The preparation of frozen amorphous nano-meter thin films of solutions containing particles, and imaging with energy filtered TEM, opens for the first time the possibility to map the elemental distribution in solids interacting with liquids. The future possible areas of research in solution include: dynamic of crystal growth processes, adsorption mechanisms, ion exchange, structure determination of nano-sized solids in equilibrium with different solvents, etc.

The sample preparation uses a controlled-environment vitrification system. Solidification of the liquid phase was achieved by plunging the solution, suspended in the holes of a lacy carbon on a copper grid, into liquid ethane (-174 °C). The specimen was transferred into the microscope by an Oxford CT3500 cryo-holder. The specimen temperature in the microscope column can be kept at -183 °C. The thickness of the vitrified film's, including the particles, should be about 50-100 nm or preferably less. The Philips CM120 BioTWIN Cryo microscope, here used for cryo-EFTEM, has a focal length of 6 nun and a structural resolution of 0.4 nm.

From the late 1960s onwards the author embarked on a series of electron microscopic adventures using progressively more sophisticated techniques which yielded structural information and uncovered physics-chemical phenomena that would have been irretrievable by other methods. Illustrative examples include; (i) proof that photoreactivity and unexpected photoproducts of organic molecular crystals are governed by stacking faults, and that applied stress converts some photostable organic solid to photactive ones; (ii) elucidation of interdependence of photoluminesence and polymorphism in organic crystals; (iii) determination of surface pointdefect-concentration at, and discovery of catalytic channeling by metals in the oxidation of, graphite and molybdenite; (iv) establishing the mechanism of interconversion of “stages” in graphite intercalates, and the discovery of incommensurate guest-hosts-structures (with graphiteiron chloride); (v) rationalization of the structures of the many seemingly unrelated phases of bismuth molybdate catalysts (for oxidation) in terms of a common, defect-fluorite (Bi2O3) archetype;

Zeolites are crystalline aluminosilicates with frameworks built from corner-sharing TO4- tetrahedra(where T is Si or Al but can also be substituted with P, Ga, Ge, etc.) to produce channels or cavities of molecular dimensions. Owing to these characteristic features, zeolites have attracted much attention not only for catalytic applications but also as containers of confined materials. In most circumstances zeolites can only be synthesized as fine powders, ca. 1 μm, and the additional presence of defects or intergrowths makes structure solution difficult. HREM is therefore one of the most important tools for the investigation of such structures and the early work of Thomas and his group in Cambridge were dedicated to developing such techniques. The advantage of HREM has been subsequently demonstrated especially for characterizing and determining fine structures, e.g. (i) zeolite intergrowths structures such as ERI/OFF and FAU/EMT, (ii) enantiomeric intergrowths of structural units in ETS-10 and structural solution, (iii) surface structures and growth units and (iv) size of clusters and their registry with the framework structures.

The engineering of a new generation of advanced materials based on nanoparticles demands the fabrication of self-assembled arrays of passivated metal, oxide and semiconductor clusters (1 -). In particular the case of self-assembled gold clusters passivated with an organic molecule has attracted the attention of several researchers (2-3). Because its unique properties gold metal is a leading candidate for the fabrication of single electron tunneling devices.

Passivated gold nanoclusters were produced using the method developed by Brust et.al. (4) with the modifications of Whetten et.al (5) n-alkylthiol molecules were used as passivating agent. Carbon chains from C=4 to C=18 were used. It was found that C=12 dodecanethiol was optimum for forming ordered arrays of the clusters. To produce the superlattice crystallization a toluene vapor atmosphere was used. The passivated clusters were deposited on a copper electron microscope grid covered with carbon.

CeO2 is an important material in many catalyst applications. CeO2, PrO2 and TbO2 are the only lanthanides known to exist as oxides in both 3+ and 4+ oxidation states. The high oxygen mobility at low temperature (≈300°C) results in easy oxidation-reduction cycles; a property utilized in the catalyst industry, especially for CeO2. Studying the oxidation-reduction behavior is thus very important to understanding the reactivity of CeO2 as a catalyst. We have studied CeO2 by in situ electron diffraction, high resolution electron microscopy (HREM) and electron energy-loss spectroscopy (EELS), not only to understand the reduction behavior but also to develop a method to quantify the reducibility of CeO2 or mixed oxides containing CeO2 by EELS. We have applied this method to study the behavior of ZrO2-CeO2 catalyst during reduction.

