Since skin basement membrane protein components are labile to conventional chemical fixation and since skin is not amenable to vibratome sectioning, frozen skin sections are routinely used for light microscopic immunohistochemical study of the skin basement membrane zone. However, inherent limitations of conventional frozen sections, including compromised morphology and a requirement for glass slidemounting, usually limit study to the light microscopic level. In the present study, we introduce the use of unfixed, free-floating cryostat sections to characterize immunolocalizations of selected basement membrane protein components at both the light and electron microscopy level. The new procedure employs free-floating cryostat sections that can be processed as routine tissue specimens and can be subjected to a variety of special staining procedures including immunohistochemistry. Especially useful is the ease of progressive processing of the same tissue specimen from light microscopy to electron microscopy.

In cell culture models various and distinct manipulations can be performed in a defined environment. This makes cell cultures very popular for immunohistochemical studies. Such studies are mostly performed at the light microscopic level where fluorescent probes and confocal microscopy provide detailed insights into the distribution and localization of antigens inside cells. In many such cases further studies at the electron microscopic level would give additional information and an often more detailed view. As compared to light microscopy not only is the resolution much higher, but also and even more importantly labeling information is completed with a wealth of cytological details.

This said it is surprising that studies on cell cultures using immunoelectron microscopy are rarely seen. Even more rare are reports in which monolayer cells are fixed and processed in situ without prior trypsinization. Such studies are essential though when cytoarchitecture is of importance or especially when cell-cell adhesion is an issue.

Biochemical studies have documented a role for oxidative stress in complications of diabetes. Our previous cytochemical and immunocytochemical studies demonstrated increased levels of NADH oxidase in retinal endothelial cells and pericytes of the BBZ/Wor diabetic rat which coincided with disruption of the blood retinal barrier. Lipid peroxidation and damage to outer segments was demonstrated in retinas of a streptozotocin-induced rat model of diabetes. Xanthine oxidase has been proposed as a source of superoxide and hydrogen peroxide (H2O2) in oxidative stress mediated complications of diabetes; however, there are no studies which confirm the role and cellular sites of xanthine oxidase in complications of diabetes. In addition, cellular sites of lipid peroxides have not been documented in diabetic retinopathy.

Xanthine oxidase was localized in retinas of BBZ/Wor diabetic rat by cerium based histochemistry using hypoxanthine and NADH as substrates.

In life sciences, the essential part of the functional molecular analysis is the unambiguous identification of biochemical composition of the observed structures. This analysis is expected to create a bridge between functional data pouring from biochemistry and molecular biology laboratories with the molecular architecture data available from ultrastructural images. This goal can be attained by application of various ultrastructural tags (See: Albrecht et al. 1992).

A new promising approach for high fidelity labeling is offered by molecular cloning and expression of molecules containing metal binding sites making them suitable for electron spectroscopic imaging (ESI) (Malecki 1995). A truly enormous potential of ESI relies in its ability for mapping of various elements within the same sample. Interactions of electrons with an atom result in the electrons specific energy loss. Based upon these energy losses distribution of the elements within the sample can be mapped.

Proeutectoid ferrite (bcc α) nucleation on the inclusions and precipitates dispersed in austenite (fee γ), denoted as intragranular ferrite transformation, has been used to refine the microstructure in the heat affected zone to improve the toughness of low and medium carbon steels. It is currently considered that Bl(NaCl)-type complex inclusions/precipitates (e.g. oxide, sulfide, carbide, nitride) are promising ones as ferrite nucleation sites. The present study aims to study the ability of various complex inclusions/precipitates in austenite as nucleation sites in proeutectoid ferrite transformations by standard and analytical electron microscopy.

Table 1 shows the chemical composition of Fe-2Mn-0.2C hypoeutectoid steels with various alloying element additions to change the inclusions/precipitate in austenite. Steel A contains a large density of MnS with the sulfur addition of 470ppm. Steels B and C also contain similar dispersion of MnS as Steel A.

