bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microscopy of ceramics: Through the looking glass and out the other side
Authors: Hobbs Linn W. 
Published: June 2020

Because this exposition will be followed by nine distinguished symposium contributions detailing better than could any single individual the modern approaches to microscopical analysis of surfaces and interior microstructures of ceramic solids, I have thought it the wiser course to adopt an historical approach and identify those significant points of departure where substantial leaps were made in our understanding of ceramic materials through the application of microscopical techniques. Developments in two techniques are outlined here.The light microscope was developed in the Netherlands by Hans Jensen and his son Zacharias between 1590 and 1610. This was a compound microscope, consisting of two lenses, but it was the single lens microscope, extensively exploited by Anthony van Leeuwenhoek and Robert Hooke in the 17th century, that provided the first significant microscopical advances, notably in biology. In 1733 an English barrister, Chester More Hall, discovered that a compound lens comprising glass elements of different dispersion could correct the chromatic aberration which limited the resolution of the compound microscope, although the principle was not applied to microscopy until 1791; and not until 1830 that another barrister, Joseph Lister, set forth the principles underlying correction of spherical aberration.
High-resolution microscopy of ceramic surfaces
Authors: Bentley J. 
Published: June 2020

The characterization of ceramic surfaces plays an important role in understanding a wide variety of properties such as fracture, wear, crack initiation, oxidation, sintering, and thin film growth on substrates. Three major microscopies are employed to obtain nanometer-scale resolution of ceramic surfaces: scanning electron microscopy (SEM), (scanning) transmission electron microscopy (STEM or TEM) especially in the glancing-incidence reflection modes, and scanning tip microscopies - most notably atomic force microscopy (AFM). Each technique has its own set of characteristics, advantages, and disadvantages and is usually complementary to the others.Conventional SEM is quick and easy to implement. As a mature technique, the contrast mechanisms, although sometimes complex, are largely well understood; computer programs for image simulation are available. The technique is applicable to a wide range of materials and specimen sizes; usually, little specimen preparation is involved. Charging of electrically insulating ceramics has traditionally been overcome by coating but, at high resolution, the faithful representation of the structure then becomes of some concern.
Atomic morphology of the γ/γˊ interface
Authors: Fonda Richard W. , Jin Xuegen , Luzzi David E. 
Published: June 2020

Nickel-based superalloys are well known for their high temperature strength. These alloys consist of two phases, γ and γˊ, which in combination produce an alloy of higher strength than either phase alone. A significant factor in this strength increase is the interface between the two phases. The γ phase is a fcc solid solution of nickel, while the γˊ phase has a Ll2 structure based on Ni3Al. The difference in lattice parameter between these two phases is very small, producing large regions of coherent interface between the two phases. This interface between γ and γˊ was examined by high resolution electron microscopyThe nickel-based superalloy (René N4) was generously supplied by Dr. R. Field of GE Aircraft Engines. TEM samples were cut from this oriented single crystal, mechanically thinned, then electropolished in a solution of 10% perchloric acid in ethanol. A Philips 400T TEM was used for conventional imaging and a JEOL 4000EX was used for high resolution imaging.
TEM Study of Co/Pd and Co/Au Multilayers
Authors: De Veirman A.E.M. , Hakkens F.J.G. , Coene W.M.J. , den Broeder F.J.A. 
Published: June 2020

There is currently great interest in magnetic multilayer (ML) thin films (see e.g.), because they display some interesting magnetic properties. Co/Pd and Co/Au ML systems exhibit perpendicular magnetic anisotropy below certain Co layer thicknesses, which makes them candidates for applications in the field of magneto-optical recording. It has been found that the magnetic anisotropy of a particular system strongly depends on the preparation method (vapour deposition, sputtering, ion beam sputtering) as well as on the substrate, underlayer and deposition temperature. In order to get a better understanding of the correlation between microstructure and properties a thorough cross-sectional transmission electron microscopy (XTEM) study of vapour deposited Co/Pd and Co/Au (111) MLs was undertaken (for more detailed results see ref.).The Co/Pd films (with fixed Pd thickness of 2.2 nm) were deposited on mica substrates at substrate temperatures Ts of 20°C and 200°C, after prior deposition of a 100 nm Pd underlayer at 450°C.
Grain separation enhanced magnetic coercivity in Pt/Co multilayers.
Authors: Bertero G.A. , Sinclair R. 
Published: June 2020

