bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Electron Microscopical study of an incoloy 800H pipe used in the petrochemical industry
Authors: Tekin Erdoğan 
Published: June 2020

Alloy 800 is a family of fully austenitic Fe-Ni-Cr alloys containing minor amounts of C, Al and Ti. These alloys are used for high temperature applications as they have good creep properties.Incoloy 800H is a high carbon version (0.07%C) and is used extensively in the petrochemical industry. Most of the information on incoloy 800H concerns microstructural changes that occur below 850°C and there is hardly any study available on the microstructural effects at or above 900°C. The present study was carried out to determine the microstructural effects that are produced at service temperatures of 960-970°C.Specimens were prepared from 2 different pipe samples: One in the as-received condition and the other had been in service for over 4 years at 960-970°C. The SEM specimens were examined in a JEOL 840A model SEM having attachments for x-ray point analysis and elemental x-ray mapping.
Micropore structure of carbon by HREM and adsorption
Authors: Fryer J.R. , Innes R.W. , Stoeckli H.F. 
Published: June 2020

Investigations have been undertaken on a series of microporous carbons, using both the technique of high resolution electron microscopy(HREM) and of immersion calorimetry. The combined use of these methods in elucidating the micropore size distribution, has enabled us to measure the interaction radius of an adsorbate molecule and show that the radius is reduced on adsorption within a micropore, as was previously suggested from theoretical calculations of Everett and Powl . The data obtained in the present work, however, shows that the reduction is greater than previously thought.A series of carbons,of differing degrees of burn-off, were prepared from a soft wood precursor, by activation in a fluidised bed reactor using carbon dioxide at 850°C. Micropore size distributions were obtained from these carbons by the technique of immersion calorimetry. This technique involves the exposure of the surface to molecules of different sizes,so that the heat evolved indicates the extent to which the molecules were capable of entering and adsorbing into micropores.
The microstructure of ultrafine carbonyl iron powder
Authors: Lin X. W. , Chen L. M. , Zhu Jing 
Published: June 2020

Carbonyl iron powder has a wide application in the electrical and magnetic industry. In this paper a ultra-fine carbonyl iron powder (UFCIP) of about 20nm in size was examined by CTEM, EELS, HREM and microdiffraction on JEOL—2000FX operating at 200kv. The UFCIP was suspended in ultrasonically agitated alcohol before it was spreaded on a micromesh.Two types of particles exist in that UFCIP as shown in Fig. 1. The larger particles ranging from 50 to 80 nm are zeta—Fe2N, that was identified by microdiffraction. The majority of the UFCIP particles ranging from 5 to 30 nm in diameter were determined to be Fe3O4 and alpha—Fe by the selected area diffraction. At higher magnification it was found that there are two kinds of fine powder in smaller particles: one has a dark core and another one has a bright core. The microdiffractions with a probe of about 6nm in diameter were performed, it indicated that the dark core is the particles of alpha—Fe enclosed in 5nm thick skin of polycrystalline Fe3O4 as shown in Fig. 2 and that the particles with a bright core are composed of polycrystalline gamma—Fe2O3. The HREM images in Fig. 3a and 3b were taken from a same particle but had two orientations with about 10 degree difference related to the incident beam, as the particle was rotated, the bright core remained visible and a round core became an elliptical core.
HREM study of Fe—pillared smectite
Authors: Hansen P.L. , Bender Koch C. , Mørup S. 
Published: June 2020

During the process of pillaring smectite, a metal oxide precursor is introduced into the interlayer space of the layered clay mineral. By subsequent heating of the precursor, a metal oxide forms, increasing the interlayer spacing 0.5—1.0 nm, as observed in XRD.Pillaring of clays increases the active surface area, and the materials may find use as molecular sieves and catalysts.Most of the information on the oxide pillars has been derived from indirect spectroscopic and structural methods. In the present study we have used HREM to obtain direct evidence for the pillar formation.
TEM study on the formation and charge stabilization of nanosized colloidal particles
Authors: Liu Jun , Sarikaya Mehmet , Shih Wan Y , Shih Wei-Heng , Aksay Ilhan A. 
Published: June 2020

