To address how the chemical and structural heterogeneity of Pt50Ru50 nanoparticles affects methanol oxidation activity, we have employed an arsenal of transmission electron microscopy techniques (conventional bright field-imaging, selected area diffraction, atomic-resolution lattice imaging, electron-energy loss spectroscopy, and energy-dispersive x-ray spectroscopy) to characterize 2.5-nm particles in differing oxidation and hydration states. Our studies demonstrate that electrocatalysts containing a high fraction of Ru-rich hydrous oxide, as apposed to the anhydrous PtRu bimetallic alloy, have as much as 250x higher methanol oxidation activity

The nominally 2.5-nm Pt50Ru50 particles were studied in as-received, reduced and reoxidized forms. The reducing treatment consisted of 2 h at 100 °C in flowing 10% PL/argon mixture. For re-oxidation, the reduced particles were heated for 20 h at 100 °C in an H2O-saturated oxygen atmosphere. The particles were suspended in methanol, and pipetted onto holey-carboncoated Cu grids for TEM studies.

Metallic nanoparticles play an important role in heterogeneous catalysis; these nanoparticles are usually finely dispersed onto high-surface-area supports and act as active centers during a catalytic reaction. The performance of a supported metal catalyst is often directly related to the size and spatial distribution of the nanoparticles. Traditionally, TEM/STEM techniques have to be used to visualize highly dispersed nanoparticles. A major limitation of TEM/STEM techniques is, however, the stringent requirements of samples that can be examined: Useful information can be extracted from only very thin areas of a sample. The preparation of samples suitable for TEM/STEM observation can also pose a challenging problem for examining certain types of catalyst samples such as catalyst beads, pellets, powders, cylinders, or other forms that are often used in industrial applications. These and other limitations preclude the application of TEM/STEM techniques to extracting useful information about the surface or subsurface properties of thick or bulk catalyst samples.

Automotive catalysts are regularly examined using several methodologies such as X-ray fluorescence (XRF), X-ray powder diffraction (XRD), wavelength dispersive spectroscopy (WDS), and analytical electron microscopy (AEM) since no single analytical technique is capable of fully characterizing and measuring changes in morphology and chemistry that occur in emission system materials with use. Each analytical technique provides a specific piece of information, such as elemental weight percentages, phase identification, or spatial distribution of elements. However, in aggregate too much information from too many different specimens is often present, making assimilation and processing difficult. A computerized method using data mining techniques could greatly improve the quality of the interpretation and allow discovery of trends that are not readily apparent. However, finding an appropriate method of combining the disparate types of information is a challenge

The first step was to collect and archive the data in a relational database. This task comprised a large percentage of the development process since the data are initially created in several locations and must be collected, cleaned, and stored.

Princeton Materials Institute, Princeton University, Princeton, New Jersey 08544 Some biological materials exhibit structural robustness, despite the brittle nature of their constituents.Nacre (mother-of-pearl), the pearly internal layer of many mollusc shells, is addressed in this study. This material comprises about 95% aragonite tablets (a mineral form of CaC03), The polygonal tablets were glued with only a few percent of biological macromolecules into layered structure. The goal of the present study is to elucidate the basic inelastic deformation mechanisms.

Typical stress /strain curves in tension and compression are plotted in Fig. 1. All tensile curves exhibited extensive inelastic deformation. After testing, the samples were initially examined using a stereo microscope (Leica MZ8) and a metallurgical microscope (Leica MEF4M) followed by analysis of the structural details using scanning electron microscopy (Philip XL-30). Optical imaging provided a visualization of the inelastic zone, manifest as white tension lines.

In 1980’s the discovery of multicomponent systems with exceptional glass forming ability enabled the synthesis of metallic glasses at relatively low cooling rates, 10−1 — 102 K/s and at a larger thicknesses. Bulk metallic glasses normally have very high yield stress, σy = 0.02 · Y (Y is Young’s modulus), high elastic limit of about 2%, but fail with very little global plasticity, typically along a localized shear band at a 45 degree angle with respect to the applied stress.

The material studied in the present work is a two-phase Zr56.3Ti13.8Cu6.9Ni5.6Nb5.0Be12.5 alloy,prepared by in-situ processing. The alloy consists of amorphous and crystalline phases. In-situ TEM straining (tensile) experiments were performed at room temperature in JEOL 4000EX operating at 300kV. The experiments were carried out in the Center for Microanalysis of Materials in the University of Illinois at Urbana-Champaign. The goal of the study was to understand the deformation mechanisms of such composite material.

