bluuebunny/crossref_metadata_2025_split huggingface dataset:
A study of microstructures in ferroelectric Pb(Zr,Ti)O3 and KNbO3 thin films
Authors: Kingon A. I. , Rou S. H. , Chen Y. L. 
Published: June 2020

Oxide ferroelectric thin films are receiving considerable attention due to their potential application in a wide range of devices including ferroelectric nonvolatile memory, dynamic random access memory (DRAMs) electrooptic phase modulators, and laser light source frequency doublers. However, the complexity of the oxide materials has resulted in a relatively slow development of structureprocessing property relationships. In this paper, we review in turn how the microstructures of epitaxial KNbO3 and Pb(Zr Ti)O3 have been significantly improved over a period of time.In the case of epitaxial KNbO3 on oxide single crystal substrates, defect types which need to be controlled include 221-type misorientations, low angle boundaries, multiposition domains, and inversion domains. Several of these defect types are controlled via the substrate surface preparation. The role of lattice mismatch between film and substrate on the formation of the low angle boundaries remains an unresolved issue. We are currently comparing via TEM the KNbO3(100) films on (100)MgO, (100)MGAl2O4, (100)NdGaO3 and (100)KTaO3 substrates; these substrates covering a range of values of lattice mismatch between 0.1% and 5.0%.
AEM of shock-synthesized niobium silicide composites
Authors: Strutt A. J. , Meyers M. A. , Vecchio K. S. 
Published: June 2020

In-situ composites of thermodynamically compatible phases have been the subject of recent investigations and in particular, those comprising 2-phase Nb/Nb5Si3 structures. Chemical reactions initiated by high velocity shock waves can be extremely rapid and (unlike more conventional techniques) are capable of forming composite compounds with carefully controlled, fine-scale microstructures. The current investigation involves the use of SEM, TEM and EDX to fully characterize the microstructure of niobium silicide specimens (of initial bulk compositions Si 40 at.% Nb and Nb 33 at.% Si) formed by shock-synthesis of nominally 5 μm size particles in a powder gas gun at an impact velocity of 1.3 km/s.Recovered specimens were in the form of 34 mm diameter × 7 mm thick disks. Metallographic sectioning and examination by SEM in the backscattered imaging mode showed that both disks had undergone a chemical reaction with the exception of the peripheral regions which were merely compacted. Examination was also performed using a Philips CM30 analytical TEM at 300 keV in addition to EDX with a Link Systems ultrathin window detector.
Determination of interface structure and bonding at atomic resolution in the STEM
Authors: Pennycook S. J. , McGibbon A. J. , McGibbon M. M. , Browning N. D. , Chisholm M. F. , Jesson D. E. 
Published: June 2020

Theo scanning transmission electron microscope can now routinely produce a probe of atomic dimensions, 2.2Å at 100 kV and 1.3Å at 300 kV. This capability opens up a new strategy for determining the structure and bonding of materials at the atomic scale, which is particularly advantageous for complex interfaces such as grain boundaries. The Z-contrast image allows the high-Z column locations to be determined by direct inspection, and quantified through maximum entropy methods to a positional accuracy of currently ~0.2Å. With the same electron probe, located to sub-Ångstrom precision with reference to the Z-contrast image, parallel detection EELS can determine light element coordination from core edge fine structure, in principle around a single atomic column.The attractive features of this approach are the increased resolution associated with incoherent imaging, 0.44 Cs1/4 λ3/4 compared with 0.66 Cs1/4 λ3/4 for phase contrast imaging, and the highly local nature of the image, which makes possible a greatly extended regieme of intuitive image interpretation, and also permits column-by-column spectroscopy without beam broadening.
HREM study of NiO electrochromic film and interace with ITO layer
Authors: Song X. Y. 
Published: June 2020

