It is known that radiation produces microscopic and macroscopic changes in silicas and other silicate glasses that result in densifications of several percent [1], This change in density is matched by a corresponding linear change in refractive index via the Lorentz-Lorenz relation such that where R is the molar polarizablilty, V the molar volume and n the refractive index.- Measurements of neutron irradiated bulk a-Si02 yield an exact correlation between the refractive index and density as shown by Fig. 1 such that dn/dp =185 m3/kg [ 1 ].

Utilizing a VG HB603 STEM fitted with a parallel EELS, measurement of irradiation-induced density changes in silicas were attempted using the 0-100 eV low-loss region of the electron energy-loss spectrum. The dielectric function and refractive index changes were extracted from these data using a modified Kramers-Kronig analysis (Fig. 2).

Grain boundaries have long been known to have a dominant effect on the electronic properties of polycrystalline materials. In the case of electroceramic oxides, the thermodynamics of defect formation (vacancies or interstitials, cations or anions) are usually invoked to predict the presence of a space charge potential at the grain boundaries. The relative energetics for the formation of each type of defect determines the size and sign of this potential barrier and thus, the effect that boundaries have on the overall electronic properties of the materials. However, a limitation to this continuum thermodynamics approach is that it does not consider the effect of the grain boundary structure.

To investigate whether the grain boundary atomic structure can have an effect on the energetics of defect formation and hence the electronic properties, here we examine the structure of Σ5 boundaries in two systems, SrTiO3 (perovskite) and TiO2(rutile).

The technique of electron backscatter diffraction (EBSD) in the scanning electron microscope is becoming a standard technique for the characterization of materials. EBSD has evolved into a tool that can determine the orientation of a crystalline area of interest or the technique can be used for the identification of unknown phases from their composition and crystallography. The application of the technique to ceramic materials has demonstrated the many advantages of this technique over classical x-ray diffraction techniques or electron diffraction in the TEM.

EBSD patterns are obtained by illuminating a highly tilted sample (>45° from horizontal) with a stationary electron beam. Electrons that are backscattered from the sample may satisfy the condition for channeling (or diffraction) and produce images that contain bands of increased and decreased intensity that are equivalent to channeling patterns. The patterns are imaged by placing a phosphor screen near the sample and imaging the screen with either TV rate or a slow scan CCD camera.

Highly textured (Bi,Pb)2Sr2Ca2Cu3O10(Bi-2223)/Ag composite tapes have received considerable attention as high-Tc superconducting materials for electric power and high-magnetic-field applications because of their relatively high-critical current densities and their flexibility. In order to improve the performance of these tapes for many commercial applications, it is essential that the mechanisms that limit the critical current density are fully understood. Previous microscopical studies of these tapes have revealed that interfaces such as grain boundaries strongly influence the transport of large currents1. From a morphological point of view, several models have been proposed to describe potential current transport mechanisms. However, as these models consider mainly the large-scale configuration of the boundaries, the underlying mechanism controlling the properties is still unclear. In order to elucidate the exact role of grain boundaries, systematical studies on the effect of the atomic structure as well as any chemistry change that occurs at the interface are required.

Silicon carbide is a versatile material possessing properties such as a wide energy bandgap, high thermal conductivity, high elastic modulus and high-temperature creep resistance, which enable it to be used in a variety of electronic, optical and structural applications. Chemical vapor infiltration/deposition (CVI/CVD) coupled with the application of a temperature gradient and forced flow of reagents is particularly suited to the production of SiC structural composites due to the benefits of reduced infiltration time and uniform composite density. In this work, the growth and orientation of polycrystalline SiC on graphite during CVI is investigated using TEM and HRTEM.

The composites studied possess a laminated matrix of alternating layers of carbon and SiC which were deposited by alternating the reagent streams from one layer to the next. Specimens for TEM examination were obtained by cutting ∽1 mm thickness slices from the bulk sample with a low speed diamond saw.

Liquid-Phase Sintering (LPS) is a conventional fabrication route for the densification of alumina and other ceramics. The polycrystalline ceramics processed by LPS contain siliceous phases along the grain boundaries. This wetting of the grain boundaries has a strong dependence on the crystallography of the boundary. The liquid preferentially wets certain orientations while some special boundaries are ‘dry’. The mechanism of dewetting of these boundaries is not well understood. Several approaches have been adopted to study the nature of the liquid-solid interaction at the grain boundaries. In commercial alumina, anorthite is the most commonly found intergranular phase.

