Underglaze copper‐red decoration, i.e. the copper colourant used to paint diversified patterns on the surface of a body and then covered by transparent glaze and fired at high temperature in a reductive firing environment, is famous all over the world. However, the red colouration mechanism generated by underglaze copper remains unclear. In particular, the fact that the edges of the red patterns are orange has been ignored in previous research. Here, non‐destructive analysis has been carried out on a precious fragment of early underglaze red porcelain using synchrotron radiation X‐ray fluorescence, X‐ray absorption near‐edge spectroscopy (XANES) and reflection spectrometry techniques. The results suggest that the copper content in the red region is higher than that in the orange region, and other colour generation elements do not have obvious content difference, indicating that the colour generation effect of the underglaze red product is related to the copper content. XANES analysis shows that the valence states of copper in the red and orange regions are similar and metal copper contributes to their hues. The results of reflection spectrometry demonstrate that tiny orange hues could be attributed to the Mie scatting effect. Therefore, light‐scattering effects should be considered when researching the colouration mechanism of underglaze red. 相似文献
During X‐ray absorption spectroscopy (XAS) measurements of arsenic (As), beam‐induced redox transformation is often observed. In this study, the As species immobilized by poorly crystallized mackinawite (FeS) was assessed for the susceptibility to beam‐induced redox reactions as a function of sample properties including the redox state of FeS and the solid‐phase As speciation. The beam‐induced oxidation of reduced As species was found to be mediated by the atmospheric O2 and the oxidation products of FeS [e.g. Fe(III) (oxyhydr)oxides and intermediate sulfurs]. Regardless of the redox state of FeS, both arsenic sulfide and surface‐complexed As(III) readily underwent the photo‐oxidation upon exposure to the atmospheric O2 during XAS measurements. With strict O2 exclusion, however, both As(0) and arsenic sulfide were less prone to the photo‐oxidation by Fe(III) (oxyhydr)oxides than NaAsO2 and/or surface‐complexed As(III). In case of unaerated As(V)‐reacted FeS samples, surface‐complexed As(V) was photocatalytically reduced during XAS measurements, but arsenic sulfide did not undergo the photo‐reduction. 相似文献
X‐ray magnetic circular dichroism (XMCD) is one of the most powerful tools for investigating the magnetic properties of different types of materials that display ferromagnetic behavior. Compared with other magnetic‐sensitive techniques, XMCD has the advantage of being element specific and is capable of separating the spin and magnetic moment contributions associated with each element in the sample. In samples involving, for example, buried atoms, clusters on surfaces or at interfaces, ultrathin films, nanoparticles and nanostructures, three experimental conditions must be present to perform state‐of‐the‐art XMCD measurements: high magnetic fields, low temperatures and an ultra‐high‐vacuum environment. This paper describes a new apparatus that can be easily installed at different X‐ray and UV beamlines at the Brazilian Synchrotron Light Laboratory (LNLS). The apparatus combines the three characteristics described above and different methods to measure the absorption signal. It also permits in situ sample preparation and transfer to another chamber for measurement by conventional surface science techniques such as low‐energy electron diffraction (LEED), reflection high‐energy electron diffraction (RHEED), X‐ray photoelectron spectroscopy (XPS) and X‐ray photoelectron diffraction (XPD). Examples are given of XMCD measurements performed with this set‐up on different materials. 相似文献
Electromagnetic (EM) materials with perfect absorption have long been investigated for their important applications in many practical technologies. The trial‐and‐error method has been mostly employed to achieve this target, either by varying the constituent compositions for traditional natural material absorbers or by running computer simulations for general metamaterial (MM) absorbers. In this work, the authors propose a new method with analytical guidance to build omnidirectional perfect absorbers inspired by the recently proposed spatial Kramers‐Kronig (KK) nonreflecting dielectric profile. The subtle combination of the spatial and time dispersions in the metamaterial‐engineered KK profile gives the desired broadband response property. More importantly, these features remain invariant when the sample is uniformly compressed or stretched with large thickness change, i.e., this particular broadband absorber is deformable, which has been firstly reported in the literature. The current results will pave a new way to design high‐efficiency EM absorbers that could also be extended in general to manipulate waves for other fields or applications.