Pt/Co multilayers displaying perpendicular (out-of-plane) magnetic anisotropy and 100% perpendicular remanent magnetization are strong candidates as magnetic media for the next generation of magneto-optic recording devices. The magnetic coercivity, Hc, and uniaxial anisotropy energy, Ku, are two important materials parameters, among others, in the quest to achieving higher recording densities with acceptable signal to noise ratios (SNR). The relationship between Ku and Hc in these films is not a simple one since features such as grain boundaries, for example, can have a strong influence on Hc but affect Ku only in a secondary manner. In this regard grain boundary separation provides a way to minimize the grain-to-grain magnetic coupling which is known to result in larger coercivities and improved SNR as has been discussed extensively in the literature for conventional longitudinal recording media.We present here results from the deposition of two Pt/Co/Tb multilayers (A and B) which show significant differences in their coercive fields.
Domains and domain nucleation in magnetron-sputtered CoCr thin films
Authors: Demczyk B. G. 
Published: June 2020

CoCr thin films have been of interest for a number of years due to their strong perpendicular anisotropy, favoring magnetization normal to the film plane. The microstructure and magnetic properties of CoCr films prepared by both rf and magnetron sputtering have been examined in detail. By comparison, however, relatively few systematic studies of the magnetic domain structure and its relation to the observed film microstructure have been reported. In addition, questions still remain as to the operative magnetization reversal mechanism in different film thickness regimes. In this work, the magnetic domain structure in magnetron sputtered Co-22 at.%Cr thin films of known microstructure were examined by Lorentz transmission electron microscopy. Additionally, domain nucleation studies were undertaken via in-situ heating experiments.It was found that the 50 nm thick films, which are comprised of columnar grains, display a “dot” type domain configuration (Figure 1d), characteristic of a perpendicular magnetization. The domain size was found to be on the order of a few structural columns in diameter.
HREM of electron-irradiated silicas
Authors: Qin L.C. 
Published: June 2020

Silica (SiO2) crystals exist in various polymorphs which have different densities and different crystal structures, such as quartz, tridymite, and cristobalite, though all of these have in common the network structure which is formed by corner-sharing of SiO4 tetranedra. All these structures are sensitive to electron irradiation. Amorphization occurs when they are irradiated by energetic electrons.In the present study three polymorphs of silica crystals, α-quartz, α-tridymite and α-cristobalite crystals2 were used as starting materials. Electron irradiation experiments were carried out in situ in the electron microscope. The structural changes of the specimens were monitored using high-resolution electron microscopy (HREM).The amorphization of α-quartz crystals was found to progress through two morphologies: (a) nucleation and growth of amorphous nuclei with a sharp boundary with the crystalline matrix (figure 1); and (b) crystallinity lost gradually and more uniformly. Figure 2 shows a series of HREM images showing the amorphization of a tridymite crystal.
TEM/HREM study of mechanical alloyed Cu-Zr powders
Authors: Chiou W. A. , Lin C. S. , Liu P. 
Published: June 2020

New technologies for the synthesis of materials with unique microstructures and properties have always been of great interest to materials scientists and engineers. It has recently been shown that the preparation of amorphous and nanocrystalline powders by mechanical alloying (MA) can be of great potential. While various mechanisms of amorphization have been proposed, the real process remains unclear. To understand the process/mechanism of amorphization and nanocrystalline formation, investigations of the interfacial regions between collided ball-milled elemental powders is essential. This paper presents an interfacial study of the agglomerated CuZr powders after ball milling.Samples of commercially produced (AESAR) fine-grained (325 mesh, or 44 μm) Cu (99.3 %) and Zr (99%) powders were weighed to a weight ratio of 1 : 1 (atomic ratio 1.4 : 1) as the starting materials. These powders were mixed together in a steel vial and ball-milled in a SPEX mixer/mill machine. All the process of powder loading/unloading and ball milling were done in an argon gas chamber.
Characterization of microwave-sintered ceramic composites
Authors: Zhang X. , Pan Y. , Meek T.T. 
Published: June 2020

