It is of fundamental and practical interest to understand the oxidation process since a desirable property for metals is resistance to corrosion. But there is a wide gap between information provided by surface science methods and that provided by bulk oxidation studies. The former have mainly examined the adsorption of ∼ 1 ML of oxygen on the metal surface, where as both low and high temperature bulk oxidation studies have mainly focused on the growth of an oxide layer at the later stages of oxidation.

We are probing the initial oxidation stage of a model metal system by in situ ultra-high vacuum (UHV) transmission electron microscopy (TEM) in order to gain insights into the initial kinetics of oxidation. We have previously shown that the growth mechanism of the cuprous oxide is initially dominated by oxygen surface diffision.

The mechanical alloying (MA) process is an effective method to develop strategic materials with novel structures. These can be solid solutions (even in immisible systems), amorphous phases, fine particle sized and nano-metric crystals etc. Conventional powders metallurgy routes can process the mechanical alloyed products. However, the novel features conferred into the powders, can be lost during the sintering operations. The spark plasma sintering process (SPS) is an alternative route to dense mechanically alloyed products at a high grade while retaining their novel structures. Co-Ti alloys were produced by mechanical alloying the elemental powders mixtures with nominal composition Co50Ti50 (at. %). Details on the preparation and characterisation of the milled products can be found in related publications. Densification of the powders products was conducted using a Dr. Sinter equipment. Previous studies on Co-Ti alloys processed by MA and SPS have shown that the final products are composed of mixtures of metastable intermetallic compounds.

Mn oxides of pervoskite-related structure containing Mn ions have attracted considerable interest due to the colossal magnetoresistence (CMR) effect. Doping the family of compounds La1-x Cax MnO3 with divalent Ca ion oxidizes Mn+3 to Mn4+, introducing holes in the 3d bond orbital that give rise to a series of interesting physical properties. The parent compound LaMnO3 (Pbnm) with unit cell of a=5.5367Å b=5.7473Å and c=7.6929Å, is an antiferromagnetic insulator in which orbital ordering is established due to the cooperative Jahn-Teller (JT) effect breaking the degeneracy of the electronic configuration of Mn3+ (t2g3eg1). This particular C-type orbital ordering is responsible for the A-type magnetic structure observed by Wollen and Kohler. Theoretical Monte-Carlo simulation has shown that the A-type antiferromagnetic state is stable in a model based on JT phonons, using coupling values physically reasonable for LaMnO3 and considering the small but important effect of octahedral tilting.

Doping carbon nanotubes with either electron donors or acceptors can improve their electrical conductivity [1-2]. In order to fully understand the doping mechanisms and the corresponding changes in the electronic properties, it is essential to reveal the spatial distribution of the dopants within the carbon nanotubes. In this study we have investigated both iodine- and bromine-doped single wall carbon nanotubes(SWNT) by Z-contrast scanning transmission electron microscopy (STEM). The SWNT bundles were made by arc-discharge method and doped with either molten iodine or bromine vapor. Both iodine and bromine were incorporated linearly within the nanotube bundles as shown in Fig. l and Fig.2 respectively. Higher resolution images of iodine doped nanotubes reveals that two iodine atomic chains are inside each individual SWNT as shown in Fig. lc. This unexpected result is contrary to the common belief that dopants can only enter interstitial site of the SWNT bundles.

Discoveries of C multi-walled (MWNTs) and single-walled (SWNTs) nanotubes opened up a wide horizon for applications of these nanostructures as electronic and structural materials. Later on, it has been realized that the nanotubular structures are formed in other layered compounds, e.g. in the B-C-N materials. However, in contrast to the C-based nanotubes whose synthesis parameters are well-established, synthesis of B- and N-doped C and pure BN nanotubes is a challenging issue. The present paper reports on large-scale synthesis and detailed HRTEM and EELS characterization of nanotubes in the B-C-N system.

MWNTs and SWNTs of B-C-N and BN were produced from C nanotube templates via a substitution chemical method through oxidation by B2O3, in a flowing N2 atmosphere at 1573- 1773 K. HRTEM of a product was carried out using a high-resolution field emission transmission electron microscope JEM-3000F (JEOL) equipped with a parallel EELS detector Gatan 666 and an ultra thin window Si(Li) EDS detector.

