Transition metals supported on oxides have important catalytic properties and are also used in chemical gas sensors for increasing sensitivity and selectivity. In order to understand growth and reactivity in the Au/TiO2 system, we have performed surface studies on a model system consisting of ultrathin, discontinuous Au films on TiO2 (110) single crystals. In this paper we are presenting results obtained by high resolution scanning electron microscopy (HRSEM) on the effects of substrate temperature and average Au thickness on particle size, density and coverage.

The TiO2 (110) single crystal surfaces used in this study were prepared in UHV using surface science tools followed by in-situ Au deposition for different substrate temperatures and for various film thicknesses. After deposition, the samples were transferred in air to the Field Emission Scanning Electron microscope (LEO 982 Gemini) for high resolution imaging.

Typical high resolution scanning electron microscopy (HRSEM) images of Au films deposited at 300 K are shown in Fig. 1 for two film thicknesses of 0.22 and 1.0 nm.

Multilayer thin films of Co/Au with large magnetic anisotropy are attracting strong interest. Among the factors affecting the film properties are the layer thicknesses of the Au layer and the Co layer. This paper reports the detailed HRTEM study of the nanostructure evolution of Co/Au films as a function of the Au thickness. Two DC-magnetron sputtered films with the same Co thickness 5Å but different Au thicknesses (Au60Å/Co5Å)x9/Au400Å (denoted Au60) and (Au10Å/Co5Å)x50/Au400Å (denoted Au 10) were chosen for detailed study. The Au60 film shows a well defined perpendicular magnetization loop with loop squareness S=l and an anisotropy value of 3xl06erg/cm3 while the Au 10 film shows an irregular perpendicular magnetization loop with S=0 and an anisotropy value of 1.5xl06erg/cm3.

For cross sectional TEM samples, bright field TEM images show that the grain size of the Au underlayer is about 20-80 nm. Slight convex curvature of the multilayers is observed.

Cu-refractory metal composites such as Cu-Ta alloys are attracting research interest because of their potential high electrical and thermal conductivity and high mechanical strength at elevated temperatures [1]. In the previous study, it has been shown that the hardness of Cu-Ta is three times of the Cu substrate [2] and the Ta was found to exist as discrete particle and aligned particles. In this presentation, we report the detailed study on the microstructure of the heat treated film and hot-pressed film.

The Cu-6at%Ta films were deposited on Cu foil at 100°C by RF co-sputtering. The films examined in this study was hot-pressed under 35 MPa pressure at Ar atmosphere for 1 hour. Cross-sectional TEM samples were examined using a Hitachi 9000 high resolution transmission electron microscope (HRTEM) at the Center for Microanalysis, Materials Research Laboratory, University of Illinois at Urbana-Champaign.

Si3N4/SiC nanocomposites have been shown to exhibit excellent strength and fracture toughness compared to monolithic Si3N4 materials. Recently, the microstructure and chemistry of Si3N4-based nanocomposites fabricated by hot-pressing amorphous Si-C-N precursor powders has been investigated. In the present work, our studies on the microstructure of Si3N4/SiC nanocomposites made by hot-pressing the mixture of Si3N4 and SiC commercial powders are reported.

Si3N4/SiC nanocomposites were prepared by hot-pressing at 1750 °C for 1 hour at 40 Mpa in a nitrogen atmosphere, with sintering aids of 5.5 wt% Y2O3 and 3 wt% Al2O3. The details of the processing procedure have been reported elsewhere. Two different materials were investigated in this work: specimen A consisting of 5 vol% β-SiC; and specimen B consisting of 5 vol% α-SiC. TEM specimens were prepared by conventional procedures. The microstructure and chemical composition were studied in the University of Michigan Electron Microbeam Analysis Laboratory on a JEOL 2000FX.

Ion implantation can be used to alter the optical response of insulators through the formation of embedded nano-sized particles. Single crystal alumina has been implanted at ambient temperature with 50 keV Ca+ to a fluence of 5 x 1016 ions/cm2. Ion channeling, Knoop microhardness measurements, and transmission electron microscopy (TEM) indicate that the alumina surface layer was amorphized by the implant. TEM also revealed nano-sized crystals ≈7 - 8 nm in diameter as seen in Figure 1. These nanocrystals are randomly oriented, and exhibit a face-centered cubic structure (FCC) with a lattice parameter of 0.409 nm ± 0.002 nm. The similarity between this crystallography and that of pure aluminum (which is FCC with a lattice parameter of 0.404 nm) suggests that they are metallic aluminum nanocrystals with a slightly dilated lattice parameter, possibly due to the incorporation of a small amount of calcium.Energy-filtered transmission electron microscopy (EFTEM) provides an avenue by which to confirm the metallic nature of the aluminum involved in the nanocrystals.