Industrial microwave heating technology has emerged as a new ceramic processing technique. The unique advantages of fast sintering, high density, and improved materials properties makes it superior in certain respects to other processing methods. This work presents the structure characterization of a microwave sintered ceramic matrix composite.Commercial α-alumina powder A-16 (Alcoa) is chosen as the matrix material, β-silicon carbide whiskers (Third Millennium Technologies, Inc.) are used as the reinforcing element. The green samples consisted of 90 vol% Al2O3 powder and 10 vol% ultrasonically-dispersed SiC whiskers. The powder mixture is blended together, and then uniaxially pressed into a cylindrical pellet under a pressure of 230 MPa, which yields a 52% green density. The sintering experiments are carried out using an industry microwave system (Gober, Model S6F) which generates microwave radiation at 2.45 GHz with a maximum output power of 6 kW. The composites are sintered at two different temperatures (1550°C and 1650°C) with various isothermal processing time intervals ranging from 10 to 20 min.
Phase composition and local grain alignment at the Ag/superconductor interface in Ag-sheathed Bi-Sr-Ca-Cu-O tapes
Authors: Feng Yi , Larbalestier D.C. , Babcock S.E. , VanderSande J.B. 
Published: June 2020

Texturing of the superconductor phase and proximity to a sourse of silver appear to be crucial to the development of high critical current density tapes of the Bi-Sr-Ca-Cu-O (BSCCO) high-temperature superconductors, yet relatively little is understood about the mechanism(s) by which the [001] texture develops and the complex role that the silver sheath material plays. We have studied the phase composition, alignment, and bonding at the Ag/BSCCO interface for silver-sheathed tapes of both the 2212 and 2223 phases that have been processed under fundamentally different conditions. High-resolution TEM imaging revealed details of the interface that give insight into these important questions.Ag-sheathed BSCCO tapes with cation compositions Bi2Sr2CaCu2Ox (2212) and Bi1.8Pb0.4Sr2.0Ca2.2Cu3Ox (2223) were prepared by standard powder-in-tube methods. 2212 sample A was heat-treated at 920°C for 15 minutes to melt the superconductor core, then cooled at 240°C/h from 920°C to 840°C and annealed at 840°C for 70 hours.
AEM of a Ag-Y-Ba-Cu superconductor precursor material
Authors: Strutt A. J. , Simnad M. T. , Lavernia E. , Vecchio K. S. 
Published: June 2020

Analytical electron microscopy (AEM) has been used to characterize a Ag-rich superconductor precursor material whose composition (before oxidation) was based on 10 wt.% of a YBa2Cu3 alloy and 90 wt.% Ag, and the same material after an oxidation heat treatment of 690°C for 24 hours. The material had been produced by a melt spinning process as a metallic alloy to permit deformation of the material (in the metallic state) prior to subsequent oxidation to form the ceramic superconducting Y-Ba-Cu oxide phase.The microstructure was characterized using a Philips CM30 AEM, at 300 kV, using specimens thinned to electron transparency by ion-milling. Energy dispersive X-ray spectroscopy (EDX) was performed using the same instrument, with a Link Analytical solid-state X-ray detector with an ultra-thin window.In the as-formed condition, the Y-Ba-Cu alloy phase exists as discrete particles at the triple points of the relatively fine (approx. 250 nm.)
A high-resolution fraunhofer in-line electron holography
Authors: Matsumoto Takao , Tanji Takayoshi , Tonomura Akira 
Published: June 2020

