bluuebunny/crossref_metadata_2025 huggingface dataset:
A morphological and energy-dispersive x-ray spectroscopy (EDS) investigation of separator-grade cellophane
Authors: Rock Michael E. , Kennedy Vern , Deodhar Bhaskar , Stoebe Thomas G.
Published: June 2020

Cellophane is a composite polymer material, made up of regenerated cellulose (usually derived from wood pulp) which has been chemically transformed into "viscose", then formed into a (1 mil thickness) transparent sheet through an extrusion process. Although primarily produced for the food industry, cellophane's use as a separator material in the silver-zinc secondary battery system has proved to be another important market. We examined 14 samples from five producers of cellophane, which are being evaluated as the separator material for a silver/zinc alkaline battery system in an autonomous underwater target vehicle. Our intent was to identify structural and/or chemical differences between samples which could be related to the functional differences seen in the lifetimes of these various battery separators. The unused cellophane samples were examined by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). Cellophane samples were cross sectioned (125-150 nm) using a diamond knife on a RMC MT-6000 ultramicrotome. Sections were examined in a Philips 430-T TEM at 200 kV. Analysis included morphological characterization, and EDS (for chemical composition). EDS was performed using an EDAX windowless detector.
TEM investigations of self-assembly through physical synthesis
Authors: Walker S. , Naranjo E. , Chiruvolu S. , Zasadzinski J.
Published: June 2020

A novel way of enlarging the realm of surfactant solution microstructure is the "physical synthesis" of new microstructures and surfactant-templated materials by mixing simple surfactants or surfactant and inorganic and ionic species. Mixing can often produce properties not possessed by any one species alone. As we have recently shown, mixtures of single-tailed cationic and anionic surfactants associate in solution to form a quasi-double-tailed catanionic surfactant that forms bilayers rather than the simple micelles each species would form on its own. Mixed surfactant systems apparently produce new microstructures by altering the intermolecular and interaggregate forces in ways impossible for single component systems. In addition to spontaneous vesicles, we have found other new microstructures including dilute lamellar and L3 phases depending on the details of the surfactant mixture. Surfactant interactions with ionic species also play an important role in the in synthesis of a new M41S family of mesoporous silicas, and are likely to be important in the templating of biominerals at interfaces. By understanding the molecular and chemical basis of these interactions, we can begin to tailor new microstructured and/or biomimetic materials by controlling surfactant aggregation and phase behavior through physical synthesis rather than through much more elaborate chemical synthesis.
Two interpenetrating monoclinic superlattices of a self-assembling rodcoil copolymer thin film
Authors: Li L. S. , Stupp S. I.
Published: June 2020

In earlier work, we showed that the rodcoil copolymer (I), containing a rigid board-like mesogenic block connected to a flexible coil-like diblock of approximately 7 isoprene and 7 styrene units, undergoes a microphase separation in thin films cast from solution. The thin films exhibit a lamellar morphology with a mesogenic core sublayer, a polyisoprene (PI) sublayer and a polystyrene (PS) sublayer alternating along the normal to the layers. If the ratio of the molecular volume of the coil-like chain block to that of the mesogenic block could be increased to a certain value a different morphology of thin films would be expected. After cross-linking among the PI blocks, a molecular object with mesogenic core axes oriented perpendicular to the film plane could be formed which would significantly affect physical properties of thin films. In an attempt to obtain a different micTodomain morphology in thin films a similar rod-coil copolymer with approximately 15 isoprene and 15 styrene units in the coil-like chain block (II) was synthesized in our laboratory.
Semiautomatic liquid-nitrogen delivery system for safe refilling of overhead instrument dewars
Authors: Behrens Melanie A. , Laurion Tristan A. , Yanarella James A. , White John E. , Landol Marie D.
Published: June 2020

On many instruments, a liquid nitrogen dewar is positioned above the easy reach of a person who has to refill it regularly. Under these circumstances, it is necessary to devise a safe way with which to add LN2 without the operator coming in contact with this potentially hazardous cryogenic liquid. We have such a LN2 dewar on an energy dispersive X-ray detector for a scanning electron microscope in our laboratory. Refilling the dewar is performed about every three days. Because refilling is not needed every day and because we wished to be present when filling, we chose not to fully automate the delivery system. Instead, we designed a semiautomatic delivery system which allows us to push a button to start delivery and yet shuts off automatically when the dewar is full.

A low level sensor is already included as part of the EDX system. This sensor fits along the cap and the probe reaches down inside the dewar canister. When the level of LN2 drops below the probe tip an alarm sounds.
Developments in TEM for life-science research
Authors: Lücken U. , Busing Wim M. , Felsmann Michael , de Jong Frank , Otten Max T.
Published: June 2020

The study of Life Science materials with the TEM faces a number of problems such as low contrast in unstained specimens and specimen sensitivity to electron-beam damage and poor vacuum. Providing solutions to these problems has been the basis for several new developments on the Philips CM-series TEMs.