Spherical colloidal silica particles of uniform size are formed through aggregation. This observation contradicts the well-accepted concept that aggregation must be inhibited to produce monosized colloidal particles. In an attempt to explain this dilemma, the present work was undertaken to address the following questions: (i) why do particles form aggregates first and then break into small particles in later stages, (ii) what determines the final particle size, and (iii) why do final particles have a narrow size distribution.Colloidal gold particles, which were produced by reducing gold chloride with sodium citrate in dilute aqueous solution, were the chosen system. The particles were studied by TEM at different stages of the formation process with a Phillips EM 430T at 300 kV. The TEM samples were prepared by transferring a small amount of the solution onto a TEM copper grid covered with a carbon film and the excess water was removed immediately by filter paper. During the formation stages, the mobility of the particles was also monitored by electrophoretic light scattering.
Studies of copper selenide ultrafine particles by newly developed gas evaporation method
Authors: Kaito Chihiro , Saito Yoshio 
Published: June 2020

The direct evaporation of metallic oxides or sulfides does not always given the same compounds with starting material, i.e. decomposition took place. Since the controll of the sulfur or selenium vapors was difficult, a similar production method for oxide particles could not be used for preparation of such compounds in spite of increasing interest in the fields of material science, astrophysics and mineralogy. In the present paper, copper metal was evaporated from a molybdenum silicide heater which was proposed by us to produce the ultra-fine particles in reactive gas as shown schematically in Figure 1. Typical smoke by this method in Ar gas at a pressure of 13 kPa is shown in Figure 2. Since the temperature at a location of a few mm below the heater, maintained at 1400° C , were a few hundred degrees centigrade, the selenium powder in a quartz boat was evaporated at atmospheric temperature just below the heater. The copper vapor that evaporated from the heater was mixed with the stream of selenium vapor,and selenide was formed near the boat. If then condensed by rapid cooling due to the collision with inert gas, thus forming smoke similar to that from the metallic sulfide formation. Particles were collected and studied by a Hitachi H-800 electron microscope.Figure 3 shows typical EM images of the produced copper selenide particles. The morphology was different by the crystal structure, i.e. round shaped plate (CuSe;hexagona1 a=0.39,C=l.723 nm) ,definite shaped p1 ate(Cu5Se4;Orthorhombic;a=0.8227 , b=1.1982 , c=0.641 nm) and a tetrahedron(Cu1.8Se; cubic a=0.5739 nm). In the case of compound ultrafine particles there have been no observation for the particles of the tetrahedron shape. Since the crystal structure of Cu1.8Se is the anti-f1uorite structure, there has no polarity.
High-resolution imaging of symmetric tilt and mixed character boundaries in Al
Authors: Shamzuzzoha M. , Deymier P.A. , Smith David J. 
Published: June 2020

The determination of the core structure of grain boundaries is central to a better understanding of the properties of polycrystalline materials. With the recent advent of intermediate-voltage electron microscopes (300-400kV), it is possible to obtain atomic-resolution images of grain boundaries in many metals - for example, the atomic structure of periodic grain boundaries in selected metals has been studied. Our knowledge of materials properties can be further enhanced by investigating more complex, arbitrarily misoriented grain boundaries. In this paper, we will report HREM imaging of a symmetric tilt low-angle grain boundary and a twist-and-tilt (mixed character) grain boundary in Al.The Al bicrystals used in this study were produced by cross-rolling and annealing methods described in detail elsewhere. Thin foil specimens of 3mm diameter containing specific boundaries were obtained by spark-cutting and subsequent electropolishing in 73% methanol, 25% nitric acid and 2% hydrochloric acid. HREM was performed with a JEM-4000EX operated at 400kV, using axial illumination and without an objective aperture. High-resolution electron micrographs were recorded near the optimum defocus, typically at a magnification of 500,000 times.
Crystal structures and transformation of Cu-Se and Ag-Te in solid-solid reactions
Authors: Hirota Yoshihiro , Isshiki Toshiyuki , Shiojiri Makoto 
Published: June 2020