Basal twist boundaries in alumina which contain a thin layer of anorthite glass have been investigated in the present study. Pulsed laser deposition has been used to deposit thin films of anorthite glass on optically flat basal sapphire. The substrate-film assembly is then bonded to an optically polished basal sapphire by sintering the assembly at 1650°C for 2h.

The knowledge of interface properties is important in understanding the adhesion of metal films to glasses. To simplify the analysis, silicate glasses are usually regarded as amorphous SiO2. Comparing the measured energy loss functions of Code 7059 (BaO-B2O3-SiO2) and Code 1737 (Al2O3-B2O3-Si2) glasses by EELS with the calculated result of a-Si02 from optical data, this is a fairly good assumption in bulk materials. Depositing metals, which have strong affinity for oxygen on glasses, however, may result in minor elements, such as Ba in both 7059 and 1737 glasses, segregating to interfaces, and breaking down the chemical balance.

Figs. 1 and 2 show the EELS spectra acquired with a 2Å electron probe in Cr film, interface and bulk glass respectively. The Cr film in Fig. 1 was sputtered on 7059 glass at room temperature, and annealed at 450°C in compressed Ar gas for 10 min. The preparation of Cr thin film in Fig. 2 is mentioned elsewhere.

High efficiency solar cells require large surface layers as acceptor [1], Nanoporous titanium dioxide film is an optimun choice for that purpose. For instance, porous titanium dioxide film of one micrometer thickness, prepared by colloidal chemistry, has a porous surface whose area is 100 times larger than the surface of a compact planar film. Obviously, accessibility to surface and crystal phase of the titanium dioxide are of prime importance. In this work, we characterize nanoporous titanium dioxide membranes on Si substrate by means of high-resolution transmission electron microscopy and electron diffraction.

Colloidal TiO2 sols were prepared by a wet chemical method [2]. The resulting colloidal TiO2 sol was autoclaved in a titanium autoclave for 12h at 230°C. A portion of the autoclaved sol was concentrated under vacuum at 30°C until a concentration of 20% TiO2 (by weight) was reached. 40% (by weight of Ti02) carbowax was added to this paste and stirred over night at room temperature.

Spectrum imaging, where a complete spectrum is acquired at each pixel in an image, is potentially a very powerful technique for the characterization of materials. The primary challenge to overcome is to extract all of the relevant information from what are typically large data sets that cannot be readily visualized in their entirety. For energy-dispersive X-ray (EDX) spectrum images, simple mapping has typically been done. In this work, the application of multivariate statistical analysis (MSA) to the characterization of a metal/alumina braze by SEM-EDX spectrum images is described.

The braze characterized in this work joins polycrystalline alumina and a copper-silver eutectic alloy containing some titanium (an ‘active’ metal). The specimen geometry consisted of a sandwich of two pieces of alumina, two braze layers and a Kovar (primarily Fe, Ni and Co) filler layer in the middle. The entire assembly was heat-treated to bond the interfaces and then a polished cross-section was prepared.

The large number of minor elements present in geological specimens and nuclear waste materials, can make TEM/EDS analysis of such samples troublesome. With a parallel detector such as the Gatan PEELS 666, the second difference technique has been shown to be effective at removing the channel-to-channel gain variation [1]. As spectroscopy performed with the Gatan Imaging Filter (GIF200) averages over a 2D array, gain variations are minimal; however, the second-difference technique selectively enhances the high frequency features such as the “white line” absorption edges, particularly of rare earth elements (REE) and transuranics (TRU). The second difference method may thus still have merit with the GIF200. A script was created within the controlling software program (DigitalMicrograph ™) which permitted second difference acquisition [2]. The Spectroscopy Package was also modified with ResEdit and the required values were added to the Global Tags to enable easy application of the second difference routine.