Electrochromic nickel oxide films are of interest in the development of electrochromic devices (“smart windows”) for a variety of applications including architectural and automotive glazings. Structural characterization of NiO films has been performed by Lampert and Agrawal et. al using transmission electron microscopy (TEM), although only in plan view of NiO films which had been deposited on carbon-coated copper grids. However, finer structural features in the NiO electrochromic film and the interface between the NiO film and the indium tin oxide (ITO) layer have not been reported. The purpose of this investigation is to characterize nanometer scale structures in NiO films and the NiO/ITO interface using cross-sectional high resolution electron microscopy (HREM).The NiO films were deposited using a JS-450D rf sputtering coater. A nickel target of 99.9% purity with a 100 mm diameter was used. ITO coated glass with a sheet resistance of 40 ohm/sq. was used as a substrate, and both target and substrate were water cooled and were separated by 50 mm.
The changes caused by activation and reaction conditions on the morphology of iron catalysts
Authors: Kalakkad D. S. , Shroff M. , Datye A. K. 
Published: June 2020

Iron is considered to be one of the most active/low cost catalysts for Fischer-Tropsch synthesis (FTS) used to produce higher order hydrocarbons and synthetic fuels from coal. One of the biggest obstacles faced by the industry in the use of iron is that of rapid deactivation and attrition. While it is generally accepted that deactivation occurs due to carbon deposition or “coking”, the actual steps involved in the formation and deposition of carbon have not yet been thoroughly understood. Also, the causes for attrition in these catalysts have not yet been established.Our present study involves use of transmission electron microscopy to find the effect of various pretreatment and reaction conditions on the microstructure of Fe catalysts and scanning electron microscopy to study the problem of attrition. The transmission electron microscopy was performed on a 200 kVJEOL JEM 2000FX microscope and the SEM was done using a Hitachi S800 microscope.
Observation of the evolution of 55-atom icosahedral Ag clusters by coherent electron nanodiffraction in a UHV stem
Authors: Liu J. , Spinnler G. E. 
Published: June 2020

The morphology of metallic nano particles fluctuates and rapidly changes under the influence of electron beam irradiation. Structural transformations of small Au particles and disordering of small Pt clusters have been reported. Although the existence of a quasimolten state in nano particles has been experimentally observed there are still many unanswered questions concerning the onset of this unstable state. The previous experiments were carried out in non-UHV microscopes and the particles were prepared ex situ. We report preliminary observations of the evolution of clean Ag nano particles in a UHV scanning transmission electron microscope (STEM).The experiments were performed on a UHV STEM (VG HB-501S), known by the acronym MIDAS (Microscope for Imaging, Diffraction and Analysis of Surfaces). The probe size used for nanodiffraction was approximately 1 nm in diameter with a beam current density of 104 A/cm2. Silver nano particles were formed by evaporating Ag onto a pre-cleaned thin (< 5 nm in thickness) carbon film inside the UHV specimen preparation chamber attached to the MIDAS column.x
Oxygen vacancy clustering in YBa2Cu307-x (x < 0.15)
Authors: Storey B. G. , Kirk M. A. , Marks L.D. 
Published: June 2020

There have many studies of oxygen vacancy ordering in highly oxygen deficient YBa2Cu3O7-x (YBCO) however little has been done to investigate oxygen vacancies for x<0.15. Information on defects in asgrown fully oxygenated YBCO is important when generating flux pinning defects by irradiation damage. It has been found that samples with little flux pinning before irradiation have the best flux pinning after irradiation. It is believed that pre-existing defects interfere with the production of irradiation induced defects, therefore, there is a great interest in the behavior of the oxygen vacancies. There is also a hypothesis that oxygen vacancy clusters could be low temperature flux pinners.It is well known that YBCO is generally oxygen deficient and that at large deficiencies the oxygen vacancies have a long-range order. If the oxygen loss and/or disorder is great enough the material will undergo an orthorhombic to tetragonal phase transition. Most studies of oxygen vacancies have been of materials with x>0.2, however if Tc>90K then x<0.15.
Atomic-force microscopy of a fractured rubber-toughened epoxy
Authors: Shaffer O. , Qian J. , Dimonie V. , Pearson R. , El-Aasser M. 
Published: June 2020

