The objective of this study was to simulate the aqueous corrosion of the nuclear waste glass over extended periods of time using vapor phase alteration by which reaction progress of glass corrosion is accelerated to form a characteristic suite of secondary alteration phases. In this study, extensive SEM/EDS, AEM, and HRTEM have been performed on the French SON68 waste glasses which were reacted in saturated water vapor at 200 °C for 908, 1013, and 1021 days, respectively. In order to study chemistry and microstructure of surface layers, TEM specimens were prepared in cross-section using the ultramicrotomy slicing technique. In this process, small chunks containing the surface layer and a thin layer of unaltered glass were broken off from the sample surface and each of these chunks was then embedded in resin to form a block. Finally, thin sections, approximately 50-90 nm thick, were microtomed from these blocks and were transferred to holey carbon coated copper grids.

Previous TEM study of natural Amelia albite (Ab99.3An0.1Or0.6) isothermally annealed at 1073°C for various periods revealed distinct tweed microstructures from the intermediately disordered albite samples (intermediate albite), but not from both the natural sample (low albite) and the highly disordered samples (high albite).1 These tweed microstructures seemed to correlate well with the degree of peak broadening and distortion in corresponding conventional powder X-ray diffractograms. Previous XRD, synchrotron radiation and TEM studies on the annealed albite samples at 1080°C for various periods gave rise to similar results.

Reinvestigation of the annealed albite samples with distinct tweed microstructures by TEM confirmed their existence in wide areas, giving two-directional streaking in the corresponding SADP’s (Fig. 1 and 2). Tweed directions are roughly perpendicular to and parallel to the trace of albite twin plane, {010}, as shown in Fig. 3. This tweed microstructure is apparently unaffected by the twinning and probably formed after it.

Todorokite is a manganese oxide mineral that occurs in widespread terrestrial and marine deposits. It is a major component of manganese nodules which occur in large quantities on ocean and some lake floors (>1012 tons). Todorokite has been linked to the presence of potentially mineable transition elements in manganese nodules. Todorokite is an octahedral molecular sieve material and has been termed by some in the chemical community as OMS-1. Many of the properties of synthetic and natural varieties have been characterized and potential applications include use for adsorption, as oxidation catalysts and in electrochemical devices.

The todorokite structure consists of a framework of MnO6 octahedra that are edge- and corner-linked to form tunnel structures. Several tunnel structures have been found in naturally occurring todorokite ranging from the most basic 3×3 structure to 3×8 and larger structures. Large cations and water occur in the tunnel interiors.

Asbestos is a common name of a number of fibrous mineral silicates which differ in chemical composition. The asbestos fibres are classified into two groups: serpentine (chrysotile) and amphiboles (anthophyllite, amosite, actinolite, tremolite, crocidolite).

Inhalation of asbestos dust fibres involves a health risk. It is therefore of great importance to develop quick and reliable methods to check for the presence of asbestos fibres in suspected materials. Some common analysis methods for asbestos detection are: optical microscopy scanning or transmission electron microscopies (SEM ,TEM) often combined with energy dispersive X-ray analysis (EDX) and selected area electron diffraction (SAED) in the TEM where the crystal structure is determined.

The EBSD technique in the SEM has in this work been applied to achieve electron backscattering patterns (EBSP) from four types of asbestos fibres. The pattern quality has been studied as a function of specimen preparation and SEM settings.

A method has been developed to identify asbestos-bearing samples. This technique, using scanning and transmission electron microscopy (SEM/TEM) coupled with X-ray fluorescent spectroscopy (XFS), X-ray elemental spectral analysis (EDS/EDAX), and X-ray diffractometry (XRD), supplements the traditional use of dispersion staining and polarized-light optical microscopy. The traditional method is subject to a statistical variance associated with analyzing a small volume of sample and projecting the results to the entire volume of the sample which in many cases is non homogeneous. [1] The simultaneous use of the aforementioned analyses in the new method improves the quantitative identification of highly heterogeneous unknowns.

The primary purpose of this study was to determine the essential steps of the identification process that will serve as the basis in the development of an automated particle/fiber recognition program. Five commercially pure asbestos samples of actinolite, amosite, chrysotile, crocidolite, and tremolite, and four common ‘household’ samples were examined.

Radiation damage in quartz has been of interest to the semiconductor industry, optical fiber industry, and nuclear industry. Cross-section transmission electron microscopy (TEM) is a powerful tool for investigating the irradiation effects since it provides a direct measurement of the ion and the damage distributions, and can also provide detailed microstructural information such as the presence of amorphous regions and the size, density and chemical nature of defect aggregates. The results reported below are from a systematic cross-section TEM study on 1.5 MeV Kr+ ion irradiated quartz.