Delamination related research in fiber-reinforced composites has attracted considerable interest due to its significant practical importance. Significant difference in deformation patterns in the crack tip vicinity were observed for Mode I and Mode II delaminations and reported by several authors including [1-3]. A sequence of 45° (with respect to the crack plane) microcracks is believed to form beyond the Mode II crack tip in polymer composites. The propagation of a Mode II crack is believed to be a result of rupture and coalescence of these tension microcracks.

A Philips XL30 ESEM scanning electron microscope was used for testing. A three-point bend stage was designed to perform in situ end notch flexure tests on a pre-cracked miniature (1.4” long and 0.25” wide) 24-ply unidirectional specimen. The material system utilized in the experiment was a toughened carbon epoxy unidirectional composite, IM7/977-3. The miniature specimen was cut out of a standard size (8” long, 1” wide) specimen after a shear crack formed in the course of ENF testing.

Aluminum nitride (AlN) is known to have a high thermal conductivity and is one of the valid candidates as substrate material for integrated circuits. The material also has a potential in metal production and handling. However, AlN has only a moderate flexural strength and fracture toughness. It has been reported that SiCA1N composites (SiC/AIN ratio ≥ 50%) can be manufactured by means of pressureless sintering. Furthermore, it is possible to fabricate self-reinforced SiC-based materials with whisker-like crystals in composite ceramics by choosing appropriate sintering additive and condition. in the present study, we investigated the possibility to prepare in-situ formed SiC-whisker reinforced AlN-materials and studied the microstructure of the composite.

An AlN-SiC composite ceramic sample (20 vol% SiC) was prepared for the investigation. The AlN-SiC composite was processed from a mixture of the starting powders with 2.5 wt% Al2O3-Y2O3 as a sintering additive.

SESAM stands for "Sub- eV -sub- Ångstrøm -Microscope". The aim of the project is to develop a TEM/STEM which combines the advantages of both types of instruments. The SESAM project is based on three development stages, specifications of which are shown in Table 1. in the final stage an information limit below 1Å and an energy resolution of 0.2 eV is strived for.

Compared to previous energy-filtering microscopes SESAM I is equipped with a 2nd order corrected energy filter [1]. Due to the high transmissivity [2] large scattering angles up to 150mrad at ΔE=20 eV are accepted by this filter which can be used in electron diffraction experiments. A diffraction pattern of amorphous SiBCN ceramic is shown in Fig.l together with a profile. Since the diffracted intensity can be integrated over 2π, high statistical accuracy is achieved even at a moderate exposure time (10s). in energy-filtered imaging large specimen areas are imaged isochromatically.

Recently, energy filtering technique in the transmission electron microscopy (EF-TEM) is becoming widely used in both materials and biological science.

In this paper, newly developed EF-TEMs for both 200 kV (JEM-2010FEF) and 300 kV (JEM- 3100FEF) are introduced. Figure 1 shows appearances of the instruments. Those instruments have a field emission gun and an OMEGA type spectrometer.

The features of JEM-2010FEF and JEM-3100FEF EF-TEMs are as follows [1,2]:

1. 3 pre-filter lenses and 3 post-filter lenses are used.

Additional intermediate lens is employed for covering filtered images in low magnification range from x200 - x 1,500,000 magnification for JEM-2010FEF, x200 - x2,000,000 for JEM- 3100FEF. in diffraction mode, from 200 mm - 2,000 mm in camera length for JEM- 2010F, 200 mm- 1,500 mm are covered for JEM-3100FEF.

2. Large energy dispersion.

The energy dispersion is 1.2 μm/eV at 200 kV and 0.85 μm/eV at 300 kV.

FEI is currently finishing the construction of a monochromized 200kV (S)TEM which aims at 0.1 eV resolution in Electron Energy Loss Spectroscopy (EELS). This requires improvement of the 200kV supply, improvement of the EELS spectrometer, and the incorporation of an electron beam monochromator. This microscope will be delivered to the National Centre for High Resolution Electron Microscope at the University of Delft.

The present 200kV supply contributes 0.2 eV to the energy resolution because of its instabilities, drift and high frequency ripple. in order to reduce this, mechanical as well as electrical damping elements are being added, and sources of cross-talk between the high frequency generator and the high tension are eliminated. in this paper, we present preliminary results obtained with a standard 200kV supply; we expect to present results of the improved 200kV supply at the conference.