Cu-Se and Ag-Te crystals which grew by solid-solid reactions of vacuum-deposited metal and chalcogen films were investigated with a JEM 200-CX electron microscope (Cs= 1.2 mm), with the aid of image simulation and optical diffraction.Fig. 1 shows an image of a slender crystal observed 10 days after an amorphous Se film was mounted on a holey Cu film. The image in A matches with a calculated image shown in Fig. 2a. The calculation was carried out for a CuSe crystal (P63/mmc, a=0.394, c=1.725 nm) 20 nm thick, with the a-axis relatively tilted at 1° about the [012] axis to the incident electron beam, at an underfocus of Δf=50 nm. The optical diffractogram from the image of the area A was used for the calibration of the distance in the optical diffractograms from the other areas B∼ E. The crystal in B formed before the formation of the CuSe crystal.
Electron channelling contrast imaging of dislocations
Authors: Czernuszka J.T. , Long N.J. , Hirsch P.B. 
Published: June 2020

In the 1970s there was considerable interest in the development of the electron channelling contrast imaging (ECCI) technique for imaging near surface defects in bulk (electron opaque) specimens. The predictions of the theories were realised experimentally by Morin et al., who used a field emission gun (FEG) operating at 40-50kV and an energy filter such that only electrons which had lost no more than a few 100V were detected. This paper presents the results of a set of preliminary experiments which show that an energy filter system is unneccessary to image and characterise the Burgers vectors of dislocations in bulk specimens. The examples in the paper indicate the general versatility of the technique.A VG HB501 STEM with a FEG was operated at l00kV. A single tilt cartridge was used in the reflection position of the microscope. A retractable back-scattered electron detector was fitted into the secondary electron port and positioned to within a few millimetres of the specimen. The image was acquired using a Synoptics Synergy framestore and digital scan generator and subsequently processed using Semper 6.
Atomic resolution Z-contrast imaging of bulk crystal surfaces in Scanning Reflection Electron Microscopy
Authors: Wang Z. L. , Bentley J. 
Published: June 2020

The success of obtaining atomic-number-sensitive (Z-contrast) images in scanning transmission electron microscopy (STEM) has shown the feasibility of imaging composition changes at the atomic level. This type of image is formed by collecting the electrons scattered through large angles when a small probe scans across the specimen. The image contrast is determined by two scattering processes. One is the high angle elastic scattering from the nuclear sites,where ϕNe is the electron probe function centered at bp = (Xp, yp) after penetrating through the crystal; F denotes a Fourier transform operation; D is the detection function of the annular-dark-field (ADF) detector in reciprocal space u. The other process is thermal diffuse scattering (TDS), which is more important than the elastic contribution for specimens thicker than about 10 nm, and thus dominates the Z-contrast image. The TDS is an average “elastic” scattering of the electrons from crystal lattices of different thermal vibrational configurations,
A search-match program for materials identification in the Transmission Electron Microscope using electron diffraction pattern analysis
Authors: Vale S.H. 
Published: June 2020

A program has been written for an energy dispersive x-ray microanalysis system computer to identify a sample by combining data from an electron diffraction pattern collected in a TEM with chemical information from the sample. The combined information is compared with a large database held on the computer to find a suitable set of matching compounds.The program was written for a Link Analytical AN10000 microanalysis system which is based on a computer with a 16 bit word length, 20 MHz CPU with 512 kbyte of memory for programs and data, 40 Mbyte hard disk and a 512 × 512 pixel colour image display with its own memory. The database used was the NBS/SANDIA/ICDD electron diffraction database adapted for the AN 10000 computer. This database contains about 70000 compound entries and occupies 9 Mbyte of disk space.
Structure refinements in M7C3 (M=Cr,Fe) carbide
Authors: He A.Q. , Ye H.Q. , van Tendeloo G. , Kuo K.H. 
Published: June 2020

The crystal defects in M7C3 (M=Cr,Fe) have been investigated by electron microscopy. The results show that there exist a lot of planar defects such as antiphase boundaries, and twin boundaries in it. According to Rouault et al., the structure of Cr7C3 is orthorhombic but based on a hexagnoal sublattice with a=0.701, b=1.214, c=0.452nm, i. e b/a=. For a perfect hexagonal sublattice the defects in {110} would be invisible both in electron diffraction patterns and in electron microscopic images when detected exactly along [001], So, these defects in M7C3 were observed by diffracted contrast method in which electron beam tilts a little from c axis or by HREM image with special beam direction but not [001] zone.e have found however in our sample the strcture of the M7C3 is probably orthorhombic but b/a≠3, such that no hexagnoal sublattice. A structure based on a non-hexagnoal lattice which produces twining is no longer invisble along [001] by HREM.Powder of M7C3 carbide was extracted by electricity chemistry from a cast-iron superalloy. The composition (wt) is: Cr-24.94%, Ni-20%, Mn-0.43%, Si-1.42%, S-0.017%, P-0.017%, C-0.41%. It was collected by carbon grid, and examined in JEOL 200CX.
High-temperature high-resolution in-situ microscopy of grain boundary migration and structure change
Authors: Ichinose Hideki , Kizuka Tokuji , Ishida Yoichi 
Published: June 2020