It has been well known that Au single crystal undergoes reconstruction in vacuum as well as in acidic solutions at negative electrode potentials. The reconstruction is lifted when electrode potential sweeps to positive values. Taking into account of these facts we considered when Au particles grow on an electrode in solution at different electrode potentials, morphology of the particles may be different. Based on this idea, we investigated formation of Au, Pt and Au-Cu alloy particles grown in solutions and observed icosahedral and decahedral particles of Au and Pt formed at negative potentials. These particles are identical with multiply twinned particles (MTPs) observed in vacuum.

Particles were electrodeposited on an amorphous carbon film which was evaporated on a collodion film supported by a Au mesh as required for viewing in a transmission electron microscope (TEM). A three-compartment electrochemical cell was employed at room temperature with Pt wire counter electrode

The nano-structure science have become popular as the nano-fabrication technology has progress recently. Among the nano-structures, the nano-wires have been attracted attention because they show quantized conductance which would be used in quantum devices[l]. The quantized conductance has been observed even at room temperature with the nano-wires prepared by tip-indentation in scanning tunneling microscope [2-4]. However, the direct observation of the nano-wires has not been examined because of lack of their stability and difficulty of specimen preparation.

We have generated a gold thin wire with the thickness ranged 0.8-2 nm, referred to as a nano bridge (NB)[5], in an ultrahigh vacuum transmission electron microscope (UHVTEM) [6]. The NB is stable at room temperature and shows good reproducibility. The shape of NB is surprisingly uniform (see Fig. 2). The structure is stabilized by stable hexagonally-closed-pack (hcp) planes for the NB of 2 nm in thickness [5]. The well-defined structure provide a good opportunities for applied and theoretical studies.

Fullerenes have many families such as simple ball-shaped fullerenes, nanotubes, and onions. Additionally torus, Y-shaped particle, and graphitic network with periodic holes or dimples have been theoretically anticipated. The presence of various shapes in fullerenes is mainly attributed to the combination of five-membered and seven-membered rings in addition to six-membered rings composing ordinary graphite crystal. The five-membered rings are necessary for positive curvature of the fullerenes, while the seven-membered rings for negative curvature. Experimentally, the negative curvature has been restricted so far to the joint between cone and tube in nanotubes and the spiral tubes. We have found a new type of multishell fullerenes with negative curvature which consist of three horns protrude into three-fold symmetric directions, referred as three-horned multishell fullerene (THF) in this report, using a high resolution transmission electron microscope (TEM). Here, we first describe the formation briefly and secondly concerned with procedure to determine the structure of the THF.

High resolution transmission electron microscopy (HRTEM) and diffraction technique, with their high sensitivity to small variations in periodic structure or lattice imperfections within individual crystals, have made it possible to relate nanostructure to physical properties of individual fullerenes(C60, C70, etc.) and carbon nanotubes. Using HRTEM imaging, in tandem with dynamic image simulation, we have examined the etching patterns of carbon nanotubes in terms of tip geometry and bond strains. Our studies indicate that the progression of oxidation is not random, and is fully determined by the tip structure, of which only a finite number of classes exist. Oxidation of carbon nanotubes prefers to start at the positions which are most strained, which is associated with the arrangement of pentagons.

Carbon nanotubes were synthesized using the carbon arc method similar to that used for the synthesis of fullerences. The carbon nanotubes are often capped by carbon shells that fit continuously on the ends of the long cylinder

Nanoscale pattering of inorganics can be facilitated by using complex fluids as templates. One such approach is to use block copolymeric nanodomains in solid films (< 50 nm) as the template for patterning ceramic clusters with desired shapes and orientations. For instance, we use a triblock copolymer of polystyrene (PS) -polybutadiene (PB) - polystyrene (PS) - Kraton Dl 102® (MW = 71,000 and PS/PB = 28%/78%) as a template material to pattern barium titanate for energy storage applications. The important features of our approach are that (i) the interdomains of PBs in the preformed solid thin films are chemically OH-functionalized in situ, and (ii) the barium titanate precursors are solely localized within and reacted to the interdomains of PBs in solid thin films by condensation.