Objective lenses traditionally have been optimised for parameters that are important in materials science: high resolution and very small spot sizes. With these parameters comes a short focal length which reduces the contrast from the specimen - no problem in the high-contrast materials science specimens, but highly problematic in the case of low-contrast biological specimens. A new objective lens - the BioTWIN - has been developed specifically for high-contrast imaging and analysis of biological specimens. Its long focal length (6.2 mm; 2 to 3 times larger than that of a typical materials science objective lens) ensures high contrast by enabling the removal of the majority of elastically and inelastically scattered electrons by the objective aperture. Figure 1 shows a comparison of images of a stained section imaged at low magnification, recorded with a TWIN and a BioTWIN lens.
The (111)/(100) interface in cubic materials
Authors: Ramamurthy Sundar , Carter C. Barry
Published: June 2020

Descriptions of crystalline interfaces have concentrated on grain boundaries using the framework of the coincident-site-lattice (CSL) model. Within this framework, an interface-plane scheme can be formulated to describe all types of crystalline interfaces, homophase or heterophase. Low Σ values, the inverse density of CSL sites, are associated with boundaries with low energies. However, stable interfaces that cannot be described by such models are often found experimentally in thin-film, semi-bulk and bulk forms. The stability of such interfaces thus depends on factors other than the geometry of the interface.

Crystallography of the (111)/(100) interface in the cubic system has been studied extensively in a wide range of materials using different electron-microscopy techniques. Recently, this interface has spurred interest in the growth of tri-crystal microstructures to study junctions in polycrystalline thin films where three identical grain boundaries meet along a line. In this paper we review the (111)/(100) interface showing different examples from our recent work.
Characterization of diamond single-crystal substrates and homoepitaxial films
Authors: Posthill J. B. , Graham R. J. , Malta D. P. , George T. , Rudder R. A. , Hudson G. C. , Humprheys T. P. , Thomas R. E. , Markunas R. J.
Published: June 2020

We have continued to investigate different diamond single crystal substrates to assess their suitability for the growth of homoepitaxial diamond. Surface topography and defect microstructure of the resulting films are two important qualifiers for the choice of a suitable substrate. Previously developed methods to prepare plan-view TEM samples from bulk diamond substrates and homoepitaxial films have been employed. This contribution describes some of our most recent observations of the surfaces andmicrostructure of natural and synthetic diamond single crystals and homoepitaxial diamond thin films using SEM and TEM - including spatially resolved cathodoluminescence (CL) results.

Figs. 1 and 2 show TEM micrographs taken from a (100) natural type Ila diamond crystal and a (100) synthetic type lb diamond that have been ion milled to electron transparency. The mottled background contrast observed in both images which has been observed previously and is believed to result from the extended ion milling used to produce these thin foils.
Reflection electron microscopy of ferroelectric domains
Authors: Tsai Feng , Cowley J. M.
Published: June 2020

The intersections of ferroelectric domain boundaries with crystal surfaces have been studied by optical microscopy. The method is widely used but usually of low resolution. Transmission electron microscopy (TEM) can provide high-resolution images but may not be appropriate for studying crystal surfaces. Scanning electron microscopy (SEM) has also been used to study the intersections of ferroelectric domain boundaries with the surfaces of ferroelectric crystals. However, the resolution is still low and is destructive if an etched crystal surface is used. Other alternatives have also been attempted to study ferroelectric domain boundaries on surfaces, such as scanning tunneling microscopy (STM), atomic force microscopy (AFM). But, no reports have been known so far.

On the other hand, reflection electron microscopy (REM), as a branch of dark-field imaging technique dedicated for surface studies in TEM, has been developed to study crystal surfaces, surface reconstruction and surface defects with a resolution of about 10Å. It has been considered as a powerful technique to study surface defects and may be used to study the ferroelectric domain boundaries emerging on surfaces.
TEM studies of sol-gel derived ferroelectric oxide thin films
Authors: Mecartney M. L.
Published: June 2020

Sol-gel processing has proven to be a commercially viable process for the production of certain ferroelectric films, most notable Pb(Sr, Ti)O3 (PZT) and related compounds. The extension of this process to other ferroelectric oxide systems is still in the developmental stages because much is not yet understood about how the specific sol-gel chemistry influences microstructural development. In the PZT system, optimization of the sol-gel chemistry and the resultant microstructure were key developments in obtaining optimal ferroelectric properties. In this talk, the role of analytical TEM in studying microstructural development in sol-gel derived ferroelectric oxide thin films will be discussed. Examples will be drawn from LiNbO3, KNbO3, (Sr, Ba)NbO3 (SBN), and BaTiO3.

Mixed alkoxide precursors were used as sols and all films were spin coated onto substrates. Substrate choices ranged from (100) MgO for SBN, BaTiO3 , and KNbO3 and (0001) Al2O3 for LiNbO3 as well as (100) and (111) Si and Pt coated Si. Films were pyrolized after each coating at temperatures from 300-400°C.
Diffraction in the SEM: A significant role in materials research
Authors: Sutliff John A.
Published: June 2020