Experiments were performed on a PHILIPS-430 electron microscope operated at 300KV, fitted with a differentially pumped environmental cell and a Gatan Imaging Filter (GIF).

Silicon dioxide is an important catalyst material, a mainstay insulator in microelectronics, and a widely distributed terrestrial and marine skeletal mineral. Geologically, it is found in one of a large number of polymorphic crystalline states, but can also be rendered “amorphous” by rapid cooling from the melt through a glass transition, depositing from a vapor or from solution (in radiolaria skeletons), oxidizing silicon, or irradiating with electrons, ions or neutrons. While the structures of the crystalline polymorphs are well documented, the structure of even the exhaustively studied vitreous silica remains largely enigmatic. Diffraction provides average information about short-range order—which appears to comprise [SiO4] tetrahedral units in all but a high-pressure crystalline polymorph—but is relatively insensitive to alternative medium-range arrangements of these structural units. One sensitive, but little understood, indicator is the position and shape of the first sharp diffraction peak (FSDP).

In 1999 NCEM's One Ångstrom Microscope (OAM) became fully operational. The OAM is a Philips CM300 FEG/UT field emission microscope with holographic capabilities that is equipped with a Gatan Image Filter (GIF) and operates at 300 kV. It was designed to reach a resolution close to the “magic barrier” around one Ångstrom (100 pm) by combining mid voltage technology with advanced computer processing [1,2]. Ahardware correction of the three-fold astigmatism allows for aberration free imaging down to sub Ångstrom values [3]. In this contribution it will be shown that the instrument's performance exceeded expectations because sub Ångstrom resolution can be achieved by reconstructing electron exit waves from focal series [4].

Figure la depicts a simulated [110] lattice image of a 90° partial dislocation in silicon. Tersoff potentials were used to calculate the exact atomic positions around dislocations with different core structures [5].

One of the great challenges of nanotechnology is how to produce and modify objects at nanoscale dimensions. The search for physical and chemical methods for controlled synthesis, modification and characterization of semiconductor nanocrystals is of special interest due to their novel electronic and optical properties. Recently we have achieved the first laser-induced phase transformation in semiconductor nanocrystals [1], irradiating colloidal solutions of CdS nanocrystals with 7 ns pulses of 532 nm wavelength. We used established wet-chemistry methods to synthesize the CdS nanocrystals, and a combination of electron microscopy methods to determine the structure, size and composition of the nanocrystals. In the present paper we report a wavelength dependence of the laser-induced phase transformations in CdS. We also explore electron-induced transformations in comparison with their photon counterparts.

Aqueous colloidal solutions of CdS nanocrystals were prepared by mixing of CdCl2 with Na2S in the presence of Sodium Mercaptoacetate and HC1 [2].

When Pt particles of sub-nanometer dimensions are inserted into the linear channels of the potassium ion form of zeolite L, the resultant Pt/KL catalyst converts linear n-C6 hexane into cyclic C6 benzene with remarkable efficiency [1,2].

However, a drawback to Pt/KL catalysts is that they are exquisitely sensitive to sulfur contamination in the n-hexane feed. The catalyst deactivates rapidly when there are trace amounts (> 50 parts per billion) of sulfur in the feed. Bright field TEM studies show that the Pt particles remain finely dispersed within the channels after sulfur poisoning, with typical particle widths < 1.5 nm, implying that a large percentage of the Pt atoms still reside on the surfaces of the particles. For heterogeneous catalysts such as Pt/γ-alumina, where the Pt particles are always readily accessible on the external surface of the alumina support, such sulfur concentrations are tolerated.

Confocal laser scanning microscopy (CLSM) has been used to generate three dimensional projection maps of less fluorescent domains caused by asphaltene aggregates in the autofluorescent matrix of crude oil. Heavy crude oils contain asphaltene particles resulting in the production of optically observable micron sized asphaltene aggregates. This technique has been employed to determine the volume fraction of aggregated asphaltenes, øagg, and the time evolution of this phenomenon. The measurements cover a range of various concentrations of asphaltene volume fractions of the heavy asphaltenic oil, øm, from øm = 0 to øm = 0.6.