Atomic force microscopy (AFM) is a powerful scanning probe technique, which is capable of imaging polymer surfaces. This technique is complementary to the scanning electron microscope (SEM) but because of the AFM's sensitivity in the z direction surfaces that are too smooth to image by SEM can easily be imaged by AFM. This study utilizes transmission electron microscopy(TEM) to image the morphology of the latex rubber particles; SEM and AFM are used to study the degree of dispensability of the latex particles in the epoxy, and the fatigue-fracture surface of the rubber modified epoxy.Core-shell latex particles were prepared with a core of poly(butadiene-styreiie) |P(B-S)| and a shell Poly(methyl methacrylate)(PMMA). In order to study the interaction between the core/shell particles and the epoxy matrix, the shell is systematically varied in terms of chemical bonding, physical interaction and the extent of these interactions by incorporating acrylonitrile(AN). glycidyl-methacrylate(GMA). and crosslinking agent divinylbenzene(DVB) of varying concentrations in the shell.
Correlation of micro-structural, micro-chemical and micro-magnetic properties of longitudinal recording media using CM20FEG Lorentz TEM
Authors: Nolan T. P. , Sinclair R. , Yamashita T. , Ranjan R. 
Published: June 2020

Cobalt alloy on chromium thin film magnetic media are used in industry computer hard disk drives because of their large values of coercivity (Hc), remanent magnetization (Mr), squareness (S*), and relatively low noise. The magnetic performance depends strongly on processing conditions and the resulting nanometer scale microstructure.A complete structure-processing-properties analysis requires effective measurement of magnetic and microstructural properties. To date, most structure-properties analyses have involved correlation of bulk magnetic (hysteresis loop) properties and magnetic recording measurements with physical microstructures observed by high-resolution SEM and TEM.The nanoscale microstructural features that dramatically affect magnetic properties are difficult to observe but careful TEM analysis has been used to observe subtle, important differences in the atomic scale physical microstructure. Even these impressive capabilities are becoming insufficient for continued development of improved magnetic recording media. Microstructural design is moving into a regime where appropriate control of magnetic properties requires control of elemental composition and second phase formation as well as crystallography and morphology, at near-atomic levels.
Quantitative image analysis of polymer blends
Authors: Zhang X. , Berry V. K. 
Published: June 2020

Quantitative image analysis is important in understanding the role of microstructure in polymer blend properties, as revealed by the TEM. This paper presents an example of the application of the image analysis method to the study of structure/property relationship of an acrylonitrile-butadiene-styrene (ABS) polymer.ABS is a rubber-toughened two-phase polymer blend. As shown in Figure 1, the microstructure of ABSconsists of small rubber particles embedded in a styrene-acrylonitrile copolymer (SAN) matrix. The morphologies of these blends, which depend on the polymerization conditions, play a key role to the overall physical and mechanical properties of the blends. The quantitative characterization of the rubber phase involves measuring its volume fraction as well as the particle size distribution.Four ABS samples, available commercially, with different levels of styrene butadiene rubber (SBR),were used in this study. The samples were block stained, using osmium tctroxide (OsO4) solution, and thin sectioned in an ultramicrotome.The thin sections were examined in a JEM-100CX II TEM, operated at 60KV. The representative images were acquired on a SEMICAPS Imaging System using a GATAN CCD TV rate camera.
High-resolution annular dark-field STEM imaging
Authors: Hillyard Sean , Silcox John 
Published: June 2020

Annular dark field STEM imaging has become an important tool as both a high resolution imaging technique showing Z-contrast, and as a way to locate the probe on the specimen while simultaneously recording other data such as electron energy loss spectra. It is intrinsically quantitative since image data can be recorded directly from linear detectors into digital memory Experiments on simple samples,and a multislice simulation approach backed by experimental evidence has been used to explore the image dependence on experimental factors such as inner detector angles and other elements in the imagingprocess Earlier work demonstrated marked thickness dependence in high Z specimens.In annular dark field imaging, the resolvable spatial resolution is roughly equal to the size of the electron probe One important factor in forming a small probe, and therefore in getting high resolution images, is an electron gun with a small virtual source size. An example is shown in Figure 1, which plots the relativestrengths of the 2.9Å and 2.1 Å fringes taken from experimental images of InP (100) What is seen is that the 2.1Å fringe intensity, at the extreme limits of resolution for this probe (approx 2.2Å in size), changes greatly in comparison with the more easily resolvable 2.9Å fringe as the source demagnification, in effect the source size, is changed.
Limits of SEM resolution
Authors: Joy D. C. 
Published: June 2020