Since the discovery of fullerenes and carbon nanotubes, the deposits on arc electrodes produced at high gas pressure have been investigated intensely. Despite of the enthusiasm, little work was reported about the initial deposition processes. In principle, such processes could be followed by reducing the amount of products, i.e. a short discharge with a small current. In practice, however, this was prevented by two practical obstacles, arc instability and possible byproducts originated from reactions with remaining impurities in the vacuum chamber. In the present study, we reported a new kind of compact preparation system which allowed stable arc with a small current and a clean environment.

Figure 1 shows a schematic diagram of the system. For higher arc stability, the system had a small cylindrical shape which would reduce the effect of convection. Both electrodes were aligned on the axis inside the cylinder and their gap was adjustable by a micrometer.

Since their discovery, steady state arc discharge has been used for fullerenes and nanotubes production. Unfortunately this method intrinsically made it difficult to understand their growth mechanisms since the discharge included many complicated physical processes and the growth happened in the non-equilibrium arc plasma. Processes such as heating of the cathode by cation bombardment, emission of thermal electrons, and heating of the anode by electron bombardment are important in order to follow the mechanism, but it is difficult to study them separately. In the present work, however, it was shown that a pulse-arc discharge with a small current for a short time could simplify the discharge process and provide as-quenched arc products, which should be useful to understand the mechanisms.

Short discharges with a small current were performed on the pulse-arc system, which was developed by the authors.

Currently there is a strong interest in fabricating nanoporous metal arrays using various template methods. Porous opal membranes of close-packed silica beads, for example, have a unique template structure due to their tetrahedral and octahedral interstices. Such structures can be infiltrated with a variety of materials, especially metals, to form continuous inverse networks. Interest in these forms comes from their potential application in a variety of areas including photonics, magnetics, catalysis, and thermoelectrics. In this paper, we present electron microscopy characterization of inverse nickel photonic materials prepared by electrodeposition method.

Electrodes were formed from opal pieces (typically 7 x 10 x 1.5 mm with silica spheres about 300 nm) by first depositing about 0.5 micron thick copper films on one side of the piece with magnetron sputtering. A length of wire was then attached to the copper backing with silver paste.

Nanoparticles (1-100 nm) of semiconductors and metals have shown some unique optical, electric and magnetic and catalytic properties which are greatly different from their bulk materials. Recently the use of these nanoparticles as quantum dots in nanoelectronics requires their arrangement in one, two, and three dimensions (1D, 2D and 3D). Therefore more attention has been paid to the organization of these nanoparticles into ordered arrays in order to achieve novel collective properties. Gold colloids have been well studied for its self-organization in several systems. Here we present 1D, 2D and 3D gold self-organization nanostructure generated from reverse micelles (microemulsion system).

Gold nanoparticles were prepared by the reduction of HAuCU in CTAB (cetyltrimethylammonium bromide)/Octane+l-Butanol/H2O microemusion system using NaBH4 as the reducing agent. Typically, 0.3g of CTAB, 0.148ml of 0.056M HAuCl4 aqueous solution, l.Og octane (surfactant) and 0.25g 1-butanol (cosurfactant) were mixed together and stirred vigorously for 10 min until a homogenous phase was obtained.

The ability to accurately and precisely measure the thickness of ultrathin (∼ 3 nm) dielectric films, used as gate dielectrics in integrated circuits, is critical to the continued success of the semiconductor manufacturing industry. Many metrology tools have been applied to this problem in the past, but recent research has focussed on ellipsometry, x-ray reflectivity, secondary-ion mass spectrometry, capacitance-voltage curves, medium energy ion scattering, high resolution transmission electron microscopy (HRTEM), and grazing incidence x-ray photoelectron spectroscopy (GIXPS). Unfortunately, these techniques disagree about a given film's thickness by amounts larger than their individual precisions. To support the statistical process control methodologies used in production wafer fabrication, these disagreements need to be investigated and the true accuracy and precision of the tools need to be determined. This work compares the ability of two techniques, HRTEM and GIXPS, to measure the thickness of silicon oxynitride films on silicon substrates.

The formation of nano-particles in silica glass by ion implantation has attracted great attentions because of the applications for visible luminescence and nonlinear optical devices. Ion implantation is a unique technique for producing nano-particles, with the advantages of high controllability of beam position, depth and distribution of projectiles, concentration, high purity and ability to overcome low solubility restrictions.

