bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental and theoretical X-Ray distribution function, δ(ρz), for microanalysis of thin
Authors: Zreiba N. A. , Pico C. A. , Kelly T. F. 
Published: June 2020

Absorption and fluorescence corrections used in the quantitative microanalysis of thin specimens usually require prior knowledge of the variation of the generated x-ray intensity, ϕ(ρz), with mass depth, ρz. In the analysis of electron-transparent thin foils, ϕ(ρz) is generally assumed to be independent of mass thickness. This assumption may not apply when absorption and/or fluorescence corrections are necessary. As shown by Stenton et al, the x-ray distribution, ϕ(ρz) in thin foils can be determined experimentally by using the Tracer technique. ϕ(ρz)s for thin specimens have also been calculated theoretically by using the Monte Carlo technique.In our laboratory submicron spheres of pure or stoichiometric compound materials have been produced by a process called electrohydrodynamic (EHD) atomization for the purpose of determining the detector efficiency function of electron microscope x-ray detectors. Because the assumption of constant ϕ(ρz) may not apply for compounds that require absorption and/or fluorescence corrections, it was necessary to determine ϕ(ρz) for thin spheres.
AEM analysis of condensed-phase xenon in UO2 spent fuel
Authors: Thomas L. E. , Guenther R. J. 
Published: June 2020

Release of the abundant fission gases xenon and krypton in UO2 reactor fuels is a limiting factor in normal performance of fuel rods and a concern in possible accidents involving transient overheating of the fuel. Consequently, a knowledge of the fission gas behavior in fuel is of great interest. Although fission gases in fuel are widely believed to exist as gas bubbles or atoms in solution in the UO2, we have obtained evidence by analytical electron microscopy that the xenon and krypton can also exist as a condensed phase, i.e. as a liquid or solid at high internal pressures in the UO2. This finding is likely to be important in modeling fission gas release.In a typical light-water power reactor (LWR), operating temperatures vary from about 650K at the edge of a fuel pellet to about 1400K at peak-power axial regions. Samples prepared from different radial locations in peak-power sections of low gas-release LWR fuels ATM-101 and ATM-103 were examined in a 200 KV AEM to determine how the gas and solid fission products varied with local fuel operating temperature.
Elemental microanalysis of the human lens
Authors: Shuting Ma , Shilling Zhang , Shoujing Fu 
Published: June 2020

Some chemical elementals, such as K, P, Na, Ca and Cl are widely implicated in a variety of lens cel1-functions. For an exact assessment of their role one needs to know the quantitative distribution of these elements in and around the lens cells. The EDXA of bulk specimens possibly permits such measurement to be made in a reliable and nondestructive way. The paper on the distribution of the elements in human normal lens, which was finished with the technique of electron prob x-ray microanalysis has not been published. The purpose of the present study is to explore the intracellular K/Na ratios and the elemental distribution between human normal and cataractous lens.In this study, only human lenses were used and the fresh tissues were obtained at cataractous and traumatic surgery. All the samples were rapidly frozen on a metal disc maintained at liquid nitrogen temperatures. The frozen samples were fractured, lyophilized and coated.
Formation of eta-phase in CVD-coated cemented carbides
Authors: Skogsmo J. , Norden H. 
Published: June 2020

Chemical vapour deposition (CVD) is commonly used to produce wear resistant coatings on cemented carbide cutting tools. These coatings may consist of several layers but the innermost layer is usually TiC. The adherence and mechanical properties of the coated tool are mainly determined by the composition of the transition region substrate-coating. The high process temperature and the presence of reactive gases can result in a decarburizing of the substrate surface layer. If the cobalt binder phase is decarburized, its solubility of W will increase and this may eventually lead to the formation of a new phase, the eta-phase commonly of the type Co6W6C, which is very brittle and can have detrimental effect on the coating.In this study two types of specimens were used, very sharp (apex radius 50 nm) needles and flat cutting tool inserts. The coating process was performed with CH4 at 1000 °C and 50 torr, using very short (30s-3min) deposition times to obtain sufficiently thin layers. The needles have the advantage that they can be examined directly by STEM-EDS without any further specimen preparation, Fig.1.
A TEM investigation of a hyper-eutectic lead-tin alloy
Authors: Sutliff John A. 
Published: June 2020

