Quantitative Bulk and Trace Element X-Ray Mapping Using Multiple Detectors

X-ray mapping using energy dispersive spectroscopy or wavelength dispersive spectroscopy is a very popular characterisation tool for determining the elemental distribution in materials. Furthermore, quantitative X-ray mapping has become a very powerful technique enabling reliable quantitative results that can be an order of magnitude better than traditional analysis. Quantitative X-ray mapping is also far superior to regions of interest X-ray maps where low levels of an element or elemental overlaps are present. The one major drawback with X-ray mapping is the time required to obtain a high resolution X-ray map with good statistics at low levels of concentration. The use of multi-detectors, and just developed dual turret detectors for X-ray mapping, allows improvement in performance at low levels without compromising quantification quality and precision of traces, even in the presence of overlaps. However, for quantitative X-ray mapping to work properly, the characteristics of each detector must be accurately determined so that the final quantification of the individual detectors can be summed. To accomplish this effectively, the full spectrum at each pixel for each energy dispersive detector should be saved. As a final check for consistency between detectors, a technique was developed that involves assigning a different red-green-blue colour for each detector for the same element. By doing this, when we combine the three maps of the same element, we should obtain a grey scale map that indicates total correlation between the three detectors at the most critical final stage of quantification. To reduce contrast noise and further improve the quality of quantitative X-ray mapping images, a filter referred to as a “speckle filter” has been developed that allows the eye to see a more correct elemental concentration relationship.     

Assessment of the Fe-Sn-Zn phase diagram at 450°C

The Fe-Sn-Zn system is of interest because Sn is one element added to the Zn galvanizing bath to overcome the drawbacks due to the presence of Si in semi-killed steels. This work has been undertaken with the aim to understand the tin effect on the microstructure and the layers growth in batch galvanized coatings on low alloyed steels. Various experimental techniques such as metallography, scanning electron microscopy (SEM) coupled with X-ray energy dispersive spectroscopy (EDX) are used in order to characterize the microstructure and the properties of such coatings elaborated in a zinc bath enriched with tin. Solidification phenomena and layers growth mechanisms during galvanization are explained by means of the ternary phase diagram Fe-Sn-Zn at 450°C. The Calphad method allows to obtain this phase diagram from the three optimized binary phase diagrams Fe-Sn, Fe-Zn and Sn-Zn and some experimental data inside the ternary Fe-Sn-Zn system.     

Time- and frequency-resolved coherent anti-Stokes Raman scattering spectroscopy with sub-25 fs laser pulses

In general, many different diagrams can contribute to the signal measured in broadband four-wave mixing experiments. Care must therefore be taken when designing an experiment to be sensitive to only the desired diagram by taking advantage of phase matching, pulse timing, sequence, and the wavelengths employed. We use sub-25 fs pulses to create and monitor vibrational wavepackets in gaseous iodine, bromine, and iodine bromide through time- and frequency-resolved femtosecond coherent anti-Stokes Raman scattering (CARS) spectroscopy. We experimentally illustrate this using iodine, where the broad bandwidths of our pulses, and Boltzmann population in the lower three vibrational levels conspire to make a single diagram dominant in one spectral region of the signal spectrum. In another spectral region, however, the signal is the sum of two almost equally contributing diagrams, making it difficult to directly extract information about the molecular dynamics. We derive simple analytical expressions for the time- and frequency-resolved CARS signal to study the interplay of different diagrams. Expressions are given for all five diagrams which can contribute to the CARS signal in our case.     

