Supported transition metal particles are often used as heterogeneous catalysts. Elemental mapping with energy-filtered transmission electron microscopy (EFTEM) offers distinct advantages over conventional TEM and x-ray analysis for these systems. Thickness maps, metal identification, support identification, and direct imaging of oxide layers all represent key new information made possible with EFTEM. Energy-filtered transmission electron microscopy with an omega filter has been used to show Ni, Cu and Cr distributions in an alumina-supported catalyst. in this paper we look at analogous cobalt particles from a colloidal suspension supported on a carbon film.

Energy-filtered TEM maps were obtained using a Gatan Image Filter at 200 kV integrated with an FEI CM200FEG microscope. The colloidal cobalt particles have a nominal diameter of 10 nm, providing an excellent model system when supported on thin amorphous carbon supports. Figures 1 - 3 show cobalt L23, oxygen K and elastic micrographs of partially oxidized cobalt particles (native oxide present after drying).

The heterogeneous catalytic system Pt/SiO2 is widely used in “three-way” catalysts, because of its highly selective catalytic reduction of NO by hydrocarbons at low operating temperatures. Although used effectively for more than a decade, in recent years it has become clear that the core phenomena of heterogeneous catalysis can occur at interfaces. in the work presented here, we seek to better understand the role of the atomic and electronic structure of interfaces in making particular reactions facile and moderating the stability and selectivity of a catalytic system.

We investigate model supported platinum catalysts by atomic resolution Z-contrast imaging and EELS using a 200 kV STEM/TEM JEOL2010F with a post column GIF. The combination of these techniques allows us to obtain direct images of the metal particle and its interface with the supporting SiO2, and to correlate that with the modulation of the Si L-edge fine structure.

Antimony-doped tin oxide (ATO) catalysts are used for the oxidation of propylene to acrolein, the ammoxidation of propylene to acrylonitrile and the oxidative dehydrogenation of butanes to 1,3- butadiene. The distribution and valence states of Sb in ATOs are key in determining their catalytic activities. While these materials have been subjects of intensive studies for more than 20 years, X-ray photoelectron spectroscopy, Mössbauer spectrometry, and X-ray absorption spectroscopy4 have so far provided only indirect data for the distribution of Sb and its valence states. in particular, while has been hypothesized that the tin (IV) oxide contains Sb (V) within the bulk lattice and Sb (III) located at surface sites, no direct experimental evidence for this has been provided.

Here we use electron energy loss spectroscopy (EELS) combined with Z-contrast imaging in a JEOL 2010F field emission STEM/TEM operating at 200 KV to analyze ATO catalysts.

Many catalytic materials, especially the maximum valence transition metal oxides, are particularly susceptible to electron beam irradiation and thus undergo structural changes. Hence knowledge about the behaviour of catalytic materials under the electron beam is of importance for all TEM investigations of such materials. On the other hand, this effect can be utilised for an in-situ study of the reductive property, phase transition and/or phase stability of various transition metal oxides in an inert, simple ambient high-vacuum. The knowledge so obtained is needed for understanding the reduction mechanism of catalysts in more complicated chemical environments. in the present work, we study the electron beam induced change in MoO3 and TiO2 (anatase) by means of electron energy-loss spectroscopy (EELS), electron diffraction and high-resolution electron microscopy (HREM).

Molybdenum trioxide, MoO3, important as catalyst in the selective oxidation of hydrocarbons, forms an orthorhombic crystal layer structure. Fig. 1 shows oxygen AT-edges recorded at various irradiation periods in a Philips 200 FEG electron microscope.

Industrial catalysts are often chemically and physically complex systems resulting from many years of technology, science, and art. Successful development of commercial catalysts requires talents of many disciplines including chemistry, chemical engineering, surface science, materials science, and physics. A better understanding of the relationship between catalyst structure and activity can provide a scientific prediction of catalytic properties. The insight gained from catalyst characterization can provide guidance for designing and synthesizing better commercial catalysts. Characterization of industrial catalysts is challenging and expensive; however, it can be highly rewarding in developing commercial catalysts used for manufacturing multibillion-dollar products.

The ultimate goal of catalyst characterization is to correlate the physical, chemical, mechanical, and electronic properties of a catalyst to its activity, selectivity, and stability. in industrial practice, however, because of the complexity of the catalysts, the time limit, and the available resources, the goal of characterizing industrial catalysts is often to elucidate the key performance indicators of a catalyst; these key performance indicators, such as the size and spatial distribution and the composition of the active components and promoters, can then be used to provide guidance for manufacturing better catalysts with desired properties.