In-line holography is advantageous in terms of contrast in imaging weak phase objects. However, most of the recent articles on electron holography had an off-axis configuration employing an electron biprism and were applied successfully only to objects with a rather strong phase shift such as magnetic flux and thin crystals. When it comes to the observation of considerably weak phase object, the off-axis method fails. We applied Fraunhofer in-line electron holography to observe an undecagold cluster, the core of which has a diameter of 0.82 nm, and obtained a high resolution image with high contrast that has been obtained neither by off-axis electron holography nor by conventional transmission electron microscopy.A Hitachi HF-2000 electron microscope equipped with a 200-kV cold field emission gun was used during the experiment. The specimen, Monoamino-Undecagold (NanoProbes, Inc., Stony Brook, N.Y.), was prepared in a highly dispersive form on a thin carbon film supported by a thick holey carbon film.
The effect of core size on the holographic interference images of superconducting fluxons in tilted specimens
Authors: Pozzi G. , Bonevich J.E. , Tonomura A. 
Published: June 2020

Recently, observations of quantized flux lines in thin superconducting specimens have been successfully carried out in transmission electron microscopy by means of standard methods of Lorentz microscopy and also by electron holography. The breakthrough with respect to the previous unsuccessful attempts is represented by the fact that the specimen is observed tilted with respect both to the electron beam and the ancillary magnetic field that is used to introduce and stabilize the fluxons in the specimen.Although a reduction of the phase difference with respect to the optimum situation of fluxons perpendicular to the beam is expected in this set-up, it has nonetheless been possible to ascertain by means of a simple model that this reduction is not below the detectability limit that can be reached by the most advanced phase sensitive methods available today in electron optics, such as electron holography. However calculations have been carried out so far either for the single fluxon case, taking into account also its core structure, or for an array of 25 flux tubes (i.e. fluxons with negligible core size) arranged in a triangular lattice.
Electron diffraction analysis using a personal computer
Authors: Sutliff J. A. , Notis M. R. 
Published: June 2020

The analysis of electron diffraction patterns (EDPs) by manual calculation is difficult in two important cases. The first is when there are many phases that must be included in the search for a pattern’s solution. The second is when, due to the structure of the phases being considered, many solutions for a pattern are possible. In these cases, it is very time consuming to ensure that all possible solutions are found and that the best solution is chosen. A computer can provide tremendous help for the EDP analyst in these situations. Through its ability to make rapid calculations and display data graphically, a computer can relieve the analyst of much of the work involved in a thorough electron diffraction analysis.In analyzing EDPs a standard procedure is adopted. The analyst first assembles a data base of phases that could be present in the sample being studied. Tables of interplanar spacings and interplanar angles are calculated from crystal structure data on each phase. The positions of spots on experimental patterns are then recorded and radii from the transmitted beam spot to diffracted beams’ spots are measured. Ratios of radii and angles between radii are tabulated.
Development of imaging plate for a TEM and its characteristics
Authors: Mori N. , Oikawa T. , Harada Y. , Miyahara J. , Matsuo T. 
Published: June 2020

The Imaging Plate (IP) is a new type imaging device, which was developed for diagnostic x ray imaging. We have reported that usage of the IP for a TEM has many merits; those are high sensitivity, wide dynamic range, and good linearity. However in the previous report the reading system was prototype drum-type-scanner, and IP was also experimentally made, which phosphor layer was 50μm thick with no protective layer. So special care was needed to handle them, and they were used only to make sure the basic characteristics. In this article we report the result of newly developed reading, printing system and high resolution IP for practical use. We mainly discuss the characteristics of the IP here. (Precise performance concerned with the reader and other system are reported in the other article.)Fig.1 shows the schematic cross section of the IP. The IP consists of three parts; protective layer, phosphor layer and support.
Development of 350-KV holography electron microscope equipped with magnetic type field-emission electron gun
Authors: Endo J. , Kawasaki T. , Masuda T. , Tonomura A. 
Published: June 2020

