Combined X-ray Fluorescence Research Articles

A laboratory X-ray microbeam for combined X-ray diffraction and fluorescence measurements

A prototype instrument has been developed which allows the simultaneous acquisition of both X-ray diffraction and X-ray fluorescence data at a microscopic length scale for mapping studies on materials. The instrument takes full advantage of the performance of recently developed optics and detectors to optimize the detection of low-intensity signals with a monochromatic X-ray microbeam of 20 µm diameter with a laboratory X-ray source.

SEM-EDS, EPMA and MRS analysis of neo-crystallisations on weathered glasses

When a glass is exposed to the atmosphere the combined action of water and environmental elements leads to the weathering of the glass surface. Both the chemical composition of the glass and the environmental parameters influence the mechanism of glass weathering mainly consisting in the formation of a layer of hydrated leached glass and salt deposits. The study of these phenomena is very important for both industrial and cultural heritage applications. In order to study the weathering mechanism of glasses exposed outdoor the chemical composition of the glass and the chemical and mineralogical nature of the reaction products should be determined. X-ray micro-analytical techniques such as scanning electron microscopy and X-ray microanalysis (SEM-EDS) and electron probe microanalysis (WD-EPMA) are traditionally employed in this type of investigation. Nevertheless particular compounds are hardly detected with this technique (for ex. nitrates) and no direct information can be obtained on the mineralogical features of the reaction products. Moreover, X-ray diffractometry (XRD) cannot be successfully used because of the very low amounts of deposited material. This work reports the results of a combined complementary X-ray fluorescence spectrometry (WD-XRF), SEM-EDS, WD-EPMA and μ-Raman spectroscopy (MRS) investigation on the surfaces of an industrial float glass and a glass reproducing the low-durable glass of ancient stained windows exposed sheltered outdoor for 6 months. The investigation enabled the identification and characterisation of different reaction products (soluble salts) confirming the need of this analytical approach for the study of the glass weathering process.

First combined total reflection X-ray fluorescence and grazing incidence X-ray absorption spectroscopy characterization of aeolian dust archived in Antarctica and Alpine deep ice cores

Aeolian mineral dust archived in polar and mid latitude ice cores represents a precious proxy for assessing environmental and climatic variations at different timescales. In this respect, the identification of dust mineralogy plays a key role. In this work we performed the first preliminary X-ray absorption spectroscopy (XAS) experiments on mineral dust particles extracted from Antarctic and from Alpine firn cores using grazing incidence geometry at the Fe K-edge. A dedicated high vacuum experimental chamber was set up for normal-incidence and total-reflection X-Ray Fluorescence and Absorption Spectroscopy analyses on minor amounts of mineral materials at the Stanford Synchrotron Radiation Laboratory. Results show that this experimental technique and protocol allows recognizing iron inclusion mineral fraction on insoluble dust in the 1–10 µg range.

High-throughput evaluation of domain switching in piezoelectric ceramics and application to PbZr0.6Ti0.4O3 doped with La and Fe

A combinatorial material synthesis and characterization technique is introduced and demonstrated wherein the ferroelectric behavior of a compositionally graded bulk ceramic is investigated during electrical loading. Using combined high-energy x-ray microdiffraction and fluorescence spectroscopy, non-180° domain wall motion of different compositions is measured and quantified as a function of composition across the gradation. The greatest amount of non-180° domain wall motion is found in samples containing the highest measured fraction of La dopant (2mol%).

Advantages of combined μ-XRF and μ-XRD for phase characterization of Ti–B–C ceramics compared with conventional X-ray diffraction

Design and processing of new materials with improved high-temperature properties is one of the most challenging tasks of modern engineering. Among such materials, nonoxidic ceramics hold an important place. When optimizing the synthesis conditions of these new materials in an largely empirical manner, the use of analytical methods that can fully document the resulting phase compositions is of great importance. In this paper, we demonstrate the advantages of using combined microbeam X-ray diffraction and X-ray fluorescence over conventional X-ray diffraction as the characterization method in the specific case of Ti-B-C ceramics. Ceramic samples were synthesized by the pulse plasma method starting from high-purity powders of titanium, boron, graphite, and nickel. Different mixtures were heated in a pulsed fashion and sintered by combustion synthesis at various temperatures and time durations, as is the case during empirical optimization of a synthesis procedure. Conventional X-ray diffraction showed the presence of two phases at the end of the sintering process, TiB(2) and TiC, irrespective of the conditions employed. Scanning micro-XRF/micro-XRD on the other hand allowed one to detect and visualize the distribution of additional phases present in the sintering products, during which a dependence on sintering conditions was apparent. The micro-XRD results showed that three phases (TiB(2), TiC, and TiB) instead of two were present in samples sintered during a short time interval. The addition of metallic Ni to the initial mixture as a sintering facilitator resulted in the formation of a Ni(3)B phase. All phases proved to have strongly heterogeneous distributions above the 15-microm level with the presence of TiB(2) anticorrelated to that of TiC and TiB, emphasizing the necessity of the use of laterally resolved methods of characterization.