Thin films were prepared by spin casting a 1% w/w Kraton D1102®/toluene solution on a coverglass. Thin films were transferred to gold TEM specimen grids by the water lift off method.

In the last few years there has been a growing interest in nanoparticles and nanophase materials. Nanoparticles are considered to be a new state of the condensed matter due to the high relation of atoms in the surface respect to the number of atoms in the volume, and their properties are neither those of atoms nor those of bulk materials.

There are many interesting questions still to be answered and processes to be understood, from nucleation and growth processes to properties

In the present work we report the results of the fabrication of Mo, MoW and MoNi, particles by d.c. sputtering, under different pressures, from 0.2 torr to 0.8 torr. Their morphology, size distribution, aggregation and structure has been studied by Transmission Electron Microscopy.

We analyzed our results contrasting them with those of Chow 1,2 and Birringer 3 and try to explain with a new perspective the formation mechanism of the particles, and the dependence of particle size with Ar pressure.

Research on nanocrystalline materials, a new class of materials with a grain size of less than 20-30 nm in diameter, has flourished in the last decade because of their unique properties and Characteristics. While enormous amounts of nanocrystalline intermetallic alloys have been made by high energy mechanical alloying, little of this research has been carried out to study the formation of alloys of very low solid solubility elements such as Ag and Ni (0.1 at % at 750 °C).Upon quenching atoms in a state of high mobility, they can be “frozen” into unconventional random positions and thermodynamically metastable or unstable phases can be formed. This research was thus undertaken to synthesize nanocrystalline AgxNi1-x solid solution because fiber composites of this system have been widely used in low-voltage electrical circuits. This paper presents a TEM/AEM investigation of the traditionally immiscible nanocrystalline AgxNi1-xsolids formed by gas evaporation - vapor quenching method.

The selectivity and activities of platinum (Pt) particles strongly depend on their sizes and shapes. A technique has been recently reported for controlling the shapes and sizes of Pt particles [1]. Pt particles were prepared by bubbling Ar gas through the solution of K2PtCl4, and the Pt ions were reduced by flowing H2 gas through the solution. The shape control was performed by changing the ratio of the concentration of the capping polymer material to that of the platinum cations used in the reductive synthesis of colloidal particles in solution at room temperature [2]. High percentage of cubic, tetrahedral and octahedral particles have been prepared at room temperature, making it possible for studying the chemical activities of particles with different shapes and facets. This paper aims to study the surface structures of Pt particles prepared by the shape-controlling synthesis technique using high-resolution transmission electron microscopy (HRTEM).

Silver nanocrystals passivated by dodecanethiol self-assembled monolayers were produced using an aerosol technique described in detail elsewhere [1]. Self-assembling passivated nanocrystal-superlattices (NCS's) involve self-organization into monolayers, thin films, and superlattices of size-selected nanoclusters encapsulated in a protective compact coating [2,3,4,5,6,7]. We report the preparation and structure characterization of three-dimensional (3-D) hexagonal close-packed Ag nanocrystal supercrystals from Ag nanocrystals of ˜4.5 nm in diameters. The crystallography of the superlattice and atomic core lattices were determined using transmission electron microscopy (TEM) and high-resolution TEM.

SEM was used to image the nanocrystal superlattices formed on an amorphous carbon film of an TEM specimen grid (fig. la). The superlattice films show well shaped, sharply faceted, triangular shaped sheets. Figure lb depicts numerous Ag nanocrystal aggregates uniformly distributed over the imaging region. Inset in this figure is an enlargement of the boxed region at the edge of a supercrystal typifying the ordered nanocrystal packing.

Antimony-doped tin oxide (ATO) materials have many interesting and useful properties for industrial applications. Important uses of ATO include anti-static pigments, catalysts, electrochromic devices, solar cells, gas sensors, etc. Although the electro-optical and the structural properties of ATO materials with low dopant levels have been extensively investigated,the fundamental structural/chemical properties of heavily doped ATO materials have not been well understood. We report here some preliminary results of a systematic study of the structural evolution of tin oxide nanopaiticles heavily doped with antimony.

The ATO powders were prepared by adding a mixture of antimony(V) chloride and tin(IV) chloride to deionised water with concurrent addition of sodium hydroxide. The resulting white precipitates were filtered, washed and dried at room temperature. A series of Sb-doped SnO2 samples was obtained by annealing the precipitates at various temperatures. Samples suitable for high resolution transmission electron microscopy (HRTEM) were prepared by dry-dispersing ATO powders onto holey carbon films.