The resolution of a present-day standard 200kV spectrometer is now typically 0.4 eV. in order to improve on this, GATAN has developed a HR-EELS spectrometer for the monochromized TEM.

The Gatan Enfina EELS spectrometer, featuring a new generation of detection system, was recently developed to upgrade or replace Gatan PEELS / DigiPEELS systems. Major advantages of the system include significant improvements to the detector point spread function, readout speed, sensitivity, readout noise, and increased number of detection channels. This design was until now not available for VG STEM systems because compatible detectors must not significantly degrade the UHV column vacuum and must survive column baking. in this abstract we report on a new detector system with comparable specifications to the standard Enfina system but designed for new or for upgrading existing Gatan UHV PEELS / DigiPEELS systems on the VG STEM.

The standard Enfina design has the scintillator, fibers, CCD, CCD socket board, flex-cables, thermo electric cooler and coupling grease in the shared vacuum of the EELS spectrometer and the electron microscope.

The ability to obtain elemental maps processed by using inelastically scattered electrons in a transmission electron microscope (TEM) or a scanning transmission electron microscope (STEM) is extremely useful in the analysis of materials, and semiconductor devices such as ULSI’s and GMR heads. Electron energy loss spectra (EELS) also give useful information not only to identify unknown materials but also to study chemical bonding states of the objective atoms. Hitachi developed an elemental mapping system, consisting of a STEM (Hitachi, HD- 2000) equipped with a two-window energy filter (Hitachi, ELV-2000), and performed realtime conventional jump-ratio images with nanometer resolution by in-situ calculation of energy-filtered signals [1]. Additional function of acquiring EELS along any lines on specimen has been developed in this system to investigate the energy loss near edge structure (ELNES).

Figure 1 shows a schematic figure of the two-window energy filter, consisting of two quadrupole lenses for focusing and zooming spectra, respectively, a magnetic prism spectrometer, a deflection coil and two kinds of electron beam detectors.

Energy filtering transmission electron microscopy (EFTEM) has matured into an important nanoanalytical technique in both materials and life sciences. One of the technique′s main advantages stems from the possibility to quickly form images that contain two-dimensional elemental information for most elements (Li to Pu) from relatively large specimen areas with nanometer resolution. Over the last years numerous and wide-ranging applications have demonstrated its almost unrivalled power for assessing typical materials science questions.

Both in-column or post-column filter microscopes have reached a high performance level, but future improvements are still desirable, in particular with respect to increased transmissivity, improved isochromaticity and higher detection efficiency. Current instruments allow to acquire elemental maps with 1-5 nm spatial resolution limited mainly by the aberrations of the microscope and by the quality of the specimen. As recently shown 0.4 nm resolution is feasible.

One major practical problem of EFTEM compositional mapping is the poor signal-to-noise ratio, which means that experimental parameters have to be chosen very carefully in order to optimize this ratio.

It is now becoming increasingly more commonplace to acquire three-dimensional EELS data sets, whether by parallel acquisition of a linear series of spectra to form an EELS spectrum-image, or by discretely sampling energy-loss space through a series of energy-filtered images to build an EFTEM image-spectrum. These data sets can contain large amounts of both spectral and spatial information, and, as a result, the distinction between the two acquisition modes is becoming increasingly blurred. Accordingly, approaches are required that facilitate both the techniques developed for EFTEM and EELS analyses, in order to obtain optimal information from the acquired data.

An example of such an approach is illustrated by means of characterisation of a Mn and Fe rich intermetallic particle in a cast aluminium alloy (Figs. a-f). A continuous EFTEM image-series was acquired from 0-800 eV loss, using a CM300 FEGTEM equipped with a 2k Gatan Imaging Filter.

The optimized performance of Co(CrTaPt) thin-film longitudinal magnetic recording media (for computer hard discs) depends critically on the grain size distribution and on intergranular Cr segregation that magnetically isolates the grains. These microstructural aspects of both model and commercial media have been extensively investigated at ∽1 nm resolution with quantitative elemental mapping by energy-filtered transmission electron microscopy (EFTEM) of Cr, Co, and O, but not Ta and Pt which unfortunately are not amenable to quantitative elemental mapping by EFTEM. Procedures for data acquisition and processing have been refined in order to provide robust methods for measuring intergranular compositions for statistically significant numbers of grains. Figure 1 shows results obtained with a Gatan imaging filter (GIF) interfaced to a LaB6 Philips CM30 for a carbon-capped 25-nm-thick film of Co80Cr16Ta4 grown on a Cr underlayer. Typical acquisition parameters have been described previously. to avoid the Cr underlayer, foil thicknesses t<0.2X are used, including the carbon overlayer (λ = inelastic mean free path ≌100 nm).