Internal elemental microanalysis combining x-ray fluorescence, Compton and transmission tomography

Conventional x-ray transmission tomography provides the spatial distribution of the absorption coefficient inside a sample. Other tomographic techniques, based on the detection of photons coming from fluorescent emission, Compton and Rayleigh scattering, are used for obtaining information on the internal elemental composition of the sample. However, the reconstruction problem for these techniques is generally much more difficult than that of transmission tomography, mainly due to self-absorption effects in the sample. In this article an approach to the reconstruction problem is presented, which integrates the information from the three types of signals. This method provides the quantitative spatial distribution of all elements that emit detectable fluorescent lines (Z⩾15 in usual experimental conditions), even when the absorption effects are strong, and the spatial distribution of the global density of the lighter elements. The use of this technique is demonstrated on the reconstruction of a grain of the martian meteorite NWA817, mainly composed of low Z elements not measured in fluorescence and for which this method provides a unique insight. The measurement was done at the ID22 beamline of the European Synchrotron Radiation Facility.

Elemental analysis of multilayer samples by means of combined laser ablation and x-ray fluorescence spectrometry

Even though absolutely noninvasive techniques are ideally required for the analysis of valuable works of art, in some cases, the historical study or the restoration would benefit from deep investigations that require some kind of alterations on the sample. This is the case when a stratigraphic analysis of a paint has to be carried out to determine pigments and ligants used by the painter. To perform this task, a fully automated device working in situ without physical contact with the sample is certainly the best choice in terms of minimal damage, ease of operation, and quickness of analysis. Such a device could result from the combination of the state of the art portable x-ray fluorescence (XRF) analyzer with a digging tool capable of micrometric control of positioning and depth of operation. In this article, we propose a new method for the determination of chemical element distribution in multilayer samples, based on the use of an alternate sequence of laser photoablations and XRF analysis. The laser source used in this work is a flash lamp pumped Er:YAG laser (2.94 μm), assembled in our laboratories. It operates at a repetition rate of 8 Hz in a Q-switching regime and generates an average power of 60 mW. The XRF spectrometer is a portable instrument based on a Peltier-cooled silicon drift detector (operated at about −10 °C) which is characterized by an energy resolution of about 155 eV full width at half maximum at 6 keV. An x-ray tube with a tungsten anode is used as excitation source. In this article, the measurement technique is described and the first experimental results obtained on samples composed by layers of different thickness and composition are presented.

Robotic search for ices and hydrous minerals at the lunar poles using a combined X-ray diffraction and fluorescence instrument

There is a growing body of evidence that points to the survival of water or hydrous minerals on the Moon and the potential for large aqueous reservoirs in shadowed craters at the lunar poles. CheMin, an XRD/XRF instrument that is currently under development, could provide a definitive test of whether the polar hydrogen signal measured by the recent Lunar Prospector mission is an indication of a significant water reservoir or merely reflects an anomalously rich accumulation of solar-wind hydrogen. Proposed enhancements of CheMin could be used in conjunction with a drilling system capable of penetrating the upper few tens of centimeters of the lunar regolith to search for ices or hydrous minerals. This advanced version of the CheMin instrument would be within the size, mass, and power constraints of Ariane 5 micromissions.

Deciphering Ni sequestration in soil ferromanganese nodules by combining X-ray fluorescence, absorption, and diffraction at micrometer scales of resolution

X-ray microprobes are among the most important new analytical techniques to emerge from third generation synchrotron facilities. Here we show how X-ray fluorescence, diffraction, and absorption can be used in parallel to determine the structural form of trace elements in heterogeneous matrices at the micrometer-scale of resolution. Scanning X-ray microfluorescence (microSXRF) and microdiffraction (microSXRD) first are used to identify the host solid phase by mapping the distributions of elements and solid species, respectively. Micro-extended X-ray absorption fine structure (microEXAFS) spectroscopy is then used to determine the mechanism of trace element binding by the host phase at the molecular scale. To illustrate the complementary application of these three techniques, we studied how nickel is sequestered in soil ferromanganese nodules, an overwhelmingly complex natural matrix consisting of submicrometer to nanometer sized particles with varying structures and chemical composition s. We show that nickel substitutes for Mn3+ in the manganese layer of the MnO2-Al(OH)3 mixed-layer oxide lithiophorite. The affinity of Ni for lithiophorite was characteristic of micromodules sampled from soils across the U.S.A. and Europe. Since many natural and synthetic materials are heterogeneous at nanometer to micrometer scales, the synergistic use of microSXRF, microSXRD and microEXAFS is expected to have broad applications tomore » earth and materials science.« less