3-mm discs of quartz (along 010 face) were prepared with 100 μm in thickness. One side for each discs was well polished using a 0.05 μm diamond paste. The well-polished side was irradiated at room temperature with 1.5 MeV Kr ions in the HVEM-Tandem Facility at Argonne National Laboratory. Following irradiation, cross-section TEM specimens were prepared using the so-called T-tool technique, a modified tripot technique

Zirconolite (CaZrTi2O7) is the major host phase for actinides in Synroc, a promising waste form for the immobilisation of high-level radioactive waste. The effect of radiation damage on the structure and durability of zirconolite are important to predictive modelling of zirconolite's behaviour in the repository environment and risk assessment.

In this study, radiation damage effects in zirconolite were investigated by irradiating samples with 1.5 MeV Kr+ ions using the HVEM-Tandem at Argonne National Laboratory (ANL) and energy loss electron spectroscopy (EELS). The HVEM-Tandem consists of a modified AEI high votage transmission electron microscope interfaced to to a 2 MV tandem ion accelerator. EELS spectra were collected using a Philips 420 TEM, operated at 120 kV, fitted with a Gatan Model 607 Serial EELS. EELS data were recorded at resolutions of ˜1.0 eV and at a dispersion of about ˜0.25 eV.

Selected area diffraction patterns (SADs) of individual grains of various zirconolites were monitored as a function of dose to establish the critical dose for aniorphisation (Dc).

Emission of pollutants from automobiles is regarded as one of the major causes of air pollution in many cities around the world. However, the pollutants could be almost eliminated by using catalytic purification of exhaust gas, thus making a better environment. The metallic material for catalytic converters made of ferritic stainless steel, Sandvik 0C404 (20.0 Cr-5.0 Al-Fe balance in wt % plus the addition of rare earth elements), offers a number of advantages over a ceramic one: better thermal conductivity, higher mechanical strength and toughness, thinner walls, larger effective area, greater catalytic capacity, smaller and more flexible design; better resistance to thermal shock. The formation of a homogenous A12O3 layer at high temperature is essential for providing corrosion resistance in such applications because of its high corrosive environment.

A prolonged oxidation of ferritic stainless steel Sandvik 0C404 at 1100 °C resulted in an accelerated oxidation (as schematically illustrated in Fig.l).

The purpose of this investigation is to evaluate the effects that relatively minor changes in phosphoric acid anodizing (PAA) parameters (voltage, temperature, time) have on oxide morphology and the subsequent penetration of an applied adhesive-primer into the porous oxide. This preliminary study examines two cases, one in which industry-standard PAA parameters have been followed, and a second in which the PAA parameters are slightly above industry limits.

Baseline PAA parameters have been developed in the aerospace industry from extensive empirical testing in order to maximize adhesive bond strength and durability in the presence aggressive environments. It has been noted that for effective mechanical strength of structurally bonded elements, penetration of the adhesive primer into the porous oxide formed by an anodizing pre-treatment is critical. Verifying primer penetration is somewhat problematic due to the high spatial resolution required to both structurally and chemically characterize an oxide film on the order of one micron in thickness.

The microstructure of Zr-2.5wt%Nb pressure tubes used in CANDU reactors consists α-Zr grains with a [110] texture in the radial direction and surrounded by a thin layer of metastable β-Zr. Information on oxide formed on β-regions have been reported. For the predominantly monoclinic ZrO2 (a=0.514, b=0.521, c=0.531nm, β=99.2°) formed α-Zr, two types of grain morphology and texture have been observed. In some areas of the oxide, columnar grains with a fibre texture exhibit no specific orientation relationship with the metal; such regions are not the subject here. Results presented here address a textured growth mode which is sensitive to the metal orientation.

Plan-view foils of oxide on the pressure tube radial-normal surface formed by a treatment of 24 hours in steam were prepared by ion-beam thinning and examined in a JEOL 2010 TEM. Selected area diffraction (SAD) and convergent beam diffraction (CBD) patterns showed that oxide growth mode was dominated by a [001] growth and consisted of a combination of orientation related [001] growth and mixed [001]/[100] growth.