Near-eutectic Pb-Sn alloys are important solders used by the electronics industry. In these solders, the eutectic mixture, which solidifies last, is the important microstructural consituent. The orientation relation (OR) between the eutectic phases has previously been determined for directionally solidified (DS) eutectic alloys using x-ray diffraction or electron chanelling techniques. In the present investigation the microstructure of a conventionally cast, hyper-eutectic Pb-Sn alloy was examined by transmission electron microscopy (TEM) and the OR between the eutectic phases was determined by electron diffraction. Precipitates of Sn in Pb were also observed and the OR determined. The same OR was found in both the eutectic and precipitation reacted materials. While the precipitation of Sn in Pb was previously shown to occur by a discontinuous precipitation reaction,3 the present work confirms a recent finding that volume diffusion controlled precipitation can also occur.Samples that are representative of the solder's cast microstructure are difficult to prepare for TEM because the alloy is multiphase and the phases are soft.
The hierarchy of grain boundary structures in SiC bicrystals
Authors: Ishida Y. , Ichinose H. , Inomata Y. 
Published: June 2020

The standard geometrical theory having been developed to describe periodically ordered grain boundaries in metals, ie coincidence-site lattice theory faces a new frontier to be expanded in terms of hierarchy of atomic structures in low energy grain boundaries of polytype SiC bicrystals. The unit translation lattice of the polytype crystal is large and elongated in the direction perpendicular to the basal plane. With the elongated translation lattice, the coincidence-site lattice is generally very large. Often too large to be physically significant, although the predictive role of the coincidence-site lattice theory in specifying the orientation of periodically ordered interface was still preserved. Such periodically ordered boundaries were indeed found to occur in the present SiC bicrystals as is predicted by the geometrical theory. A dual description of the grain boundary structure in terms of hierarchy of atomic structures is shown useful in characterizing the bicrystal boundaries.High purity SiC bicrystals were produced by sublimation-deposition method by cooling the encapseled SiC slowly from 2800K.
Crystallizing Y2Si2O7 at the grain boundaries of a Si3N4 ceramic
Authors: Hiltnas G. E. , Lee W. E. 
Published: June 2020

Improving the high temperature properties of Si3N4 containing glass at the grain boundaries may be possible by crystallizing the glass to a refractory phase as first suggested by Tsuge et al. AEM has recently been used to examine the morphology of cordierite (Mg2Al4Si5O18) and garnet (Y3Al5O12) crystallized at the grain boundaries of SiAlON ceramics. We present here results of an AEM investigation of the morphology of Y2Si2O7 crystallized from a 6 weight % Y2O3-Si3N4 ceramic.Bars were isostatically pressed and then sintered at 2140°C for 2 hours in 50 atm N2. Crystallization was at 1500°C in 50 atm N2 for various times up to 20 hours. Microscopy samples were prepared using conventional techniques and examined in a JEOL 200CX AEM.The microstructure of an as-sintered specimen is shown in Figure 1. A few of the hexagonal β-Si3N4 grains contain dislocations (arrowed). These are most likely simple growth defects from the a →β-Si3N4 solution-reprecipitation sintering process.
Minimum-dose electron energy-loss spectroscopy
Authors: Kundmann Michael K. , Krivanek Ondrej L. , Martin J.M. 
Published: June 2020

Parallel-detection electron energy-loss spectrometers have greatly reduced the irradiation doses needed to acquire electron energy-loss spectroscopy (EELS) data. This raises the possibility that changes in chemical bonding due to radiation damage, which usually precede changes incomposition, may be studied by examining alterations in low-loss and core-edge fine structure with increasing dose.The quality of data attainable with low-doses in parallel-detection EELS is illustrated by Fig. 1, which shows the K-edge region for a thin amorphous carbon film. This spectrum was collected in 2sec with a 1pm-diameter probe at 100kV in (microscope) diffraction mode. A 20cm camera length ensured that virtually all scattered electrons passed through the 3mm entrance aperture of the spectrometer. Spectrum dispersion is 3eV/channel and the energy resolution is ∼1eV/channel as the π* peak is clearly resolved. The total incident current, as determined in image mode (no objective aperture) from the viewing-screen meter, was only 40pA. The total dose for this K-edge spectrum was consequently only 6.4e-/Å2.
Design of a high-performance auger spectrometer in the STEM
Authors: Ouyang Feng 
Published: June 2020