Optical grade silica glasses were used as the substrates. Ion implantation was performed with a 1.7 MV tandem-type ion accelerator (NEC 5SDH-II pelletron accelerator) of NERIN. The substrates were implanted with 1.0 MeV O+ and 1.8 MeV Cu+. Projected ranges were calculated by SRIM-2000 to be 1.5 μm (for O+) and 1.4 μm (for Cu+). Samples were cooled with liquid nitrogen to reduce the beam heating. The ion current densities of O+ and Cu+ were 6 and 2 μA/cm2, respectively.

Characterizing the physical properties of individual nanostructures is rather challenging because of the difficulty in manipulating the objects of sizes from nanometer to micrometer. Most of the nanomeasurements have been carried using STM and AFM. In this presentation, we demonstrate that transmission electron microscopy can be a powerful tool for quantitative measurements the mechanical, electrical and thermodynamic properties of a single nanostructure, such as a carbon nanotube or a nanoparticle.

Using a customer-built specimen holder, in-situ measurements on the mechanical properties of carbon nanotubes has been carried out using the resonance phenomenon induced by an externally applied alternating voltage [1]. If an oscillating voltage is applied on the nanotube with tunable frequency, resonance can be induced (Fig. 1). The bending modulus is calculated from the resonance frequency. The bending modulus is as high as 1.2 TPa (as strong as diamond) for nanotubes with diameters smaller than 8 nm, and it drops to as low as 0.2 TPa for those with diameters larger than 30 nm.

Automotive exhaust catalysts are typically operated under stoichiometric conditions to minimize nitrogen oxide, hydrocarbon, and carbon monoxide pollutants. These catalysts do not form carbon filaments under normal operating conditions. In development of catalysts, however, a stabilization procedure is sometimes utilized on used catalysts (dynamometer or vehicle) to purge the catalyst of sulfur prior to measuring the catalytic activity in sweep and light-off testing. The stabilization procedure consists of running the catalyst under rich (excess fuel) conditions for 0.5hr. This study documents the existence of carbon filaments due to the stabilization procedure and discusses the effect of filaments on subsequent testing.

Two separate catalysts were used in this study. The first was a 50,000 mile vehicle aged catalyst that had also been through the stabilization procedure and then sweep and light-off tested. The other was only dynamometer aged for 120hr at 850°C (1560°F).

In the last decades, amorphous alloys have been the focus of many researchers around the world. Rapid solidification is one of the most employed techniques in obtaining amorphous structures. Important limits of this technique are the high melting point alloys, and in many cases it is restricted to compositions near eutectic deeps. By mechanical alloying it has been possible to obtain amorphous structures in several alloy systems, and in compositions different to eutectic points.

Amorphous phases by mechanical alloying in the Ni-Mo system has been reported before. This work is focused to the characterisation of amorphous structures obtained by mechanical alloying in a Mo-47 at. % Ni alloy. This composition corresponds to the equiatomic NiMo intermetallic. The characterisation was carried-out by XRD, SEM-EDS, DSC and TEM. Full amorphization was obtained after 32.4 ks of milling in a Simoloyer ball mill, as shows conventional XRD, Figure 1.

Drawing on nature, synthetic opals (e.g., gilsonite) consist of uniformly sized ceramic spheres ordered into large close-packed domains. In order to improve the toughness or appearance of these chemically bonded ceramics, a polymer is often infiltrated into the interconnected space between the packed spheres. In a similar fashion, colloidal crystal arrays of submicrometer silica or polymer spheres have been employed as templates for periodic porous solids. All the methods for preparing periodic macroporous materials share a common synthetic thread: first, the colloidal crystals are formed from monodisperse spheres; next, the void spaces are filled and solidified; finally, the template is removed by heat, by refluxing in a solvent such as THF (in the case of polymer spheres), or by soaking in hydrofluoric acid (in the case of silica spheres). The product, which can be thought of as an “inverse opal,” often exhibits the same iridescence as a natural opal due to the similarity between the periodicity of the wall structure and the wavelength of light.