On the structure of binary mixtures of non-symmetric liquid crystal dimers: the alpha-(4-cyanobiphenyl-4-yloxy)-omega(4-alkylanilinebenzylidene-4-oxy) alkanes

Liquid crystal dimers, in which two mesogenic groups are linked by a flexible spacer, exhibit a rich smectic polymorphism for both symmetric and non-symmetric dimers which differ in the nature of the mesogenic groups. For example, smectic phases having monolayer, interdigitated and intercalated structures have been discovered. We have extended our studies of such systems to binary mixtures in an attempt to understand the origin of the different phase structures at the molecular level. The dimers studied include non-symmetric systems differing in the parity of the spacer and in the length of the terminal chains; for comparison we have also studied a mixture of symmetric dimers differing solely in the parity of the spacer. We have constructed the phase diagrams for the various mixtures and found that for certain systems the smectic phases exhibited by either one or both components can be destroyed. To investigate the local structure of the nematic phase for mixtures in which a smectic A phase is eliminated from the phase diagram we have determined their orientational order using NMR and ESR spectroscopy. To provide more direct information on the local structure an X-ray diffraction study was undertaken on certain of the mixtures.     

Structural and Chemical Analysis of Materials with High Spatial Resolution

 An understanding of the correlation between microstructures and properties of materials require the characterization of the material on many different length scales. Often the properties depend primarily on the atomistics of defects, such as dislocations and interfaces. The different techniques of transmission electron microscopy allow the characterization of the structure and of the chemical composition of materials with high spatial resolution to the atomic level: high resolution transmission electron microscopy allows the determination of the position of the columns of atoms (ions) with high accuracy. The accuracy which can be achieved in these measurements depends not only on the instrumentation but also on the quality of the transmitted specimen and on the scattering power of the atoms (ions) present in the analyzed column. The chemical composition can be revealed from investigations by analytical microscopy which includes energy dispersive X-ray spectroscopy, mainly quantitatively applied for heavy elements, and electron energy-loss spectroscopy. Furthermore, the energy-loss near-edge structure of EELS data results in information on the local band structure of unoccupied states of the excited atoms and, therefore, on bonding. A quantitative evaluation of convergent beam electron diffraction results in information on the electron charge density distribution of the bulk (defect-free) material. The different techniques are described and applied to different problems in materials science. It will be shown that nearly atomic resolution can be achieved in high resolution electron microscopy and in analytical electron microscopy. Recent developments in electron microscopy instrumentation will result in atomic resolution in the foreseeable future.     

Analysis of inorganic materials by beam techniques — the challenge of high technology

For property-related characterization of inorganic materials, information is needed about bulk composition, distribution of elements, compounds, phases and structural features. Photons, electrons, charged ions or neutrons, often used as focused beams provide access to this information. The major trends in this field are the development or improvement of methods to obtain new information or to increase spatial resolution, detection power, precision and accuracy of analysis. The present state of the analysis of inorganic materials by using beam techniques is discussed in a selective manner. Emphasis is placed on the following problems, which are important for basic research and for development of high-technology materials: ultratrace bulk analysis in the pg g^?1 to ng g^?1 range; analysis for phases, trace elements and isotopes, including structural characterization; and surface analysis, with emphasis on the characterization of trace elements at surfaces, quantitative distribution of trace elements in heterogeneous structures, and surface structural analysis with atomic resolution.     

Multielemental fast analysis of vegetation samples by wavelength dispersive X-ray fluorescence spectrometry: Possibilities and drawbacks

X-ray fluorescence spectroscopy (XRF) is universally recognized as a non-destructive method for rapid and sequential, or simultaneous analysis of elemental composition of a material. The use of this technique for the direct determination of chemical elements in plant matrices has increased over the last few years.In the present study, a wavelength dispersive X-ray fluorescence (WDXRF) method for the quantitative analysis of some major elements (Na, Mg, Al, P, S, K, Ca), trace elements (Mn, Fe, Co, Zn, As) and non-essential elements (Sr, Pb) in vegetation specimens has been developed. The method uses a quick and easy sample preparation procedure since only drying, pulverizing and pressing of the samples are necessary. The calibration procedure was established by employing four plant reference materials and several synthetic cellulose calibrators spiked with appropriate amounts of analytes. Matrix effects were corrected employing the method of the influence coefficients on the basis of the computerized routine program linked to the equipment.Trueness of the experimental procedure was checked by using the standard reference material GBW07602 “Bush branches and leaves”. In general, good agreement was achieved between certified values and the measured ones with recoveries ranging from 94% to 107%. Moreover, quality parameters, including repeatability and reproducibility of the developed method, were also evaluated.On the whole, from results obtained, WDXRF method proposed prove to be good and effective tool for environmental investigation and quality control processes in vegetation specimens.     