Size-quantized CdS nanocrystals, synthesized within phosphatidylcholine (PC) vesicles by reaction compartmentalization, were observed in situ to confirm the proposed method of formation and to investigate the concept of membrane-mediated crystal growth. Vesicle solutions representing three different CdS nanocrystal sizes, and a solution containing unreacted CdCl2 inside vesicles, were analyzed using cryo-transmission electron microscopy (cryo-TEM). Cryo-TEM has proved capable of resolving both the vesicle bilayer and the encapsulated nanocrystal, and yields previously unknown positional information for the crystal in relation to the bilayer.

Egg-PC vesicles containing Cd2+ were formed by detergent depletion, yielding vesicles of uniform size and a defined internal Cd2+ concentration. External Cd2+ was removed from the solution by cation exchange. Ammonium sulfide was added to the vesicle dispersion to produce nanocrystals via diffusion of S2- across the vesicle membrane. Particle size was predicted based upon the vesicle size, as determined from light scattering, and the encapsulated Cd2+ concentration.

New structural forms of carbon have been discovered in recent years, the most notable being the fullerenes and nanotubes. The notion that curvature is readily accommodated by graphite sheets has led to speculation about other possible topologies that incorporate pentagons or heptagons in hexagonal graphite nets. by consideration of Euler’s theorem and the symmetry of a graphite sheet, five conical structures can be predicted. If pentagonal defects only are present, cone angles are completely determined by the total number of pentagons, n, where 0≤n≤6 for open structures. In the absence of heptagons, growth of any graphitic structure containing more than 6 pentagons leads inevitably to the closed n =12 form. Consequently, five cone angles are possible, with disk (n=0) and tubular (n=6) forms representing the end-members of the topological series. Ge and Sattler1 have observed the smallest-angle member of this series with a cone angle of 19.2° (n=5).

Nanostructured materials have attracted great attention because their physical and chemical properties may differ significantly from those of the bulk material. In the equilibrium state, the solid solubility between Fe and Cu is negligibly small. However by using methods as vapor quenching, ball milling or chemical reduction, a Fe-Cu solid solution can be formed. In the present work, colloidal solutions incorporating mixtures of iron (II) and copper (II) functionalized surfactants are used to obtain FexCu 1-x(B) alloys and composite. Different ranges of composition (x=0.3 and x=0.7) can be produced by varying the relative concentration of the surfactants.

The samples are characterized by different techniques, some of them such as X-ray diffraction, 57Fe Mössbauer spectroscopy, and magnetization measurements, provide an information averaged over the whole specimen. Transmission Electron Microscopy, together with electron diffraction and EDS analysis, constitutes a first step towards submicrometer analysis of the produced material available as aggregates of nanosized particles deposited on holey carbon films.

Low-dose high resolution electron microscopy (HREM) is a useful technique for elucidating the structure of zeolites. In recent years a number of zeolite structures have been solved using combinations of different characterization techniques including adsorption measurements, powder x-ray diffraction and low-dose high resolution electron microscopy (for example see ref. 2). We have used these techniques to study the structure of a novel zeolite material. However, great care must be exercised when interpreting data from these techniques in terms of crystal structural units. In this particular case, the structure was recently determined using single crystal x-ray diffraction and showed some surprises.

Details of the synthesis of this zeolite are given elsewhere. The high adsorption capacity suggested that this zeolite possessed two interpenetrating channels (either a 10 and a 12 ring or two 12 ring channels). X-ray powder diffraction showed the material to be monoclinic with a= 18.5Å, b= 13.4 Å, c= 7.6 Å β = 101.5°).

Knowledge of catalysts' sizes and shapes on their support material is crucial in understanding catalytic properties. With increasing interest in nanosized catalytic materials, it is vital to obtain structural information at the nanometer level in order to understand their catalytic behavior. We have recently demonstrated that very high angle (˜100mrad) annular dark-field (HAADF) images in a dedicated scanning transmission electron microscope (STEM) can be used to quantitatively measure the number of atoms of individual nano-sized clusters on a support material We are presently applying this technique to a bimetallic catalyst, PtRu5, where our data suggest that the shape of the PtRu5 particle is, surprisingly, oblate on the carbon substrate.

PtRu5 is of interest for methanol oxidation for applications in batteries. PtRu5 compounds were produced by a molecular precursor method. Imaging was performed on a Field Emission Gun (FEG) Vacuum Generators HB501 STEM operated at 100kV.