The use of electron diffraction in the SEM, particularly by the Electron Back-Scattering Pattern (EBSP) technique, has matured sufficiently to command a significant role in the materials research laboratory. The unique combination of high spatial resolution of the analyses, modest restrictions on sample size and preparation, quantitative nature of the experimental results, ease of experiment, and high sample throughput have produced a new demand for a SEM diffraction facility. In addition, x-ray diffraction facilities using tubetype generators (w/diffractometers and cameras) and electron diffraction facilities using the transmission electron microscope can both productively transfer some of their work load to a SEM diffraction facility. Some research efforts in our laboratory which depend on the SEM diffraction facility include studies of machining induced deformation structures in Ni-based superalloys, grain-structure/grain-alignment in high temperature superconductors, crystallography of fracture in Ti-based alloys, orientation relationships in direcnonally solidified multi-phase alloys, texture development during CVD diamond growth, and micro-texture effects in corrosion susceptibility of Zr-based alloys. Factors which insure continued growth in the SEM diffraction area are: relatively low cost of required instrumentation, continuing improvement in detector design and technology, continuing improvement in system automation (and therefor sample throughput), and growing awareness of the unique capabilities of SEM diffraction techniques.
Advances in strain measurement using electron-backscatter diffraction in the Scanning Electron Microscope
Authors: Dingley D. J.
Published: June 2020

The technique of electron back scatter diffraction, EBSD, is well established for measurement of crystal orientation in bulk polycrystalline samples. Analytical procedures for determining crystal phase from them have also been established. In addition several papers have been published describing the application of the method for strain measurement. In these latter studies the EBSPs were recorded on photographic film and all measurements made after digitising the patterns and transferring the data to a SEMPER image processing package. Strain measurement was based on determination of the diffuseness of the diffraction pattern. In the present studies analysis was carried out on digitised television images of the diffraction patterns imaged live on a phosphor screen.

EBSPs were obtained in a JEOL 6400 SEM fitted with a tungsten filament. The patterns were imaged on a P20/P40 phosphor directly coupled through a coherent fibre optic bundle to a SIT low light level television camera with 700 line resolution.
Automated EBSP studies of deformation microstructures
Authors: Jensen D. J.
Published: June 2020

Measurements of the crystallographic orientation within selected local areas of the microstructure is important to achieve further understanding of the development of deformation microstructures and texture; for example for studies of grain subdivision and texture formation. Different techniques may be applied. The most clear and precise results relating directly specific microstructural features to given orientations (or misorientations) are obtained by TEM methods. However, better statistical data may be obtained by the electron back scattering pattern (EBSP) technique in the SEM. The present paper concentrates on the EBSP technique and result obtained thereby.

Characterization of the distribution of orientations in the deformation microstructures by EBSP generally requires measurements of hundreds or more orientations. Automatic techniques are therefore very adequate. By using a modified Hough transform routine, lines in an EBSP are easily and rapidly identified. Figure 1 shows an example of computer identified lines in an EBSP of aluminum. Based on this data the crystallographic orientation is calculated by standard routines.
Influence of boundary microstructure on the abrasive wear of a high-alumina ceramic
Authors: Doğan C. P. , Hawk J. A.
Published: June 2020

The glassy melt present at the grain boundaries of many commercially-produced, polycrystalline ceramic materials will often crystallize during cool down from the sintering temperature, or during subsequent exposure to elevated temperatures. The extent of devitrification of the boundary glass, and the types of phases that form, depend upon the composition of the original glass melt and the thermal history of the material. In a 96% Al2O3 ceramic, for example, a boundary glass that is high in CaO will crystallize to anorthite (CaAl2Si2O8), gehlenite (Ca2Al2SiO7), garnet ((Mg,Ca)3Al2Si3O12) and spinel (MgAl2O4) upon exposure to temperatures between 1050° and 1350° C. Devitrification is essentially complete within one hour of exposure to these elevated temperatures. The microstructure of such a material, before and after a 100-hour heat treatment at 1150° C, is illustrated in Figs. 1 and 2, respectively.

Although the microstructure of such materials can change dramatically with heat treatment, there is little evidence that this difference results in a change in the room temperature mechanical properties of the bulk material.
Microstructural changes of Aluminum Nitride after laser irradiation and electroless copper deposition
Authors: Cao S. , Pedraza A. J. , Allard L. F.
Published: June 2020

Excimer-laser irradiation strongly modifies the near-surface region of aluminum nitride (AIN) substrates. The surface acquires a distinctive metallic appearance and the electrical resistivity of the near-surface region drastically decreases after laser irradiation. These results indicate that Al forms at the surface as a result of the decomposition of the Al (which has been confirmed by XPS). A computer model that incorporates two opposing phenomena, decomposition of the AIN that leaves a metallic Al film on the surface, and thermal evaporation of the Al, demonstrated that saturation of film thickness and, hence, of electrical resistance is reached when the rate of Al evaporation equals the rate of AIN decomposition. In an electroless copper bath, Cu is only deposited in laser-irradiated areas. This laser effect has been designated laser activation for electroless deposition. Laser activation eliminates the need of seeding for nucleating the initial layer of electroless Cu. Thus, AIN metallization can be achieved by laser patterning followed by electroless deposition.
Structural relationships in the synthesis of cubic boron nitride thin films by ion-assisted deposition
Authors: Medlin D. L. , Friedmann T. A. , Mirkarimi P. B. , Mills M. J. , McCarty K. F.
Published: June 2020

The allotropes of boron nitride include two sp2-bonded phases with hexagonal and rhombohedral structures (hBN and rBN) and two sp3-bonded phases with cubic (zincblende) and hexagonal (wurtzitic) structures (cBN and wBN) (Fig. 1). Although cBN is synthesized in bulk form by conversion of hBN at high temperatures and pressures, low-pressure synthesis of cBN as a thin film is more difficult and succeeds only when the growing film is simultaneously irradiated with a high flux of ions. Only sp2-bonded material, which generally has a disordered, turbostratic microstructure (tBN), will form in the absence of ion-irradiation. The mechanistic role of the irradiation is not well understood, but recent work suggests that ion-induced compressive film stress may induce the transformation to cBN.