The proeutectoid precipitation of Widmanstatten cementite has recently been shown to occur in two morphologies, either as broad monolithic plates or as aggregates of narrow laths, in a Fe-13 wt% Mn-1.3 wt% C steel, see Figure 1. Each of these morphologies correlates to a specific orientation of the cementite crystal within the austenite matrix; precipitates with a Pitsch orientation relationship adopt the monolithic plate morphology while precipitates with a Farooque-Edmonds orientation relationship develop as laths. In this paper, we examine the morphology and interfacial structure of these Widmanstatten cementite laths.

The typical three-dimensional morphology of Widmanstatten cementite laths can be revealed by etching with a 10% nitric acid solution in methanol. This procedure selectively etches the austenite matrix without affecting the cementite precipitates (see Figure 1). By similarly etching an electropolished thin foil TEM sample, the three-dimensional morphology and internal structure of entire electron transparent cementite precipitates can be examined.

For over five decades considerable attention has been given to magnesium-based alloys, primarily from the physical metallurgy point of view. The driving force for this effort has been the potential applications of Mg alloys in light weight structural components, namely in the automotive and aircraft industries. However, the processing of these alloys through conventional casting technologies have not succeed in reaching a high level of formability and ductility while preserving high specific strength. The combination of rapid solidification and consolidation techniques has arisen as a promising approach to overcome these limitations[l,2]. On the other hand, rapid solidification technologies are opening a wide field for fundamental studies, since different sets of thermodynamic (stability), kinetic and structural conditions are established to control a variety of solid-state phase transformations. The present work reports the applications of electron microscopy techniques to the characterization of the precipitation behavior in the rapidly solidified Mg-based alloys we are investigating.

Coarsening of particles involves a reduction of the total energy of the system. In fluids, the tendency for larger particles to grow at the expense of smaller ones is driven by the reduction of the total surface energy. In solids, the elastic strain energy Eel also needs to be considered. Reduction of Eel gives rise to particle alignment along elastically soft directions and changes of morphology as the particle volume increases. In addition according to several authors, reduction of Eel produces the splitting of particles that reach a critical size. Regular arrays of two, four and eight particles have been observed and explained in terms of splitting. However, splitting is unlikely from a micromechanical standpoint or as a consequence of the elastic interaction between particles. This investigation deals with the determination of translation order domains in coherent γ′ particles.

The introduction of “clean steels” was thought to have cured the problem of temper embrittlement in low alloy steels. However, even these steels exhibit temper embrittlement at services temperature above 400°C. Initial studies of temper embrittlement of clean steels used Auger electron spectrometry of fracture surfaces. The failure was found to occur along the prior austenite grain boundaries (PAGBs) where P segregation was found. It has been reported that the concentration of segregants changes along individual PAGB facets, as well as between the facets of different PAGBs. It was proposed that different elements segregate to different PAGBs, depending on their orientation. Differences in segregation along individual PAGBs were attributed to precipitation during thermal exposure, as identified by AEM. The cause of temper embrittlement is still unknown, as there are doubts about the role of precipitation. This implies that each PAGB may have a different chemistry.

The characterization of the microstructure evolution during welding of nickel base superalloys is required for efficient reuse and reclamation of used and failed components. Previous atom probe analysis of electron-beam and laser-beam welds revealed complex alloying elemental partitioning between the γ and γ phases. Rapid cooling conditions in the weld leads to non-equilibrium partitioning and large amplitude Cr and Co levels in the γ phase. These results indicated that there is a strong relationship between weld cooling rate and the precipitation of γ′ precipitates from the γ phase. To understand and develop predictive models, a systematic investigation of the microstructure evolution in CM247DS alloy under controlled thermomechanical conditions are being performed. This paper describes some recent results on the elemental partitioning between γ and γ′ phases obtained with atom probe microanalysis.

