffuse), chemical interpretation at the atomic scale across the interfaces seems unlikely without performing rigorous image simulation.
HREM of Rapidly Solidified Al-Li-Zr Based Alloys
Authors: Radmilovic V. , Thomas G. , Kilaas R. , Kim N. J. 
Published: June 2020

During aging of Al-Li-Zr based alloys δ'(Al3Li) precipitates heterogeneously around β'(Al3Zr), forming so-called composite precipitate[l-4], that has important effects on the mechanical behavior of these alloys. As has been observed in several investigations, the addition of small amount of Zr results in a fairly large volume fraction of β' in the microstructure, and this suggests that there may be a partitioning of Li in the β'. In the present investigation, high resolution electron microscopy (HREM) and image simulation have been used to perform detailed characterization of the chemistry and structure of β' precipitate.The alloy Al-3Li-1Cu-0.5Mg-0.5Zr (wt.%) has been heat treated as follows: a) solution treatment at 550°C for 2 hours and water quenching, b) aging treatment at 150°C for 4 hours or at 200°C for 8 hours and c) 10% cold working followed by aging at 175°C for 64 hours. HREM images were taken on a JEOL ARM electron microscope operating at 400 and 800kV. Simulated HREM images of the composite δ'/β' precipitate were calculated using CEMPAS multislice program described by Kilaas[5].
Theoretical and Experimental Analyses of the Effects of Composition and Strain on Image Contrast in High-Resolution Transmission Electron Microscopy
Authors: Sundo D.F. , Howe J.M. 
Published: June 2020

Although the effects of composition and strain on amplitude-contrast images in the TEM have been thoroughly developed, similar theory does not exist for phase-contrast images and only a few specific situations have been treated. The purpose of this research is to develop a quantitative understanding of the effects of composition and strain on phase-contrast images and to test this theory experimentally. A simple defect which can cause both a local change in composition and strain is a substitutional atom. Hence, this defect is treated first, with the expectation that results from this analysis can be extended to predict image contrast from larger defects under certain imaging conditions.X-ray scattering theory indicates that diffuse scattering from point defects due to composition and strain is linearly additive. For small defect concentrations, the scattered intensity Sdiff(k) is given by:
Electron Microscopy of Alcohol Oxidase Crystals from Pichia Pastoris
Authors: Vonck Janet , van Bruggen Ernst F.J. 
Published: June 2020

Several yeast species are able to grow on methanol. When they are grown in a methanol-restricted culture, their peroxisomes contain large crystalline inclusions, consisting of alcohol oxidase (AOX). A monomer of AOX has a molecular weight of ca. 74,000. Inside the peroxisome, AOX occurs as octamers.Electron microscopic studies of AOX from Hansenula polymorpha have revealed that the eight subunits are slightly elongated and form two layers of four, which are twisted relative to each other. The molecule measures ca. 12 nm in all directions.Recently, crystals suitable for x-ray diffraction have been formed of AOX from Pichia pastoris . The space group is P21, with unit cell dimensions a=157.3Å, b=171.45Å, c=231.6Å, β=94°. These dimensions indicate that the unit cell contains four octamers, too much to solve by x-ray crystallography alone. Therefore, we have started an EM study of the crystals, to get information about the organization of the molecules in the crystal lattice.