Ceramic materials are widely studied for their high temperature structural applications. In many crystalline ceramics the range of solid solution decreases with temperature and thus precipitation of a second phase occurs. Thus, ceramics can be hardened by precipitation of second phases. However little is known regarding the effect of precipitation and nanocrystalline grain structure in the ductility of ceramic materials. On the other hand, oxide ceramics are under intense-investigation for their technological advantages in magnetization, dielectric response and chemical stability in such diverse uses as magnetic recording media, induction cores and microwave resonant circuits. This investigation has been undertaken to produce, characterize and measure the properties of ceramics that can be hardened by precipitation. The selected systems include Fe(1-x)O-Fe3 and MgO MgFe2O4. Mechanical milling is used to produce nanocrystalline ceramic oxides in the systems Fe(1-x)O-Fe3 and MgO-MgFe2O4 The mechanically alloyed powders are consolidated by means of spark plasma sintering (SPS) at temperatures ranging from 673 K to 1273 K and a pressure varying from 500 to 50 MPa in vacuum.

The equilibrium condition for a liquid droplet in contact with a smooth, homogeneous, isotropic, non-deformable surface is given by the celebrated Young-Dupre equation1. This equation is based on the balance of the horizontal forces acting on the droplet. The idealised assumptions involved in arriving at the equation are seldom met in real experiments. Recently, Saiz et al have discussed the case of ridging of the solid at the three phase boundary (solid-liquid-vapour boundary) as a requirement for a stable three-phase co-existence. The wetting of anorthite on. sapphire substrates of different orientations have been studied earlier. In the present study, the wetting of anorthite liquid on m-plane of sapphire has been studied. The m-plane of sapphire is known to reconstruct in to two sets of facets and thus provides an interesting opportunity to study the wetting of liquid on a nonsmooth surface which contains linear patches with different surface energies.

There is currently an intensive effort to develop large-scale semiconductor nanowire or nanotube materials, such as Si and silicon oxide SiOx (l<x<2), with the uniform wide range of sizes up to 30nm, which would open us new opportunities in semiconductor and catalysis industries but is difficult to achieve at present. Up to our knowledge, the detailed study on macroscopic synthesis of aligned silicon oxide nanostructures with about 30nm diameter has not been carried on yet.

The ordered nanochannel-array anodic alumina were prepared via the anodization of aluminum textured pattern on the surface in a 3% oxalic acidic solution under the constant-voltage condition. It is about 6 μm and contains ordered cylindrical pores with the uniform diameter of 20-30nm and almost perpendicular to the film surface. The aligned silicon oxide nanostructures were prepared on this anodic alumina using a sol-gel method.

For sol aged at room temperature and dipped for lmin., nanowires are formed in a shorter period of aging time; while nanotubes are synthesized in a longer time (above 23 days).

Conical whiskers of layered compounds such as graphite and hexagonal boron nitride (h-BN)2 are interesting materials because their conical morphology results from the introduction of a local topological defect at the cone apex. In the honeycomb array characteristic of graphite and h-BN basal planes, this topological defect is thought to be a non-hexagonal ring (e.g. a pentagon or a square). These defects are known to form the basis of curved nanostructures like fullerenes and buckytubes. Therefore a comparison of their occurrence in two systems known to harbour nanostructures is worthy of study.

The defect structure at the apex of co-produced carbon and boron nitride whiskers was investigated by analytical transmission electron microscopy (TEM). The instrument used was a field-emission JEM3000F high-resolution electron microscope, equipped with a parallel electron energy loss spectrometer (EELS).

Ordered assembly of hollow structures of silica and carbon have drawn much attention recently because of their applications in low-loss dielectrics, catalysis, filtering and photonics. The structure is ordered on the length-scale of the template spheres and the pore sizes are in submicron to micron range. Alternatively, ordered porous silica with much smaller pore sizes in nanosize range (< 30 nm), produced deliberately by introducing surfactant, has also been processed, in which the porosity is created by co-polymers. In this research, a new silica nanostructure with double length-scale ordered porosities was processed, one being at the submicron scale of hollow spheres created by a template of polystyrene (PS), and the other at nano-scale created by self-assembled co-polymers.

Typical processing route includes three steps. Firstly, the ordered template of PS was created. The as-received PS with mean particle size of 203 nm was used as the raw material.