Examining crude oils for asphaltenes aggregates using CLSM presents a challenge due to the strong absorption of the oils. This is because some molecules of the crude oil fluoresce when excited by optical laser light used as a source in the CLSM. Other molecules of the crude oils absorb light at similar wavelengths.

Direct methanol fuel cells (DMFCs) offer a simpler, safer technology for point-of-use power sources compared to other hydrogen fuel cells, by avoiding the need to store hydrogen fuel or to carry out the reformation of hydrocarbons. The direct methanol oxidation electrocatalyst of choice is a nanoscale black consisting of a 50:50 atom % mixture of Pt and Ru. It has recently become known that these presumed bimetallic alloys in fact contain an array of metal, oxide and hydrous phases, which are easily misidentified in routine x-ray diffraction measurements due to particle size-broadening and poor crystallinity. By combining transmission electron microscopy, electrochemistry and thermogravimetric studies, we demonstrate here that the route to improved catalytic activity is not by phase purification of the bimetallic alloys, but instead phase engineering of hydrous ruthenium oxide and Pt mixtures.

The ability to align single wall carbon nanotubes (SWNTs) is paramount for harnessing their remarkable anisotropic electronic and mechanical properties. D.A. Walters et al. (Rice Univ.) have succeeded in aligning milligram quantities of SWNTs using a strong magnetic field. The nanotubes were aligned in suspension and simultaneously filtered to produce a thin membrane. However, small angle X-ray scattering (SAXS) — the traditional technique for obtaining fiber patterns — has proven ineffective in determining the degree of alignment due in part to carbon's weak atomic scattering factor for X-rays.

In the present work we succeed in quantitatively characterizing this membrane using transmission electron microscopy (TEM). A self-supporting sample was prepared by peeling ∼ 0.5 mm long strips from the material. TEM images reveal that the membrane itself is not a single, large bundle (i.e. rope) of SWNTs. Instead, it has a prominent texture, corresponding to many ropes aligned parallel to the direction of the applied magnetic field.

Nanoparticles continue to attract interests because they fall into intermediate stage between molecular and macroscopic materials. Due to their large surface-to-volume ratio, nanoparticles exhibit physical and chemical properties that differ markedly from those characterizing the bulk solid state. One example is the phase diagram of a nanomaterial. Because nanocrystals display clear changes in both the thermodynamics and the kinetics of phase transitions, we expect different solubility limits in the nanometer regime. This means that phases unstable or unobserved in extended solids may be prepared as nanocrystals. We synthesized Au and Pt nanoparticles and performed chemical analysis on the sintered agglomerates.

The colloidal Au and Pt particles were synthesized according to Turkevich's method. An aqueous AuCl3 solution (50mg Au/L) was heated to 70°C. A determined amount of lwt% aqueous sodium citrate dihydrate (Na3C6H5O7.2H2O) solution was added such that the citrate-to-Au mass ratio was 10.

High spatial resolution chemical microanalysis of heterogeneous catalysts is traditionally done in transmission electron microscopy or scanning transmission electron microscopy (TEM/STEM) instruments. A major limitation of TEM/STEM techniques is, however, the stringent requirement of samples that can be examined: useful information can be extracted from only very thin areas of a sample. The preparation of suitable TEM samples may also pose a major problem for observing certain types of commercial catalysts, for example, beads, powders, or cylinders that are frequently used in catalytic reactions. These limitations preclude the application of TEM/STEM techniques to extracting information about the surface properties of thick or bulk catalyst samples.

With the recent development of high-resolution, field-emission scanning electron microscopes (FESEM), bulk samples can now be examined at a nanometer or sub-nanometer spatial resolution. At low incident beam energies, not only the emitted SE signal is more surface-sensitive but also charging of non-conducting materials is significantly reduced.