Over the past decade the achievable resolution of the scanning electron microscope (SEM) in secondary electron (SE) imaging mode has improved by about one order of magnitude. In fact, instruments capable of demonstrating a resolution of one nanometer and exhibiting a probe size of less than 0.6nm are now available. Continued improvements in electron-optics, electron sources, and in electronic and mechanical stability promise even smaller probe sizes that still contain adequate current for imaging. It is therefore relevant to consider what resolution might ultimately be achievable with an SEM in SE mode.The contrast detail in an SE image depends on two factors, the generation of secondaries, and their subsequent escape from the specimen. Changes in either, or both, of these factors will change the number of secondaries collected, and the spatial scale over which this change is accomplished will set the effective resolution of the image (assuming that the physical probe size is small enough to be neglected).
Atomic-Force Microscopy with piezoresistive cantilevers
Authors: Tortonese M. , Giessibl F. J. 
Published: June 2020

The atomic force microscope (AFM) works by measuring the deflection of a cantilever as it is scanned over a sample. A sharp tip at the end of the cantilever is responsible for the high lateral resolution achieved with the AFM. There are several ways to measure the deflection of the cantilever. The technique used to measure the deflection of the cantilever most often dictates the mechanical complexity and stability of the instrument. Electron tunneling, interferometry and capacitive sensors have been used successfully. The most common way to measure the cantilever deflection is by means of an optical deflection detector.The piezoresistivc cantilever offers a new way to measure the deflection of the cantilever, with performances comparable to the performances of other deflection detectors, and with the advantage that the sensor is incorporated in the cantilever. This simplifies the design and operation of the microscope In particular, the piezoresistive cantilever facilitates the use and often improves the performances of an AFM when operated in ultra high vacuum (UHV), at low temperature, or when used to image large samples.
Extended defects in plastically deformed superconducting ceramics
Authors: Kuroda K. , Yoshida T. , Murase T. , Saka H. 
Published: June 2020

Extended defects introduced by high temperature deformation into high Tc superconducting ceramics have been characterized by means of transmission electron microscopy.Single crystals of YBa2Cu3O7−x (YBCO) were grown from melting mixtures of yttria, barium carbonate and copper oxide contained in alumina boats. Crystals having tetragonal symmetry grew as platelets with dimensions up to 10×10×0.1 mm3 and the (001) broad surface. Crystals were deformed by Brinell indentation with an indenter of Y-doped zirconia between 550 and 900 °C in air. Most indents were done with a load of 70 grf and a loading period of up to 24 h. Thin specimens were prepared by back-thinning technique using an Ar ion beam at 4 kV.Polycrystals of Bio. 8Pbo. 2SrCa1. 1Cu1. 6Ox (BSCCO) were prepared by sintering process. Rectangular specimens 3×3×8 mm were sectioned from the sintered materials. They were deformed in commpression at 800 °C using strain rate of 1.3×10−5 s−1. Specimens could be deformed to as large as 90 % in a nominal compressive strain.
Incommensurate nature of the “decagonal” Phase Al65Cu20Co15 in the Al-Cu-Co ternary system
Authors: Ramani Atul S. , Song Shihong , Ryba Earle R. , Howell Paul R. 
Published: June 2020

The discovery of a phase in Al-14 at% Mn alloys which displays forbidden icosahedral symmetry spurred a massive effort towards synthesis, characterization and theoretical modeling of the so - called “quasicrystalline” phase. Subsequendy, “decagonal” phases in Al-Mn and Al-Fe, having diffraction patterns characteristic of a periodic stacking of two-dimensional “quasicrystalline” structures, have been discovered. The present paper, reports preliminary results of our investigation of the “decagonal” phase first discovered by He et al. in an Al65Cu20Co15 alloy.High purity metals (Al, Cu, Co) were arc-melted in an argon atmosphere into alloy buttons of nominal composition Al65Cu20Co15. Specimens for TEM were prepared by ion-beam milling in a Gatan ionmilling system operated with an argon ion-beam, at an accelerating voltage of 4 kV and at specimen current of 1 μA. The thin foils were examined in a Phillips EM 420T microscope operating at 120 kV. Selected alloy buttons were fractured and prepared for examination on an ISI - SX 40 SEM operated at 25 kV.
Twinning in ternary Ti50Ni(50−x)Mx alloys
Authors: Moberly Warren J. , Sinclair Robert , Duerig Tom W. 
Published: June 2020