Recent innovations in materials chemistry have allowed the preparation of “hierarchical” ceramic and polymer materials that possess features on several different size scales. One of the newest hierarchical materials are ceramics that exhibit a three-dimensional ordered array of half-micron voids. These macroporous structures are synthesized from a liquid ceramic precursor and a polymer colloidal crystal template. This template is extracted by either thermal or chemical methods leaving a structure such as the porous zirconia particle shown in Fig. 1. The final structure of these materials may be thought of as the opposite of opal: the spheres here are the voids. Ordered arrays of dielectric material like these could potentially be used as photonic crystals that interact with visible light. For the microscopist, these materials create new opportunities to study interrelated aspects such as templating, crystallization, and phase transformations.

Transmission electron microscopy (TEM) was carried out on a Philips CM30 TEM equipped with a LaB6 filament and operating at 300 kV.

High resolution electron microscopes with field emission sources opened the possibility to investigate solids on a 100 pm range. Either electron holograpy can be applied or an information limit that may even extend into a region below 100 pm can be exploited to reach this goal [1]. However, lens aberrations such as the three-fold astigmatism often complicate an image interpretation in the 100 pm range or even make it impossible [2]. On the other hand, there is growing need to understand physical processes at a mono-atomic level in order to further develop artificially structured materials such as nano-crystals, ceramic coatings or semiconductors. Commonly, such materials contain light elements like C, N, or O with bond lengths that are shorter than a typical 180 pm point resolution of a high resolution, electron microscope. The carbon-carbon distance of 150 pm is the shortest bond length value in crystalline solids. Moreover, any projection of a diamond lattice along a low index zone axis for lattice imaging leads to a reduced C-C distance.

An oxidation resistant interfacial layer between the fiber and the matrix is important for prolonged use of ceramic-matrix composites (CMC). The interface layer has to be chemically compatible and stable in high temperature oxidizing environments. At present various oxide based interface layers in CMC are being considered. One candidate is porous interfaces. Zircon has good thermomechanical stability with SiC and mullite, and resists pore coarsening, so it is of interest as a porous interface materials.

Ethanolic zirconia and silica precursors, complexed with polyelectrolytes to form fugitive carbon for porosity were doped with vanadium. These were used to continuously coat the 3M Nextel 720™ alumina-mullite fibers. These fibers were heat-treated in-line in argon at 1000-1300°C, with the aim of finding heat-treatment conditions that would convert the zirconia, silica, and polyelectrolyte into a fine mechanical mixture of zircon and carbon.

Microanalysis has proved crucial in developing thermal-sprayed metal coatings on the surface of reinforced concrete to serve as anodes in impressed current (ICCP) and galvanic (GCP) cathodic protection systems and in understanding their long-term performance. Corrosion of reinforcing bar in concrete bridges is the primary cause of structural deterioration in high chloride environments such as coastal locations and colder climates where roads are deiced with salt. Over 40 pet of more than 500,000 bridges surveyed in the U.S. are in need of repair or rehabilitation. Cathodic protections is the most effective method of mitigating the effects of corrosion due to chloride contaminated concrete. While a young technology, consumable thermal sprayed zinc anodes (see Figure 1 for a schematic of the process) totaling over 40,000 m2 (430,00 ft2) have been installed on the Oregon coast, primarily on the Depoe Bay, Yaquina Bay, and Cape Creek bridges.

Lead zirconate titanate (PZT) is a perovskite-staictured material which is ferroelectric over most of the solid solution and which exhibits a range of electrical and electromechanical properties depending on the Zr/Ti ratio. Thin film PZT is currently being developed for piezoelectric actuators, ferroelectric memory devices and pyroelectric detectors. The ferroelectric properties and microstructures of the PZT films depend upon numerous processing parameters.In this research, sol-gel PZT films crystallized by rapid thermal annealing at 700°C for 30 seconds were investigated. A modification of the procedure described by Budd, Dey and Payne was utilized for the solution preparation. The electrodes/substrates which have been used for the deposition of PZT are Pt/Ti/SiO,/Si. The approximate thicknesses of Pt, Ti and SiO2 layers are 150 nm, 20 nm and 1000 nm, respectively. Transmission electron microscopy (TEM) was used to reveal the microstructure of the films, including the interfacial characteristics, grain sizes and domain structures. Cross sectional specimens were prepared by the following procedures.