The large-scale commercial production of polyolefins by catalytic Ziegler-Natta polymerization have stimulated the development of the third, fourth and fifth generation heterogeneous catalysts comprising high surface area defective MgCl2 with TiCl4, electron donors, and AlR3-co-catalysts. In spite of intensive research over the years, the present level of understanding of the catalysts is still incomplete because of their complex composition leading to a multitude of local active site environments. The aim of this work is to provide a new insight into the process via in situ video microscopy of gas phase propylene polymerization over MgCl2-supported Ziegler-Natta catalysts combined with ex situ characterization by light and electron microscopy techniques (SEM, TEM, HRTEM, STEM, PEELS and windowless EDX). Procedures for catalyst synthesis are described elsewhere. The catalysts were stored in a dry box under a He atmosphere (<lppm H2O/O2). Samples were transferred to specimen holders in the dry box and then transferred into the microscopes under high purge N2 conditions to prevent poisoning of the catalysts by air and moisture.

Iterative algorithms, which use diffracted intensities and some a-priori knowledge of an image to solve the phase problem, have been under development for many years. The promised super-resolution images, reconstructed from diffraction information alone, would be of the greatest value for molecular imaging and for the image of nonperiodic structures in materials. Using simulated data it is possible, for example, to reconstruct a complex object from a knowledge of its diffracted intensities with certain known support functions. Some success has recently been achieved reconstructing micrometer-sized non-periodic objects using coherent X-rays by the Feinup method. One favorable support function consists of two holes spanned by the coherence width of the beam, with one or both holes containing an unknown object. Our simulations, which iterate between diffracted intensities and the image, applying the known support (either completely opaque or completely transparent) and intensities in each domain, confirm that image reconstruction is possible for loose supports and noiseless data.

Soot particles are generated from a number of sources, including auto emissions, aircraft emissions and various domestic and industrial combustor sources. Particle size and composition has been the focus of recent Environmental Protection Agency directives, especially due to the impact of small particulates on the inner urban environments. Single particle microanalysis is advantageous in these studies since, morphology and composition can be examined simultaneously. When a small sample size is available, single particle microanalysis is the only possible micro analytical approach. Chemical fingerprinting using the energy dispersive x-ray spectroscopy (EDS) signature of trace elements contained in the particles has shown remarkable source based uniqueness. Previous studies involving diesel soot particulates have indicated that most samples analyzed on a discrete basis are reasonably homogeneous, but questions still remain as to the ultimate statistical limit of this technique.

Nearly all metals form a passivation film due to oxidation in air at ambient temperatures, that acts as a diffusion barrier to protect the materials from further corrosion. Aluminum demonstrates excellent passivation behavior due to the formation of a protective amorphous alumina film during exposure to air at ambient temperatures. However, H. Ebinger and J. Yates discovered that the passivation of aluminum can be significantly improved by artificial oxidation. Both electron-beam induced oxidation in water vapor and oxidation in ozone atmospheres3 showed higher impedance in electrochemical impedance spectroscopy measurements to anion diffusion than the thermally grown oxides. To understand the nature of this beneficial passivation, we probed the microstructure of these amorphous oxide films by transmission electron microscopy (TEM).

The oxide films were grown on a polycrystalline Al substrate. The Al substrate was cleaned with a sputter cleaner inside a UHV (ultra-high vacuum) system.

Carbon nanotubes (NTs) have novel electronic properties and exceptionally high Young's moduli on the order of TPa. so NTs have potential applications in advanced composite materials such as conductive polymers, electromagnetic-radio frequency interference (EMI/RFI) shielding material and opto-electronic materials. The utility of the nanotubes in composite applications depends strongly on the ability to disperse the NTs homogeneously throughout the matrix without destroying the integrity of the NTs. Furthermore, interfacial bonding between the NT and matrix is necessary to achieve load transfer across the interface, which is desirable for improving the mechanical properties of polymer composites.

In this work, aligned multiwalled carbon nanotubes (MWNTs) produced by continuous chemical vapor deposition (CVD) (see Fig.l), were homogeneously dispersed in polystyrene (PS) matrices by a simple solution-evaporation method. Using this procedure, we made uniform MWNT-PS composite films ∼0.4mm thick for ex-situ mechanical tensile test and very thin films, ∼100nm, for in-situ TEM tests, as shown in Fig.2.