The Northern Front Range Air Quality Study concluded that for the Denver metropolitan area during 1996 and 1997, 55% of particles with an aerodynamic diameter 50% cutpoint of 2.5 μm (PM2.5) were attributable to motor vehicle exhaust particulates. The health effects of PM2.5 are currently unknown, but are under investigation. It is of vital interest to understand the chemistry, morphology, size distribution and microstructure of motor vehicle exhaust. The techniques of transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) appear to be well suited for the analysis of the microstructure, morphology and microchemical composition of particulate matter. Previous electron microscopy observations of particulate matter from a variety of sources have found that the chemical composition and crystal structure are characteristics of the source of the particles.

As part of an ongoing research project into the health effects of motor vehicle particulate matter, Southwest Research Institute (SWRI) is performing chassis dynamometer tests of a variety of vehicles and collecting samples from the exhaust stream for analysis.

The affinity of the binding sites on troponin C (TNC) for Ca is sensitive to the state of phosporylation of troponin 1 (TN1). Two and possibly three other myofilament proteins can be phosphorylated by physiological reactions: the mosin binding protein C (MyBP-C), the regulatory light chain of myosin (RLC), and the tropomyosin binding subunit of troponin (TNT). In MyBP-C, the phosphorylation sites are specific for cardiac muscle, an occurrence that suggests a function unique to cardiac muscle. Phosphorylation of MyBP-C and RLC can be produced by Ca regulated kinases present in the myofibrils. Phosphorylation of RLC produces an increase in Ca sensitivity of contraction at submaximal concentrations of Ca without alteration of the maximum Ca activated force (Fmax). Absence of contractile activity decreases phosphorylation of RLC. One to two hours of quiescence in normal extracellular Ca reduces phophorylation substantially, and the level rises slowly when contractile activity is resumed.

In mammalian skeletal and cardiac muscles, regulation of activity occurs when calcium binds to troponin on thin filaments, which ultimately results in exposure of myosin-binding sites on actin. However, modulation of contractile function, affecting such parameters as calcium sensitivity, the rate of rise of tension, the expression of maximum tension and/or the rate of onset of relaxation, is also calcium dependent. It is, in part, a property of the thick filament itself and its component myosin and/or accessory proteins. Among these are phosphorylation of myosin regulatory light chains or light chain 2 (RLCs; LC2) and in cardiac, but not skeletal fibers, phosphorylation of myosin-binding protein C (MyBP-C).

Gentle methods of separating thick filaments from small tissue specimens, subjected to various experimental protocols designed to explore the functional parameters of such modulatory activities, allow examination of any accompanying structural changes.

This presentation will review how myofibrils are formed in both types of vertebrate cross-striated myofibrils, i.e., cardiac and skeletal muscle.

Cardiomyocytes isolated from 7 to 9 day-old chick embryos and myoblasts isolated from 10-day old quail embryos were placed in tissue culture. The cardiac cells were allowed to spread in culture for 3 - 5 days. Similarly, the myoblasts were permitted to fuse to form myotubes which were then fixed at different points of elongation over 3 -5 days. Some cultures were fixed and stained with antibodies (e.g., sarcomeric isoform of alpha-actinin; non-muscle myosin IIB and muscle myosin II) to detect the disposition of the forming and mature myofibrils inside these cells. Sister cultures were transfected with plasmids expressing Green Fluorescent Protein (GFP) ligated sarcomeric proteins like alpha-actinin. The staining and transfection results revealed that three different types of fibrils form during myofibrillogenesis: premyofibrils, nascent myofibrils and mature myofibrils (1-2).

The mitotic spindle is responsible for chromosome movement during mitosis. It is composed of a dynamic array of microtubules and associated proteins whose assembly and constant turnover are required for both spindle formation and chromosome movement. Because microtubule assembly and turnover are necessary for chromosome segregation, we are studying how cells regulate microtubule dynamics. Microtubules are polarized polymers composed of tubulin subunits; they assemble by a process of dynamic instability where individual microtubules exist in persistent phases of elongation or rapid shortening with abrupt transitions between these two states. The switch from elongation to shortening is termed catastrophe, and the switch from shortening to elongation, rescue. Although dynamic instability is an intrinsic property of the tubulin subunits, cells use associated proteins to both speed elongation (∼ 10 fold) and regulate transitions.

The only protein isolated to date capable of promoting fast polymerization consistent with rates in vivo is XMAP215, a 215 kD protein from Xenopus eggs.