Typically, BN films are deposited at temperatures less than 1000°C, a regime for which the structure of the sp2-bonded precursor material dictates the phase and microstructure of the material that forms from conventional (bulk) high pressure treatment.
EM studies of oxidized Y and Zr-doped β-NiAl
Authors: Schumann E. , Yang J. C. , Nadarzinski K. , Ruhle M.
Published: June 2020

The highly beneficial effect of yttrium and zirconia dopants on the oxidation behaviour of β-NiAl has been known for over the past 50 years. Various theories have been proposed to explain the reactive element effect. The dopants may: improve the interfacial properties; favorably effect diffusion in the oxide scale; or getter the sulfur, which is a common impurity in nickel alloys, and prevents sulfur from diffusing to the interface where it may decrease the interfacial energy.

To help determine which theory(s) explain the reactive element effect, we have examined oxidized Zr and Y doped β-NiAl by cross-section electron microscopy techniques on a VG-HB501 STEM and JEOLARM1250 in order to characterize the microstructure and the locations of the dopants.

Polycrystalline 0.1% Y doped β-NiAl were oxidized at 1200°C for 24 hr and polycrystalline 0.1% Zr doped β-NiAl were oxidized at 1200°C for 200 hr. The CTEM images of the Zr (Fig. 1) and the Y (Fig. 2) doped NiAl show that α-Al2O3 scale forms after oxidation.
Influence of natural organic matter on the morphology of corroding copper surface
Authors: Korshin G. V. , Ferguson J. F. , Rock M. E.
Published: June 2020

Natural organic matter (NOM) is a ubiquitous and important component of natural waters. Polymeric species related to humus found in soils constitute the major part of NOM. NOM is of major importance for the speciation of metals in waters but its effects on metal corrosion are little known. The influence of NOM on the morphology of corroding copper surfaces is discussed in this communication. The studies were performed for copper coupons exposed for 7 weeks to waters supporting an intense localized corrosion attack called pitting. Two types of waters were used: highly mineralized water at pH close to 7.3 (water A) and soft water at pH close to 9.3 (water B). The morphology of the surface was examined using conventional photography and SEM (JEOL 5200). The range of accelerating voltages was from 10 to 25 kV.

Profound effects of NOM on the state of the corroding copper surface were found.
Morphology of Σ3{<110>/70.53°} grain boundaries in a C15 intermetallic compound
Authors: Chu Fuming , Pope D. P. , Zhou D. S. , Mitchell T. E.
Published: June 2020

A C15 Laves phase, HfV2+Nb, shows promising mechanical properties and here we describe the structure of its grain boundaries. The C15 Laves phase has a fcc lattice with a=7.4Å. An alloy of composition Hf14V64Nb22 (including a C15 matrix and a second phase of V-rich bcc solution) was made by arc-melting. The alloy was homogenized at 1200°C for 120h. Preliminary study concentrated on Σ3{<110>/70.53°} grain boundaries in the C15 phase using Philips 400T and CM 30 microscopes.

The most-commonly observed morphology of Σ3{<110>/70.53°} grain boundaries in the C15 phase is a faceted boundary. A bright field image (BFI) of the faceted boundary and the corresponding diffraction patterns with the grain boundary edge-on are shown in Fig. 1(a). From the diffraction patterns using a <110> zone axis for both grains, it is obvious that this is a Σ3{<110>/70.53°} grain boundary. Crystallographic analysis shows that the Σ3{<110>/70.53°} grain boundaries selectively facet with the following relationships between the two grains: {111}1//{111}2, {112}1//{112}2, {111}1//{115}2, and {001}1//{221}2.
Shape training of Ge precipitates in an Al-1.8at% Ge alloy
Authors: Hinderberger S. , Xiao S. Q. , Westmacott K. H. , Dahmen U.
Published: June 2020

Ge precipitates in Al are known to form in a rich variety of shapes and orientation relationships. In this work it is shown that initial non-equilibrium shapes such as plates, laths, needles and tetrahedra can be induced to change to the equilibrium shape of an octahedron by proper temperature cycling. Analysis of this effect in bulk samples was complemented by direct observations of its mechanisms during in-situ temperature cycling.