In high resolution electron beam instruments, Auger analysis is usually performed by keeping the sample in a field free region and employing a standard energy analyzer such as hemispherical sector (HSA) or a cylindrical mirror (CMA). In spite of its simplicity, this arrangement results in long focal length operation and consequently a relatively large spot size. In addition, the collection efficiencies of the energy analyzer coupled with such STEM/SEM/SAM systems tend to be small. If however we perform Auger analysis with the sample immersed in the objective lens field, not only would we have the capability of producing a subnanometer diameter probe, but we can also use the post- or pre-specimen field to parallelize the emitted electrons to yield higher collection efficiency.One approach is to use an electrostatic optics extraction system. In this paper magnetic optics extraction will be considered.
Quantitative evaluation of materials by scanning electron microscopy
Authors: Pignolet-Brandom S. , Reid K. J. 
Published: June 2020

QEM*SEM, or quantitative evaluation of materials by scanning electron microscopy, is a fully automated scanning electron microscope system that was designed and engineered by CSIRO in Australia for applications to the minerals industry. It is an integrated system in which the computer and its associated hardware and software control SEM operations. Minerals can be identified in point, linear or area scans. Depending on the type of scan, information is extracted from the data files and summarized in tables and graphs covering mineral abudances, associations, sizes, free surface area and the degree of liberation. In addition, area scans can be replayed on a graphics monitor to produce QEM*SEM mineral species maps.The QEM*SEM system consists of an International Scientific Instruments SX-40 scanning electron microscope with a specially designed sample chamber that permits 100 mm movement of the stage. The EDS units were designed for rapid collection of x-ray spectra and consist of four lithium drifted silicon detectors each with a separate preamplifier.
REM and RHEED investigation of the epitaxy of evaporated gold film on a CaAs (110) surface
Authors: Yao N. , Cowley J. M. 
Published: June 2020

Detailed understanding of the epitaxial grown gold thin film is highly desirable, both for fundamental physical reasons and due to increasingly sophisticated applications. In this paper, we present the utilization of the significant advantages of both REM and RHEED in a commercial Philip-400T instrument to investigate the crystalline quality and topography of epitaxical gold layers on GaAs(110) surfaces.The specimen preparation was carried out in a commercial FC-12E UHV system containing a quartz crystal sensor for thickness control. The experimental arrangement inside the UHV chamber is shown in Fig. 1, where the evaporating source is set in a position equally distance from the crystal sensor and the specimen substrate. The bulk shield next to the specimen is to block a part of the gold flux, thus the growing film with a certain variation of thickness can be formed on the GaAs (110) plane which faces the shield.
Surface resonance channelling in scanning reflection electron microscopy
Authors: Cowley J.M. , Crozier P.A. 
Published: June 2020

The phenomena of the channelling of electrons along planes or rows of atoms in the surface layers of crystals has been investigated recently in relation to microdiffraction and RHEED, REM, (reflection electron microscopy) and REELS (reflection electron energy loss spectroscopy) by using a conventional TEM in the reflection mode.The renewed interest in this phenomenon, known for many years, is the evidence from calculations of dynamical diffraction effect at surfaces that the electrons may be channelled along the topmost layers of atoms on a crystal surface and that the RHEED, REM and REELS signals may thus be sensitive to the structure and composition of the surface layer. These techniques may therefore provide a powerful new approach to the study of surfaces in which surface microanalysis and diffraction studies may be combined with nanometer-resolution imaging.An investigation has now been made of the analogous techniques which may be applied to the study of surfaces by use of a scanning transmission electron microscope.
Microdiffraction studies of small crystallites
Authors: Bradley S. A. , Robota H. J. 
Published: June 2020