A high resolution high temperature specimen stage of 200kV HRTEM was newly designed and produced in order to investigate the physical and mechanical nature of materials at high temperature.The atomic process of silicon grain boundary migration and the structure change was successfully observed in-situ at 1000K by the new specimen stage.The high temperature specimen stage consists of a heating specimen holder, a high stability power supply and a high stability current controller. Heat is provided by an induction free double spiral coil heater which is made of tungsten. Excellent current stability, better than 10−6 , prevents the objective lens from the magnetic disturbance which is caused by heating current. The highest temperature of the specimen is designed to be 1100K. The accuracy of the temperature measurement is checked by the melting test of tin. In order to keep the high resolution of the microscope(JEM-200CX) at such high temperature as 1100K an objective lens is also newly designed and produced. Aberration constants of the new lens are respectively Cs=0.7mm and Cc=1.2mm. Resulted resolution at high temperature is as same level as the that of the original JEM-200CX at room temperature. Images are recorded by a video tape recorder.
Environmental cell studies of deformation and fracture
Authors: Birnbaum H. K. , Robertson I. M. 
Published: June 2020

Studies of the effects of hydrogen environments on the deformation and fracture of fcc, bcc and hep metals and alloys have been carried out in a TEM environmental cell. The initial experiments were performed in the environmental cell of the HVEM facility at Argonne National Laboratory. More recently, a dedicated environmental cell facility has been constructed at the University of Illinois using a JEOL 4000EX and has been used for these studies. In the present paper we will describe the general design features of the JEOL environmental cell and some of the observations we have made on hydrogen effects on deformation and fracture.The JEOL environmental cell is designed to operate at 400 keV and below; in part because of the available accelerating voltage of the microscope and in part because the damage threshold of most materials is below 400 keV. The gas pressure at which chromatic aberration due to electron scattering from the gas molecules becomes excessive does not increase rapidly with with accelerating voltage making 400 keV a good choice from that point of view as well. A series of apertures were placed above and below the cell to control the pressures in various parts of the column.
An in situ TEM study of nucleation and growth of the Ω phase in an Al-4.0Cu-0.5Mg-0.5Ag alloy
Authors: Garg A. , Howe J. M. 
Published: June 2020

Addition of small amounts of Ag to Al-Cu-Mg alloy with high Cu:Mg ratios stimulates precipitation of a new phase, designated Ω, which has an orthorhombic structure and forms as thin coherent hexagonal plates on {lll} α planes. This phase significantly increases the age hardening characteristics of the alloy, particularly at elevated temperatures. The mechanism of nucleation of Ω phase is not known but is believed to be fundamentally different from that of θ’ and S’ phases which also form in these alloys. The presence of Ag and Mg only in trace quantities makes the problem of finding the actual mechanism of nucleation of Ω phase difficult.An in situ hot stage TEM study was conducted on an Al-4.0Cu-0.5Mg-0.5Ag(wt.%) alloy in order to understand the nucleation and growth behavior of Ω phase. Two types of initial microstructures were used: 1) homogenized, solution-treated and cold water-quenched, 2) as-quenched and aged for 1 hr. at 190°C. The as-quenched structure shown in Fig. 1(a) consists of a high density of small dislocation loops, some helical dislocations and a few straight dislocations. When this foil was heated in the microscope, observable precipitation occured at about 205°C.
Structural properties of GaAs/InGaAs/GaAs (001) and InGaAs/GaAs (001) heterostructures and correlation with electronic properties
Authors: Bonar J.M. , Hull R. , Malik R. , Ryan R. , Walker J.F. 
Published: June 2020