Characterization of “oil on copper” paintings by energy dispersive X-ray fluorescence spectrometry

Energy dispersive X-ray fluorescence is a common analytical tool for layer thickness measurements in quality control processes in the coating industry, but there are scarce microanalytical applications in order to ascertain semi-quantitative or quantitative information of painted layers. “Oil on copper” painting becomes a suitable material to be analysed by means of X-ray fluorescence spectrometry, due to the metallic nature of substrate and the possibility of applying layered models as used in coating industry. The aim of this work is to study the suitability of a quantitative energy dispersive X-ray fluorescence methodology for the assessment of the areal distribution of pigments and the characterization of painting methods on such kind of pictorial artworks. The method was calibrated using standard reference materials: dried droplets of monoelemental standard solutions laid on a metallic plate of copper. As an example of application, we estimated pigment mass distribution of two “oil on copper” paintings from the sixteenth and eighteenth centuries. Pictorial layers have been complementarily analysed by X-ray diffraction. Apart of the supporting media made of copper or brass, we could identify two different superimposed layers: (a) a preparation layer mainly composed by white lead and (b) the pictorial layer of variable composition depending on the pigments used by the artist on small areas of the painting surface. The areal mass distribution of the different elements identified in the painting pigments (Ca, Cr, Mn, Fe, Zn, Cd, Hg and Pb) have been determined by elemental mapping of some parts of the artworks.     

A joint application of ATR-FTIR and SEM imaging with high spatial resolution: Identification and distribution of painting materials and their degradation products in paint cross sections

A series of paint cross sections from an oil painting are studied by attenuated total reflection in conjunction with Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX). The imaging modes of both methods were employed to show their potential in the detection of various painting materials and their distribution in the paint cross sections. The goal of this work is to evaluate FTIR and SEM-EDX spectroscopy in order to understand the limitations and strengths of both approaches. It has been revealed that both techniques are complementary in the identification of pigments, extenders and binding media used by an artist. FTIR spectroscopy is also a powerful tool in the studies on degradation products that are formed due to ageing or deterioration of works of art. We attempted to identify such secondary products present in the paint cross section. Cadmium oxalate and a high concentration of zinc palmitate/stearate were detected for the first time with the use of ATR-FTIR imaging technique. These results can complement studies on the conservation issue and provide an insight into understanding the mechanisms of chemical processes that appear in art works.     

Internal conversion in energy dispersive X-ray analysis of actinide-containing materials.

The use of X-ray elemental analysis tools like energy dispersive X-ray (EDS) is described in the context of the investigation of nuclear materials. These materials contain radioactive elements, particularly alpha-decaying actinides that affect the quantitative EDS measurement by producing interferences in the X-ray spectra. These interferences originating from X-ray emission are the result of internal conversion by the daughter atoms from the alpha-decaying actinides. The strong interferences affect primarily the L X-ray lines from the actinides (in the typical energy range used for EDS analysis) and would require the use of the M lines. However, it is typically at the energy of the actinide's M lines that the interferences are dominant. The artifacts produced in the X-ray analysis are described and illustrated by some typical examples of analysis of actinide-bearing material.     