Because environment pollutants have a strong impact on ecosystems, including human health, methods of their determination and mitigation have received special attention in recent years. Taking advantage of the wide range of data that can be obtained by synchrotron radiation X‐ray fluorescence spectroscopy (SRXRF) in the field of environmental sciences, different instrumental setups were used to study the biological fates of toxic elements in volcanic environments. The elemental composition of plants, algae, and bacteria in Copahue and Domuyo volcanoes from Argentinean Patagonia was determined by SRXRF and the volcanic elements Ti, Fe, and Zn were abundant in these organisms. Interestingly, a high As concentration was found in cyanobacteria (26.2 μg/g) living in As contaminated stream (250 μg/ml). Because arsenic is toxic and human carcinogen, element‐retention capacity, element‐protein associations, and arsenic metabolism in this As resistant organism were analyzed by SRXRF. A high capacity (100–95%) of Ti > Fe > Cr > Sr > Ni > Cu > Mn > Zn > As retention was found after aqueous/alcoholic extraction assisted by ultrasonication. The cyanobacterial proteins were separated by SDS‐PAGE, electro‐transferred to nitrocellulose, and mapped by SRXRF. Defined protein bands containing Ca, Ti, Mn, Fe, and/or Zn were observed. Their ability to metabolize arsenic was revealed by combining SRXRF and X‐ray absorption near edge spectroscopy and Dimethylarsenic was found. Based on results, we speculate that these cyanobacteria could be interesting candidates for water treatment. Finally, we conclude that SRXRF is a valuable tool to study the biological cycle of environmental pollutants, including their accumulation, molecular targets, and metabolism. The SRXRF may also assist in remediation researches. 相似文献
The existence of the Stone, Bronze, and Iron Ages points to the importance of materials in humankind's development. The corresponding materials were used for art and jewelry, but most prominently for structural applications—as tools and weapons. While the ages themselves define step changes in material strength and durability, there was also significant material development within each age, such as the evolution from pure copper to alloys with tin, arsenic, and other metals in the Bronze Age. In a sense, we are still partially in the Iron Age, as steel (along with concrete) is the dominant structural material in our modern infrastructure, and continues to evolve in performance. For example, today's steels are significantly stronger and less prone to embrittlement than steel used for the RMS Titanic a century ago. On the other hand, we increasingly use specialty materials, such as polymer-metal composites, for high strength-to-weight ratio applications, and thermal-barrier coatings on Ni-based superalloys to operate turbines at very high temperatures. Most recently, the additive manufacturing revolution has opened up new possibilities for materials by design, where enhanced flexibility in composition, microstructure, and topological optimization relative to conventional processing methods offers many new opportunities and challenges. 相似文献
Laser‐induced incandescence (LII) is introduced as a valuable tool for the characterization of nanoparticles. This optical measurement technique is based on the heating of the particles by a short laser pulse and the subsequent detection of the thermal radiation. It has been applied successfully for the investigation of soot in different fields of application, which is described here in the form of an overview with a focus on work done at the LTT‐Erlangen during the last 10 years. In laboratory flames the soot primary particle size, volume concentration, and relative aggregate size have been determined in combination with the number density of primary particles. Furthermore, the primary particle sizes of carbon blacks have been measured in situ and online under laboratory conditions and also in production reactors. Measurements with different types of commercially available carbon black powders, which were dispersed in a measurement chamber yielded a good correlation between LII results and the specified product properties. Particle diameters determined by LII in a furnace black reactor correlate very well with the CTAB‐absorption number, which is a measure for the specific surface area. It turned out that the LII method is not affected by variations of the aggregate structure of the investigated carbon blacks. The LII signal also contains information on the primary particle size distribution, which can be reconstructed by the evaluation of the signal decay time at, at least, two different time intervals. Additionally, soot mass concentrations have been determined inside diesel engines and online measurements were performed in the exhaust gas of such engines for various engine conditions simultaneously providing information about primary particle size, soot volume, and number concentration. The LII results exhibit good correlation with traditional measurement techniques, e.g., filter smoke number measurements. In addition to the soot measurements, primarily tests with other nanoparticles like TiO2 or metal particles are encouraging regarding the applicability of the technique for the characterization of such different types of nanoparticles. 相似文献