X-ray Micrographs Research Articles

ChemInform Abstract: CHEMICAL REACTIONS INVOLVED IN THE INITIATION OF HOT CORROSION OF IN‐738

AbstractDie NazsO4‐induzierte Heißkorrosion der präoxidierten Ni‐Legierung IN‐738 wird unter besonderer Berücksichtigung der langen lnduktionsdauer (ca.

Three-dimensional visualization of Golgi-stained neurons by a projection X-ray microscope converted from a scanning electron microscope.

Trying to obtain the three-dimensional images of neuronal elements, Golgi-stained thick sections were examined by a projection X-ray microscope converted from a scanning electron microscope. An attachment unit for the projection X-ray microscope consists of a target holder, specimen stage and film cassette. Two kinds of target material, titanium and gold, were tested. The system was operated at 10 to 30 kV. The electron beam into the target was about 20 nA with the use of a pointed cathode. The stereopair of X-ray micrographs were taken by tilting the specimens. Quality and contrast of the X-ray micrograph taken with a titanium target was better than that with a gold target. The spatial resolution was estimated about 1 to 2 micrometers for 100 to 350 micrometers thick sections with a titanium target. Compared with the light microscope, strong penetrating ability of X-ray permitted to visualize the internal structures of optically opaque materials. Further, almost all objects were in focus in X-ray micrographs even for relatively thick sections (100 to 350 micrometers). The three-dimensional morphology of neurons and glial cells was demonstrated by a stereopair of X-ray micrographs.

Manganese toxicity in field grown tea plants and the microdistribution of manganese in the leaf tissues as revealed by electron probe X-ray micrography

Abstract Tea plants in Toyota district, Aichi Prefecture, which were suspected of Mn toxicity were studied from the viewpoint of the heavy metal interaction and from the microdistribution pattern of Mn in the leaf tissues as revealed by X-ray microanalysis. A high Mn/Fe ratio in the soils was found to be a decisive factor for the disorder in the plants. X-ray micrographs of affected field tea leaves showed that Mn was densely deposited in the epidermis, while no signs of Mn accumulation were observed in the palisade and spongy parenchyma and vascular bundle cells. The Mn distribution pattern in artificially Mn enriched leaves was found to be similar to that of the field grown Mn excess plant leaves. The deposited Mn in the epidermal cells of the artificially Mn enriched leaves was found to move easily when the leaves were dipped in water for 24 hr.

Zoned aluminium distribution in synthetic zeolite ZSM-5

ZSM-5, a prominent member of the new generation of high silica zeolites, is a potential catalyst. The activity of ZSM-5 type synthetic zeolites with respect to acid-catalysed reactions is a linear function of the Al content1 which can assume extremely low values, but in catalytic applications is typically 1–3 Al per unit cell containing 96 Si+Al atoms. We now present substantial evidence that the Al distribution in ZSM-5 crystals is non-uniform. We first noted zoning of Al in ZSM-5 when examining scanning X-ray micrographs (Al Kα) of 50 µm crystals. The comparatively large crystals necessary for detailed measurements of Al concentration profiles using electron probe analysis suggest that Al is invariably concentrated in the rim portion of the crystals. No comparable zoning has been reported previously for zeolites.

Fibrinolytic and coagulation activity level during formation of experimental thrombus in dog's saphena vein

We could success in formation of the experimental thrombus by direct insertion of bovine fibrinogen into the lateral saphena vein of the dog. This method enabled us to clearly confirm the thrombus formation by X-ray micrograph. It was confirmed that this operation did not affect fibrinolytic and coagulation factors of experimental dogs. Reproducibility and stability of the result were also confirmed. So this experimental thrombus formation model is versatile for pharmacodynamic screening tests of the fibrinolytic enzyme system.

Theoretical considerations of extra equal-thickness fringes around a dislocation outcrop observed with an X-ray plane wave

An analytical interpretation is presented of extra half-line equal-thickness fringes observed at a dislocation outcrop in X-ray and electron micrographs of wedge-shaped crystals taken at off-Bragg conditions. Extra fringes arc well explained as the interference of two wavefields deduced from Takagi's equations for dynamical diffraction in distorted crystals. Theoretical discussions given in the present paper confirm the experimentally obtained rule of Δn = h. b (h is the diffracting vector and b the Burgers vector of a dislocation), which determines the extra number of fringes, Δn, at the dislocation outcrop. When h. b ≠ integer, it is predicted that a discontinuous shift will occur in the position of equal-thickness fringes along the topographic image of a dislocation.