A field-emission electron gun is one of the most epoch-making technologies in an electron microscopic world. In a transmission electron microscope, a high brightness of this beam has been effectively employed for electron-holographic measurements, though the value is not still high enough. Development of a higher brightness beam will promise to open up unattained application possibilities of electron holography such as high resolution and high sensitivity interferometry.We developed the field emission electron microscope for electron holographic applications. Special attentions were paid for high brightness, large beam current and easy operation. Figure 1 is a schematic diagram of the electron gun. In order not to deteriorate the original high-brightness feature of the beam by the aberrations in the gun and the condenser lenses, a magnetic lens was installed between the tip and the extraction anode so that the total aberration effect might be minimized. Field emitted electron beam is converged by the magnetic and the electrostatic lenses, and accelerated in a ten-stage accelerator which is made of porcelain.
A direct measurement of diffusion jump frequency in amorphous materials using VTR-high resolution electron microscopy
Authors: Iijima Sumio 
Published: June 2020

Intensity fluctuation in HREM granular images of amorphous thin films such as spattered C and Si films has long been noticed among electron microscopists. The granular images are continuously moving as if they were a bunch of living worms. The origin of the fluctuations is believed to be caused by a charging up effect on the film surface. The present paper introduces for this first time the phenomena using a TV image recording system.An amorphous oxide thin film used in the present experiment was formed by decomposing a portion of a Tl2Ba2CaCu2O8 superconductor oxide crystal under electron beam irradiation. The structure of the film may be a random network built up by metal-oxygen polyhedra. The HREM images were recorded at a direct magnification 1.2 × 106 times on a real-time TV camera (Getan 622) attached on an electron microscope (ABT-002B, 200keV, Cs 0.4mm, resolution 0.2nm).
A confocal laser scanning microscope for fluorescence and reflection at video rates
Authors: Houpt P.M. , Draaijer A. 
Published: June 2020

In confocal microscopy, the object is scanned by the coinciding focal points (confocal) of a point light source and a point detector both focused on a certain plane in the object. Only light coming from the focal point is detected and, even more important, out-of-focus light is rejected.This makes it possible to slice up optically the ‘volume of interest’ in the object by moving it axially while scanning the focused point light source (X-Y) laterally. The successive confocal sections can be stored in a computer and used to reconstruct the object in a 3D image display.The instrument described is able to scan the object laterally with an Ar ion laser (488 nm) at video rates. The image of one confocal section of an object can be displayed within 40 milliseconds (1000 х 1000 pixels). The time to record the total information within the ‘volume of interest’ normally depends on the number of slices needed to cover it, but rarely exceeds a few seconds.
Tandem scanning confocal light microscopy as compared with x-ray diffraction for characterizing the behavior of clays in fluid-saturated petroleum reservoir rock
Authors: Stuart C.J. , Viani B.E. , Walker J. , Levesque T.H. 
Published: June 2020

Many techniques of imaging used to characterize petroleum reservoir rocks are applied to dehydrated specimens. In order to directly study behavior of fines in reservoir rock at conditions similar to those found in-situ these materials need to be characterized in a fluid saturated state.Standard light microscopy can be used on wet specimens but depth of field and focus cannot be obtained; by using the Tandem Scanning Confocal Microscope (TSM) images can be produced from thin focused layers with high contrast and resolution. Optical sectioning and extended focus images are then produced with the microscope. The TSM uses reflected light, bulk specimens, and wet samples as opposed to thin section analysis used in standard light microscopy. The TSM also has additional advantages: the high scan speed, the ability to use a variety of light sources to produce real color images, and the simple, small size scanning system. The TSM has frame rates in excess of normal TV rates with many more lines of resolution. This is accomplished by incorporating a method of parallel image scanning and detection. The parallel scanning in the TSM is accomplished by means of multiple apertures in a disk which is positioned in the intermediate image plane of the objective lens. Thousands of apertures are distributed in an annulus, so that as the disk is spun, the specimen is illuminated simultaneously by a large number of scanning beams with uniform illumination. The high frame speeds greatly simplify the task of image recording since any of the normally used devices such as photographic cameras, normal or low light TV cameras, VCR or optical disks can be used without modification. Any frame store device compatible with a standard TV camera may be used to digitize TSM images.