A bulk sample of an Al-1.8at%Ge alloy was solid solution annealed at 420°C for 2h, quenched in ice water, pre-aged at room temperature for 72h and then annealed for 5h at 250°C. Subsequently, part of the sample was repeatedly cycled between 250°C and 360°C. TEM specimens were prepared from both the cycled and non-cycled bulk sample by conventional electropolishing and examined in a JEOL 200CX electron microscope. The in-situ temperature cycling was carried out in a Kratos 1.5 MeV HVEM equipped with a double tilt heating stage.
Interaction between dislocations and the Ω. phase during deformation of Al-Cu-Mg-Ag alloys
Authors: Li Qiong
Published: June 2020

Al-Cu-Mg alloys containing a small amount of Ag have been known to show remarkable hardening by aging between 150°C and 250°C. Because of their excellent thermal stability, the alloys are leading candidates for high temperature aeronautic applications such as High Speed Civil Transportation (HSCT). Through recent investigations, it has been shown that this hardening is mainly due to the precipitation of the plate-like Ω phase on the {111} Al matrix planes. The Ω phase is semicoherent with the Al matrix and has a tetragonal structure , The nature of strengthening of the semicoherent precipitates is still unclear. This study shows that the shear of dislocations is the primary strengthening mechanism in the alloy strengthened by Ω phase.

The present study was performed with an Al-3.2Cu-0.45Mg-O.5Ag (wt%) alloy which was prepared using an induction furnace. The alloy was cast into a mold, hot rolled, homogenized, solutionized, cold water quenched and peak aged at 200°C.
A TEM microscopical investigation of the magnetic domain structure of a metastable austenitic stainless steel
Authors: Fourlaris G. , Gladman T.
Published: June 2020

Stainless steels have widespread applications due to their good corrosion resistance, but for certain types of large naval constructions, other requirements are imposed such as high strength and toughness , and modified magnetic characteristics.

The magnetic characteristics of a 302 type metastable austenitic stainless steel has been assessed after various cold rolling treatments designed to increase strength by strain inducement of martensite. A grade 817M40 low alloy medium carbon steel was used as a reference material.

The metastable austenitic stainless steel after solution treatment possesses a fully austenitic microstructure. However its tensile strength , in the solution treated condition , is low.

Cold rolling results in the strain induced transformation to α’- martensite in austenitic matrix and enhances the tensile strength. However , α’-martensite is ferromagnetic , and its introduction to an otherwise fully paramagnetic matrix alters the magnetic response of the material. An example of the mixed martensitic-retained austenitic microstructure obtained after the cold rolling experiment is provided in the SEM micrograph of Figure 1.
A bonded metal fulleride structure in the PdnC60 system
Authors: Liu M. , Cowley J. M. , Ramakrishna B. L. , Peace T. S. , Wertsching A. K. , Pena M. R.
Published: June 2020

The large-scale synthesis of C60 has stimulated considerable interest in the chemistry and structures of metal fullerides. Studies on compounds formed by C60 with metal-organic complexes have shown that some metal atoms can form bonds with the C60 molecules. Nagashima et al. have proposed that one-, two-, or three-dimensional polymers may be formed when Pd atoms link neighboring C60 molecules by being coordinated with the π electrons at the double-bond regions between hexagonal carbon rings. In the present study, PdnC60 (n= 1,3,4) were prepared from C60 and a Pd0 precursor by a liquid chemical combination method. The compositions of these compounds were determined with EELS. Their structures were examined with a Topcon 002B and a JEM-2000FX HRTEM.

The electron micrographs and diffraction patterns of the Pd1C60 preparation showed regions of small Pd crystals embedded in near-amorphous carbon and also regions of heavily faulted FCC C60 structures. Fig. 1 is a HRTEM image showing a region of FCC structure viewed in the [110] direction with several groups of stacking faults.
Single-walled carbon nanotubes grown from yttrium carbide particles
Authors: Zhou D. , Wang S. , Seraphin S.
Published: June 2020

The discovery of single-walled carbon nanotubes in the soot from the catalytic arc-discharge evaporation has enlarged the technological promises of this novel form of carbon. To produce single-walled tubes by the catalytic arc-discharge, Fe, Co, and Ni as well as a mixture of Ni and Fe have been used as the catalysts. The growth of single-walled nanotubes appears to depend on the presence of those catalysts in the gas phase of the discharge, but there is no visible evidence to relate the single-walled tubes to the catalytic particles. Recently, it has been reported that bundles of single-walled nanotubes, produced with Gd or Nd as the catalyst for the discharge, radiate from amorphous catalyst cores. We report here on the discovery of clusters of single-walled carbon nanotubes from the arc-discharge experiments with YC2 as the catalyst arranged around nuclei of yttrium carbides in a radiolarian pattern. They are present in large quantities in the primary soot.
TEM measurement of surface area of automotive catalysts
Authors: Yao M. H. , Liu D. R. , Baird R. J. , Usmen R. K. , McCabe R. W.
Published: June 2020

The specific surface area of supported noble metal particles in an automotive catalyst is defined as the exposed surface area per unit mass of these particles. It is of great importance to know this parameter, since this is one of the major factors that determine the effectiveness of the catalyst. Commonly used methods for characterizing catalysts, such as X-ray diffraction and TEM, do not directly provide a measure of surface area, but, instead, provide a measure of the “average size” of supported particles. Moreover, the “average sizes” obtained from different experimental techniques are often not comparable. Furthermore, many previous electron microscopy catalyst studies measured only simple average particle size, and no detailed procedure for measuring area-weighted average size or surface area appear to have been reported.