The field of catalysis is one of the most important areas of the nano-sciences for many years. in deed the goal of having a catalyst, with the maximum active area exposed to a chemical reaction, has produced enormous amount of research in nanoparticles. Particularly, the metal nanoparticles study is a very important field in catalysis. Electron Microscopy is one of the techniques that have played a mayor role on studding nanoparticles. Since bright field images, dark field techniques, to the high-resolution atomic images of nanoparticles and more recently the High Angle Annular dark field images or Z-contrast. However this technique provides only indirect evidence of the atomic arrangements on the particles. High Resolution Electron Microscopy (HREM) still appears as a very powerful technique to study nanoparticles and their internal structure. Among the most interesting metals to study is the palladium, which acts for instance as excellent catalyst for hydrogenation of unsaturated hydrocarbons and has many other applications such as environmental catalysts.

A vital component to nanoparticle science will be the three dimensional (3-D) characterization of both structure and chemistry of these nanoparticles on their supports at the nanometer scale and below. to achieve this goal, quantitative Z-contrast and atomic resolution will provide essential information about their structure. Z-contrast imaging is ideal for imaging these large Z nanoparticles on low Z supports. in this proceedings, we present a quantitative Z-contrast method to determine number of atoms and a few examples of a combination of electron microscopy methods to gain structural insights into supported nanoparticle, such as Pt on different support materials, PtRu5 on C and Pt-Sn on SiO2.

A relatively new and powerful method is to determine the number of atoms in a nanoparticle, by very high angle annular dark-field (HAADF) imaging or Z-contrast technique [1, 2]. We have shown that quantification of the absolute image intensity from very HAADF microscopy will provide the number of atoms in very small particles of high atomic number to ±2 atoms for Re6 nanoparticles supported on carbon [3].

Progress in the design of catalysts based on nanoparticles supported within a mesoporous silica framework requires structural analysis at high spatial resolution. While bulk analysis by X-ray diffraction and EXAFS can give the structure of active sites they are unable to determine their relative positions and local physical structure. Some success has been achieved using a combination of STEM ADF imaging and EDX mapping to elucidate such structures but these results are limited to giving 2D projections of 3D arrangements. The need exists therefore to analyse specimens in full 3D. A suitable approach is electron tomography where the 3D structure is reconstructed from a tilt series of 2D projections. in conventional electron tomography a tilt series is acquired using bright field (BF) TEM. However the large beam current means such an approach generally cannot be used on specimens based on a mesoporous silica framework as beam damage can develop rapidly.

A large number of papers have been published on using HREM to characterize the crystal structure and defects of catalysts. While such work is important to advance the scientific understanding of catalysis, the bulk of daily analytical work of an industrial catalyst microscopist focuses on analyzing the morphological features of the catalysts. That is, to find out the shape, the size, and the distribution of various phases. in the case of heterogeneous catalysts, the same information is needed for the catalytic metal particles. Ultimately, the goals are to correlate the performance of the catalyst with the size and morphology of the phases or particles. These types of information are often critical element in a patent.

Unfortunately, very little attention has been paid to properly and quantitatively describe crystal shapi crystal size, and size distribution. It is common to find in the literature, statements such as “the crystal size of this sample was 0.5 microns” or “the sample contains elongated crystals of 0.5 microns”.

Antimony compounds play a major role in commercial polyester catalysis. Antimony complexes are used in ppm quantities, not only to catalyze melt-phase reactions in which oligomers are converted to high molecular weight polymers, such as poly(ethyleneterephthalate) (PET), but to further increase chain length through a high temperature solidphase polymerization process. During the course of the melt-phase reaction the initial, clear and colorless, Sb+3 compounds are transformed to a gray product that has been linked with the reduction of Sb+3 complexes to metallic antimony (Sb°). The presence of oxygen during the solid-phase process also increases clarity and reduces color of gray polymers. to further our understanding of antimony catalysis, a field emission-based scanning electron microscope (FEGSEM) was used to study antimony transformations during melt-phase polymerization and after treatments at high temperature in oxidizing and reducing environments.

Antimony metal powder from Fisher Scientific was used in redox studies.

Transition metal oxides have been studied extensively over the last few decades, due to their electro optical and catalytic properties.The overall properties of these oxides and the heterostructures that can be built on them depend upon the surface structure, composition and morphology. However, the available information on the surface structures of transition metal oxides is scarce and often contradictory. Knowledge of the atomic structure of the catalytically active surfaces and of the adsorbed reactants and intermediates under in-situ reaction conditions is crucial for an understanding of catalytic oxidation at the molecular level, and will subsequently create possibilities for faster development of new catalysts, improve their performance on industrial level, and lower the costs associated with processing. The objective of the current work is to develop and apply the available experimental (UHV chambers, UHV-HREM, catalytic treatment chamber) and computational techniques (Direct Methods analysis and multislice simulations of electron diffraction data) to improve understanding of catalytic phenomena under various environmental conditions.

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.