Zr-2.5wt%Nb alloy is used as the pressure tube material in CANDU reactors. The pressure tube microstructure consists primarily of α-Zr (< l%Nb) grains elongated in the axial direction of the pressure tube and typically 0.3-0.5 μm thick in the radial direction. The α-Zr grains are partially surrounded by a thin layer of Nb-rich β-Zr phase (≈ 20%Nb). During corrosion, α-Zr is converted primarily to monoclinic ZrO2 with minor amounts of tetragonal ZrO2. Oxidation of α-Zr is complicated by the metastable nature of the phase below 863K. A detailed understanding of the nature of oxidized β-Zr remains a topic of on-going investigation, although some information have recently become available. Present SEM observations shed some lights on the charging characteristics of the oxidized β-Zr compared with ZrO2.

Oxide films on pre-polished surfaces perpendicular to the radial direction of the pressure tube were grown in steam at 673K in an autoclave; the treatment corresponds to the last stage of the pressure tube production.

Previous studies on the stress corrosion cracking (SCC) behavior of Alloy 600 forgings revealed a correlation between the SCC susceptibility and thermomechanical processing (specifically the final annealing temperature). (1) Detailed microstructural analyses using analytical electron microscopy (AEM) techniques showed that the materials containing dendritic-type intergranular M7C3 carbides were also more resistant to SCC initiation and propagation. This type of analysis has been extended to the evaluation of a 0.062 wt.% C Alloy 600 plate in three conditions (as-received, and heat-treated for 1 week at 982°C and water-quenched, and annealed for 24h at 1075°C and furnace-cooled). Tests were performed in PWR environments using fatigue precracked compact tension (CT) samples. In addition, detailed microstructural analyses using light optical metallography (LOM) and AEM were performed to fully characterize each material condition. The SCC fracture morphology was evaluated using scanning electron microscopy (SEM).

LOM examination of the as-received material indicated a “good” microstructure, with carbide-decorated grain boundaries as well as intragranular carbides.

Previous studies addressing the segregation of reactive elements in protective oxide scales and their beneficial effect on scale adhesion have primarily concentrated on primary alumina-formers (e.g. β-NiAl + FeCrAl).In our study the oxidation behaviour of three NiCrAl alloys, which form complex scales was studied in air at 1423 K and at 1473 K, both in isothermal (100 h) and in cyclic oxidation (100 x lh). The composition (in at.-%) of these alloys is the following: General Electric alloy René N5 (64.9 Ni, 7.8 Cr, 13.9 Al, 0.1 Fe, 2.1 Ta, 0.05 Hf, 1.6 W, 1.0 Re, 0.15 Si, 7.3 Co, 0.9 Mo, 0.003 Y, 0.003 Zr, 4 ppm S, 0.25 C), Ni-7Cr-6.5Al+Y (80.1 Ni, 7.2 Cr, 12.5 Al, 0.01 Fe, 0.14 Si, 0.012 Y, 18 ppm S, 0.05 C) and Ni-10Cr-10Al+Y (71.2 Ni, 9.9 Cr, 18.8 Al, 0.01 Fe, 0.02 Si, 0.041 Y, 16 ppm S, 0.04 C).

Corrosion of cast iron (C.I.) pipe often results in the formation of “tubercles” on the inner surface of the pipe. Tubercles are layered deposits formed by the stacking of several layers of corrosion products one on top of the other (Fig.l). Tubercles not only increase the amount of energy required for transport of water but are also considered the main source of turbidity in potable water. Their chemical and physical characteristics are important factors which affect the release of iron into the bulk water.

Tubercles are extremely complex systems. They may be highly crystalline in nature, with iron occurring in chemical structures, such as siderite (FeCO3), goethite (α-FeOOH), magnetite (Fe3O4) and lepidocrocite (γ-FeOOH) or they may be highly amorphous. Tubercles vary in height from a few millimeters to a few centimeters. They exhibit distinct layers which are formed over varying periods of time ranging from a few months to a century.

Functionally Graded Materials (FGMs) are used in a number of applications as a protective barrier to extreme environments. One such application of FGMs is to protect metal parts from high temperature environments. FGM coatings are plasma spray deposited onto surfaces of both simple and complex machined parts. Knowing the thermal conductivity of the FGM coating allows engineers to effectively develop high temperature designs with accurate estimates of heat transfer and thermal loading.