In the current study, a procedure for measuring surface area of supported particles by transmission electron microscopy(TEM) was developed, and applied to measure surface areas of various production three-way automotive catalysts.
TEM study of melt-processed “123” YBaCuO containing excess “211”
Authors: Yan Y. , Stobbs W. M. , Cardwell D. A. , Campbell A. M.
Published: June 2020

High Jc values of 104~106 A cm-2 are generally required in the use of YBCO. In this context the commonly used sintering method for making bulk high-Tc superconductors has the disadvantage that grain boundaries in such material tend to act as weak links. Melt processesing of the YBaCuO “123” phase has been found to be effective in reducing the problem. In order to understand the mechanisms involved, the physical properties (Tc, Jc, etc.) of YBa2Cu3O7-x (“123”), with varying additions of Y2BaCuO5 (“211”), are being compared and correlated with associated changes in the structure.

TEM analysis indicates that the melt processed material contains well aligned tabular “123” platelets with near to common c axis orientations (the preferred orientation for grain growth is in the a-b plane), trapping more equiaxed “211” phase particles of varying sizes. Electron diffraction (Fig.la inset) has shown that there are no large orientation changes between platelets throughout the whole specimen despite their being interconnected by “gaps” where there are phase changes.
Prospects for atom-probe analysis in biology and medicine
Authors: Panitz J. A.
Published: June 2020

The atom-probe field ion microscope may be the ultimate microanalytical tool because a single atom, chosen from its neighbors at the discretion of the experimenter, can be visualized in atomic resolution and then identified by its mass-to-charge ratio. Although the analysis procedure is destructive;the lateral and depth resolution of the atom-probe is impressive, exceeding 0.5 nm under favorable conditions. Despite these attributes, atom probe analysis has been largely confined to problems in the materials sciences. The atom probe has made no impact in biology or medicine, largely because of restrictions imposed by the technique on the preparation, imaging, and analysis of biological samples. Recent developments in each of these areas has made atom probe analysis of biological samples a more viable prospect.

Biological Sample Preparation

The atom-probe technique places severe restrictions on the type of sample that can be analyzed. Field ionization is used to image a surface in atomic resolution, and field desorption provides a source of ions for analysis. These processes occur with a high probability only in electric fields greaterthan 100 MV/cm. Electric fields of this magnitude (and the nature of the imaging process) require theuse of a needlelike substrate, known as a field-emitter "tip".
Atomic-level characterization of defects in microalloyed NiAl: An atom probe investigation
Authors: Jayaram R. , Miller M. K.
Published: June 2020

Nickel aluminides have been studied in great depth in recent years on account of their potential application in advanced aircraft and land-based turbines. Although the low density and high melting point of NiAl are particularly attractive features, its poor ductility and fracture toughness at ambient temperatures limit its technological application. Since mechanical behavior is largely governed by microstructural features, a careful microanalytical characterization is crucial to the understanding of structure-property relationships in NiAl. Defect features such as dislocations, substitutional solutes and solute segregation to grain boundaries play important roles in influencing mechanical properties. The atom probe field ion microscope (APFIM) is particularly well suited to the characterizationof such types of microstructural features.

The atom probe has been used to provide a quantitative explanation of the changes in yield stress when NiAl is doped with boron, carbon, or beryllium. An enormous increase in the yield stress is observed in boronand carbon-doped NiAl in contrast to beryllium-doped NiAl which shows only a modest increase. The matrix was severely depleted of the solute in the boron- and carbon-doped NiAl, whereas almost all of the beryllium was in solid solution. The excess boron and carbon atoms scavenged trace metallic impurities and formed highly stable ultrafine (= 2 nm diameter) precipitates with compositions that were consistent with the stoichiometry of MB2 and MC, respectively. Estimates of the yield stress increase due to a precipitation hardening mechanism were obtained based on atom probe measurements of particle size and number density. These estimates have been shown to be in agreement with experimental values.
Recent developments in position-sensitive atom-probe microanalysis
Authors: Smith G. D. W. , Cerezo A. , Godfrey T. J. , Setna R. , Hyde J. M. , Sijbrandij S. J.
Published: June 2020

The difficulties associated with the aperture geometry of the conventional atom probe have been overcome by the introduction of a new generation of wide-angle, single-atom sensitivity, positionsensitive detectors. With the aid of such detectors, it is now possible to map the locations and identitiesof atoms over regions of solid surface up to 50 nm in diameter. The nanometer-scale chemistry of successive atomic layers can be investigated during the process of field evaporation. We therefore have the new and exciting ability to investigate the atomic-scale chemistry of solids in three dimensions.
The first three-dimensional atom probe is the PoSAP (Position Sensitive Atom Probe), developed at Oxford by Cerezo and Smith. In this instrument, position sensing is carried out by means of a wedge-and-strip anode assembly, located directly behind the double microchannel plate used for primary ion detection and time of flight measurement. The detector readout functions in serial mode. Only one ioncan be successfully detected and identified for each evaporation pulse which is applied to the specimen
Pattern-recognition image processing of 3D atom-probe data
Authors: Camus Patrick P. , Larson David J. , Kelly Thomas F.
Published: June 2020