Twinning in materials results from one of two different effects. Firstly, thermal changes may give rise to growth twins during solidification, annealing twins during recrystallization, or martensitic twins during solid-state phase transformations. Secondly, shear stresses can activate mechanical twinning as a deformation mode other than dislocation slip. TiNi alloys are unusual in that they exhibit both types of twinning. Due to the submicron dimension of both types of twins, transmission electron microscopy (TEM) is used to characterize the resulting structures.TiNi is well-known for its shape memory properties resulting from a martensitic transformation of the cubic B2 structure to the monoclinic B19' structure upon cooling. Minor concentrations of various third elements can be added to modify different shape memory properties. In the case of TiNiCu ternary alloys, up to 30% Cu is substituted for Ni while retaining the shape memory effect. For small Cu concentrations the B2 austenite phase transforms, upon cooling, to the B19' monoclinic martensite typical of the binary alloy.
Quantitative stress determination in SiC reinforced Al2O3
Authors: Caspers Bernhard , Mader Werner , Angelini Peter 
Published: June 2020

Whisker and fiber reinforced ceramic composites offer the potential for increased fracture toughness and fracture strength. However, differences in thermal expansion between whisker and matrix generate residual stresses which may affect the mechanical properties of such composites. The microscopic stress can be determined by analyzing the strain contrast around SiC whiskers quantitatively, similar to the strain analysis performed on ZrO2 inclusions in AI2O3. Previously obtained experimental TEM results on strain contrast around SiC whiskers embedded in Al2O3 were only qualitatively. In the present study the experimental observations are quantitatively evaluated.Contrast simulation requires the knowledge of the matrix displacement field in the vicinity of the whisker. Due to two force-free surfaces adjacent to the inclusion, Eshelby’s method for an inclusion in an infinite matrix can not be used for the evaluation of the elastic field in a TEM foil. Therefore, the Green’s function method was applied to fulfill the elastic boundary conditions for both surfaces neglecting only the elastic interaction between the surfaces.
Toughening mechanisms in abalone shell
Authors: Gunnison Katie E. , Sarikaya Mehmet , Aksay Ilhan A. 
Published: June 2020

Abalone shell (Haliotis Rufescens) is a naturally ocurring ceramic/polymer composite material. The system displays a unique laminated structure of calcium carbonate (aragonite) crystals in a matrix of biological macromolecules. The CaCO3 crystals and the organic matrix are arranged in a miniature “brick and mortar” structure referred to as nacre. Figure 1 is a TEM bright field micrograph illustrating the high degree of order observed in this microstructure.Although the nacre region of the shell is more than 95% CaCO3 by volume, the natural matrix material and the arrangement of the microstructure lead to a substantial increase in the observed mechanical properties. Mechanical tests performed on the nacre region show a fifty-fold increase over that of pure bulk CaCO3 (Fig. 2), which also compares with other ceramic and cermet systems.Vickers microhardness testing was performed on samples polished for optical microscopy. Crack propagation features were observed by standard SEM techniques and analyzed in an attempt to identify the possible toughening mechanisms that are operating in the nacre structure. The cracks generally travel by a tortuous path, often displaying microcracks and crack branching. However, these mechanisms alone are not sufficient to account for the observed mechanical properties.
The influence of annealing on the topography of (100) and (111) surfaces of MgO
Authors: Gajdardziska-Josifovska M. , Crozier P. A. , Cowley J. M. 
Published: June 2020

The atomic structure and topography of MgO surfaces are of considerable interest because of the frequent use of MgO crystals as substrates for epitaxial growth of metal films, high Tc superconductors and model catalyst systems. In recent years, a large number of studies have appeared employing broad beam techniques to characterise MgO surfaces prepared under different conditions. However, very little has been done to characterise the topography of such surfaces using reflection electron microscopy (REM) techniques. A few studies have appeared on cleaved (100) MgO surfaces but there are no microscopy studies of the (111) surface. We have examined cleaved (100) surfaces and have investigated the effect of high temperature annealing on the surface topography of both the (100) and (111) surfaces.Single crystal MgO cut along the <010> direction was ground down to a thickness of approximately 150 μm and then cleaved with a razor blade along the (100) plane. The bulk terminated (111) surface of MgO is a polar surface and thus is not an easy cleavage direction.