Determination of quartz in bauxite by a combined X-ray diffraction and X-ray fluorescence method

Quartz is one of the important phase constituents of any bauxite and may vary from a small fraction to over 50% of the total SiO 2 concentration. At present, the most practical method of estimating quartz is by wet chemistry or by using conventional X-ray diffraction (XRD) methods. Whether employing a direct or Rietveld approach, the XRD method is difficult and not possible for small quartz concentrations because of severe line overlaps. A new method uses bauxite material calcined at 1000 °C. Major bauxite phases, such as gibbsite, boehmite, kaolinite and goethite are entirely decomposed in the calcination process. The calcination procedure converts SiO 2 containing kaolinite into XRD amorphous material. In addition to the amorphous portion, there are just four major crystalline phases present: corundum, hematite, rutile and quartz. Quartz in the calcined bauxite corresponds to the primary quartz occurring in the initial sample. Rutile is employed as the internal standard. First attempts to quantify quartz in calcined bauxite using XRD based Rietveld analysis will be described. Results are presented for the Sangaredi (Guinea) bauxite deposit.

X-ray fluorescence micro-tomography of an individual fluid inclusion using a third generation synchrotron light source

The aim of this study was to establish the feasibility of obtaining 3D elemental images of fluid inclusions, which consist of multiphase and irregular objects trapped in a host mineral. These experiments are based on the fluorescence micro-tomography technique, which combines X-ray fluorescence measurements and 2D tomographic reconstruction algorithms. For this purpose, multiphase aqueous fluid inclusions were synthesized in fractured quartz crystal within gold capsule at high temperature and pressure. A single fluid inclusion was isolated in a tiny quartz parallelepiped, polished on all its faces. On the basis of the parallel collection technique, the sample was successively scanned vertically over a few hundred micrometers, in steps of 3 μm and with an acquisition time of 1 s/point, and rotated by an angle of 2°. The 2D projection images, which consist in relative elemental concentration regions, provide the size and the location of the fluid inclusion as well as the elemental location and combination. By iterating the procedure along the horizontal rotation axis, full 3D elemental images can be obtained.

Determination of AlN and Al 2 O 3 in steels by electrolytic separation and wavelength dispersive X-ray fluorescence spectrometry

The determination of non-metallic aluminium inclusions in steel samples, mainly consisting of AlN and Al2O3, can be performed with the aid of their X-ray fluorescence Kβ-line. The enrichment of these inclusions with an electrolytic isolation is described and shown to enable the analysis of samples with even very low aluminium content. The absolute detection limit of the combined electrolysis and X-ray fluorescence spectrometric detection using the Al-Kβ line was found to be 3 μg Al in the residue that is below 0.001 mass-% in the steel sample under the given conditions. Due to low spectral resolution a deconvolution of the obtained data is required, but then a detection limit of 1.8 mass-% Al2O3 and 0.4 mass-% AlN in the binary mixture can be achieved. Sixteen samples of two low-alloyed steel qualities with a total amount of insoluble aluminium in the range of 0.003 to 0.013 mass-% have been analyzed with the procedure developed.

In situ investigation of ices and hydrous minerals at the lunar poles using a combined X-ray fluorescence and diffraction instrument

Un nombre croissant d'observations convergent vers l'hypothese d'une preservation d'eau ou de mineraux hydrates sur la Lune, voire l'existence de grandes quantites de glace dans les zones d'ombre permanente de crateres aux poles lunaires. CheMin, un instrument miniature de diffraction/fluorescence X en cours de developpement, permettait de verifier de maniere irrevocable si les recentes mesures de Lunar Prospector sont la consequence d'un reservoir aqueux ou d'une accumulation anomale d'hydrogene de vent solaire. Une version adaptee de CheMin, combinee a un systeme de forages pour la collecte d'echantillons a quelques decimetres dans le regolite lunaire, permettrait une recherche de glaces ou de mineraux hydrates. Un tel dispositif respecterait les contraintes en volume, masse et puissance des micromissions Ariane 5.