A device for taking X-ray micrographs within the SEM

A device is described which permits to take X-ray and SEM micrographs in the identical position without repressurization of the specimen chamber. Some typical examples illustrate the practical application. The X-ray and SEM micrographs shown were taken in a Leitz AMR 1000 and a Cambridge Stereoscan MK2. The device can be adapted also to other SEM's.

Laser-fusion experiments utilizing a 4π illumination system

A focusing system which utilizes two f/0.47 doublets in conjunction with ellipsoidal mirrors produces two focusing cones with half-angles of 81.5°. This system has been used with the Lawrence Livermore Laboratory Janus 1.06-μm laser to irradiate and implode DT-filled glass microshells of ∼70 μm diameter. The purpose of the system was to provide more uniform heating of the pusher and more uniform compression of the DT fuel than had been obtained when irradiating targets using f/1 lenses. Neutron yields of ∼107 per event have been obtained at power levels of ∼0.4 TW. X-ray micrographs show that improved uniformity of heating and implosion sphericity are achieved. Data are also presented which add further confirmation of the importance of absorption by plasma wave resonance for non-normal incidence of the laser light on the target surface.

Evidence for profile steepening in laser-irradiated plasmas

Experimental evidence of a steepened electron density profile near critical density has been obtained by studying the light scattered by targets (10-μm thick disks and 100-μm diam glass spherical microshells filled with deuterium and tritium gas) illuminated by linearly polarized, 1.06-μm light. Scale lengths on the order of 1 μm have been inferred both from the polarization of the reflected light and from the azimuthal asymmetry (asymmetry about the beam axis) of the time-integrated scattered light with respect to the laser electric field. Azimuthally asymmetric heating of the microshells targets is indicated both by x-ray micrographs and by the spatial distribution of the plasma blowoff.

High-Resolution Soft X-Ray Microscopy

X-ray micrographs of biological materials have been obtained with a resolution better than 100 angstroms by using x-ray resist as the recording medium. A high-resolution scanning electron microscope with a short-focal-length final lens, operating in the "low-loss" mode, is used to make the smallest features in the x-ray replica visible.

X-ray misorientation contrast for a (lineage) subgrain boundary

The separation or overlapping of adjacent subgrain images in Berg–Barrett X-ray (reflection) micrographs is described for a reasonably general misorientation between the crystal subgrains. The five crystallographic parameters which describe the diffraction experiment also specify, effectively, the direction of the rotation axis for the misorientation, the amount of the angular misorientation, and the relative orientation of the subgrain boundary interface.

EXPLODING PUSHER EXPERIMENTS UTILIZING A 4π ILLUMINATION SYSTEM

A focusing system which utilizes two f/0.47 doublets in conjunction with ellipsoidal mirrors produces two focusing cones with half angles of 81.5/sup 0/. This system has been used with the LLL Janus laser system to irradiate and implode DT filled glass microshells approximately 80 ..mu..m diameter. The purpose of the system was to provide more uniform heating of the pusher and compression of the fuel than had been obtained with Janus irradiated targets using f/1 lenses. Neutron yields of approximately 10/sup 7/ per event have been obtained and x-ray micrographs indicate tha the heating of the pusher was more uniform. Also the implosions are definitely more spherical than those obtained with the f/1 lenses. Data is also presented which add further confirmation to the importance of absorption by plasma wave resonance for non normal incidence of the laser light with the target.

X-Ray Microscopy of Biological Objects with Carbon K α and with Synchrotron Radiation

X-ray micrographs of biological objects have been obtained with a resolution better than 1000 angstroms by using poly(methyl methacrylate) x-ray resist and carbon Kalpha or synchrotron radiation. Synchrotron radiation allows short exposure times; storage rings especially designed as radiation sources and improved x-ray resists would make exposure times under 1 second possible.

Quantitative analysis of subgrain misorientations observed in Berg-Barrett X-ray micrographs

The angular misorientations of several subgrains in a zinc crystal are quantitatively measured via the “misorientation contrast” they produce in Berg-Barrett X-ray images. Although the relatively large angles of the subgrain misorientations, say, of the order of 1° prevent individual dislocations from being identified in the boundaries, useful information about their cumulative dislocation structure is obtained from a combined analysis of this misorientation contrast and the more conventional dislocation diffraction contrast. Durch den „Fehloreintierungskontrast” bei Berg-Barrett-Rontgentopographien lassen sich die Desorientierungen von durch Kleinwinkelkorgrenzen getrennten Subkornern eines Kristalles bestimmen. Obgleich die relativ grosen Kornverschwenkungen, in der Regel ungefahr 1°, die Auflosung der Versetzungen in den Kleinwinkelkorngrenzen verhindern, erhalt man brauchbare Aussagen uber Details der komplizierten Versetzungsstruktur in den Korngrenzen durch kombinierte Betrachtung des Fehlorientierungskontrastes und des konventionellen Beugungskontrastes.