In this study, a FGM made by Caterpillar, USA, was measured with our steady state thermal conductivity measurement apparatus. The sample measured is a 10 layer graded coating using a Metro* 461 bond coan4 to a Metco* 205 ceria-yittria stabilized zirconia, with a Ni-Co-Cr-Al-Y metal grading. Figure 1 shows a plot of the thermal conductivity (W/m*K) as a function of temperature (K) for this material. The sudden drop in thermal conductivity at approximately 1073K was totally unexpected

Thermal spray processing has become an important powder-consolidation technique to yield new materials for extremes of temperature, radiation, wear, corrosion and mechanical stresses. High Velocity Oxy-Fuel (HVOF) spray coating process gives higher deposition densities and coating hardness; lower oxide content and porosity. The adhesive strength of thermal spray coatings is greatly effected by the interfacial impurities. The ring shear test method shown in Fig. 1 appears to give the most accurate results on shear adhesive strength. A typical ring shear test result of 88WC12Co 1/4" ring HVOF thermal spray coating on 4140 steel rod using a Jet kote thermal spray gun is shown in Fig. 2. Repeated ring shear tests on similar samples prepared under same spray and test conditions resulted in different shear bond strength and coating ring displacement before break off. We examined the ring shear tested coatings using a Zeiss DMS942 Scanning Electron Microscope (SEM) and Kevex Energy Dispersive X-ray Spectrometer (EDXS) with LPX1 Quantum Si(Li) Detector.

Fluorescence spectroscopy is presently enjoying explosive growth due to new experimental capabilities. In this talk we summarize some recent advances which can have applications in cell biology and imaging.

We show that evanescent illumination at one wavelength and incident angle, coupled with light quenching at a second wavelength and incident angle (Figure 1), can be used for selective excitation of fluorophores located up to 5000 Å into the aqueous phase. The use of combined evanescent wave excitation and evanescent wave quenching could provide selective excitation of fluorophores in the cytoplasmic region of cells. We also reported the first experimental observation of two-photon excitation using the evanescent wave resulting from total internal reflection. Two-photon excitation of the calcium probe Indo-1 was demonstrated by the quadratic dependence on intensity (Figure 2) as well as by the anisotropy and time-resolved fluorescence measurements.

Two-photon excitation is routinely performed using a single wavelength. We recently observed two-photon excitation of organic fluorophores with two different wavelengths, a phenomenon we refer to as two-color two-photon excitation.

Optical coherence microscopy (OCM) is a novel technique complementary to optical coherence tomography (OCT) which combines low-coherence interferometry with confocal microscopy to achieve micron-scale resolution imaging in highly scattering media. OCM may be implemented using a single-mode fiber-optic low-coherence interferometer (See Fig. 1). A high numerical aperture objective is used to focus sample-arm light into the specimen, and the reference arm length of the interferometer is adjusted to match the sample arm focal plane optical depth. The sample arm of the interferometer comprises a scanning confocal microscope, in which either the sample or the probe beam is laterally scanned in a raster pattern, and the optical fiber acts as a single-mode confocal aperture for combined light illumination and collection. The reference arm length of the interferometer establishes the depth position of an interferometric “coherence gate” in the sample, from which backscattered light is preferentially collected. Initial studies of OCM in scattering phantoms have demonstrated that this technique provides increased optical sectioning depth compared to confocal microscopy alone.

The living cell is criss-crossed by dense networks of filaments providing mechanic stability, site directed molecular transport and support of other vital cell functions. With the polarized light microscope we can observe the birefringence associated with thin filaments or partially oriented filament networks and measure the birefringence directly in the living cell (Fig. 1). Filament birefringence is a consequence of the elongated shape of the molecules and occurs naturally without the need to stain or label them, as is necessary in fluorescence imaging.

We have measured the birefringence of microtubules and axoneme filaments using the new polarized light microscope (Pol-Scope).The design of the Pol-Scope is based on the traditional polarized light microscope in which the crystal compensator is replaced by a universal compensator made from two liquid crystal variable retarders. Electronic image acquisition in the Pol-Scope is synchronized to liquid crystal settings to capture a sequence of four images with circular and elliptical polarization.

The operation of protein molecular machines is essentially stochastic. One cannot predict exactly when an ion channel opens, or when a molecular motor makes a step. As such, working molecular machines cannot be synchronized with each other in a rigorous sense. To understand the mechanism of a protein machine, therefore, one has to watch conformational changes of individual molecules while they are at work. To this end, we have been trying to develop two approaches based on optical microscopy. One is to attach a small tag, a fluorescent probe, to an appropriate site on the protein molecule of interest. Polarization of the probe fluorescence, for example, will reveal the orientation of the fluorophore, and thus of the portion of the protein molecule to which the fluorophore is attached. A conformational change of the protein will be detected as the reorientation of the fluorophore. A prerequisite is the ability to image a single fluorophore in an aqueous environment, which we have achieved on an epifluorescence microscope by reducing its background luminescence by two orders of magnitude