In this study we have examined a series of strained heteropeitaxial GaAs/InGaAs/GaAs and InGaAs/GaAs structures, both on (001) GaAs substrates. These heterostructures are potentially very interesting from a device standpoint because of improved band gap properties (InAs has a much smaller band gap than GaAs so there is a large band offset at the InGaAs/GaAs interface), and because of the much higher mobility of InAs. However, there is a 7.2% lattice mismatch between InAs and GaAs, so an InxGa1-xAs layer in a GaAs structure with even relatively low x will have a large amount of strain, and misfit dislocations are expected to form above some critical thickness. We attempt here to correlate the effect of misfit dislocations on the electronic properties of this material.The samples we examined consisted of 200Å InxGa1-xAs layered in a hetero-junction bipolar transistor (HBT) structure (InxGa1-xAs on top of a (001) GaAs buffer, followed by more GaAs, then a layer of AlGaAs and a GaAs cap), and a series consisting of a 200Å layer of InxGa1-xAs on a (001) GaAs substrate.
A study of lattice distortion in GexSi1-x, superlattice by convergent beam electron diffraction
Authors: Xiaofeng Duan , Fung K. K. , Chu Y. M. 
Published: June 2020

Strained-layer superlattice GexSi1-x/Si have received much attention because of their potential applications. Convergent beam electron diffraction has been used to study strains and composition modulation in semiconductor superlattices. In this paper we report the result of a study of GeSi/Si superlattice sample with mismatch = 2% and composition and strain modulation wavelength = 30nm. The sample has been grown at temperature 470 °C on (001) Si substrate by molecular beam epitaxy (MBE), with a Si buffer layer of thickness ≈ l00nm. The sublayer thickness are tGeSi=5nm and tSi=25nm. The number of period is 20. The CBED patterns were obtained by operating Philips EM420 at 100kV.Fig.l shows a XTEM bright field image of a GeSi superlattice specimen. The interface between the GeSi layer and the Si substrate is even and clear. Also the interfaces between the sub-layers of GeSi and Si in superlattice are good. Only a few defects are visible near the bottom of the superlattice( pointed by arrow 1). Its look like microtwins.
Stereoscopic observation and determination of surface orientation of voids in stress-thermal-migrated aluminium lines of LSI with UHVEM
Authors: Ura Katsumi , Takaoka Akio , Nishino Akira , Mori Hirotaro 
Published: June 2020

The ultra-high voltage electron microscope (UHVEM) HU-2000 is a powerful tool for the observation of multilayer devices such as LSI. By using the method of stereo-microscopy, we can determine the shape and orientation of each crystal under the passivation layer. We applied it to the observation of voids in the stress-thermal-migrated aluminium lines of LSI. The acceleration voltage was 2 MV.Figure 1 shows the structure and dimension of the specimen. After the processes of these layers, the specimen was annealed at 450°C for 15 min and cooled slowly; then, the voids are generated by the stress- and thermal-induced migration. The two types of specimens for UHVEM are prepared; the passivation layer is removed by dry etching (Fig.2) and not removed (Fig.3). The voids are always observed at the grain boundary and the top side (the passivation side) of voids is wider than its bottom side. This suggests that the tension from the passivation layer is much stronger than from the substrate. The void surface is formed by some facets and its inclination angle is usually 60°∼°. The orientation of the facet is (111) in most cases as shown in Figs.2 and 3. This result agrees with the fact that the surface (111) for Al has a minimum surface energy.
Fracture analysis of soldered wire by plasma ashing and SEM
Authors: Narayan P.B. 
Published: June 2020

The increasing demand for higher quality and reliability in the computer peripherals industry requires that the components function without premature materials failure. SEM has been found to be an indispensable technique for studies leading to improved materials and processes. Because of the variety of materials used, SEM specimen preparation requires continuing innovation.Low temperature oxygen plasma-ashing was found to be a convenient technique to remove organic resins and other hydrocarbons. A gaseous plasma, consisting of neutral, energized and ionized atoms, is created by sending oxygen through a high voltage electric field. The plasma readily reacts with the hydrocarbons forming gaseous carbonaceous by-products. The addition of argon to oxygen provides sputter-etching and a more effective resin removal. The temperature of the specimen rarely goes above 50°C and so it is called low temperature gas plasma. The plasma does not alter surfaces or bulk properties of metals and ceramics.