Analysis Of Selected Areas Research Articles

Boosting photocatalytic water oxidation achieved by BiVO4 coupled with iron-containing polyoxometalate: Analysis the true catalyst

In this work, BiVO4 is selected as effective light-harvesting material to replace conventional unstable dye-sensitized photosensitizer ([Ru(bpy)3]2+) that easily occurs photodecomposition during artificial photosynthetic system. The addition of an eleven iron-containing polyoxometalate (Fe11POM) as efficient cocatalyst illustrates a dramatically improved photocatalytic water oxidation performance compared with that of pure BiVO4. Through careful characterization and analysis of selected-area, highly selective in-situ photo-deposition of Fe11POM into ultrathin nanofilm on the decisive 110 facet of BiVO4 under ultrapure water is clearly observed, and an intimate connection between nanofilm and hole-rich 110 facet is obtained in favor of enhancing surface catalytic efficiency. The exquisite decoration of ultrathin nanofilm can be further clarified as FeOx decomposed from Fe11POM, which could effectively capture the photogenerated holes and suppress the recombination of electron–hole pairs for promoting water oxidation performance through fast interfacial hole transfer process.

Selected Area XPS Analysis for Identification of Pigment Compounds in Microscopic Paint Flakes

The application of X-ray photoelectron spectroscopy to the analysis of paint flakes from a painting by Henry Fuseli (1741–1825) is presented. Historically, the application of XPS to art conservation and restoration studies has been limited by the poor spatial resolution of the technique. Presented here is the successful analysis of paint flakes in the order of 100 μm using “imaging” XPS in conjunction with selected area analysis. Raman microscopy failed to satisfactorily identify the compounds present in this instance, and energy dispersive spectroscopy could not differentiate between lead and sulphur (two of the elements of interest) due to the limited energy resolution inherent in that technique. Using XPS analysis of the lead 4f peak revealed that the pigment was a lead-based pigment, in this case comprising exclusively lead-sulphur compounds.

Carbide precipitation in martensite during the early stages of tempering Cr- andMo-containing low alloy steels

The microstructures of a 2.25% Cr–1% Mo–0.15 wt% C steel, and a steel with identical alloying additions but a higher carbon level, 2.25% Cr–1% Mo–0.4 wt% C, have been examined in the martensitic condition for a variety of tempering heat treatments by transmission electron microscopy and atom probe field ion microscopy. Ultra-thin films which were carbon enriched have been observed at some of the martensite lath boundaries. Brightly imaging clusters of Mo and C atoms, which represent the earliest stages of the precipitation of Mo 2C carbide were observed. In the very early stages of ageing at 350°C, individual molecular ions of MoN 2+ were observed using atom probe selected area analysis. No partitioning of Cr, Mo and Mn, was observed between cementite and martensite after tempering at 350°C for times up to 40 h. The enrichment behaviour and interface concentrations of Cr, Mn and Mo in the cementite after prolonged ageing at 450°C for 187 h were found to be the same in both the low and high carbon alloys, despite the fact that the predicted equilibrium concentrations of the various alloying elements in the cementite were very different. These results demonstrate that cementite, in Cr and Mo containing alloy steels, precipitates from supersaturated ferrite via a paraequilibrium transformation mechanism.

X‐ray Fluorescence and SEM Analysis of Cycled NiOOH Electrodes

Zinc negative electrodes often contain other metal compounds to minimize shape change during cycling. After cycling in a cell, these materials can be found in the positive nickel hydroxide electrode. Two complementary analytical techniques were used to characterize the distribution and amount of Co, Zn, Ca, and Pb present as components of various compounds in the nickel oxide electrode after cycling. Radioisotope‐induced x‐ray fluorescence was used to quantify the amounts of the elements at various locations across the electrode face, and scanning electron microscopy was used to determine concentration profiles of Zn within the electrode. Selected area analysis showed that the amount of Zn was lowest in areas of the positive electrode which were opposite sections of the zinc negative electrode that experienced the greatest loss of zinc material: the edges. Large amounts of Pb material were found in the positive electrode when that electrode remained on open‐circuit stand after cycling.

ATOM PROBE FIM STUDY OF G.P. ZONE AND γ" PHASE IN AN AGED Cu-2.1 wt. % Be ALLOY

The G.P. zone and γ phase precipitated in an Cu-2.1 wt.% Be alloy are studied by FIM and AP. Both precipitates form on {100} matrix planes. The dimensions of the G.P. zone and the γ phase are determined. The composition of the γ-phase is obtained from atom probe selected area analysis. A composition of 50% Cu and 50% Be was found. The kinetics of the G.P. zones aged at 200°C has also been studied by FIM.