Casting of high temperature austenitic alloys is often used to form components and structures required in the chemical industry. Alloy HP is a Nb-stabilized austenitic alloy for such applications. High carbon levels are selected in order to drive the formation of coarse, intergranular precipitates of various carbides. These precipitates provide resistance to high temperature creep by inhibiting grain boundary sliding. While these precipitates are present in the cast material prior to high temperature exposure, it is the stability of these second phase particles during ageing that determines the long-term creep resistance and lifetime of stressed components. This study deals with the phase distribution in a centrifugally-cast HP component from a steam superheater tube in a styrene furnace, which experienced temperatures from 927°C to 1066°C or more for over 105,000 h.

Materials for high-temperature application, e.g. in gas-turbine compressor discs or steam turbine rotors, are often susceptible to microstructural instabilities during long-term service. Such instabilities reduce the service life due to a deterioration of the mechanical properties. Therefore, it is most important to identify such instabilities, which often take place in sub-micrometer scale. A class of materials widely used in power generating industries are the martensitic 9-12% Cr steels. In the present work STEM-EDX mappings were used to reveal the distribution of alloying elements in 9-12% Cr steels with a martensitic-austenitic microstructure developed recently.

The chemical composition of the material investigated was Fe-10.1Cr-6.2Co-5.2Mn-2.1Ni-1.2Mo-0.47V-0.1 IN (weight-percent). The material was subjected to a two step heat-treatment of normalizing at 1175°C for 1.5h with subsequent quenching and controlled tempering at 600°C for 20h. Due to the high amount of manganese and nickel a duplex microstructure of 30-40vol.% of austenite in a matrix of tempered martensite is formed during tempering.

Inconel 600 is an austenitic Ni-Cr-Fe alloy which is extensively used for tubing in steam generators of pressurized light water reactors (PWR) and CANDU heavy water reactors, because of its excellent mechanical properties and corrosion resistance. However, there have been instances of intergranular stress corrosion cracking of tubes in operating steam generators. The chemistry and the structure of grain boundaries and grain boundary precipitation have emerged as factors of prime importance in understanding stress corrosion cracking and intergranular attack of nickel-base alloys (see e.g. ref. l).

In this study analytical electron microscopy was used to determine the microstructure of grain boundary and matrix precipitates, grain boundary chromium content and dislocation substructure of selected steam generating tubes of CANDU reactors. The results of the in-service materials are compared with as-received material. Two JEOL 2010 STEM instruments were used in this study.

We have determined the structure of the paraelectric phase of BaAl2O4, which is a stuffed tridymite, by different TEM techniques and we will describe the phase transition between the ferroelectric room temperature phase and the paraelectric high temperature phase. We have also obtained HREM images of the higly radiation sensitive acristobalite phase of (Si0,9 Ge0,1)O2 and analysed the extended defects in this material.

The stuffed tridymite BaAl2O4 is ferroelectric at room temperature and undergoes a paraelectric-ferroelectric (PEFE) phase transition. The transition is reversible, takes place over a wide temperature range (400K-670K) and has a dynamical character. BaAl2O4 is easily obtained by solid state reaction of BaCO3, and A12O4,. The stoichiometric amounts of the initial reagents were mixed, grinded in an agate mortar under acetone and pressed into a pellet. The pellet was annealed in alumina crucibles at 1000 °C and 1300 °C for 40 h in air and furnace cooled.

The focus of our study is to demonstrate experimentally how elastic stress effects diffusion behavior and coarsening kinetics in a two-phase binary alloy. This work, based on the theory of Cahn and Kobayashi, focuses on elastic stresses in a thin plate. For the case of phase separation with lattice misfit between solute-rich and solute-poor phases, the diffusion of solute distorts the host lattice and causes elastic stress in the matrix. If the plate is sufficiently thin, the stress can cause the plate to buckle. The buckling stress biases the direction of diffusion, which increases the bending stress even further. Thus, the diffusion and the buckling stress are coupled; each affects the other. The interplay between the two is easiest to observe in a solution in which the solute and solvent have high misfit.