Misorientation contrast of crystal subgrain boundaries in Berg–Barrett X-ray micrographs

A stereographic projection method of analysis has been developed for analyzing the misorientation contrast of crystal subgrain boundaries which are observed in Berg–Barrett X-ray micrographs. The boundary appearance is described in terms of the geometry of the boundary with respect to the crystal surface, the angular misorientation of the adjacent subgrains, and the X-ray diffraction conditions. The rotation axis for the misorientation of adjacent subgrains, including the sense of the rotation, and the amount of misorientation is determined from the width and relative contrast of the boundary in various images. Experimental results are described for subgrain boundaries in zinc crystals solidified along different crystallographic growth directions. The Burgers vectors of the dislocations composing the subgrain boundary are indirectly determined by this method.

Skew-reflection X-ray microscopy of the vapor-growth surface of an Al2O single crystal

The most commonly used geometry for the Berg–Barrett X-ray microscopy uses the zero-layer reflections as described by Newkirk. It can be shown that non-zero-layer reflections, skew-plane reflections, can be used equally well to obtain X-ray micrographs. The analysis of the stereographic representation of the skew-reflection geometry demonstrates the many usable reflections and gives the conditions for minimum image distortion. In these X-ray micrographs the contributions to diffraction contrast from shadowing and sub-boundaries can be identified. An estimate of the height of steps occurring on the crystal surface can also be made.

Measurements of Local Density in Artificial and Natural Hailstones

Local density measurements were performed in the internal structure of hailstones by means of photometric observations on x-ray micrographs of thin slices. Comparison with the results of measurements performed by the same technique on ice artificially grown by accretion shows that dry growth near the net limit or dry growth wetted in a final stage is probably the most common condition of growth in natural hailstones. The technique is also suggested as a method for obtaining accurate quantitative data an air bubble size and concentrations which are needed in relating structure to growth conditions,. As a cross check, measurements of the total density by the usual immersion technique were also performed on hailstones from the same hail-fall as those examined by the x-ray absorption technique.

Distribution of Contaminants in Ice Grown by Accretion

Microchemical analysis and x-ray micrographs were performed on thin slices of ice cylinders artificially grown in a tunnel by accretion of supercooled droplets of contaminated water. Characteristic distribution patterns of contaminants were determined for various types of growth, with reference to contaminant transport that can take place in bulk ice. The results, if extended to natural hail, can be very helpful in inferring the environmental growth conditions.

Measurement of Elastic Strains in Crystal Surfaces by X-Ray Diffraction Topography

AbstractThe use of X-ray topographic techniques for studying elastic strains in crystals deformed at their surfaces is becoming widespread, especially in the field of silicon semiconductor devices. Although the broad features of the phenomenological processes involved in producing the strain patterns on the X-ray micrographs are understood, little attention has been devoted to evaluating the detailed nature or range of the strain fields in the crystal. In this paper, an clastic model is proposed for cases in which a region of crystal surface is uniformly deformed over a thin layer. With this model, the associated strain field in the surrounding crystal, which is readily computed from elasticity theory, may be characterized by a single parameter. The model is in accord with observed strain patterns on topographs of abraded diamond surfaces and silicon surfaces onto which a strip of metal film has been evaporated. From the spatial range of the diffraction contrast, an estimate of the parameter characterizing the strain field may be made.

The Observation of Lomer-Cottrell Dislocations in Boron-diffused (111) Silicon by Berg-Barrett Skew Reflections†

ABSTRACT Skew reflections wore employed to obtain a series of Berg—Barrett x-ray diffraction micrographs of shallow boron-diffused layers in (111) silicon. Diffusion-induced dislocations with 〈110〉 singular lines were observed, and their Burgers vectors, distribution and relative density were determined. The dislocations are Lomer-Cottrell locks. Their distribution indicates that the two-step deposition-and-drive diffusion process, of the type commonly used in integrated-circuit fabrication, produces a solute profile which deviates considerably from the assumed Gaussian form. It is demonstrated that the images recorded on the x-ray micrographs represent well-defined dislocation aggregates rather than individual dislocations.