Glancing-incidence and glancing-takeoff x-ray fluorescence analysis of Ni-GaAs interface reactions

A thermally stable Ni-based ohmic contact is one of the most attractive contact materials for developing superior GaAs devices. To understand the interface reaction between an Ni thin film and a GaAs wafer, a combined grazing-incidence and grazing-takeoff x-ray fluorescence (GIT-XRF) method was applied. Ni thin films (∼10 nm in thickness) were deposited on GaAs wafers, then annealed at 373 and 473 K. When the conventional grazing-incidence XRF and grazing-exit XRF methods were separately applied to a sample annealed at 373 K, it was not possible to recognize interface reactions between Ni and GaAs. However, the small compositional change at the interface could be detected by the non-destructive GIT-XRF method. The diffusion of Ni atoms into the GaAs substrate, which was induced by heating at 473 K for 3 min, was clearly found by measuring the takeoff angle dependences of characteristic x-ray intensities at a grazing incidence angle of 2.5 mrad. Finally, the mixed Ni–GaAs layer was evaluated to be Ni5GaAs with a thickness of 15 nm by fitting calculated curves to experimental plots. Copyright © 2000 John Wiley & Sons, Ltd.

Combining X-Ray Fluorescence Spectrometry and Vibrational Microscopy to Assess Highly Heterogeneous, Actinide-Contaminated Materials

Combining X-ray fluorescence (XRF) spectrometry with micro-Raman and infrared spectroscopies is shown to be a powerful experimental approach in providing information on components present in highly heterogeneous materials which contain or have been in contact with actinides. In this initial study, the quantitative XRF data demonstrate a correlation in the relative amounts of plutonium with other elements such as strontium and yttrium. The XRF mapping provides further evidence for correlation of these (and other) elements and identifies regions of interest within the sample to be further studied. These regions were then examined by vibrational microscopy to supply information on molecular species present and their spatial distribution. This experimental approach provides insight into very complex samples and provides a technique capable of exploring interactions of molecular components with actinides in complex media.

Extraterrestrial Mössbauer spectrometry

We describe a combined backscatter Mossbauer spectrometer and X-ray fluorescence analyzer (BaMS/XRF) instrument suitable for planetary missions to the surfaces of Mars (MESUR Program), the Moon, asteroids, or other solid solar-system objects. The BaMS/XRF instrument is designed to be capable of concurrent analysis of a sample for its elemental abundances (XRF) and for the mineralogy of its iron-bearing phases (BaMS) without any sample preparation.

Nuclear analysis of Jordanian tobacco

The concentration of trace and minor elements in six different Jordanian and two foreign brands of cigarette tobacco and wrapping paper were determined using combined X-ray fluorescence (XRF) and Rutherford backscatteing (RBS) analysis techniques. The cigarette filter and the ash were also analyzed to determine the trapped elements on the filter and their transference with smoke. The toxic effects of some elements have been briefly discussed.

Determination of uranium isotopic composition in aqueous solutions by combined gamma-spectrometry and X-ray fluorescence

The possibility of use of combined gamma spectrometry and X-ray fluorescence for uranium isotopic analysis in dilute aqueous solutions has been studied. Uranium K X-rays were excited by gamma-rays of57Co radionuclide source and were measured together with 185.7 keV gamma-rays of235U using a planar pure Ge detector. Uranium Kα1 fluorescent X-rays were used for the evaluation. The method was proved to be independent of total uranium concentration in the region of 8–20 mg U/ml. The procedure making use of measurement of 7 ml samples and allowing to achieve an accuracy better then 1% in the region of 0.4–4.5 at. % of235U is proposed.

X-Ray Fluorescence Analysis of Individual Rare Earths in Complex Minerals

A combined chemical x-ray fluorescence method is described for determining rare-earth elements in small amounts of complex rare-earth minerals. These elements yield a complex x-ray spectrum in which many of the analytical emission Lα lines of a given element coincide with the Lβ and/or Lγ lines of a lighter rare-earth element several atomic numbers removed. The proposed analytical scheme corrects for these interferences. Sixteen elements consisting of the lanthanides, yttrium, and scandium can be determined on as little as a 1-mg portion of the separated oxides. The oxides are dissolved in 1 ml of dilute acid, absorbed onto cellulose powder and pressed into a pellet for x-ray excitation. Chemically analyzed geologic standards are not required for calibration.

Thin film analysis of gadolinium iron oxide and gadolinium iron by a combined ion exchange X-ray fluorescence method

The composition of thin gadolinium iron oxide and alloy films of limited size (weighing from 500 to 2000μg and ranging from 0.7 to 2.3 nm in thickness) was determined by first collecting and simultaneously concentrating gadolinium and iron ions from very dilute solutions on ion-exchange resin-loaded paper disks, and then analyzing the concentrated samples by X-ray fluorescence. This method of analysis allows the preparation of standards by normal solution techniques without the problem of matrix effects.