Microscale chemical effects of low temperature alteration of DSDP basaltic glasses

A novel application of X ray fluorescence, using selected area analysis, has been used to study the effect of low temperature alteration on trace elements in DSDP basaltic glasses. Major and minor element distributions were detailed through the use of electron microprobe analyses on the same sample areas. Samples include pillow basalt rinds and hyaloclastite sections from Deep Sea Drilling Project Site 396B. The glasses were found to release approximately 50% of the original Si and Al, 65% of the Mg and Na, and over 90% of the Ca originally present, during alteration to palagonite. Fe and Ti were found to be immobile, and K was increased 40‐fold by concentration from seawater. For the trace metals, over 25% of the Zn, Cu, and Ni were released, 40% of the Mn, and over 10% of the Cr. These changes apply only to the conversion of fresh glass (sideromelane) to palagonite (smectite) and do not include the effects of authigenic phillipsite and calcite reprecipitated locally. Differences between the effects of low temperature weathering on the crystalline basalts and the glasses appear to be primarily a function of the susceptibility of the primary mineral phases to attack, with the glass, as the least stable phase, most altered.

Electron channelling patterns in scanning electron microscopy

This review outlines progress in the development of SEM electron channelling pattern techniques since Coates first observed patterns and Bookeret al. explained their origin ten years ago. Discussions are included on the mechanism of electron channelling in crystals, electron optical and specimen conditions for generating patterns, pattern indexing, selected-area analysis, and applications. Progress in revealing crystal defects is also discussed.

A combined ESCA and Auger spectrometer

A system which accomplishes high−speed, electron−stimulated Auger electron spectroscopy (AES) and x−ray photoelectron spectroscopy with a double−pass cylindrical−mirror analyzer (CMA) is described. The CMA is well suited for AES because of its very high transmission, but has found very limited use in ESCA studies. In the present system the required source definition for use with a large−diameter x−ray beam is achieved with a two−stage CMA. The required energy resolution for ESCA is achieved with spherical retarding grids. A signal level of 16000 cps is attained on the Ag 3−d lines at 1.25−eV FWHM with a 400 W, Mg anode, x−ray source. Adequate luminosity is achieved primarily through high transmission, rather than a large imaged sample area. The small imaged area (less than 2−mm diam) is useful for selected area analysis and simplifies in−depth analysis when combined with inert−gas sputtering.

Electronic superposition of sample current and secondary-electron images in Auger electron spectroscopy

Selected-area analysis by Auger electron spectroscopy requires a knowledge of electron-beam location and the ability to place the beam on specified areas quickly and reproducibly. For samples with both conducting and insulating regions, it is highly desirable to use a grazing-angle-of-incidence electron beam to reduce surface-charging effects. Unfortunately, the use of grazing incidence makes the location of the area of interest and simultaneous optimization of the Auger signal rather difficult because of a parallax problem. Superposition of sample current images and secondary-electron images produced by scanning the electron beam from the grazing-incidence gun provides a solution to these alignment problems.

An X-Ray Macroprobe Analyzer Using Electron Excitation, Design, and Applications

An x-ray macroprobe attachment for the focusing CGR Cristallobloc 31 x-ray spectrometer has been developed. Selected-area analysis in the range 0.01–1 mm2 has been achieved using electron excitation. Focusing devices giving rectangular spot sizes of 1×1 mm and 2×0.15 mm have been used, and devices for sizes 0.2×0.2 mm and 0.1×0.1 mm should be feasible. All elements down to atomic number 5 (boron) can in principle be analyzed by this inexpensive device. Limits of detection of several elements in different matrices are reported. Applications to several metallurgical problems showing the versatility of the macroprobe are reported (examination of a welded joint and detection of silicon and niobium inclusions).

A Comparison of Four Slit Apertures for Selected-Area Analysis with the X-Ray Secondary-Emission Spectrometer

AbstractFour types of slit apertures—vertical, horizontal, inclined, and sirtgle-edge—for selected-area analysis with commercial X-ray secondary-emission (fluorescence) spectrometers are described, evaluated, and compared. The vertical and single-edge slits already have been described by the writer and Rizzo. The other two are described here for the first time. The vertical and horizontal slits are secondarybeam apertures; the other two lie in both the primary and secondary beams. AH the slits are mounted on the specimen drawer. No further modification of the spectrometer is required except replacement of the soller collimators with open tunnels or simple slits, and replacement of the flat crystal with a fixed-radius curved crystal to increase sensitivity. The accessories are inexpensive and can be made in even a modest machine shop. They can be installed on or removed from the spectrometer in about 5 min. The accessories are applicable ordy to linear selected areas where composition varies in the direction normal to but not along the line, for example, linear inclusions and sections of plated surfaces, diffusion couples, and interfaces. The four slits were evaluated and compared for resolution, sensitivity, and spectral-line width. Techniques for use, advantages, limitations, and means for improvement are discussed for each of the slits. The horizontal slit is of little value, but each of the others has features which permit analysis of very narrow selected areas for which pinhole apertures would not be sufficiently sensitive. Slit widths as narrow as 0,00012 in. (0.003 mm) have been used in favorable cases. The inclined slit, used with a pulse-height analyzer, is probably the most useful of the four apertures, combining high sensitivity, high resolution, and narrow spectral-line width.