Quantitative analysis of silicon-oxynitride films by EPMA

Thin films of silicon oxynitride with diverse compositions were prepared by de-magnetron sputtering of silicon, utilising oxygen and nitrogen gas flows and the sputtering power to vary the composition. In order to investigate the composition of these films, a method of analysis by electron probe micro analysis with energy dispersive detection was developed and the figures of merit were compared to the wavelength dispersive method used by other authors. The precision and repeatability of the results are evaluated and the accuracy is checked by comparison with Rutherford backscattering and nuclear reaction analysis. Energy dispersive X-ray spectrometry was proven to be applicable to analyse silicon oxynitride films of any composition yielding quantitative results for nitrogen and oxygen as well as silicon. Besides the good analytical performance, electron probe micro analysis with energy dispersive X-ray spectrometry has turned out to be a non-destructive, quick, easy to use and cost effective tool for the routine analysis of light elements in thin films.     

Macro and microchemistry of trace metals in vitrified domestic wastes by laser ablation ICP-MS and scanning electron microprobe X-ray energy dispersive spectroscopy

Management of domestic wastes often relies on incineration, a process that eliminates large amount of wastes but also produces toxic residues that concentrate heavy metals. Those hazardous secondary wastes require specific treatment. Vitrification is seen as a powerful way to stabilise them. However, concern exists about the long term behaviour of these glass wastes and the potential release of toxic species into the environment. The answers will come with further investigation into the physico-chemical evolution of the vitrified wastes and the mobility of hazardous elements within the matrix with appropriate analytical methods. Laser ablation coupled with inductively coupled mass spectrometry (LA-ICP-MS) is a challenging technique for the chemical analysis of trace elements in solid materials. This paper presents an evaluation of the potential of LA- ICP-MS for macro and microanalysis of trace metals in domestic vitrified wastes with regards to other physical analytical techniques of solids such as scanning electronprobe X-ray energy dispersive spectroscopy (SEM-EDXS). Two typical samples, vitreous and crystallised, are used to compare the analytical performances of the two techniques. SEM-EDXS was used for mineralogical characterisation and chemical analysis of the mineralogical phases. Relative micro-analysis and bulk quantitative analysis of 30 major, minor and trace elements was performed by LA-ICP-MS: precision was between 10 and 20% for most elements and quantitative analysis proved possible with an accuracy of 20% and relative detection limits of 0.1 mg kg(-1).     

Problems with the analysis of glass and glass ceramic surfaces and coatings

Summary The investigation of the composition of the surfaces and the spatial distributions of elements and phases within subsurface layers on glasses, coatings and interfacial layers is a most important, necessary requirement to understand and to control chemical interactions between glass and glass ceramic surfaces and adjacent materials. In general, this necessary requirement can be met only by using simultaneously a couple of surface analysis methods and the analytical electron microscopy. The application of single analysis methods can be sufficient, however, if basic results are available on the physics and chemistry of glasses to complement them in order to obtain the necessary information.Data are scarce on the free enthalpies of formation for non-crystalline materials, and, therefore, data on the free enthalpies of reaction cannot be calculated for the reactions with adjacent materials. Therefore, it is important to apply and to further develop methods to obtain data on the structures and microstructures of the crystalline and non-crystalline subsurface layer and coating materials, too. These data allow correlation of the differences in these structures with differences of the driving forces of the surface material reactions observed with adjacent phases and their reaction kinetics for the non-crystalline materials, too. Problems also arise with regard to the application of surface analysis methods, because changes of the spatial element distributions can be induced by a transfer of charge and energy to the surface during analysis. Furthermore, surface analysis methods must be improved to allow in-situ analysis.

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Analytische Probleme zu Glas- und Glaskeramik-Oberflächen und -Beschichtungen

     

The continental component of a Pacific Marine aerosol: Identification by combined neutron activation analysis and scanning electron microscopy with X-ray analysis

The relative merits and sampling requirements of instrumental neutron activation analysis (INAA) and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) analysis as applied to the continental component of marine aerosols are discussed. When correlated with air mass information, the quantitative INAA data on the concentrations of 15 major and minor elements in the continental dust fraction provides information on the geochemical type and location of the land source. Although the SEM/EDS technique provides only qualitative concentrations for 6 additional elements in the aerosol, the important feature of single particle analysis enables more nearly synoptic interpretation of aerosol composition and concentration. A combined INAA and SEM/EDS study of the aerosol samples is therefore preferred.     