The term “quantitative“ means many things to many people. in imaging its value is often discounted to mean only that a more intense region can be said to have more of what is being measured than a less intense region. Others may be more stringent and require an approximately linear relationship between the measured property and image intensity. (This is most often the case in EFTEM and spectrum imaging) Some specimens contain internal references (such as elements with a known stoichiometric relationship) that are sufficient to get to a true concentration calibration for an image. However, in EELS imaging this still doesn’t allow us to get an understanding of our errors and rarely is it helpful in determining detection or quantification limits.

A competent high-school chemistry or physics student could tell us that a quantitative measurement includes both a measured value and an estimate of its error.

A software package has been developed that synthesizes entire energy-loss spectra for an arbitrary distribution of impurities embedded in an arbitrary matrix, for user specified sample parameters and acquisition conditions. The simulation of a complete spectrum facilitates the estimation of quantities such as the Minimum Detectable Mass (MDM) or the Minimum Detectable Number of atoms (MDN). This is addressed with particular attention to optimising the acquisition conditions to maximize the detectability and also to estimating the error in a typical EELS quantification. It is envisaged that this approach will have wide-ranging implications for the role of EELS in quantitative microanalysis.

Electron Energy Loss Spectroscopy (EELS) is widely recognized as a microanalytical tool capable of characterizing the elemental composition of materials with nm-level resolution and sensitivity approaching single atoms. Extracting quantitative information from EEL spectra is complicated by the fact that both the cross-sections and the pre-edge background used for inner-shell analysis vary widely.

Despite of the intensive studies, Colossal Magnetoresistance (CMR) phenomena occurring in manganese oxides is still not fully understood. Theoretical studies based on an ordered crystal phase such as the charge-ordering (CO) phase have shown some successes in reproducing experimental evidences. Recently it was, however, shown that such a CO phase included giant clusters which were as large as 100 nm. This indicates the importance of the nanometer-scale information about the electronic structure to understand the CO. La0.5Sr1.5MnO4 is one of the oxides under intense investigations. in the CO phase, the eg valence electrons were found to be ordered at Mn sites. The optical responses of the CO clusters, however, has not been studied. in this study we have attempted to obtain such information from CO clusters in La0.5Sr1.5MnO4 by angular-resolved electron-energy-loss-spectroscopy (EELS) using an in-column type Ω-spectrometer.

Last year we discussed the performance of a new parallel EELS spectrometer, the ENFINA™. The spectrometer optics have been considerably improved over past designs and the detector changed from a photodiode to a charge coupled device that was designed specifically for spectroscopy. in this work we present application examples that demonstrate some of the capabilities of the ENFINA™.

STEM spectrum imaging requires a spectrometer of high speed and sensitivity if useful data is to be collected in a short period of time. The ENFINA™ spectrometer achieves both of these through a radically improved point spread function, increased sensitivity, and fast detector readout. Useful spectrum images can be acquired in a few minutes. Figure 1 shows a dark-field STEM image of a typical semiconductor. A spectrum image containing 190 x 150 spectra was acquired from within the marked area.

The hexagonal boron nitride (h-BN) exhibits a phase transformation to the cubic one (c-BN), the latter of which is well known as the second hardest material so far, under high pressure. This transformation is accompanied not only by the geometrical change in the crystal structure, e.g. stacking sequence of the close-packed planes, but also change in the chemical bonding from sp2 to sp3 characters. Electron energy-loss spectroscopy (EELS) is a hopeful way to characterize the state of bonding around the phase boundaries etc., and will provide rich information on the transformation mechanism. However, the energy-loss near-edge structure (ELNES) is rather sensitive to the orientation of specimens, if the structure is anisotropic as in the case of h-BN. This is sometimes obstructive to evaluations of ELNES, whereas a detailed investigation on this peculiar effect is needed. in the present work, the angular dependence of ELNES in h-BN was extensively studied by both calculations with DV-Xα (Discrete Variational X α cluster) method and experiments, beside investigations of the c-BN.