The ultimate three-dimensional atom probe (3DAP) system would have sufficient spatial resolution so that the crystal structure of a material could be determined directly from the atomic positions. Aberrations in the trajectories of ions evaporated from the specimen are the primary limitation on the lateral resolution of AP analysis. In the near future, it does not seem likely that these aberrationsmay be corrected physically because there is no theoretical description and there has been very little empirical work. If the lattice is known a priori, a suggestion was proposed to force the atoms to their nearest lattice sites. This work reports progress that has been made using Fourier transform (FT) and pattern recognition techniques to reconstruct an original lattice structure from simulated 3DAPdata and subsequently to force atoms to pick their nearest lattice point. Usually FT techniques areused in image processing to reduce the image noise, not actually to shift features in the image.
Atom probes of the future
Authors: Kelly T. F. , Camus P. P. , Larson D. J. , Holzman L. M.
Published: June 2020

Atom probe microscopy, which is based on the first ever atomic-scale imaging technique, field ion microscopy (FIM), has entered a new era in its development. Three-dimensional atom probes (3DAP) are now operating which produce 3D images with atomic scale resolution. It appears that the technology will soon be at hand to make 3DAPs do everything that their predecessor, the conventional atom probe, now does and also reach the third dimension. These microscopes will be simpler, smaller, faster, and much more powerful than the conventional atom probe.
Several developments are responsible for this suggestion. 1) Rapid pulsing schemes are being developed which will make it possible to achieve on the order of 106 pulses per second. 2) Highspeed position-sensitive detectors (PSDs) have been designed which can detect several ions in a givenpulse with very high precision. 3) New specimen geometries will soon become possible which will revolutionize the atom probe. Let us consider the ramifications of each of these developments in turn.
Transmission Electron Microscopy of AlxGa1-xN/SiC multilayer structures
Authors: Pike W. T. , George T. , Khan M. A. , Kuznia J. N.
Published: June 2020

The potential of wide-band-gap III-V nitrides as solar-blind ultraviolet sensors and light emitters has prompted an increasing amount of work recently, including the fabrication of the first UV sensors from as-deposited single crystal GaN. We have used high resolution transmission electron microscopy (TEM) to study the microstructure of two novel developments of wideband-gap III-V nitrides: the growth of ultra-short period GaN/AlN superlattices (digital alloys); and the incorporation of SiC layers into AlxGa1-xN structures. By varying the relative periods in a GaN/AIN superlattice, it should bepossible to tailor the band gap of the composite to lie between the elemental values of 365nm for GaN and 200nm for AIN. The group IV semiconductor, SiC, has a close lattice match (< 3%) to AlxGa1-xN forgrowth on the basal plane. Demonstration of epitaxial growth for AlxGa1-xN/SiC multilayers could enable an extension of direct band-gap material towards the visible.

The superlattice samples were grown by low-pressure metalorganic chemical-vapor deposition (MOCVD)using a unique switched atomic-layer-epitaxy (SALE) procedure (as first used by Dapkus et al. for GaAs). GaN was grown on the basal-plane sapphire substrates above a thin AlN layer, which has been foundto maximize the crystalline quality of the GaN film.
Characterization of group Ill-nitrides by high-resolution electron microscopy
Authors: Chandrasekhar D. , Smith D. J. , Strite S. , Lin M. E. , Morkoc H.
Published: June 2020

The Group III-nitride semiconductors A1N, GaN, and InN are of interest for their potential applications in short wavelength optoelectronic devices. This interest stems from their direct wideband gapswhich range from 1.9 eV (InN), to 3.4 eV (GaN), to 6.2 eV (A1N). If high quality nitride films can besuccessfully grown, then optoelectronic devices with wavelengths ranging from the visible to the deepultraviolet region of the electromagnetic spectrum are theoretically possible. Recently, LED's basedon GaN and InGaN QW's were demonstrated. Also, their excellent thermal properties make them ideal candidates for high-temperature and high-power devices. Many problems plague nitride research, especiallythe lack of suitable substrate materials that are both lattice- and thermal-matched to the nitrides. The crystal structure of these materials is strongly influenced by the substrate and its orientation.For example, although the equilibrium crystal structure of these nitrides is wurtzite, zincblende phase can be nucleated under nonequilibrium growth conditions but only on cubic substrates. These zincblende nitrides represent new material systems with properties that differ from their wurtzite counterparts. Recently, good quality material has been produced employing metalorganic vapor phase epitaxy (MOVPE) and reactive molecular beam epitaxy (RMBE) techniques with incorporation of buffer layers.
TEM characterization of WSix films
Authors: Kannan V. C. , Merchant S. M. , Irwin R. B. , Nanda A. K. , Sundahl M. , Rambabu B. , Singh A. K.
Published: June 2020

Metal silicides such as WSi2, MoSi2, TiSi2, TaSi2 and CoSi2 have received wide attention in recent years for semiconductor applications in integrated circuits. In this study, we describe the microstructures of WSix films deposited on SiO2 (oxide) and polysilicon (poly) surfaces on Si wafers afterdeposition and rapid thermal anneal (RTA) at several temperatures. The stoichiometry of WSix films was confirmed by Rutherford Backscattering Spectroscopy (RBS). A correlation between the observed microstructure and measured sheet resistance of the films was also obtained.