Ab initio computation of low-temperature phase diagrams exhibiting miscibility gaps

A new methodology for the computation of the low-temperature part of phase diagrams without recourse to any experimental information is presented. A central element is a procedure for deciding whether formation of crystalline solid solution phases can take place in the chemical system. Via global exploration of the enthalpy landscapes for many different compositions in the system, candidates for ordered stoichiometric and crystalline solid solution phases are identified. Next, their free enthalpies are computed at ab initio level and a low-temperature phase diagram is derived. As examples, the low-temperature phase diagrams for the ternary alkali halides NaCl/LiCl NaBr/LiBr and NaCl/KCl are presented.     

Nuclear analytical methods on ancient Thai rice

For more than half of humanity, rice is life. Rice is a grain which has shaped the history, culture, diet and economy of billions of people in Asia. In Thailand, it is the essence of life. Archaeological evidence revealed that rice had been planted in northeastern area of Thailand more than 5,500 years ago which is earlier than in China and India. The ancient rice grains were found in various archaeological sites in Thailand such as Nakhon Nayok, Suphan Buri and Prachin Buri Provinces. In this work, the ancient black rice from Nakhon Nayok Province was elementally analyzed using scanning electron microscope coupled with energy dispersive X-ray fluorescence spectroscopy, proton induced X-ray emission spectroscopy and micro-beam energy dispersive X-ray fluorescence spectroscopy. Infrared (IR) spectroscopy was also used to study the chemical composition and bio-molecular structure. The grains were oblique in shape with a rough surface. Three major elements (Si, Ca and Al) and other trace elements were detected. The IR spectra provided some information about the presence of molecular bonds.     

Soft X‐ray emission electron microscopy: chemical state microscopy from interface and bulk

Scanning electron microscopy (SEM) has long been a workhorse of materials science and provides information on morphology, structure and elemental composition. However, information as to the chemical state of the elements is only available for deep lying core levels of the heavy elements and not the light elements. Whilst considerable advances have been made in high‐resolution wavelength dispersive spectroscopy (WDS) and energy dispersive spectroscopy (EDS), electron microscopy in the soft X‐ray region of ≈ 50–1500 eV is lacking. We present first results for a combined instrument of a soft X‐ray emission (SXE) spectrometer together with a spatially resolving (<100 nm) electron gun. Copyright © 2008 John Wiley & Sons, Ltd.     

High-throughput assisted rationalization of the formation of metal organic frameworks in the Iron(III) aminoterephthalate solvothermal system

Through the use of high-throughput methods, solvothermal reactions of FeCl 3 and 2-aminoterephthalic acid in protic as well as aprotic reaction media were systematically studied. Thus, the fields of formation of the isoreticular structures of MIL-53, MIL-88, and MIL-101 based on Fe(III) and aminoterephthalate could be identified for the first time. The resulting 3D framework materials with amino-functionalized pores have been characterized using X-ray diffraction; IR spectroscopy; and thermogravimetric, elemental, and energy dispersive X-ray analysis. Due to the applied high-throughput method, a high density of information was obtained in a short period of time, which allows the extraction of important reaction trends and contributes to a better understanding of the role of compositional as well as process parameters in the synthesis of inorganic-organic hybrid materials. We have found that the nature of the reaction medium has the most profound impact on structure formation. Furthermore, the concentration of the starting mixture (i.e., the solvent content) and the temperature have also been identified as key parameters for the formation of the different hybrid phases.     

铝合金建材的X射线荧光分析

用高性能飞利浦PW2424型X射线荧光光谱仪,测定铝合金建材中的Si、Fe、Cu、Mn、Mg、Zn、Ti、Cr、Ni等9个化学元素的含量.给出各元素的干扰校正系数和基体效应校正系数.方法准确、灵敏,稳定性好,速度快.