Identification of nano-crystallites (<5 nm) on a high surface area support such as a catalyst is critical in the development of improved catalysts. Bright field imaging of small particles can be obscured by the phase contrast of the support. A common approach is to utilize annular dark field microscopy; however, wide angle scattering from the high surface area support can easily appear in the annular dark field image. Often one utilizes the energy dispersive detector to identify conclusively the nanosized metal crystallite, but this approach is troublesome when crystallites are very thin since counting times for imaging can become excessive. One technique for avoiding some of these difficulties is to utilize microdiffraction to identify the crystallite and then to image the crystallite by axial dark field microscopy.In the work reported here, the imaging was performed with a dedicated VG HB-5 scanning transmission electron microscope.
Void nucleation by interface decohesion in whisker-reinforced composites
Authors: Nutt S.R. 
Published: June 2020

Metal-matrix and ceramic-matrix composites reinforced with whiskers or short fibers exhibit improvements in certain mechanical properties. In the case of metal-matrix composites, improvements in yield strength and modulus are commonly achieved, but often at the expense of ductility and fracture toughness. Interestingly, ceramics reinforced with whiskers frequently show improvements in fracture toughness, while there is little effect on fracture strength compared with the unreinforced material. Also, both classes of materials are generally more resistant to creep deformation. Mechanisms of damage leading to composite failure can be directly observed in the TEM by examination of specimens from tests interrupted at specific stages prior to failure. One damage mechanism common to both types of composites is the nucleation of voids at fiber interfaces. This process can be simulated in model-based calculations, yielding quantitative information about interface properties.Creep tests were conducted on 2124 Al-SiC and Al2O3-SiC composites in which the whisker reinforcement loadings were 13 and 33 v/o respectively.
HREM interface studies in SiC-whisker-reinforced Al2O3and Si3N4ceramics
Authors: Braue W. , Carpenter R.W. , Smith D.J. 
Published: June 2020

Whisker and fiber reinforcement has been established as an effective toughening concept for monolithic structural ceramics to overcome limited fracture toughness and brittleness. SiC whiskers in particular combine both high strength and elastic moduli with good thermal stability and are compatible with most oxide and nonoxide matrices. As the major toughening mechanisms - crack branching, deflection and bridging - in SiC whiskenreinforced Al2O3and Si3N41are critically dependent on interface properties, a detailed TEM investigation was conducted on whisker/matrix interfaces in these all-ceramic- composites.In this study we present HREM images obtained at 400 kV from β-SiC/α-Al2O3and β-SiC/β-Si3N4interfaces, as well as preliminary analytical data. The Al2O3- base composite was hotpressed at 1830 °C/60 MPa in vacuum and the Si3N4-base material at 1725 °C/30 MPa in argon atmosphere, respectively, adding a total of 6 vt.% (Y2O3+ Al2O3) to the latter to promote densification.
Image analysis and SEM characterization of SiC whiskers and ceramic composites
Authors: Chen R. T. , Jamieson M. G. 
Published: June 2020

Recently, attention has been focused on whisker reinforced ceramic composites Ipecause of their potential in high temperature structural applications. Aspect ratios of whiskers and particle size distributions of the matrix ceramic powders are critical parameters which can effect processing and microstructure/properties of the final composite materials. In this paper, quantification of these parameters using SEM and automated image analysis, as well as their significance in the development of whisker reinforced ceramic composites will be discussed.The present study involved the evaluation of microstructures of SiC reinforced alumina ceramic composites. In the evaluation of SiC whiskers, good whisker dispersal is a prerequisite for automated image analysis. A dispersion technique was used to break up the agglomerated SiC whiskers. Whiskers were dispersed on glass slides and aspect ratios were measured using a Quantimet-970 image analyzer interfaced to an optical microscope. Because of the submicron nature of the starting alumina powders, SEM was needed to provide images. For grain size evaluation, both fracture surfaces and polished/etched surfaces were examined in a JEOL JXA-840 SEM.
TEM study of the T2 phase in Al-Li-Cu alloys at elevated temperatures
Authors: Reed J. R. , Michel D. J. 
Published: June 2020