Phase separation by spinodal decomposition of body centered cubic Fe-Cr binary alloys to form isotropic fully interconnected nanostructures of Fe-rich α and Cr-enriched α′ phases typically on a scale of 2 to 10 nm is scientifically intriguing and technologically important. In aged dual-phase steels, it is the decomposition of the ferrite to form such α-α′ composition modulations that is primarily responsible for the increased ferrite hardness that contributes to embrittlement. The α′ structures are isotropic since the lattice constants of the two phases are almost identical and consequently the strain energy is small. In other spinodal systems larger strain energy leads to triaxially modulated structures aligned along <100> in cubic materials. A review of TEM characterization of spinodal alloys revealed that aligned structures had received the most attention, because they are more common and their characterization by TEM is more tractable.

Alloys based on the ferromagnetic τ-phase, which may be established in the Mn-Al system for near equiatomic composition [1], exhibit high magnetocrystalline anisotropy and coercivity and are of interest for advanced permanent magnet applications [2], Their technologically important properties depend strongly on the microstructure and defect structure development associated with the transformation from the disordered hexagonal (A3) ε-phase to the ordered tetragonal (L10) τ-phase. The structure, morphology and chemistry of the (ε/τ) interphase interfaces have been studied by methods of optical and electron microscopy (OM, SEM and TEM) in order to determine the nature of this technically important and scientifically interesting phase transformation. The optimization of processing-property relationships for this class of ferromagnetic materials requires a detailed understanding of the mechanisms facilitating the ordering process.

The τ-phase nucleates at prior ε-grain boundaries (ε-GB) and exhibits a serrated, faceted growth morphology (FIG. l).

Ceramic materials in the system FeO-Fe3o4 have been produced by means of mechanical milling and sintering for application of their physical properties. Starting from powder mixtures of Fe and Fe3o4 or Fe and Fe2o4, as well as pure Fe3o4, a metastable solid solution of Fe and O has been produced. The amount of Fe dissolved varies according to the milling time and its initial content in the mixture. A protective Ar atmosphere is used in all stages of the milling process in order to avoid contamination. X-ray diffraction patterns show a clear displacement of the intensity maxima as a function of the milling time, suggesting the formation of a solid solution from the initial mixture. Use of Mossbauer spectroscopy reveals an increasingly higher amount of metastable wustite (Fe(1-X) as a function of milling time i.e., 500 h and 1000 h of milling produce 67 and 74 mol % Fe(1-X)O, respectively.

Argonne National Laboratory has developed an electrometallurgical treatment process for metallic spent nuclear fuel from the Experimental Breeder Reactor-II. This process stabilizes metallic sodium and separates usable uranium from fission products and transuranic elements that are contained in the fuel. The fission products and other waste constituents are placed into two waste forms: a ceramic waste form that contains the transuranic elements and active fission products such as Cs, Sr, I and the rare earth elements, and a metal alloy waste form composed primarily of stainless steel (SS), from claddings hulls and reactor hardware, and ∼15 wt.% Zr (from the U-Zr and U-Pu-Zr alloy fuels). The metal waste form (MWF) also contains noble metal fission products (Tc, Nb, Ru, Rh, Te, Ag, Pd, Mo) and minor amounts of actinides. Both waste forms are intended for eventual disposal in a geologic repository.

Work undertaken on the Al-Cr-Ru system has shown excellent oxidation resistance in air up to 1500°C for compositions between Al20:Cr60:Ru20 and Al35:Cr32:Ru33 (at.%). Since no phase diagram data for the Al-Cr-Ru system have been published to date, an investigation was initiated. This part of the investigation is to identify the phases which form on solidification, and to derive the liquidus surface for alloys containing in excess of 50 at. % aluminium.

Samples were prepared as arc-melted buttons from 99.9% pure elements, and were analysed in the as-cast state in the SEM using EDS with elemental standards, and by X-ray diffraction.

The B2 phase, based on AlRu, extends to at least 25 at. % Cr. The Al3Ru2 phase has not been identified, except perhaps as a thin peritectic layer which was too fine to analyse. This is not surprising, since it exhibits very limited extension in other Al- Ru-X ternary systems, and in the Al-Ru binary system reacts peritectically forming AlRU2, and also subsequently decomposes at lower temperatures.