WSix films were deposited by physical vapor deposition (PVD) using magnetron sputteringin a Varian 3180. A high purity tungsten silicide target with a Si:W ratio of 2.85 was used. Films deposited on oxide or poly substrates gave rise to a Si:W ratio of 2.65 as observed by RBS. To simulatethe thermal treatments of subsequent processing procedures, wafers with tungsten silicide films were subjected to RTA (AG Associates Heatpulse 4108) in a N2 ambient for 60 seconds at temperatures ranging from 700° to 1000°C.
STEM study of the high-pressure oxidation of GeSi
Authors: Lee Tan-Chen , Theodore N. David , Silcox John
Published: June 2020

GeSi alloys are of interest because of their potential applications in optical and electronic devices. Understanding the growth of thermal oxide is very important for the GeSi system if an adaptationof the existing Si technology is going to be used. Thermal oxidation of GeSi leads to a Ge-rich layerat the GeSioxide interface. By sufficiently speeding up the rate of oxidation at a given temperature,such as with high pressure oxidation, it is possible to convert both Ge and Si into oxide and suppress the Ge pile-up at the oxide front. This was observed in the oxidation of GeSi films (Ge concentration 5-17 at.%) using pure oxygen at 600 atm and 550 °C. The segregation of Ge oxide from Si oxideand the Ge pile-up in high pressure oxidized GeSi, which are difficult to observe with other techniques, were studied by using a dedicated STEM.

An epitaxially grown Si (2500 Å)/Ge.15Si.85 (500 Å) hetero-structure on Si(100) was oxidized in a wet ambient at 750 °C and 25 atm. It was then made into anXTEM (cross-sectional transmission electronmicroscope) sample and characterized using a VG HB 501A STEM equipped with EELS (electron energy lossspectrometry) and a windowless X-ray detector. STEM BF (bright field) and ADF (annular dark field) images are shown in Fig. 1(a) and 1(b). STEM BF images are similar to conventional TEM BF images. Fig. 1(a) shows that three layers of oxides are grown on the Sisubstrate.
Specimen preparation for scanning-probe microscopy of materials by ultramicrotomy
Authors: Shaapur F. , Rez P. , Yaniv D. R. , Drach G. W.
Published: June 2020

Scanning Probe Microscopy (SPM) has been traditionally employed for the characterization of exposed and naturally occurring surfaces. An extension of the technique for studying the bulk properties of materials is limited by the ability to produce and expose a perfectly clean, defect-free, smooth, flat surface within the body of the sample. With the exception of monocrystals with a preferred cleavage plane, most materials for SPM bulk examination have been prepared using conventional lapping procedures. Generally, as a result of surface scratches or residual lapping debris, a surface prepared in such a way is not sufficiently smooth or clean for its intended application. In addition, such a sample is not representative of the bulk material due to the surface defects commonly caused by the use of abrasives. In the case of particulate materials these difficulties are compounded by the need to support and immobilize the particles and generate a sufficiently large surface for SPM.
Specimen preparation of irradiated materials for examination in the atom probe field ion microscope
Authors: Russell K. F. , Miller M. K.
Published: June 2020

The atom probe field ion microscope (APFIM) is well suited to the characterization of the fine scale features and defects that are formed in materials due to exposure to neutron irradiation. However, in order for the technique to be effective, suitable specimens are required. Atom probe field ion microscopy specimens are in the form of ultrasharp needles that are usually produced by a series of mechanical and chemical or electrochemical methods. These needles have a typical end radius of approximately 10 to 50 nm and a taper angle of between 1 and 5. The small dimensions mean that the specimens are extremely fragile and difficult to handle and do not easily lend themselves to remote operations in a hot cell. The small size and mass of the APFIM specimen has the advantage that the amount of material required is minimal.

A concept in working with irradiated materials is to keep exposure to the operator "as low as reasonably achievable" (ALARA).
Microstructural characterization of sol-gel coating on PET films
Authors: Chen R. T. , Norwood R.A.
Published: June 2020

Sol-gel processing has been used to control the structure of a material on a nanometer scale in preparing advanced ceramics and glasses. Film coating using the sol-gel process was also found to be a viable process technology in applications such as optical, porous, antireflection and hard coatings. In this study, organically modified silicate (Ormosil) coatings are applied to PET films for various industrial applications. Sol-gel materials are known to exhibit nanometer scale structures which havepreviously been characterized by small-angle X-ray scattering (SAXS), neutron scattering and light scattering. Imaging of the ultrafine sol-gel structures has also been performed using an ultrahigh resolution replica/TEM technique. The objective of this study was to evaluate the ultrafine structures inthe sol gel coatings using a direct imaging technique: atomic force microscopy (AFM). In addition, correlation of microstructures with processing parameters, coating density and other physical properties will be discussed.

The materials evaluated are organically modified silicate coatings on PET film substrates. Refractive index measurement by the prism coupling method was used to assess density of the sol-gel coating.AFM imaging was performed on a Nanoscope III AFM (by Digital Instruments) using constant force mode. Solgel coating samples coated with a thin layer of Ft (by ion beam sputtering) were also examined by STM in order to confirm the structures observed in the contact type AFM. In addition, to compare the previous results, sol-gel powder samples were also prepared by ultrasonication followed by Pt/Au shadowing and examined using a JEOL 100CX TEM.