Abstract: Uncommon, micro-sized particles with different morphologies were found in sintered aluminous electrical porcelains. The presence of these particles seems to be relatively insensitive to changes in composition of the porcelain system as well as in firing temperatures. X-ray energy-dispersive spectrometry (EDS) microanalysis showed that some particles, those with very well–defined geometries, were composed of K, Si, Al, and O with empirical formula KAlSi2O6—that is, leucite particles. Other particles showed less well–defined geometries, including some composed of Na, Si, Al, and O, corresponding to a sodium aluminum silicate structure, and others of K, Si, Na, Al, and O, corresponding to the leucite composition, where some K has been substituted for Na. The well–defined geometry particles were detected most often, and diffraction analysis with backscattering electrons showed that their unit cell was cubic, with unit cell parameter a = 1.343 nm. The formation of these particles may be the result of the relatively high concentration of K2O and/or Na2O in some very localized zones of the glassy phase due to weak coupling (e.g., alkali-enriched or -depleted melts) during diffusion at a slow cooling rate in the presence of catalytic agents such as TiO2.

Abstract: Quantitative X-ray mapping in the analytical electron microscope (AEM) could improve the statistics of grain-boundary segregation measurements if high spatial resolution can be maintained at lower magnifications (<500 kX). Typically, only about 10 boundaries are analyzed because of the difficulty of conventional AEM measurements; however, a low-magnification quantitative X-ray map could contain twice this number of boundaries in a single field of view. Microscope conditions and mapping parameters have been explored for operation at ∼250 kX, under a variety of conditions to illustrate the trade-offs between various characteristics, such as analytical resolution, counting statistics, magnification, and acquisition time. From these data, it is possible to extrapolate to maps generated under different conditions and estimate their limitations with respect to these characteristics. A simple model has been developed to describe the behavior of inclined grain boundaries that can be used to estimate the detectability of segregant as a function of boundary tilt. Using quantitative X-ray maps, grain boundary Cu coverage has been measured from 55 boundaries in Al–4 wt.% Cu with minimal user effort. For fine-grained thin films, mapping is substantially more efficient than other methods of data acquisition and may be used to measure segregation at large numbers of boundaries.

Abstract: Washcoat loading on automotive exhaust catalysts is normally determined, in production, by a weight gain procedure, which gives an accurate measure of washcoat weight present on an individual catalyst but does not address such parameters as uniformity of washcoat loading and geometric surface area within the monolith. Both issues are important factors that affect the catalytic activity (especially during catalyst lightoff) and catalyst cost (due to a thick, less functional washcoat) in an automotive exhaust system. Washcoat loading also plays a role in post-use analysis to determine possible reasons for changes (i.e., loss) in catalytic activity. For the post-use examinations weighing techniques are not useful since the washcoat cannot be preferentially removed and part of the weight gain is due to contamination from the combustion process. In the present work a combination of scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) X-ray mapping, light microscopy, and digital image processing was used. Two methods have been demonstrated for the determination of the density of calcined alumina washcoats. Additionally, a method has been developed to determine catalyst washcoat loading, either on a sampling basis after manufacture or in studies of catalysts after use. Methods also have been developed to determine other important parameters such as monolith wall thickness, percent open area in a catalyst monolith, geometric surface area, and hydraulic diameter. A linear correlation has been shown between hydrocarbon conversion efficiency and measured geometric surface area, with a coefficient of determination (r2) of 0.84.

Abstract: We compare here multi-photon excitation microscopy and tandem scanning reflected light confocal microscopy for the microscopic observation of human skin in vivo. Multi-photon excitation is induced by a 80-MHz pulse train of femtosecond laser pulses at 780 nm wavelength. This nonlinear microscopic technique is inherently suitable for tissue fluorescence imaging because of its deeper penetration depth and lower specimen photodamage. This technique has noninvasively obtained tissue structural information in human epidermis and dermis. Alternatively, tandem scanning confocal light microscopy based on a white light source can provide video-rate image acquisition with high resolution and high contrast. Reflected light confocal methods have been used to obtain images from the skin surface to the epidermal–dermal junction. The relative merits of these two techniques can be identified by comparing three-dimensionally resolved images obtained from the forearm skin of the same volunteer.

Abstract: A two-dimensional formalism is provided for analyzing the probe–sample interaction of optical near-field images in transmission mode. The numerical simulation is performed on a dielectric surface with sub-wavelength structures. The constant-height, near-field intensity through two Gaussian ridges has been calculated for p-polarized incident light. The influence on the signal by the dielectric function of the probe, the size of the scatterers, and the angle of incidence is investigated. The passive probe model is compared when equipped with and without the tip and the near-field intensity is simultaneously calculated.