The discovery of an alloy phase exhibiting five-fold symmetry in rapidly quenched Al-Mn alloys has led to reports of similar phases in other alloys systems. Other studies have suggested that the T2 phase in Al-Li-Cu alloys exhibits five-fold symmetry and forms as a stable phase by solidification directly from the bulk alloy. Although considerable effort has been expended to investigate the icosahedral phases, including the T2 phase in the Al-Li-Cu system, the thermal stability of this phase remains unknown. The purpose of this paper is to report results from an investigation of the thermal response of the T2 phase in Al-Li-Cu alloys during an in-situ elevated temperature transmission electron microscope study.The 3-mm diameter specimens used for the transmission electron study were prepared from a specially melted Al-2.5 Li-2.5 Cu alloy produced by conventional procedures. The TEM disc specimens were solutioned 1 h at 550°C and aged 50 h at 190°C in air to develop the microstructure.
Electron microscopy of modulated and ordered alloys
Authors: Bentley J. 
Published: June 2020

Modulated and ordered alloys are of interest not only from a basic standpoint but also because they often possess interesting properties or form the basis of commercial materials. Transmission electron microscopy (TEM) provides much unique and valuable information in the study of phase transformations in such alloys but, as this overview of the applicable methods will try to illustrate, the experimental work is often challenging and data interpretation is rarely straightforward.In alloys with a modulated structure, spinodal decomposition is the transformation process of most interest. In cubic crystals, elastic anisotropy usually leads to triaxially modulated structures with composition modulations along <100>, whereas in isotropic systems, randomly oriented, highly interconnected structures are formed. TEM has most commonly been used to image the spinodal microstructure and to measure wavelength and waveshape. The observations are often only qualitative because of the complex nature of the image, but quantitative measurements of coarsening behavior have been attempted.
A Transmission Electron Microscopy study of the B2-DO3 ordering phase transformations in Fe-6.3wt% Si after rapid quenching and annealing
Authors: Wittig J. E. 
Published: June 2020

Iron-silicon alloys are extensively used in transformer cores owing to exceptional soft magnetic behavior that is optimized at about 6.5 wt% Si. Unfortunately this equilibrium microstructure is completely brittle at room temperature. The brittle behavior coincides with the onset of an ordering reaction of the disordered A2 into the B2 and DO3 superlattices at approximately 5 wt% Si. Rapid solidification methods have been shown to improve the ductility of Fe- 6.3 to 6.5 wt% Si. In this investigation, rapidly quenched and annealed samples of Fe-6.3wt% Si were examined in the transmission electron microscope (TEM) to study the ordering phase transformations of this alloy and its effect on the mechanical behavior.Samples of Fe-6.3wt% Si were rapidly solidified by melt spinning into ribbons (t=20-80 microns) as well as by splatting using an opposing piston double anvil method. Rapidly quenched samples were subsequently heat treated in evacuated quartz tubes at 500, 600, and 700 C for 24 h.
Disordering and phase decomposition of a nickel-aluminum intermetallic under lowtemperature electron irradiation
Authors: Kenik E. A. , Nastasi M. 
Published: June 2020

In situ electron irradiations at 300 and 1000 kV have been performed at 100 and 300 K on Ni2Al3 for comparison with its response under ion irradiation. In addition, the behavior of Ni2Al3 will be compared to that of NiAl3 reported previously. Thin multilayered films of alternating nickel and aluminum were electron beam deposited onto a NaCl substrate. The substrate was dissolved in deionized water and the Ni/Al film was mounted on 3 mm diam grids. The films were vacuum annealed for 1—2 h at 623 K to allow interdiffusion between the layers. Electron diffraction indicated that the films were fine-grained (∼20 nm diam) Ni2Al3, which is the prototype for the hexagonal D513 structure. No appreciable amount of other phases was detected.The specimens were irradiated with 1000 kV electrons in a Hitachi HU-1000B or with 200—300 kV electrons in Philips EM430 and CM30 microscopes. All three microscopes are equipped for nominal room temperature or low temperature (∼100 K) irradiations.